The Conception, Types, and Applications of Heat Pipe Solar Collector

1-Conception of heat pipe in general, types , and
applications.
2-Comparsion between flat plate, parabolic trough , and
heat pipe solar collector.
3-CFD analysis of heat pipe.
Topics of Symposium

The Objectives
1-To know the effect of heat pipe on the performance of
solar collectors.
2-To predict the thermal behavior of a solar heat pipe to
cover all details of design parameters of operation
condition with the CFD model.

George M. Grover
In 1963, Dr. Grover was working at the Los Alamos National Laboratory on the idea
of using a nuclear reactor to generate electricity in space when he developed the
first working heat pipe as a way to move heat out of the reactor very efficiently.

 A heat pipe heat exchanger is a simple device which is
made use of to transfer heat from one location to another,
using an evaporation-condensation cycle.
 Heat pipes are referred to as the "superconductors" of heat
due to their fast transfer capability with low heat loss[1].
What is a Heat Pipe?

• Container
• Working fluid
• Wick or Capillary structure

Working Principle
• The heat input region of the heat pipe is called evaporator(heat
source), the cooling region is called condenser (heat sink).
• In between the evaporator and condenser regions, there may be
an adiabatic region[1].

Thermodynamic cycle of a typical heat pipe[2]

1.Container
The function of the container is to isolate the working fluid from
the outside environment.
Selection of the container material depends on
many factors. These are as follows[3]:
• Compatibility (both with working fluid and external
environment)
• Strength to weight ratio
• Thermal conductivity
• Ease of fabrication, including welding, machinability and
ductility

2.Working Fluid
• The prime requirements are[3]:
1. Compatibility with wick and wall material
2. Good thermal stability
3. Vapor pressure not too high or low over the operating temperature
range
4. High latent heat
5. High thermal conductivity
6. Low liquid and vapor viscosities
7. High surface tension
8. Acceptable freezing

3.Wick Structure
1. It is a porous structure made of materials like steel, aluminium, nickel or copper
in various ranges of pore sizes.
2. The prime purpose of the wick is to generate capillary pressure to transport the
working fluid from the condenser to the evaporator.
3. It must also be able to distribute the liquid around the evaporator section to any
area where heat is likely to be received by the heat pipe.
4. The maximum capillary head generated by a wick increases with decrease in pore
size.

Heat pipe withstands more than one heat transfer limitation
such as Viscous, sonic, flooding, capillary and boiling
limitations. These limitations are depending on the working
fluid, wick structure, dimensions of the heat pipe and the heat
pipe operational temperature. The driving mechanism in the
heat pipe is the heat input, Q, which is related to the mass flow
rate of the working fluid and latent heat of vaporization(hfg
)[5].
Comparison between a Heat Pipe and a
Thermosyphon Performance with Variable
Evaporator Length
Anwar A. YousifDr. Hussain H. Ahmad

Thermosyphon Loop heat pipe Oscillating heat pipe
Variable conductance Rotating and Revolving

Electronics cooling Solar energy
Heat exchanger Dehumidifier
production tools, medicine and human-Other applications
body temperature control, engines and automotive industry[6].

A passive solar system heat-driven convection or heat pipes to circulate the
working fluid. Passive systems cost less and require low or no maintenance, but
are less efficient. Overheating and freezing are major concerns
An active solar system use one or more pumps to circulate water and/or heating
fluid. This permits a much wider range of system configurations[7].

Passive
CHS system with tank above
collector
Active
system with pump and controller
driven by a photovoltaic panel.

Evacuated Glass Tube [9,10,11]

Evaporator
Condenser
Structure & Operation of Heat pipe[13]

Flat Plate Evacuated Tube Collector[14]

A Laundromat in California with
panels on the roof providing
hot washing water[7]
A solar water heater installed
on a house in Belgium [7]

Advantages of flat plate solar heat pipe is [15]:-
 It can easily achieve a temperature 60-80 OC
above ambient temperature,
 It uses both beam and diffuse radiation,
 Does not require tracking,
 Requires little maintenance,
 Efficiency:- 45% at 80 OC
 Applications:- air heating, industrial process heating, and
passive air conditioning

Flat plate Evacuated Tube
Flat Plate Vs Evacuated Tube Collector[14]

Comparison of the characteristics of flat plate and
evacuated tube solar collectors [17]

Water
Parabolic Trough Collector
Glass Tube
Copper Tube
Storage Tank
Pump
Tin
Tout
Parabolic Collector [18]

Side ViewFront View
Evaporator
Condenser
Parabolic with Evacuated Tube [19]

Evacuated glass Tube
Evaporator Section
Tw
Tco
Qloss,tank
Ta
Condnser Section
Storage Tank
Solar Radiation
A
A
B
B
Qs
Water
Parabolic Trough Collector
Glass Tube
Copper Tube
Storage Tank
Pump
Tin
Tout
30%
Temperature Distribution with Time [19]

Temperatures in the two separate reservoirs (red picnic coolers) were logged
automatically throughout the day as was the ambient temperature in a shaded location
near the solar test jig[21].
George Plhak
October,09 ,2011
Ontario, Canada

Several points may be considered [22]:-
1- Reflecting surfaces are structurally simpler than flat
plate collectors.
2- The absorber area of a concentrator system is smaller
than that of flat plate system for the same solar energy
collection.
3- Heat lost to the surrounding per unit area of the solar
energy collecting is less than that of the flat plate.
4- Working fluid can attain higher temperature in the
concentrating collector.

Azad
( 2008)
Presented experimental work to study of the performance of a flat plate solar
collector utilizing heat pipes. The solar collector was installed and tested under
conditions in Tehran (longitude 52.3oE; latitude 35.7oN)
It was found that with the increase of the heated length-cooled length, Le/Lc, the
absorber area will increase and thus both the heat loss from the absorber and the
absorbed solar energy by absorber plate will increase. On the other hand the heat
transfer coefficient in condenser will increase and lead to increase the heat transfer
rate in the condenser. The experimental efficiency was 55.6%.
LITERATURE REVIEW
Flat Plate

Ruchi
( 2014)
presented experimental study of a flat-plate solar collector to investigate the
performance of thermosyphon solar water heating (SWH) system using R744(CO2) as
.the working fluid
The results indicated that, the heat recovery efficiency (ηRE) and the time-averaged
collector efficiency (ηcol) were calculated around 45% and 59%, respectively.
LITERATURE REVIEW
Flat Plate

LITERATURE REVIEW
Ramsey et al
( 1977)
They evaluated the performance of the parabolic trough solar collector by using
three different absorbers. The tests were conducted at a desert test site at a latitude
of 34° N near Phoenix, Arizona .
1-The peak efficiency for the collector in the absence of heat losses is approximately
62% when the incoming solar energy is normal to the collector aperture.
2-The losses which occurred at elevated temperatures (300oC) decreased the peak
efficiencies to 50% and 30%, respectively, for the selectively coated and black
painted tubes.
Parabolic Trough

LITERATURE REVIEW
Presented experimental study for a U-type natural circulation heat pipe system
was designed and applied to a parabolic trough solar collector for generating mid-
temperature steam.
Liang et al
( 2012)
1-The system can generate mid-temperature steam of a pressure up to 0.75 Mpa.
2-The thermal efficiency was found to be 38.52% at discharging pressure of 0.5
MPa during summer time.
Parabolic Trough

Selvakumar et al
( 2014)
Presented experimental study for the evacuated tube(heat pip) collector using
synthetic oil as heat transfer fluid coupled with parabolic trough collector for instant
hot water generation in the presence of low solar irradiance.
1-The system can produce instant hot water at temperatures between 40 oC & 68 oC
under low solar radiation.
2-Using of parabolic trough along with evacuated tube can increase the heating
efficiency by 30% in the instant hot water generation process.
LITERATURE REVIEW
Parabolic Trough

Jafari et al
( 2015)
Presented experimental work combination of a heat pipe and a twin-glass evacuated
tube collector is utilized with a parabolic through solar collector for desalination
system.
The results showed that the rate of production and efficiency of desalination
systems can reach to 0.27 kg/(m2.h) and 22.1% respectively when aluminum
conducting foils are used in the space between the twin-glass evacuated tube
collector and the heat pipe to transfer heat from the tube collector to the heat pip.
LITERATURE REVIEW
Parabolic Trough



 t
a
sstfstwst
s
dttIA
TTcM
0
)(
)(

 

 
 t
a
t
t
loadinloadoutwloadsstfstwst
s
dttIA
dtTTcmTTcM
0
,,
.
)(
)(
2
1

Without Load
With Load
Overall system performance with loading is always greater than the overall
system performance of solar system without load because the extra energy
(water flow rate) added to the storage energy inside the tank [19].

The sub-discipline of heat pipe science
has its foundation in several classical
fields
Fluid Mechanics
Thermodynamic
Heat Transfer
Mass Transfer
Type of Flow
2D or 3D
Unsteady Sate
Laminar
Two Phase

Momentum Equation
Continuity Equation
Energy Equation

Mesh Generation
Near the left and right walls,
five layers of cells are used to
capture the thin liquid film
near the wall[30]

Results
Contour plots of vapor volume fraction in the evaporation
section[30]

Results
The CFD predicted fluid flow, temperature and condensation
at top of the condenser [30]

1-Solar heat pipe can be used as a good alternative of
direct solar collector.
2-Flat plate solar heat pipe collector is efficient than flat
plate solar collector.
3-Parabolic trough solar heat pipe collector is better
than flat plate solar heat pipe in terms of obtaining large
thermal energy.
4- Ansys program gave a good results for thermal behavior
.of a solar heat pipe

1-select heat pipe according to Heat transport limitation
[5] .
2-Using Nanofluid as a working fluid inside solar heat pipe.
3-Use Ansys program original version may lead to solve the
problem of solar heat pipe.
4-Use computers network station to solve solar heat pipe by
Ansys Program.

•1-Vijayakumar,P., Sajairaj,S., and Santhoshkumar,R."Review on Conventional, Modern Heat Pipes and Its
Applications "International Research Journal of Engineering and Technology,Vol.3,pp.513-518,2016.
2-Ong,K."Heat pipes"Jurutera.pp.16-18,2008.
3-Bahman,Z." Heat Pipe Design and Technology": Modern Applications for Practical thermal Management"2011.
4-Shigeki,H., Shota,S.& Tsuyoshi,K. "Study On Heat Transfer Characteristics of Loop Heat Pipe for Solar Collector"
Transaction on Control and Mechanical Systems,Vol.2,No.4,pp.149-154,2013.
•5-Hussain,H&Anwar,A. "Comparison Between a Heat Pipe and a Thermosyphon1 Performance with Variable
Evaporator Length “Journal of Al Rafdain Engineering,Vol.21,No.2,pp.1-12,2011.
http://www.thermalfluidscentral.orgFluids Central"–Heat pipe "Thermal-6
7-Solar water heating"WIKIPEDIA"https://en.wikipedia.org/wiki/Solar_water_heating
8-Overview of Flat Plate Collectors
"685/node/811education.psu.edu/eme-https://www.e"
“Tube Solar CollectorsEvacuated-9
"solar.htm1904http://www.homebuildercanada.com/
•10-Evacuted Tbes
•http://www.platek.com/solar/tube_products.html

11-HAY RIVER SOLAR THERMAL DOMESTIC HOT WATER SYSTEM
"http://aea.nt.ca/blog/2015/02/hay-river-solar-thermal-domestic-hot-water-system"
12-Heat Pipe Manifold
"http://webcache.googleusercontent.com/search?q=cache:http://www.sltenergy.com/heat-pipe-manifold/"
13-Heat Pipes
"http://www.apricus.com/html/solar_collector_heat_pipe.htm#.WsdTIYhubIU"
14- "https://www.youtube.com/watch?v=rJP7y_7gN9Y&t=965s"
15-G.Sawhney"NON CONVENTIONAL RESOURCES OF ENERGY",2012.
16-Solar Collectorhttp://www.ecosmart.com.au/products/solar-collector
17-Solar Water Heaters https://solartown.com/learning/solar-water-heaters/solar-water-heater-choices-flat-plate-or-
evacuated-tube-collectors/
18-Mohamad,A.,Orfi,J., Alansary,H." Heat losses from parabolic trough solar collectors",Int.J.Energy Res,2013
19- Muhammad,A. "Heat Pipe Solar Collector With Automatic Tracking system “Doctoral Thesis,Mech.Eng.Dept.,College of
Engineering, University of Technology ,2016.
20-Parabolic Solar Trough" http://www.parabolicsolartrough.com/“
21- Comparing concentrator to flat plate solar collector" https://georgesworkshop.blogspot.com/2011/10/comparing-
concentrator-to-flat-plate.html"
22- Pradeep ,K. &Venkatesh,R. "Design, Fabrication and Experimental Testing of Solar Parabolic Trough Collectors With
Automated Tracking Mechanism", International Journal of Research in Aeronautical And Mechanical Engineering, Vol.1
issue.4, pgs 37-55,2013.
23- Renewable Space Heating" https://www.epa.gov/rhc/renewable-space-heating"

24- Azad,E. "Theoretical and Experimental Investigation of Heat Pipe Solar Collector "Journal of Experimental Thermal and
Fluid Science,Vol.32,pp.1666-1672,2008.
25- Ruchi,S.&Sumath,K. "Performance Evaluation of a Thermosyphon Solar Water Heater Using Supercritical CO2 as
Working Fluid "International Journal of Advances in Mechanical & Automobile Engineering,Vol.1,pp.43-48,2014.
26- Ramsey,J.W,Gupta,B.P.&Knowles,G.R. "Evaluation of a Cylindrical
Parabolic Solar Collector”Journal of Heat Transfer,Trans.,Vol.99,pp.163-168,May,ASME,1977,ASME.
27- Liang,Z.,Wujun,W., "An Experimental Investigation of a Natural Circulation Heat Pipe System Applied to a Parabolic
Trough Solar Collector Steam Generation System"Journal of Solar Energy,vol.86,pp.911-919,2012.
28- Selvakumar,P., Somasundaram, P., Thangavel,P. "Performance Study on Evacuated Tube Solar Collector Using Therminol
D-12 as Heat Transfer Fluid Coupled with Parabolic Trough", Journal of energy Conversion and Management,vol.85,pp.505-
510,2014.
29- Jafari,M.,Jahangiri,M & Shafii"A new Desalination System Using a Combination of Heat Pipe, Evacuated Tube and
Parabolic Trough Collector"Journal of energy Conversion and Management,vol.99,pp.141-150,2015.
30- Asghar,A.,Masoudi,R.&Ammar,A. "CFD Modeling of Flow and Heat Transfer in a Thermosyphon",International
Communication In Heat and Mass Transfer,Vol.37,pp.312-318,2010

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