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Figure Source:1.12. Fujitsu
• L2: Maximum height difference between indoor unit and indoor unit = 15m
• L3: Maximum piping length from outdoor unit to first separation tube = 70m
• [L3+L4+L5+L6]: Maximum piping length from outdoor unit to last indoor unit = 100m
• L6 & L7: Maximum piping length from header to indoor unit = 40m
• Total piping length = 200m (Liquid pipe length)
1.3.11 Building Load Profile:
When selecting a VRF system for a new or retrofit application, the following assessment
tasks should be carried out:
• Determine the functional and operational requirements by assessing the cooling load
and load profiles including location, hours of operations, number/type of occupants
equipment being used etc.
• Determine the required system configuration in terms of the number of indoor units and
the outdoor condensing unit capacity by taking into account the total capacity and
operational requirement, reliability and maintenance considerations](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-26-320.jpg)
![30
locations differ by 4:1 or greater. Except for desert climates, the latent loads are always higher
than the sensible loads. Where there is an economic benefit to controlling humidity combined
with large ventilation loads, the ventilation air should be examined carefully, and perhaps
singled-out for attention separate from the balance of the system. This suggestion is supported
by the fact that the latent and sensible loads are so different in dimension, and are seldom
concurrent.[1996]. Sam C M Hui and K P Cheung."Application of Building Energy Simulation to
Air-conditioning Design.” He suggested that the Simulation methods can provide analytical
power for the study and improvement of building performance; at the same time, we must
understand its properties and review the traditional building design procedure. Building energy
simulation is closely related to air-conditioning design. If a better building energy efficiency is to
be achieved, building energy simulation should be promoted wider in air conditioning design.
They point out that the development and implementation of building energy efficiency
standards is more complicated than the older ones which are often prescriptive in nature and
energy simulation software is often required for developing them. Through the comparison and
analysis of energy targets, one can determine whether the efficiency requirement has been
satisfied or not. The future trend of building energy efficiency standards is to adopt a
“performance-based” approach and it will require heavily on the support of simulation
techniques. Air-conditioning design should include energy simulation in the design process so as
to facilitate the development of building energy standards. . Building designers are often limited
by time and resources, and they usually can only use simple and quick method for analysing and
solving the design problems. During the outline design stage, because the building design may
often change and the building structure and materials may still not decided, designers can only
use rough calculation method for their analysis. At the 21 detailed design stage, designers may
then adjust their data based on actual information and then calculate carefully the load and
energy consumption again. If building energy simulation models can be set up in early design
stage, it will help designers understand the relationship between design and energy
performance and make the correct design decisions. At a later design stage, the simulation
results may provide detailed information for assessing the performance of the building and its
air. conditioning design. When the building is completed, building simulation may also be used
to assist the energy management and operation of the building.[1998]. Tianzhen Hong, S.K.
Chou*, T.Y. Bong. “Building simulation: an overview of developments and information sources.”](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-30-320.jpg)
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They Suggest that the growing trend towards environmental protection and achieving
sustainable development, the design of `green' buildings will surely gain attention. Building
simulation serves not only to reveal the inter- actions between the building and its occupants,
HVAC systems, and the outdoor climate, but also to make possible environmentally-friendly
design options. We have shown how important computer-aided building simulation is in the
study of energy performance and the design and operation of energy-efficient buildings. Future
development and application of information technology in the building industry will lead to a
completely new building design philosophy and methodology. As the actual building and HVAC
systems are often too complex to represent, some simplifications have to be made. For
example, a real building may consist of hundreds or thousands of rooms with defferent thermal
conditions, and some rooms may be of irregular shape (e.g., having round roofs and curved
envelopes). In such cases, the user has to simplify the real building into an ideal building
consisting of selected zones. Each zone is of regular shape that can be handled by the program,
and has uniform indoor conditions. The number of zones, always limited by the program, should
not be too large otherwise the calculating time will be quite long. Some applications, like
overheating risk analysis, will require the user to select a worst- case zone from a building. It is
believed that the zoning of a building is often one of the toughest tasks in building simulation.
The representing of buildings and HVAC systems depends upon the degree of accuracy of
simulation desired. It is often approximated at the early design phase and is progressively
reined at later phases. The energy requirements of a building depend not only on the individual
performance of the envelope components (walls, windows and roofs) and HVAC and lighting
systems, but also on their overall performance as an integrated system within the unique
building.[2000]. Michal Duška, Jan Lukeš, Martin Barták, František Drkal and Jan
Hensen “ Trends in heat gains from office equipment.” They focused on the trend in heat gains
from PCs and monitors as widely used IT equipment. The typical heat gains should be used with
respect to the design purpose. Personal computers and information systems (IT) are widely
applied in most of the buildings today. Internal heat gains from the office equipment represent
a major portion of cooling load. The diversity factor of equipment (defined as the ratio of
measured actual heat gains of all equipment to the sum of the peak gain from all equipment)
quantifies changes of actual gains (Wilkins and McGaffin 1994). The diversity factor depends on
occupants, type of their work, type of used equipment and it may range from 37 % to 78 % as](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-31-320.jpg)
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found by the study in five office buildings. Wilkins, McGaffin and other researchers presented
that computers and monitors do not reduce consumption at idle mode, with the exception of
computers with Pentium processors and some monitors measured by Hosni at al. (1999). The
reduction in consumption at idle mode is, however, significant for printers and copying
machines.[2005]. Ahmed Chérif Megri and Marjorie Musy. “ Building Zonal Thermal and
Airflow Modelling”. Suggested that the amount of energy used to heat and cool buildings is a
significant concern that impacts on issues from national policies to personal desires of cost and
comfort. The key to achieving optimum performance is the control of the energy flows in the
building and its environment. Such control is secured through monitoring and altering the
driving sources to maintain the desired thermal and air quality conditions in a space while
external and internal conditions (e.g. seasonal climate, indoor heat gains, pollutants etc.)
change over time. Thermal modelling tools are essential for the energy efficient design of
buildings and their associated control systems. They are used for a wide range of tasks including
policy making, cost analysis and comfort evaluation. They point out that For over three decades,
building thermal load and energy calculation programs have used a multi-room modelling
approach (Megri et al., 1996). This approach represents each room or, sometimes several
rooms within a building, as one single zone, called a node. Each node is separated from adjacent
nodes by means of the heat and airflow components dictated by walls, doors, ducts and fans as
well as windows and outside doors. This approach has the advantage of user friendliness in
terms of problem definition, straightforward internal representation and calculation
procedure.[2008]. Arlan Burdick and IBACOS, Inc , “Strategy Guideline: Accurate Heating and
Cooling Load Calculations” gives her views that right-sizing the HVAC system begins with an
accurate understanding of the heating and cooling loads on a space. The values determined by
the heating and cooling load calculation process dictate the equipment selection and the duct
design needed to deliver conditioned air to the rooms of the house to meet the occupant’s
comfort expectations.
Examples in this guide showed the implications when inaccurate or inappropriate adjustments
are applied during the heating and cooling load calculation process. Seemingly small
manipulations such as changing the outdoor/indoor design conditions can result in exaggerated
loads. For example, the Orlando House manipulations of outdoor/indoor design conditions](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-32-320.jpg)
![33
showed a 9,400 Btu/h (45%) increase in the total cooling load, which may increase the system
size by 1 ton when the ACCA Manual S procedures are applied. [2011]. Hiroyasu Okuyama and
Yoshinori Onishi “System parameter identification theory and uncertainty analysis methods for
multi-zone building heat transfer and infiltration”. Gives her views that Parameters related to
the energy efficiency of heating and cooling, as well as to the thermal comfort of the building
environment, include the coefficient of external wall heat transmission, solar heat gain, and
effective thermal capacity. In addition, parameters such as infiltration rate and effective mixing
volume are related to healthy indoor air quality. Methods for on-site measurement of building
thermal performance system parameters such as coefficient of heat loss, solar heat gain,
effective thermal capacity, infiltration rate, and effective mixing volume are very important, yet
a nontrivial task. Although these are steady-state parameters, on-site measurements are
exposed to changing meteorological conditions and are affected by the thermal capacity of the
building. They Improves the estimation methods for system parameters of building heat
transfer and infiltration systems.[2012]. Rachel Becker. “Improving thermal and energy
performance of buildings in summer with internal phase change materials.” Gives her views that
the worldwide ultimate aim of building energy performance research and development (R&D) is
to lead to the design and construction of positive-energy or at least near-zero-energy buildings,
which can be served entirely by systems that are based on clean and renewable energies. As the
energy efficiency. of such systems is still very low (Burkart and Arguea, 2012), major reductions
in heating and cooling demands are essential before zero- or positive-energy buildings can be
realized. For summer conditions, however, internal heat sources should be a major concern
(Jenkins, 2009; Jenkins et al., 2008). Surprisingly, a non-trivial part of literature still ignores them
when studying building thermal and energy performance in warm climates and the effects of
various means for their improvement. He envisaged that internal phase change materials
(PCMs) coupled with night ventilation comprise a possible solution to insufficient internal
thermal mass The main aim of the research presented in this article is to investigate the
possible thermal and energy improvements achieved in predominantly warm climates by
applying PCMs inside occupied spaces (e.g. applying PCM products in the form of panels or
boards at the room-facing surfaces of the partitions and walls instead of the regularly applied
gypsum wallboards, plywood panels orcementitious renderings. He suggest that during daytime](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-33-320.jpg)
![34
occupancy hours, more latent heat is charged in the PCM as the difference between room
temperature, Tin, and PCM fusion temperature, Tpcm (i.e. Tin - Tpcm), increases. Heat flow rate
into the PCM is of course larger for lower values of TPCM, implying that TPCM should be as low
as possible in comparison to the daytime prevailing values of Tin.[2013]. Robert L. Tazelaar, PE,
LEED AP. “Current Trends in Low-Energy HVAC Design.” They conclude that throughout the 20th
century, trends in HVAC design have been determined largely by technological advances and
energy costs. Engineers have always sought to find new ways to ensure occupant comfort, but
the level of attention devoted to finding innovative ways to reduce energy use has fluctuated
over the last few decades. When energy costs have risen, energy efficiency has become a
priority; when they have been low, it has been less of a design driver. This article identifies
several trends which are being used to reduce energy use in commercial buildings. The trends
to be considered include decoupling of ventilation and heating cooling, designing systems for
optimal efficiency, increased analysis in system design, and total building integration. This
article is not intended to be a technical argument or justification for selection of one system
against another. Many technical articles are available for more complete handling of each of the
trends. As prices soared during the energy crisis of the 1970s, engineers looked for a way to
reduce costs and improve space comfort conditions. One solution, dual duct systems, provided
warm air through one duct and cool air through another. The air would then be mixed at the
zone level to provide appropriate temperature supply air for the zone’s needs, typically at
constant volume. Dual duct systems allowed buildings to be divided into many more zones
while using a larger central fan system. Dual duct systems also eliminated the need to re-heat
air at the zone level resulting in less re-heat energy and reducing the piping network throughout
the building[2013]. Zhen Liu, Fang ting Song, Ziyan Jiang and , Xiaohong Guan.“ Optimization
based integrated control of building HVAC system” They suggest that Improving the control
strategy of building HVAC (heating, ventilation, and air-conditioning) systems can lead to
significant energy savings while preserving human comfort requirements. This paper focuses on
the analysis of the optimal control strategy of the whole HVAC system itself (such as set point
value curves for different parts, number control curves of different components) and the
followed operating curves of each equipment and device With the help of simulation technique
simulation results show that there are some variables which have not been fully explored in the
conventional control strategies. They have big potentials for energy saving, e.g. the number of](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-34-320.jpg)
![35
working cooling towers, supply air temperature of AHU, differential pressure of chilled water
pump, and supply chilled water temperature of chiller. More cases with different HVAC systems
and different weather should be studied to find the regular control rules. It will be helpful for
application.[2014]. Roth et.al (2002)[1]: present the paper on VRF installed costs are highly
dependent on the application, construction and lay out of the building and whether the installation
is new or retrofit. Lack of familiarity with the technology in the U.S will add to VRF costs. Total costs
of VRF systems are likely to be about 5% to 20% higher than chilled water systems of similar
capacity. Hai, Xiaohong (2006)[2] et al present the paper on. It is an effective method to combine
the ice-storage technology with VRV system in commercial central air conditioning system and the
system has the merits of flexible controls, simple operation and compact construction, which need
not the big space and difficult construction like the big central ice-storage system. William Goetzler
(2007)[3] et al present the paper on VRF systems are not suitable for all commercial building
applications. However, they are an excellent option for certain projects, and one more tool for
engineers to consider. Johnson (2007)[4] et al present the paper on Ozone depletion issues became
an increasing concern at that time issues of a high refrigerant charge of multi split system was likely
a strong negative for the system. Since that time, refrigerant developments, advances in charge
management, control and inverter technology. Increasing market acceptance of VRF technology.
Morton Blatt,(2008)[5] et al present It observed to VRF systems are enhanced versions of ductless
multi-split systems. VRF systems are very popular in Asia and support from major U.S. Main impact
of this system on the electric utility, application recommendations and technology attributes. John
Rogers,(2008)[6] et al present this paper reviews The India Low Carbon Growth study is developing
a bottom-up model that covers the electricity supply, residential, nonresidential buildings, transport,
industry, and agricultural sectors. In heating/cooling includes like electric water heater, air cooler,
fans, air conditioning. It can be seen that by 2031 the difference amounts to 135,240GWh/year,
equivalent to the total output of approximately thirty eight 500MW power stations. Qiu Tu
(2010)[7] et al present the paper on The heating control strategy is key technology for stable and
reliable heating operation of variable refrigerant flow air conditioning system with multi-module
outdoor units. Li and Wu (2010)[8] et al present the paper on the heat recovery VRF system can
save up to 17% of the energy consumption compared to a heat pump VRF system set up. This heat
recovery VRF system offered an additional advantage that it can provide cooling and heating for
different zones at the same time. Tolga N. Aynur (2010)[9] et al present the paper on VRF system to
control refrigerant mass flow rate according to cooling and heating load. This detailed review](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-35-320.jpg)
![36
indicates that the researchers focus on three main subjects: (a) Control strategies of the A Review of
a HVAC With VRF System (IJIRST/ Volume 1 / Issue 10 / 003) All rights reserved by www.ijirst.org
Brian Thornton (2012)[10] et al present the paper on Main Challenges of VRF system like [1]
Suppliers manufactures provide VRF technology through an integrated supply system which includes
installation, quality control and design training [2] Cost can be high compared to conventional
alternatives [3] Uncertainty about energy saving.
CHAPTER - 3
METHODOLOGY
The total load is the summation of external and internal load or both sensible and latent
loads. Usually 10% safety margin is added but it all depends on how accurate are the inputs.
The final load is than used to size the HVAC equipment. HVAC equipment is rated in Btuh,
but is commonly expressed in tonnage. A Btu (British thermal unit) is the amount of heat
needed to raise one pound of water one degree Fahrenheit. A “Ton” of cooling load is
actually 12,000
Btu per hour heat extraction equipment. The term ton comes from the amount of cooling
provided by two thousand pounds or one ton of ice. Traditionally, cooling loads are
calculated based on worst case scenarios. Cooling loads are calculated with all equipment &
lights operating at or near nameplate values, occupant loads are assumed to be at a
maximum, and the
extreme outdoor conditions are assumed to prevail 24 hours per day. Real occupant loads are
seldom as high as design loads. In detailed designing, the internal and external loads are
individually analyzed, since the relative magnitude of these two loads have a bearing on
equipment selection and controls. For example check the figure below:](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-36-320.jpg)
+[Refurbishing costs of A - Refurbishing costs of B](P/F, i, n1)
-[Annual savings for A - Annual savings for B](P/S, i, n)
-[Salvage value of A - Salvage value of B](P/F, i, n)
Where n is the time period, i is the interest rate, and n1 is the time when refurbishing is done,
5.4 RATE OF RETURN
In the preceding section, we discussed cost comparisons for different courses of action in
order to choose the least expensive one. These ideas can easily be extended to evaluate
potential investments and to determine the most profitable investment. Thus, net present
worth, payback period, and rate of return are commonly used methods for evaluating
investments.
The net present worth approach calculates the benefits and the costs at time zero
using the prevailing interest rate i or a minimum acceptable return on capital. Therefore, the
following expression may be used for the net present worth (NPW).
NPW = Present worth of benefits – Present worth of costs
= [Annual income – Annual costs](P/S, i, n)
+ [Salvage values](P/F, i, n) – Initial cost](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-55-320.jpg)
+[Refurbishing costs of A - Refurbishing costs of B](P/F, i, n1)](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-56-320.jpg)
-[Salvage value of A - Salvage value of B](P/F, i, n)
Neglecting Refurbishing Cost,
P/F = (I + i)-n
= (1+0.085)-10
= 0.4422
P/S = P/S= (1+i)n
-1/ i(1+i)n
= (1+0.085)10
-1/(0.085)(1+0.085)10
= 6.561348
LCS = (79.2-52.8) + (29.9 – 36.25) * (6.561348) – (1.18) * (6.561348) –
(0.638348 - 42.61193) * (0.4422)
= 4.45 LAC
Conclusions:
Based on comparative analysis of alternative with operating cost and life cycle cost, a VRF
(variable refrigerant flow) system is selected for a particular project of 149.5 TR. The total
HP outdoor unit in VRF system is installed load for the diversity of VRF units is 80 - 90%.
It is found that units electricity is consumed 3,30,000 units/year for VRF System and
4,22,500 units/year for split system. The life cycle analysis has been also done for useful life
of 10 years for split units and 12 years for VRF units. Life cycle saving has been also done
on Split and Multi- Split Variable Refrigerant Flow (VRF) System for a period of ten years
with interest rate 0.085. It is found that Life Cycle Saving is about 4.45 Lac in Multi-Split
VRF System compare to Split System. However if we will analyze that same of a period of
22 years which is useful life of VRF System then saving will be more in VRF System.](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-57-320.jpg)
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REFRENCES:
[1] Refrigeration And Air Conditioning by Arora C.P;-English-Tata Mcgraw Hill Education
Private Limited-Paperback_Edition-3 (English) 3rd Edition
[2] A Textbook of Refrigeration and Air Conditioning Paperback – December 1, 2006
by R. S. Khurmi (Author), J.K. Gupta (Author).
[3] A Course in Refrigeration And Air Conditioning C.P Arora, Domkundwar Dhanpat Rai
& Co. (P) Ltd.
[4] Cooling load calculation manual prepared by the American Society of Heating, Refrigerating
and Air-Conditioning Engineers, Inc., U.S. Department of Housing and Urban Development.
[5] ASHRAE, Handbook of Fundamentals, Ch. 28. American Society of Heating, Refrigerating
and Air-Conditioning Engineers, U.S.A. (1997).
[6] A Bhatia, HVAC Made Easy: A Guide of Heating and Cooling Load Estimation, PDH online
course M196 (4PDH).
[7] Handbook of Air Conditioning System Design /Carrier Air Conditioning Co. by Carrier Air
Conditioning Pty. Ltd
[8] Andersson,B., Wayne P. and Ronald K., " The impact of building orientation on residential
heating and cooling" , Energy and Buildings,1985; 8; 205-224.
[9] Al-Rabghi,O. and Khalid A. , " Utilizing transfer function method for hourly cooling load
calculations" Energy Conversion and Management,1997; 38; 319-332.
[10] Shariah,A., Bassam S., Akram R. and Brhan T.," Effects of absorptance of external surfaces
on heating and cooling loads of residential buildings in Jordan" Energy Conversion and
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[11] Kulkarni K., P.K. Sahoo and Mishra M., “Optimization of cooling load for a lecture theatre
in a composite climate in India” Energy and Buildings, 2011; 43; 1573-1579.
[12] Suziyana M. D., Nina S. N., Yusof T. M. and. Basirul A. A. S., “Analysis of Heat Gain in
Computer Laboratory and Excellent Centre by using CLTD/CLF/SCL Method” Procedia
Engineering, 2013; 53; 655 – 664.](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-58-320.jpg)
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[13] Hani H. Sait, “Estimated Thermal Load and Selecting of Suitable Air-Conditioning Systems
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[15] Roth, kurt, et al. “energy consumption characteristics of commercial building HVAC
system volume III: energy saving potential” TIAX LLC FOR DOE,2002
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[16] Hai, Xiaohong; Tao, Zhang; Yun, Fanhua; and Jun, Shen, "Design and Research of the
Commercial Digital VRV Multi-Connected Units With Sub-Cooled Ice Storage System"
(2006). International Refrigeration and Air Conditioning Conference. Paper 759.
http://docs.lib.purdue.edu/iracc/759
[17] William Goetzler, Member ASHRAE, ASHRAE Journal, April 2007
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narrative” June26, 2007.
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_2.pdf.
[19] Ammi Amarnath, “Variable Refrigerant Flow: An Emerging Air Conditioner and Heat
Pump Technology” Electric Power Research Institute. Morton Blatt, Energy Utilization
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[20] John rogers, “RESIDENTIAL CONSUMPTION OF ELECTRICITY IN INDIA”
Background Paper India: Strategies for Low Carbon Growth, July 2008 The World Bank.
[21] Qiu Tua,b, Ziping Fenga,b, Shoubo Maoc, Kaijun Donga,b, Rui Xiaoa,b, Wenji Songa
“Heating control strategy for variable refrigerant flow air conditioning system with multi-
module outdoor units” Guangzhou Institute of Energy Conversion, Chinese Academy of
Science, Guangzhou 510640, China b Key Laboratory of Renewable Energy and Gas
Hydrate, Chinese Academy of Science, Guangzhou 510640, China c Haier Air-Conditioning
Electronic Co. LTD., Qingdao 266510, China](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-59-320.jpg)
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[22] Li, Y.M., Wu, J.Y., and Shiochi, S., “Experimental validation of the simulation module
of the water-cooled variable refrigerant flow system under cooling operation”, Applied
Energy, vol. 87, pp. 1513-1521, 2010.
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Environmental Energy Engineering, Department of Mechanical Engineering, University of
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[24] Brian Thornton ,Senior Researcher, Pacific Northwest National Laboratory, Green
Proving Ground Program www.gsa.gov/gpg or “Variable Refrigerant Flow Systems” which
is available from the GPG program website, www.gsa.gov/gpg. December 2012.
[25] Daikin AC. www.daikinac.com.
[26] Goetzler, W. (2007). Variable refrigerant flow systems. ASHRAE Journal.
[27] VARIABLE REFRIGERANT FLOW SYSTEMS Technology Overview ASHRAE
NB/PEI,SEPTEMBER 2011 Roger Nasrallah, ing. Enertrak inc.
[28] HVAC Variable Refrigerant Flow Systems BY A BHATIA. Continuing Education and
Development, Inc. 9 Greyridge Farm Court Stony Point, NY 10980
[29] Bonneville Power Administration Prepared by: 570 Kirkland Way, Suite 200 Kirkland,
Washington 98033
Codes and Standards
NBC - National Building Code
ASHRAE - American Society of Heating, Refrigeration and Air-Conditioning
Engineers.
ARI - Air-conditioning and Refrigeration Institute
NFPA - National Fire Protection Association
UL - Underwriters’ Laboratories
AMCA - Air Movement and Control Association](https://image.slidesharecdn.com/lifecycleanalysisofhvacdesiningmultisplitvrfsystem-170927083338/85/Life-cycle-analysis-of-hvac-desining-multi-split-vrf-system-60-320.jpg)
Life cycle analysis of hvac desining multi split vrf system
- 1. 1 Life Cycle Analysis of Split and Multi-split Variable Refrigerant Flow (VRF) System: Case Study M.Tech Dissertation In Mechanical Engineering (Thermal Engineering) By Md. Khurshid Alam (MTTE-15-07) Department of Mechanical Engineering Al-Falah University, Dhauj, Faridabad, Haryana, (India) Jan-June 2017
- 2. 2 Life Cycle Analysis of Split and Multi-split Variable Refrigerant Flow (VRF) System: Case Study A Dissertation Submitted In partial fulfillment of the Requirement for the award of the degree Of Master of Technology In Mechanical Engineering (Thermal Engineering) By Md. Khurshid Alam (MTTE-15-07) Under the supervision of Dr. Shah Alam Department of Mechanical Engineering Al-Falah University, Dhauj, Faridabad, Haryana, (India) Jan-June 2017
- 3. 3 CERTIFICATE I hereby certify that the work which is being presented in the M.Tech. major project “Life Cycle Analysis of Multi Split VRF (Variable Refrigerant System) air- conditioning system: case study” in partial fulfillment of the requirement for the award of the Master of Technology in Thermal Engineering and submitted to the Department of Mechanical Engineering is an authentic record of the work carried out from various research papers under the supervision of Dr. Shah Alam, Department of Mechanical Engineering. The matter presented in this project has not been submitted by me for the award of any other degree elsewhere. Md. Khurshid Alam MTTE-15-07 This is to certify that the above statement made by the candidate is correct to the best of my Knowledge Dr. Shah Alam Prof. Dr. Mohd. Parvez Associate Prof. HOD.(Mechanical Engg.) Jamia Millia Islamia, New Delhi Al-Falah University, Faridabad, Haryana
- 4. 4 DECLARATION I declare that this written submission represents my ideas in my own words and where others’ ideas or word have been included, I have adequately cited and referenced the original sources. I also declare that I have adhered to all principles of academic honesty and integrity and have not misrepresented or fabricated or falsified any idea/data/fact/source in my submission. I understand that my violation of the above will be cause for disciplinary action by the institute and can also evoke penal action from the sources which have thus not been properly cited or from whom proper submission has not been taken when needed. Date: Md. Khurshid Alam MTTE-15-07
- 5. 5 List of Figures Figure No. Name Page 1.0 Split Air Conditioning System 12 1.1 Typical Multi Split System 13 1.2 Either Heating Or Cooling Mode 15 1.3 Schematic VRF Arrangement is Indicated 16 1.4 Separation Tube 17 1.5 Header Liquid & Gas Pipe 17 1.6 2 Pipe & 3 Pipe Heat Recovery System 18 1.7 Cooling Type VRF System 19 1.8 Heat Recovery Type VRF System 20 1.9 Basic Refrigerant System 21 1.10 VRF Outdoor Unit 25 1.11 VRF Outdoor to Indoor Unit Piping Length 26 1.12 VRF Electricity Consumption Graph 27 3.1 Cooling Load Distribution Graph 37 3.2 HVAC Layout For First Floor Appendix A
- 6. 6 List of Tables Table No. Name Page 1.1 Comparison of VRF and Unitary HVAC Systems 28 3.1 Solar Gain Glass 43 3.2 Solar Gain Wall 43 3.3 Design Parameter 45 3.4 Heat Load Sheet in Appendix B 3.5 Summery sheet 46 3.6 Selection of VRF 48 3.7 Operating Cost Compression 52 9 Interest Rate on Future Worth Monthly compression 45 10 Annual Cost Method 48
- 7. 7 ABBREVIATION/SYMBOLS TR = Ton of Refrigeration, HP =Horsepower, KW = Kilowatt, BTU= British Thermal Unit, DBT = Dry Bulb Temp. WBT = Wet Bulb Temp. CFM= Cubic Feet Per Minutes, Effective Room Sensible Heat (ERSH) Effective Room Latent Heat (ERLH) ESHF:(Effective Sensible Heat Factor ERTH (Effective Room Total Heat) ADP: Apparatus Dew Point, BF: Bypass Factor, Dew Point (DP, DPT) Relative Humidity (RH, rh) PW= Present Worth P/F = present worth factor i = interest rate, n = numbers of year, FW= Future Worth LCS= Life- Cycle Savings NPW= Net Present Worth
- 8. 8 ACKNOWLEDGEMENT First of all, I am thankful to “Allah” for compilation my project and to the entire crew of this project, I would like to extend a giant thank to my supervisor Mr. Dr. Md. Shah Alam, Mechanical Engineering Department, for their intuitive and meticulous guidance in completion of this minor project report. I want to express my profound gratitude for his genial and kindly co-operation in scrupulously scrutinizing the manuscript and his valuable suggestions throughout the work. I will like to thank the Prof. (Dr.) Md. Parvez, HOD, Deptt. of Mechanical Engineering and all other professors for his valuable support in carrying out my work with sincere efforts. I am especially indebted to my parents especially my father S.M. Zahir Ahmad. for their love and support. They are my first teachers after I came to this world and have set great examples for me about how to live, study and work. I am gratuitously thankful to Mr. Dr. Shah Alam. Associate Professor, Department of Mechanical Engineering, Jamia Millia Islamia, New Delhi for guiding, advising and helping me to carry out this work with sincere efforts Lastly I would like to express my heart–felt gratitude to those people who were knowingly or unknowingly involved in this project. Md. Khurshid Alam
- 9. 9 Contents: Certificate ……………………………………………………………………… 3 Deceleration…………………………………………………………………………4 List of Figures …………………………………………………………………… 5 List of Tables ……………………………………………………………………. 6 Abbreviation ……………………………………………………………………... 7 Acknowledgement ………………………………………………………………. 8 Abstract …………………………………………………………………………. 10 1. INTRODUCTION……….……………………………………………………. 11-29 2. LITERATURE OVERVIEW………………………………………………… 30- 36 3. METHODOLOGY............................................................................................... 37- 52 3.1 Statement of Problem 3.2 Selection of location 3.3 Data Heat load Calculation.................................................................................................33-43 4.1 heat load of floor 4.2 Selection of components of VRF system 5. Life Cycle Analysis……………………………………………………………53- 57 5.1 Present worth method 5.2 Future worth method 5.3 Life cycle saving 5.4 Rate of Return REFERENCES …………………………………………………………..58- 60
- 10. 10 ABSTRACT In this work a building having ground and first floor located in A.M.U. Aligarh has been selected for HVAC purposes. The total area of building is 18327 square feet. The total cooling load of ground floor and first floor is 149.5 TR. The total cooling load is ground floor is 89 TR and first floor is 61 TR. The total HP outdoor unit in VRF system is installed load for the diversity of VRF units is 80 - 90%. The load is calculated on the basis of occupants, electric loads, exposed area to sun etc. We have found that total HP outdoor unit and TR indoor units are needed. The total consumption of electricity for running VRF units is also calculated. It is found that units electricity is consumed 3,30,000 units/year for VRF System and 4,22,500 units/year for split system. The life cycle analysis has been also done for useful life of 10 years for split units and 12 years for VRF units. The aim is to create thermally controlled environment within the space of a building envelope by designing and planning a HVAC system for the project with the objective that the system designed and built is cost-wise economical, energy efficient as well as simple, flexible with regard to its operation, maintenance. This document mentions the codes, standards and criteria that will generally be used in the design and constructions of HVAC system for this project.
- 11. 11 CHAPTER -1 INTRODUCTION Heating, ventilation, and air conditioning (HVAC) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a sub discipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and transfer. Refrigeration is sometimes added to the field's abbreviation as HVAC & R or HVACR, or ventilating is dropped as in HACR (such as the designation of HACR-rated circuit breakers). The primary function of all air-conditioning systems is to provide thermal comfort for building occupants. There are a wide range of air conditioning systems available, staring from the basic window-fitted unit to the small split systems, medium scale package units, large chilled water systems and very latest variable refrigerant flow (VRF) system. Split type air conditioning systems are one to one system consisting of one evaporator (fan coil) unit connected to an external condensing unit. Both the indoor and outdoor unit are connected through copper tubing and electrical cabling The indoor part (evaporator) pulls heat out from the surrounding air while the outdoor condensing unit transfers the heat into the environment. The advantages of split systems are: • Low initial cost, less noise and ease of installation; • Good alternative to ducted systems; • Each system is totally independent and has its own control. Apart from this there are several disadvantages of this system given as: • There is limitation on the distance between the indoor and outdoor unit i.e. refrigerant piping can’t exceed the limits stipulated by the manufacturer (usually 100 to 150 ft) otherwise the performance will suffer; • Maintenance (cleaning/change of filters) is within the occupied space; • Limited air through, which can lead to possible hot/cold spots;
- 12. 12 • Impact on building aesthetics of large building because too many outdoor units will spoil the appearance of the building VRV System: The term VRF refers to the ability of the system to control the amount of refrigerant flowing to each of the evaporators, enabling the use of many evaporators of differing capacities and configurations, individualized comfort control, simultaneous heating and cooling in different zones, and heat recovery from one zone to another. VRF systems operate on the direct expansion (DX) principle meaning that heat is transferred to or from the space directly by circulating refrigerant to evaporators located near or within the conditioned space. Refrigerant flow control is the key to many advantages as well as the major technical challenge of VRF systems. Note the term VRF systems should not be confused with the centralized VAV (variable air volume) systems, which work by varying the air flow to the conditioned space on variation in room loads. 1.1 Split Air-conditioning Systems: Split type air conditioning systems are one to one system consisting of one evaporator (fan coil) unit connected to an external condensing unit. Both the indoor and outdoor unit are connected through copper tubing and electrical cabling. The indoor part (evaporator) pulls heat out from the surrounding air while the outdoor condensing unit transfers the heat into the environment. Fig.1.0 Split Air-conditioning System
- 13. 13 1.2 Advantages of using Split Air conditioners: • Low initial cost, less noise and ease of installation; • Good alternative to ducted systems; • Each system is totally independent and has its own control. 1.3 Disadvantages: • piping can’t exceed the limits stipulated by the manufacturer (usually 100 to 150 ft) otherwise the performance will suffer; • Maintenance (cleaning/change of filters) is within the occupied space; • Limited air throw, which can lead to possible hot/cold spots; • Impact on building aesthetics of large building because too many outdoor units will spoil the appearance of the building. 1.2.1 Multi Split Systems: A multi type air conditioning system operates on the same principles as a split type air conditioning system however in this case there are ‘multiple’ evaporator units connected to one external condensing unit. These simple systems were designed mainly for small to medium commercial applications where the installation of ductwork was either too expensive, or aesthetically unacceptable. The small-bore refrigerant piping, which connects the indoor and outdoor units requires much lower space and is easier to install than the metal ducting. Each indoor unit has its own set of refrigerant pipe work connecting it to the outdoor unit.
- 14. 14 Fig. 1.1 Multi-Split System 1.2.2 Advantages of Multi-splits: • The fact that one large condenser can be connected to multiple evaporators within the building reduces and/or eliminate the need for ductwork installation completely. • Multi-splits are suitable for single thermal zone* applications with very similar heat gains / losses. 1.2.3 Drawbacks: • Multi-split systems turn OFF or ON completely in response to a single thermostat/control station, which operates the whole system. These systems are therefore not suitable for areas/rooms with variable heat gain/loss characteristics. *Thermal zone: A thermal zone is referred to a space or group of spaces within a building with similar heating and cooling requirements. Each thermal zone must be ‘separately controlled’ if conditions conducive to comfort are to be provided by an HVAC system. Any area that requires different temperature, humidity and filtration needs shall be categorized as an independent zone and shall be controlled by dedicated control or HVAC system. Few examples below illustrate and clarify the zone concept: gned for 50 people occupancy shall experience lower temperatures when it is half or quarterly occupied. The design thus shall keep provision for a dedicated temperature controller for this zone; • A smoking lounge of airport has different filtration, ventilation (air changes) and pressure requirement compared to other areas therefore is a separate zone; • A hotel lobby area is different from the guest rooms or the restaurant area because of occupancy variations; • In a commercial building, the space containing data processing equipment such as servers, photocopiers, fax machines and printers see much larger heat load than the other areas and hence is a different thermal zone;
- 15. 15 • A hospital testing laboratory, isolation rooms and operation theatre demand different indoor conditions/pressure relationships than the rest of areas and thus shall be treated as a separate zones; • A control room or processing facilities in industrial set up may require a high degree of cleanliness/positive pressure to prevent ingress of dust/hazardous elements and thus may be treated as separate zone. 1.3.1 Variable Refrigerant Flow or VRF Systems: VRF systems are similar to the multi-split systems, which connect one outdoor section to several evaporators. However, multi-split systems turn OFF or ON completely in response to one master controller, whereas VRF systems continually adjust the flow of refrigerant to each indoor evaporator. The control is achieved by continually varying the flow of refrigerant through a pulse modulating valve (PMV) whose opening is determined by the microprocessor receiving information from the thermistor sensors in each indoor unit. The indoor units are linked by a control wire to the outdoor unit, which responds to the demand from the indoor units, by varying its compressor speed to match the total cooling and/or heating requirements VRF systems promise a more energy-efficient strategy (estimates range from 11% to 17% less energy compared to conventional units) at a somewhat higher cost.
- 16. 16 Fig. 1.3 Either Heating or Cooling Mode The modern VRF technology uses an inverter-driven scroll compressor and permits as many as 48 or more indoor units to operate off one outdoor unit (varies from manufacturer to manufacturer). The inverter scroll compressors are capable of changing the speed to follow the variations in total cooling/heating load as determined by the suction gas pressure measured on the condensing unit. The capacity control range can be as low as 6% to 100%. Refrigerant piping runs of more than 200 ft are possible, and outdoor units are available in sizes up to 240,000 Btu/h. 1.3.2 A schematic VRF arrangement is indicated below: Figure 1.4 VRF systems are engineered systems and use complex refrigerant and oil control circuitry. The refrigerant pipe-work uses number of separation tubes and/or headers (refer schematic figure above).
- 17. 17 Separation tube has 2 branches whereas header has more than 2 branches. Either or both the separation tube and header can be used for branches, but the separation tube is never provided after the header because of balancing issues Figure1.5 Figure1.6
- 18. 18 Compared to multi-split systems, VRF systems minimize the refrigerant path and use less copper tubing. Minimizing refrigerant path allows for maximizing efficiency of refrigerant work. Figure 1.7 1.3.3 Types of VRF: VRV/VRF systems can be used for cooling only, heat pumping and heat recovery. On heat pump models there are two basic types of VRF system: heat pump systems and energy- recovery. 1.3.4 VRF heat pump systems: VRF heat pump systems permit heating in all of the indoor units, or cooling in all the units, but NOT simultaneous heating and cooling. When the indoor units are in the cooling mode, they act as evaporators; when they are in the heating mode, they act as condensers. These are also termed two-pipe system.
- 19. 19 Fig. 1.8 Cooling Type VRF System VRF heat pump systems are effectively applied in open plan areas, retail stores, cellular offices and any other areas that require cooling or heating during the same operational periods. 1.3.5 Heat Recovery VRF system (VRF-HR): Variable refrigerant flow systems with heat recovery (VRF-HR) capability can operate simultaneously in heating and/or cooling mode, enabling heat to be used rather than rejected as it would be in traditional heat pump systems. VRF-HR systems are equipped with enhanced features like inverter drives, pulse modulating electronic expansion valve and distributed controls that allow system to operate in net heating or net cooling mode as demanded by the space. Each manufacturer has its own proprietary design (2-pipe or 3-pipe system), but most uses a three-pipe system (liquid line, a hot gas line and a suction line) and special valving arrangements. Each indoor unit is branched off from the 3 pipes using solenoid valves. An indoor unit requiring cooling will open its liquid line and suction line valves and act as an evaporator. An indoor unit requiring heating will open its hot gas and liquid line valves and will act as a condenser. Typically, extra heat exchangers in distribution boxes are used to transfer some reject heat
- 20. 20 from the superheated refrigerant exiting the zone being cooled to the refrigerant that is going to the zone to be heated. This balancing act has the potential to produce significant energy savings. Fig. 1.9 Heat Recovery Type VRF System VRF-HR mixed mode operation leads to energy savings as both ends of the thermodynamic cycle are delivering useful heat exchange. If a system has a cooling COP (Coefficient of Performance) of 3, and a heating COP of 4, then heat recovery operation could yield a COP as high as 7. It should be noted that this perfect balance of heating and cooling demand is unlikely to occur for many hours each year, but whenever mixed mode is used energy is saved. Units are now available to deliver the heat removed from space cooling into hot water for space heating, domestic hot water or leisure applications, so that mixed mode is utilized for more of the year. VRF-HR systems work best when there is a need for some of the spaces to be cooled and some of them to be heated during the same period; this often occurs in the winter in medium-sized to large sized buildings with a substantial core or in the areas on the north and south sides of a building.
- 21. 21 1.3.6 COP – Performance rating used primarily in heat pumps. The Coefficient of Performance - COP – is defined as the ratio of heat output to the amount of energy input of a heat pump. It compares the heat produced by the heat pump to the heat you would get from resistance heat. COPs vary with the outside temperature: as the temperature falls, the COP falls also, since the heat pump is less efficient at lower temperatures. ARI standards compare equipment at two temperatures, 47°F and 17°F, to give you an idea of the COP in both mild and colder temperatures. 1.3.7 Refrigerant Modulation in VRF System: VRV/VRF technology is based on the simple vapor compression cycle same as conventional split air conditioning systems, but give you the ability to continuously control and adjust the flow of refrigerant to different internal units, depending on the heating and cooling needs of each area of the building. The refrigerant flow to each evaporator is adjusted precisely through pulse wave electronic expansion valve in conjunction with inverter and multiple compressors of varying capacity in response to changes in the cooling or heating requirement within the air conditioned space. We will discuss this further but before that let’s refresh basic refrigeration cycle
- 22. 22 Figure 1.10 The fundamental of an air conditioning system is the use of a refrigerant to absorb heat from the indoor environment and transfer it to the external environment. In the cooling mode, indoor units are supplied with liquid refrigerant. The amount of refrigerant flowing through the unit is controlled via an expansion valve located inside the unit. When the refrigerant enters the coil, it undergoes a phase change (evaporation) that extracts heat from the space, thereby cooling the room. The heat extracted from the space is exhausted to ambient air. Refrigeration systems can operate on reverse cycle with an inclusion of special 4-way reversing valve, enabling the absorption of heat from the external environment and using this heat to raise the internal temperature. When in the heating mode, indoor units are supplied with hot gas refrigerant. Again, the amount of hot gas flowing through the unit is controlled via the same electronic expansion valve. As with the liquid refrigerant, the hot gas undergoes
- 23. 23 a phase change (condensation), which releases heat energy into the space. These are called heat pump system. Heat pumps provide both heating and cooling from the same unit and due to added heat of compression, the efficiency of heat pump in heating mode is higher compared to the cooling cycle. Expansion valve is the component that controls the rate at which liquid refrigerant can flow into an evaporator coil. The conventional refrigeration cycle uses “thermostatic expansion valve (TXV)” that uses mechanical spring for control. It has its drawbacks. • TXV operation is totally independent of compressor operation; • TXV is susceptible to hunting i.e. overfeeding and starvation of refrigerant flow to the evaporator. As evaporator load increases, available refrigerant will boil off more rapidly. If it is completely evaporated prior to exiting the evaporator, the vapor will continue to absorb heat (superheat). Although superheating ensures total evaporation of the liquid refrigerant before it goes into the compressor, the density of vapor which quits the evaporator and enters the compressor is reduced leading to reduced refrigeration capacity. The inadequate or high super heat in a system is a concern. • Too little: liquid refrigerant entering compressor washes out the oil causing premature failure. • Too much: valuable evaporator space is wasted and possibly causing compressor overheating problems. The shortcomings of TXV are offset by modern electronic expansion valve 1.3.8 Electronic Expansion Valve (EEV): With an electronic expansion valve (EEV), you can tell the system what superheat you want and it will set it up. The primary characteristic of EEV is its ability to rotate a prescribed small angle (step) in response to each control pulse applied to its windings. EEV consists of a synchronous electronic motor that can divide a full rotation into a large number of steps, 500
- 24. 24 steps/rev. With such a wide range, EEV valve can go from full open to totally closed and closes down when system is satisfied. EEV in VRF system functions to maintain the pressure differential and also distribute the precise amount of refrigerant to each indoor unit. It allows for the fine control of the refrigerant to the evaporators and can reduce or stop the flow of refrigerant to the individual evaporator unit while meeting the targeted superheat 1.3.9 Design Considerations for VRF Systems Deciding what HVAC system best suits your application will depend on several variables viz. building characteristics; cooling and heating load requirements; peak occurrence; simultaneous heating and cooling requirements; fresh air needs; accessibility requirements; minimum and maximum outdoor temperatures; sustainability; and acoustic characteristics. 1.3.10 Building Characteristics: VRF systems are typically distributed systems – the outdoor unit is kept at a far off location like the top of the building or remotely at grade level and all the evaporator units are installed at various locations inside the building. Typically the refrigerant pipe-work (liquid and suction lines) is very long, running in several hundred of feet in length for large multi-storied buildings. Obviously, the long pipe lengths will introduce pressure losses in the suction line and unless the correct diameter of pipe is selected, the indoor units will be starved of refrigerant and it will result in insufficient cooling to the end user. So it is very important to make sure that the pipe sizing is done properly – both for the main header pipe as well as the feeder pipes that feed each indoor unit. The maximum allowable length varies among different manufacturers; however the general guidelines are as follows: • The maximum allowable vertical distance between an outdoor unit and its farthest indoor unit is 164 ft; • The maximum permissible vertical distance between two individual indoor units is 49 feet,
- 25. 25 unit is up to 541 ft. Note: The longer the lengths of refrigerant pipes, the more expensive the initial and operating costs Figure Source:1.11. ASHRAE As stated the refrigerant piping criteria varies from manufacturer to manufacture; for example for one of the Japanese manufacturer (Fujitsu), the system design limits are:
- 26. 26 Figure Source:1.12. Fujitsu • L2: Maximum height difference between indoor unit and indoor unit = 15m • L3: Maximum piping length from outdoor unit to first separation tube = 70m • [L3+L4+L5+L6]: Maximum piping length from outdoor unit to last indoor unit = 100m • L6 & L7: Maximum piping length from header to indoor unit = 40m • Total piping length = 200m (Liquid pipe length) 1.3.11 Building Load Profile: When selecting a VRF system for a new or retrofit application, the following assessment tasks should be carried out: • Determine the functional and operational requirements by assessing the cooling load and load profiles including location, hours of operations, number/type of occupants equipment being used etc. • Determine the required system configuration in terms of the number of indoor units and the outdoor condensing unit capacity by taking into account the total capacity and operational requirement, reliability and maintenance considerations
- 27. 27 Building load profile helps to determine the outdoor condensing unit compressor capacity. For instance, if there are many hours at low load, it is advantageous to install multiple compressors and with at least one with inverter (speed adjustment) feature. Figure below shows a typical load profile for an office building. Figure 1.13. The combined cooling capacity of the indoor sections can match, exceed, or be lower than the capacity of the outdoor section connected to them. But as a normal practice: • The indoor units are typically sized and selected based on the greater of the heating or cooling loads in a zone it serves i.e. maximum peak load expected in any time of the year. • The outdoor condensing unit is selected based on the load profile of the facility which is the peak load of all the zones combined at any one given time. The important thing here is that it is unlikely all zones will peak at a given time so an element of diversity is considered for economic sizing. Adding up the peak load for each indoor unit and
- 28. 28 using that total number to size the outdoor unit will result in an unnecessarily oversized condensing unit. Although an oversized condensing unit with multiple compressors is capable of operating at lower capacity, too much over sizing sometimes reduces or ceases the modulation function of the expansion valve. As a rule of thumb, an engineer can specify an outdoor unit with a capacity anywhere between 70% and 130% of the combined capacities of indoor units. Comparison of VRF and Unitary HVAC Systems; Item Description VRF System Unitary System 1 Condensing units components 1.1 Single or multiple compressor Yes Yes 1.2 Oil separator for each compressor or for all compressors Yes Yes 1.3 Oil level control Yes Yes 1.4 Active oil return Yes In some units 1.5 Option for heating and cooling Yes Yes for hot gas defrost Simultaneous heating / cooling Yes No 1.6 Air cooled or water cooled condenser Yes Yes 1.7 Liquid receiver Yes Yes 1.8 Control of the refrigerant level in the liquid receiver Yes Yes 1.9 Condensing temperature control Yes It is an option 1.10 Capacity control by the Yes Yes
- 29. 29 suction pressure 1.11 Compressor cooling capacity control by speed (RPM) or steps Yes Yes 1.12 Suction accumulator Depending on the System Yes 2.0 Refrigerant lines 2.1 Long liquid lines to many evaporators Yes Yes 2.2 Refrigerant pipes special design procedure due to pressure drop and oil return Yes Yes 3.0 Internal units 3.1 Several units any size Yes Yes 3.2 Independent control for each evaporator by an electronic expansion valve Yes Yes CHAPTER -2 LITERETURE REVIEW Lewis G. Harriman and Douglas Kosar, “Dehumidification and Cooling Loads From Ventilation Air”. He gives her views regarding latent heat loads and sensible heat loads .He suggested that One might expect that sensible heat loads and moisture loads generated by ventilation air would be similar, but that is not the case. None of the locations shown here have equal latent and sensible loads. In fact, all locations have loads that differ by at least 3:1, and loads at most
- 30. 30 locations differ by 4:1 or greater. Except for desert climates, the latent loads are always higher than the sensible loads. Where there is an economic benefit to controlling humidity combined with large ventilation loads, the ventilation air should be examined carefully, and perhaps singled-out for attention separate from the balance of the system. This suggestion is supported by the fact that the latent and sensible loads are so different in dimension, and are seldom concurrent.[1996]. Sam C M Hui and K P Cheung."Application of Building Energy Simulation to Air-conditioning Design.” He suggested that the Simulation methods can provide analytical power for the study and improvement of building performance; at the same time, we must understand its properties and review the traditional building design procedure. Building energy simulation is closely related to air-conditioning design. If a better building energy efficiency is to be achieved, building energy simulation should be promoted wider in air conditioning design. They point out that the development and implementation of building energy efficiency standards is more complicated than the older ones which are often prescriptive in nature and energy simulation software is often required for developing them. Through the comparison and analysis of energy targets, one can determine whether the efficiency requirement has been satisfied or not. The future trend of building energy efficiency standards is to adopt a “performance-based” approach and it will require heavily on the support of simulation techniques. Air-conditioning design should include energy simulation in the design process so as to facilitate the development of building energy standards. . Building designers are often limited by time and resources, and they usually can only use simple and quick method for analysing and solving the design problems. During the outline design stage, because the building design may often change and the building structure and materials may still not decided, designers can only use rough calculation method for their analysis. At the 21 detailed design stage, designers may then adjust their data based on actual information and then calculate carefully the load and energy consumption again. If building energy simulation models can be set up in early design stage, it will help designers understand the relationship between design and energy performance and make the correct design decisions. At a later design stage, the simulation results may provide detailed information for assessing the performance of the building and its air. conditioning design. When the building is completed, building simulation may also be used to assist the energy management and operation of the building.[1998]. Tianzhen Hong, S.K. Chou*, T.Y. Bong. “Building simulation: an overview of developments and information sources.”
- 31. 31 They Suggest that the growing trend towards environmental protection and achieving sustainable development, the design of `green' buildings will surely gain attention. Building simulation serves not only to reveal the inter- actions between the building and its occupants, HVAC systems, and the outdoor climate, but also to make possible environmentally-friendly design options. We have shown how important computer-aided building simulation is in the study of energy performance and the design and operation of energy-efficient buildings. Future development and application of information technology in the building industry will lead to a completely new building design philosophy and methodology. As the actual building and HVAC systems are often too complex to represent, some simplifications have to be made. For example, a real building may consist of hundreds or thousands of rooms with defferent thermal conditions, and some rooms may be of irregular shape (e.g., having round roofs and curved envelopes). In such cases, the user has to simplify the real building into an ideal building consisting of selected zones. Each zone is of regular shape that can be handled by the program, and has uniform indoor conditions. The number of zones, always limited by the program, should not be too large otherwise the calculating time will be quite long. Some applications, like overheating risk analysis, will require the user to select a worst- case zone from a building. It is believed that the zoning of a building is often one of the toughest tasks in building simulation. The representing of buildings and HVAC systems depends upon the degree of accuracy of simulation desired. It is often approximated at the early design phase and is progressively reined at later phases. The energy requirements of a building depend not only on the individual performance of the envelope components (walls, windows and roofs) and HVAC and lighting systems, but also on their overall performance as an integrated system within the unique building.[2000]. Michal Duška, Jan Lukeš, Martin Barták, František Drkal and Jan Hensen “ Trends in heat gains from office equipment.” They focused on the trend in heat gains from PCs and monitors as widely used IT equipment. The typical heat gains should be used with respect to the design purpose. Personal computers and information systems (IT) are widely applied in most of the buildings today. Internal heat gains from the office equipment represent a major portion of cooling load. The diversity factor of equipment (defined as the ratio of measured actual heat gains of all equipment to the sum of the peak gain from all equipment) quantifies changes of actual gains (Wilkins and McGaffin 1994). The diversity factor depends on occupants, type of their work, type of used equipment and it may range from 37 % to 78 % as
- 32. 32 found by the study in five office buildings. Wilkins, McGaffin and other researchers presented that computers and monitors do not reduce consumption at idle mode, with the exception of computers with Pentium processors and some monitors measured by Hosni at al. (1999). The reduction in consumption at idle mode is, however, significant for printers and copying machines.[2005]. Ahmed Chérif Megri and Marjorie Musy. “ Building Zonal Thermal and Airflow Modelling”. Suggested that the amount of energy used to heat and cool buildings is a significant concern that impacts on issues from national policies to personal desires of cost and comfort. The key to achieving optimum performance is the control of the energy flows in the building and its environment. Such control is secured through monitoring and altering the driving sources to maintain the desired thermal and air quality conditions in a space while external and internal conditions (e.g. seasonal climate, indoor heat gains, pollutants etc.) change over time. Thermal modelling tools are essential for the energy efficient design of buildings and their associated control systems. They are used for a wide range of tasks including policy making, cost analysis and comfort evaluation. They point out that For over three decades, building thermal load and energy calculation programs have used a multi-room modelling approach (Megri et al., 1996). This approach represents each room or, sometimes several rooms within a building, as one single zone, called a node. Each node is separated from adjacent nodes by means of the heat and airflow components dictated by walls, doors, ducts and fans as well as windows and outside doors. This approach has the advantage of user friendliness in terms of problem definition, straightforward internal representation and calculation procedure.[2008]. Arlan Burdick and IBACOS, Inc , “Strategy Guideline: Accurate Heating and Cooling Load Calculations” gives her views that right-sizing the HVAC system begins with an accurate understanding of the heating and cooling loads on a space. The values determined by the heating and cooling load calculation process dictate the equipment selection and the duct design needed to deliver conditioned air to the rooms of the house to meet the occupant’s comfort expectations. Examples in this guide showed the implications when inaccurate or inappropriate adjustments are applied during the heating and cooling load calculation process. Seemingly small manipulations such as changing the outdoor/indoor design conditions can result in exaggerated loads. For example, the Orlando House manipulations of outdoor/indoor design conditions
- 33. 33 showed a 9,400 Btu/h (45%) increase in the total cooling load, which may increase the system size by 1 ton when the ACCA Manual S procedures are applied. [2011]. Hiroyasu Okuyama and Yoshinori Onishi “System parameter identification theory and uncertainty analysis methods for multi-zone building heat transfer and infiltration”. Gives her views that Parameters related to the energy efficiency of heating and cooling, as well as to the thermal comfort of the building environment, include the coefficient of external wall heat transmission, solar heat gain, and effective thermal capacity. In addition, parameters such as infiltration rate and effective mixing volume are related to healthy indoor air quality. Methods for on-site measurement of building thermal performance system parameters such as coefficient of heat loss, solar heat gain, effective thermal capacity, infiltration rate, and effective mixing volume are very important, yet a nontrivial task. Although these are steady-state parameters, on-site measurements are exposed to changing meteorological conditions and are affected by the thermal capacity of the building. They Improves the estimation methods for system parameters of building heat transfer and infiltration systems.[2012]. Rachel Becker. “Improving thermal and energy performance of buildings in summer with internal phase change materials.” Gives her views that the worldwide ultimate aim of building energy performance research and development (R&D) is to lead to the design and construction of positive-energy or at least near-zero-energy buildings, which can be served entirely by systems that are based on clean and renewable energies. As the energy efficiency. of such systems is still very low (Burkart and Arguea, 2012), major reductions in heating and cooling demands are essential before zero- or positive-energy buildings can be realized. For summer conditions, however, internal heat sources should be a major concern (Jenkins, 2009; Jenkins et al., 2008). Surprisingly, a non-trivial part of literature still ignores them when studying building thermal and energy performance in warm climates and the effects of various means for their improvement. He envisaged that internal phase change materials (PCMs) coupled with night ventilation comprise a possible solution to insufficient internal thermal mass The main aim of the research presented in this article is to investigate the possible thermal and energy improvements achieved in predominantly warm climates by applying PCMs inside occupied spaces (e.g. applying PCM products in the form of panels or boards at the room-facing surfaces of the partitions and walls instead of the regularly applied gypsum wallboards, plywood panels orcementitious renderings. He suggest that during daytime
- 34. 34 occupancy hours, more latent heat is charged in the PCM as the difference between room temperature, Tin, and PCM fusion temperature, Tpcm (i.e. Tin - Tpcm), increases. Heat flow rate into the PCM is of course larger for lower values of TPCM, implying that TPCM should be as low as possible in comparison to the daytime prevailing values of Tin.[2013]. Robert L. Tazelaar, PE, LEED AP. “Current Trends in Low-Energy HVAC Design.” They conclude that throughout the 20th century, trends in HVAC design have been determined largely by technological advances and energy costs. Engineers have always sought to find new ways to ensure occupant comfort, but the level of attention devoted to finding innovative ways to reduce energy use has fluctuated over the last few decades. When energy costs have risen, energy efficiency has become a priority; when they have been low, it has been less of a design driver. This article identifies several trends which are being used to reduce energy use in commercial buildings. The trends to be considered include decoupling of ventilation and heating cooling, designing systems for optimal efficiency, increased analysis in system design, and total building integration. This article is not intended to be a technical argument or justification for selection of one system against another. Many technical articles are available for more complete handling of each of the trends. As prices soared during the energy crisis of the 1970s, engineers looked for a way to reduce costs and improve space comfort conditions. One solution, dual duct systems, provided warm air through one duct and cool air through another. The air would then be mixed at the zone level to provide appropriate temperature supply air for the zone’s needs, typically at constant volume. Dual duct systems allowed buildings to be divided into many more zones while using a larger central fan system. Dual duct systems also eliminated the need to re-heat air at the zone level resulting in less re-heat energy and reducing the piping network throughout the building[2013]. Zhen Liu, Fang ting Song, Ziyan Jiang and , Xiaohong Guan.“ Optimization based integrated control of building HVAC system” They suggest that Improving the control strategy of building HVAC (heating, ventilation, and air-conditioning) systems can lead to significant energy savings while preserving human comfort requirements. This paper focuses on the analysis of the optimal control strategy of the whole HVAC system itself (such as set point value curves for different parts, number control curves of different components) and the followed operating curves of each equipment and device With the help of simulation technique simulation results show that there are some variables which have not been fully explored in the conventional control strategies. They have big potentials for energy saving, e.g. the number of
- 35. 35 working cooling towers, supply air temperature of AHU, differential pressure of chilled water pump, and supply chilled water temperature of chiller. More cases with different HVAC systems and different weather should be studied to find the regular control rules. It will be helpful for application.[2014]. Roth et.al (2002)[1]: present the paper on VRF installed costs are highly dependent on the application, construction and lay out of the building and whether the installation is new or retrofit. Lack of familiarity with the technology in the U.S will add to VRF costs. Total costs of VRF systems are likely to be about 5% to 20% higher than chilled water systems of similar capacity. Hai, Xiaohong (2006)[2] et al present the paper on. It is an effective method to combine the ice-storage technology with VRV system in commercial central air conditioning system and the system has the merits of flexible controls, simple operation and compact construction, which need not the big space and difficult construction like the big central ice-storage system. William Goetzler (2007)[3] et al present the paper on VRF systems are not suitable for all commercial building applications. However, they are an excellent option for certain projects, and one more tool for engineers to consider. Johnson (2007)[4] et al present the paper on Ozone depletion issues became an increasing concern at that time issues of a high refrigerant charge of multi split system was likely a strong negative for the system. Since that time, refrigerant developments, advances in charge management, control and inverter technology. Increasing market acceptance of VRF technology. Morton Blatt,(2008)[5] et al present It observed to VRF systems are enhanced versions of ductless multi-split systems. VRF systems are very popular in Asia and support from major U.S. Main impact of this system on the electric utility, application recommendations and technology attributes. John Rogers,(2008)[6] et al present this paper reviews The India Low Carbon Growth study is developing a bottom-up model that covers the electricity supply, residential, nonresidential buildings, transport, industry, and agricultural sectors. In heating/cooling includes like electric water heater, air cooler, fans, air conditioning. It can be seen that by 2031 the difference amounts to 135,240GWh/year, equivalent to the total output of approximately thirty eight 500MW power stations. Qiu Tu (2010)[7] et al present the paper on The heating control strategy is key technology for stable and reliable heating operation of variable refrigerant flow air conditioning system with multi-module outdoor units. Li and Wu (2010)[8] et al present the paper on the heat recovery VRF system can save up to 17% of the energy consumption compared to a heat pump VRF system set up. This heat recovery VRF system offered an additional advantage that it can provide cooling and heating for different zones at the same time. Tolga N. Aynur (2010)[9] et al present the paper on VRF system to control refrigerant mass flow rate according to cooling and heating load. This detailed review
- 36. 36 indicates that the researchers focus on three main subjects: (a) Control strategies of the A Review of a HVAC With VRF System (IJIRST/ Volume 1 / Issue 10 / 003) All rights reserved by www.ijirst.org Brian Thornton (2012)[10] et al present the paper on Main Challenges of VRF system like [1] Suppliers manufactures provide VRF technology through an integrated supply system which includes installation, quality control and design training [2] Cost can be high compared to conventional alternatives [3] Uncertainty about energy saving. CHAPTER - 3 METHODOLOGY The total load is the summation of external and internal load or both sensible and latent loads. Usually 10% safety margin is added but it all depends on how accurate are the inputs. The final load is than used to size the HVAC equipment. HVAC equipment is rated in Btuh, but is commonly expressed in tonnage. A Btu (British thermal unit) is the amount of heat needed to raise one pound of water one degree Fahrenheit. A “Ton” of cooling load is actually 12,000 Btu per hour heat extraction equipment. The term ton comes from the amount of cooling provided by two thousand pounds or one ton of ice. Traditionally, cooling loads are calculated based on worst case scenarios. Cooling loads are calculated with all equipment & lights operating at or near nameplate values, occupant loads are assumed to be at a maximum, and the extreme outdoor conditions are assumed to prevail 24 hours per day. Real occupant loads are seldom as high as design loads. In detailed designing, the internal and external loads are individually analyzed, since the relative magnitude of these two loads have a bearing on equipment selection and controls. For example check the figure below:
- 37. 37 Figure 3.1 Analysis of this breakup provides an idea of how much each component of the building envelope contributes to theoverall cooling load and what can be done to reduce this load. Reducing solar heat gain through windows is clearly oneof the key areas. The architect must also be aware of the heat load equations and the calculation methodology as these influence the architectural design decisions that will in turn influence the energy consumption and comfort potential of the facility.The majority of these decisions are made--either explicitly or by default--during the architectural design process.Information on each of the components of cooling load equations -- and the design decisions that lie behind these equations -- is covered in the subsequent sections. Ton Of Refrigeration - The amount of heat required to melt a ton (2000 lbs.) of ice at 32°F =288,000 BTU/24 hr. =12,000 BTU/hr. 1 Horsepower = 33,000 ft.-lb. of work in 1 minute 1 Horsepower = 746 Watts Converting Kw to Btu: 1 KW = 3413 BTU’s Example: A 20 KW heater (20 KW X 3413 BTU/KW = 68,260 BTU’s
- 38. 38 Converting Btu To Kw: 3413 BTU’s = 1 KW Example: A 100,000 BTU/hr. oil or gas furnace (100,000 ¸ 3413 = 29.3 KW) Watts (POWER) = volts x amps or P = E x I P(in KW) = E x I 1,000 Dry Air = 78.0% Nitrogen = 21.0% Oxygen = 1.0% Other Gases Wet Air = Same as dry air + water vapor Specific Density = 1/Specific Volume CFM = Area (sq. ft.) * Velocity (ft. min.) How to Calculate Duct Area; Rectangular Duct = A = L x W Round Duct = A = D2 /4 OR r2 Return Air Grilles – Net free area = about 75% • Critical points: The critical inputs and their associated risks discussed in this project are: • Design Conditions Location Latitude Elevation Outdoor temperature and relative humidity • Internal conditions Indoor temperature and relative humidity Insulation levels of walls, ceilings, and floors Window specification
- 39. 39 Thermal conductivity Solar Heat Gain Coefficient (SHGC) Infiltration and ventilation levels Interior and exterior shading • Internal loads Number of occupants Electronics, lighting and appliances. Formulas: The following formula’s and psychometric properties used in this project Effective Room Sensible Heat (ERSH) is the sum of all sensible heat gain that occurs in the room including the gain due to the portion of the ventilation air which is bypassed Effective Room Latent Heat (ERLH) is the sum of all latent heat gain that occurs in the including the gain due to the portion of the ventilation air which is bypassed. ESHF: ESHF (Effective Sensible Heat Factor (ESHF) is the ratio of ERSH to ERTH ESHF= ERTH (Effective Room Total Heat) = ERSH+ERLH No of fresh air change per hour = Floor Area (cu.ft) ×1×1/60 ADP: Apparatus Dew Point is defined as the effective surface temperature of the cooling coil. It is also the temperature at a fixed flow rate at which both sensible and latent heat gains are removed (from the conditioned space) at the required rates. It is also often called as the ‘Coil Temperature’ BF: Bypass Factor is part of the total air through the coil which fails to come into contact with the surface of the cooling coil. Dehumidification: The process in which the moisture or water vapour or the humidity is removed from the air keeping its dry bulb (DB) temperature constant is called as the dehumidification process. Dew Point (DP, DPT) is the temperature at which water vapour in moist air starts condensing when it is cooled Dry Bulb Temperature (DB, db, DBT, dbt) is the temperature registered by an ordinary thermometer. Db represents the measure of sensible heat, or the intensity of heat
- 40. 40 Wet Bulb Temperature (WB, wb, WBT, wbt) is the temperature registered by a thermometer whose bulb is covered by a wetted wick and exposed to a current of a rapidly moving air having a velocity of around 5 m/s. WB is measured by a sling psychomotor which has a set of dry and wet bulb thermometers. The psychomotor is whirled at such revolutions per second that the velocity of the bulb will be 5 m/s approx (in still air). Relative Humidity (RH, rh); (expressed in percentage) is the ratio of actual partial pressure of water vapour to its saturation pressure corresponding to the same db. Alternate definitions are – ratio of amount of moisture present in the air to the amount the same air holds at saturation at the same temperature, It indicates the ability of air to absorb additional moisture. Selection of Location; The layout of building floor is as given in Appendix A. CHAPTER – 4 DATA ANALYSIS & HEAT LOAD CALCULATION In this analysis we have taken first floor of a building located in A. M. U. Aligarh (U. P.). The area of building is 18327 square feet. First we got the plan of building. With the help of plan we have calculated all dimensions like length width of each wall, partition wall, window, floor area. Then according to the climate of AMU U.P, We select recommended outdoor condition with the help of Weather Data Handbook published by ISHRAE carrier hand book. We get all the specification such as height of walls, glasses and ceiling height from architecture drawing and calculated the area of all walls, partition walls and windows, of conference room which we can get fresh air, Dehumidified air and TR. On the basis of cooling load we have selected air conditioning system. Basis of Design Ambient Summer Conditions : DBT 110°F (43.3°C)
- 41. 41 : WBT 75°F (23.9°C) RH 60% Ambient Monsoon Conditions : DBT 95°F (35.0°C) WBT 83°F (28.3°C) RH 88% Indoor Temperature & : 73 ± 2°F in Office and 74 ± 2°F in Lift Lobby & Entrance Hall etc. RH : RH may exceed 65% in peak monsoon. Monsoon Reheat is not considered hence humidity may increase up to 65-70% during peak monsoon. Occupancy : 80 Sq. ft per person in office at chargeable area, chargeable area is 22 % more than air conditioned area, 125 Sq. ft per person in entrance lobby, Equipment Load : 3.5 W/sq. ft in Office area Lighting Load : 1.25 W/ft² in Office, 1.25 W/ft² in Lobby Fresh Air : As per ASHRAE standard 62.1-2007 (5 CFM per person+0.06 cfm/sqft) + 30 % higher
- 42. 42 to meet LEED requirement for Office area, lobbies. The loads modeled by the heating and cooling load calculation process will dictate the equipment selection to deliver conditioned air to the rooms of the house. In this project we have taken the building and calculate the heat load calculation. First we got the plan of building. With the help of plan we have calculated all dimension like length width of each wall, partition wall, window, floor area. Then according to the climate of Delhi-NCR we select recommended outdoor condition with the help of Weather Data Handbook published by ISHRAE carrier hand book. We get all the specification such as height of walls, glasses and ceiling height from architecture drawing. • Calculate the area of all walls, partition walls, windows, area of various office room, corridors, library, canteen and lobby by which we can get fresh air, Dehumidified air and TR. • Drawing preparation marking showing space marking for AHU unit in each air conditioning space. • Working of air distribution system through duct to grills and diffuser to the room and measurement of their sizes. CALCULATION: The calculation of the building for 1st floor given below ; FOR CONFERENCE ROOM Solar Gain Glass Height of Glass =8.47ft Area of N-Glass =8.5*8.47 =72 sq.ft
- 43. 43 TABLE- 3.1 Solar gain glass Item Area (sq.ft) Sun Gain (btu/h.sq.f t) Factor N-Glass 0 14 0.56 HEAT GAIN = 0*14*0.56 = 0 btu/hour Solar& Trans gain walls and roof Height of wall =12ft Remaining brick wall except Glass = 12-8.47 = 3.53 Area of N-Wall = 8.5*3.53 = 30 sq.ft TABLE – 3.2 Item Area (sq.ft) Eq.temp diff (oF) U(Btu/h.s q.ft) N-WALL 55 46 0.38 HEAT GAIN = 55*46*0.38 = 961 BTU/HR Room Sensible Heat = Taking 7.5% Heat gain from other source i.e supply duct heat gain + supply duct leak loss + Heat gain from fan hp Safety Factor 5% Basic Formula; CFM = (Area * Height * Air Change)/ 60
- 44. 44 BTU/HR = Net. Area * Factor u * Temp. difference Bypass Factor = Supply CFM – Dehumidified CFM Temperature rise = (1 – bypass factor)*(DB – ADP) Dehumidified CFM = ERSH/ (1.08 * Temp. Rise) Outlet td. = RSH/ (1.08* Dehumidified CFM) Supply Air CFM = RSH/ (1.08* Desire td.) Fresh Air Change = Fresh Air CFM * 60/ Volume (Sq. ft) Fresh Air for office = (People * 5 + Area sq ft * 0.06) + 30% Extra from ISHARE Light load = Area sq ft * Watt Equipment load HP = Area sq ft * Watt/ 1000*1.34 Tons = Grand total heat (Btu/hr)/12000 Fan (HP) = (CFM * Static Pressure (wg))/6356 * Efficiency
- 45. 45 TABLE 3.3 Design Parameter: Design parameters Description Lighting load (watt/ft2 ) Equipment load (watt/Ft2 ) Occupancy (sqft/person) Fresh air Cfm/person Cfm/sq.ft Shops 1.2 2 40 7.5 0.12 Office 0.8 3 60 5 0.06 Atrium 1.2 0.5 40 5 0.06 Food court 1.2 5 20 7.5 0.18 Hyper store 1.2 5 100 7.5 0.12 Spa 0.8 2 100 5 0.06 Squash court 0.8 1 100 20 0.06 Banquet hall 1.2 4 20 7.5 0.12 Common area(office) 0.8 0.5 100 5 0.06 Common area(Retail) 1.2 0.5 40 7.5 0.12 U-value (BTU/hr/sqft/f) Shade coefficient Glass 0.290 0.29 Wall 0.080 Roof 0.060 Temperatures Summer DBT 110 Summer WBT 95 Supply temp(◦F) 54 Occupied space temp(◦F) Retail 73 Note:-Temp in farenheit Occupied space temp(◦F) Retail(Corr) 75 Occupied space temp(◦F) Office 75 Occupied space temp(◦F) Office(Corr) 77
- 46. 46 TABLE 3.4 The Heat Load of Conference Room is given in Appendix B. TABLE 3.5 Summery sheet: S.No. Description Area (Sq.ft) Dehumidified CFM(Summer) Tonnage Summer Proposed Tonaage System Proposed (VRV) System Proposed(SPLIT) GROUND FLOOR 1 RECEPTION 850 3821 8.56 6.53TR+4.55TR DUCTABLE - 2 ADMIN OFFICE 1095 1891 4.63 6.53TR DUCTABLE - 3 DEAN ROOM 480 1492 3.58 1TR*2+1.5TR*1 - HI-WALL 4 CHAIRMAN ROOM 480 1491 3.58 1TR*2+1.5TR*1 - HI-WALL 5 FACULTY ROOM 08 240 593 1.35 1.5TR - HI-WALL 6 FACULTY ROOM 07 240 593 1.35 1.5TR - HI-WALL 7 FACULTY ROOM 06 240 753 1.65 2.0TR - HI-WALL 8 FACULTY ROOM 05 180 654 1.46 1.5TR - HI-WALL 9 FACULTY ROOM 04 180 543 1.25 1.5TR - HI-WALL 10 FACULTY ROOM 03 180 543 1.25 1.5TR - HI-WALL 11 FACULTY ROOM 02 180 639 1.43 1.5TR - HI-WALL 12 FACULTY ROOM 01 180 726 1.52 2.0TR - HI-WALL 13 COMMON DISCUSSION AREA 410 1094 3.42 3.98TR DUCTABLE - 14 LIBRARY READING ROOM 1977 3757 9.67 6.53TR+4.55TR DUCTABLE - 15 LIBRARY BOOKS 1292 3738 9.05 6.53TR+4.55TR DUCTABLE - 16 LECTURE HALL 01 1300 3055 10.65 6.53TR+3.98TR DUCTABLE - 17 LECTURE HALL 02 1280 3091 10.72 3.98TR+4.55TR DUCTABLE - 18 LT AND UPS ROOM 180 1165 2.34 1.5TR*4 - HI-WALL Total 10964 29639 77.46 89 63 26
- 47. 47 FIRST FLOOR 1 CONFERENCE ROOM 1087 1945 4.78 6.53TR DUCTABLE - 3 FC 22 172 557 1.28 1.5TR - HI-WALL 4 FC 21 210 709 1.56 2.0TR - HI-WALL 5 FC 20 206 706 1.56 2.0TR - HI-WALL 6 FC19 172 625 1.41 1.5TR - HI-WALL 7 FC 18 172 557 1.28 1.5TR - HI-WALL 8 FC17 174 558 1.28 1.5TR - HI-WALL 9 FC16 174 623 1.4 1.5TR - HI-WALL 10 FC 15 174 634 1.42 1.5TR - HI-WALL 11 STORE 174 663 1.48 1.5TR - HI-WALL 12 FC 14 174 550 1.27 1.5TR - HI-WALL 13 FC 13 172 624 1.4 1.5TR - HI-WALL 14 FC 12 172 624 1.4 1.5TR - HI-WALL 15 FC11 174 419 1.02 1.0TR - HI-WALL 16 FC 10 174 419 1.02 1.0TR - HI-WALL 17 FC 09 172 499 1.17 1.5TR - HI-WALL 18 COMPUTER LAB 635 1748 4.18 2.55TR*2 DUCTABLE - 19 RESEARCH SCHOLAR SECTION 1295 3485 8.13 3.98TR+6.53TR DUCTABLE - 20 CL 01 420 1304 3.82 3.98TR DUCTABLE - 21 CL02 420 1202 3.61 3.98TR DUCTABLE - 22 CL 03 420 1202 3.61 3.98TR DUCTABLE - 23 GIRLS COMMON ROOM 420 1354 3.92 3.98TR DUCTABLE - Total 7363 21007 52 61 38 22.5 SUB TOTAL 18327 50646 129.46 149.5 101 49
- 48. 48 TABLE 3.6 SELECTION OF (VRF) OUTDOOR UNIT Indoor TR Outdoor TR Diversity 85% 89 TR 108 HP 92 HP 61 TR 74HP 62 HP Outdoor HP = Indoor TR/ 0.825 Normal cooling Capacity = KW/ 3.51 Design Requirements It is often a practice to design an Air Conditioning system for peak load conditions. However, the average usage of an Air Conditioning system during a year is between 65% to 75%. Hence, the proposed system to be adopted for this project will be planned & selected for : Lowest capital cost. Flexibility to shut down in the areas that are not in use. Energy efficiency. Minimum Outdoor Units.
- 49. 49 System Design (OPTION-1) It is proposed to provide air cooled type multi split units of small capacity in the range of 1 to 4 TR for all area to ensure independent usage. These type of machines can have 2 to 6 indoor units with a single outdoor unit interconnected with copper refrigerant piping. Indoor units can be of Hi wall in faculty block and Ceiling concealed type unit in reception, academic block and library block or depending upon the choice of owner/Client. There will be few outdoor machines hence maintenance would be easier. Average life of this type of system is 10 to 12 years. Diversity on the installed capacity can not be taken in this type of system. (OPTION-2) VRV System It is proposed to provide VRV (Variable Refrigerant Volume) system some of the areas. The VRV system is similar to a split unit system with multiple indoor units and a common unit connected through a refrigerant pipes. The outdoor unit has compressors of variable capacity. The combination of these compressors taken the advantages of the diversity in use of indoor units thereby varying the load as required reducing the compressor running time and saving on power (Running cost)
- 50. 50 This is the most modern system available in the market today and it is used extensively in the western countries. This system is less noisy and consumes 20-25% less power than any other system of Air conditioning. The system maintains indoor air quality as per latest norms. Operating & initial cost of the VRV system is economical then central AC Plant. The indoor units shall be Hi-wall/Ceiling mounted type and the outdoor units shall be placed on terrace. The capacities of the units shall be as per the requirement. This system has operational flexibility in a way that the A.C can be switched on only in the areas, which are operational. Rest all areas can be shut down. In view of the above, VRV system is proposed in the areas which are likely not to all the time, such as meeting rooms or cabin etc. The indoor and outdoor unit shall be interconnected through copper Refrigerant piping. Estimated Cost Estimated Cost for all options is given in Annexure-I. Estimated Power Requirement
- 51. 51 Estimated power (Connected) requirement for the air conditioning system would be around 130 KW of 3 Ph, 50 Hz, 415 V A.C and around 75 KW of single phase. Recommendation: Based on our previous experience and after going through the usage of the building we feel that mixed usage of both option shall be a suitable system design. For the faculty area it is proposed to install Split units and for the Class and library it is suggested to go with the ductable type VRV units. (As shown in the table of item 6.0 System Requirement)
- 52. 52 TABLE 3.7 Operating Cost Compression: (Based on 2500 Hours per year) VRV System Air Cooled Split Units 1. Total Installed Load 120 TR 130 TR 2. Repair & Maintenance cost per Year 3,50,,000/- 2,45,000/- 3 Power consumption / Hour (KWH) 132Units (@ 1.1 KW per Ton) 169Units (@ 1.3 KW per Ton) 4 Total Power consumption (Units Per Year) 3,30,000 Unit 4,22,500 Unit 5 Cost @ Rs 8/- per Unit in one Year 26,40,000/- 33,80,000/- Total running cost including Maintenance in 1 Years 29,90,000/- 36,25,000/- 9. Difference in running cost/Year -- Approx.6,35,000/- 10 Installation cost Approx. 79.2 Lacs Approx. 52.8 Lacs 11 Difference in Installation cost -- Approx. 26.4Lacs Pay Back Period (Using VRV System) Around 4.2Years LIFE CYCLE 12 YEARS 10 YEARS
- 53. 53 CHAPTER- 5 LIFE CYCLE ANALYSIS 1. WORTH OF MONEY AS A FUNCTION OF TIME: It is seen from the preceding discussion that the value of money is a function of time. In order to compare or combine amounts of different times, it is necessary to bring these all to a common point in time. Once various financial transactions are obtained at a chosen time, it is possible to compare different financial alternatives and opportunities in order to make decisions on the best course of action. Different costs, over the expected duration of a project, and the anticipated returns can then be considered to determine the rate of return on the investment and the economic viability of the enterprise. Two approaches that are commonly used for bringing all financial transactions to a common time frame are the present and future worth of an investment, expenditure, or payment. 5.1 PRESENT WORTH As the name suggests, the present worth (PW) of a lumped amount given at a particular time in the future is its value today. Thus, it is the amount that, if invested at the prevailing interest rate, would yield the given sum at the future data. Which gives the resulting sum F after n years at a nominal interest rate i. Then p is the present worth of sum F for the given duration and interest rate. Therefore, the present worth of a given sum F may be written, for yearly compounding, as PW = P = F (I + i)-n = (F) (P/F, I, n) Where P/F is known as the present worth factor and is given by P/F = (I + i)-n
- 54. 54 If the interest is compounded m times yearly, Equation may be used to obtain the present worth as PW = P = (F) (P/F, i/m, mn) Where the present worth factor P/F is given by P/F = 1/(1 + i/m) = (1+ i/m)-mn Similarly, for continuous compounding P/F = e-ni Therefore, the present worth factor P/F may be defined and calculated for different frequencies of compounding. The present worth of a given lumped amount F representing a financial transaction, such as a payment, income, or cost. at a specified time in the future may then be obtained from the preceding equations. 5.2 FUTURE WORTH The future worth of a lumped amount p, given at the present time, may similarly be determined after a specified period of time. Therefore, the future worth (FW) of p after n years with an interest rate of i, compounded yearly or m time yearly, are given respectively, by the following equation: FW = F = P (I +i)n = (P)(F/P, i, n) FW = F = P(1 + i/m)mn = (P)(F/P, i/m, mn) Where F/P is known as the future factor worth or compound amount factor, For continuous compounding, F/P = eni . Therefore the future worth of a given lumped sum today may be calculated at a specified time in the future if the compounding conditions and the interest rate are given. It is better to use present worth since the interest rates are better known close to the present. In addition, the duration of a given enterprise may not be specified or a definite time in the future may not clearly indicated, making it necessary to use the present worth as the basis for financial analysis and evaluation.
- 55. 55 5.3 Life- Cycle Savings It is obvious that the comparison between any two alternatives is a function of the prevailing interest rate and the time period considered. Depending on the values of these two quantities, one or the other option may be preferred. The life - cycle savings considers the difference between the present worth of the costs for the two alternatives and determines the condition under which a particular alternative is advantageous. Life - time savings, or LCS, is given by the expression LCS = (Initial cost of A – Initial cost of B) +[Annual costs for A – Annual costs for B](P/S, i, n) +[Refurbishing costs of A - Refurbishing costs of B](P/F, i, n1) -[Annual savings for A - Annual savings for B](P/S, i, n) -[Salvage value of A - Salvage value of B](P/F, i, n) Where n is the time period, i is the interest rate, and n1 is the time when refurbishing is done, 5.4 RATE OF RETURN In the preceding section, we discussed cost comparisons for different courses of action in order to choose the least expensive one. These ideas can easily be extended to evaluate potential investments and to determine the most profitable investment. Thus, net present worth, payback period, and rate of return are commonly used methods for evaluating investments. The net present worth approach calculates the benefits and the costs at time zero using the prevailing interest rate i or a minimum acceptable return on capital. Therefore, the following expression may be used for the net present worth (NPW). NPW = Present worth of benefits – Present worth of costs = [Annual income – Annual costs](P/S, i, n) + [Salvage values](P/F, i, n) – Initial cost
- 56. 56 Preference is given to the project with the largest positive net present worth. The payback period is the time needed to fully recover the initial investment in the enterprise. The prevailing interest rate may be used to obtain a realistic time period for recovery, as outlined in the preceding section. Therefore, in the above expression for the NPW. The value of n at which the NPW becomes zero is the payback time. If the NPW is set equal to zero, the resulting nonlinear equation may be solved by iteration to determine n. The investment with a shorter payback period is preferred. Life Cycle Analysis using Annual Cost Analysis method: C= M+E+I / (P/S, i %, n) – S/ (F/S, i %, n). F/S = (1+i)n -1, P/S= (1+i)n -1/ i(1+i)n , OPTI ON INSTALLAT ION (LAC) MAINTANA NCE (LAC) ELECTRIC CONSUMPT ION (LAC) INTRE ST RATE (LAC) YEA R ANNUA L EXPENS ES (LAC) SPLIT 52.8 2.45 33.8 0.085 10 42.61193 VRF 79.2 3.5 26.4 0.085 12 0.638348 Calculation of LCS: Life Cycle Saving (LCS) For Both System: LCS = (Initial cost of A – Initial cost of B) +[Annual costs for A – Annual costs for B](P/S, i, n) +[Refurbishing costs of A - Refurbishing costs of B](P/F, i, n1)
- 57. 57 -[Annual savings for A - Annual savings for B](P/S, i, n) -[Salvage value of A - Salvage value of B](P/F, i, n) Neglecting Refurbishing Cost, P/F = (I + i)-n = (1+0.085)-10 = 0.4422 P/S = P/S= (1+i)n -1/ i(1+i)n = (1+0.085)10 -1/(0.085)(1+0.085)10 = 6.561348 LCS = (79.2-52.8) + (29.9 – 36.25) * (6.561348) – (1.18) * (6.561348) – (0.638348 - 42.61193) * (0.4422) = 4.45 LAC Conclusions: Based on comparative analysis of alternative with operating cost and life cycle cost, a VRF (variable refrigerant flow) system is selected for a particular project of 149.5 TR. The total HP outdoor unit in VRF system is installed load for the diversity of VRF units is 80 - 90%. It is found that units electricity is consumed 3,30,000 units/year for VRF System and 4,22,500 units/year for split system. The life cycle analysis has been also done for useful life of 10 years for split units and 12 years for VRF units. Life cycle saving has been also done on Split and Multi- Split Variable Refrigerant Flow (VRF) System for a period of ten years with interest rate 0.085. It is found that Life Cycle Saving is about 4.45 Lac in Multi-Split VRF System compare to Split System. However if we will analyze that same of a period of 22 years which is useful life of VRF System then saving will be more in VRF System.
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