Computational fluid dynamic analysis of solar chimney design

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 07 | July 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 755
Computational fluid dynamic analysis of solar chimney design
Bhushan Verma1, Chandrakant Mengoliya 2, Purushottam Sahu3
1Research Scholar, BM College of Technology, Indore RGPV, Bhopal
2 Chandrakant Mengoliya BM College of Technology, Indore RGPV, Bhopal
3 Professor and HEAD, Dept. of Mechanical Engineering, BM College of Technology, Indore RGPV, Bhopal
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Abstract - For both configurations with and without the
geothermal mechanisms, the CFD analysis of such a solar
chimney is performed using ANSYS CFX. Investigations are
conducted into the typical room temperature, air flow rate,
and radiation level. Moving away from the left glass, where
solar radiation is incident, reduces the average radiation
intensity in the room. Radiation levels are lowest at the
room's centre. Geothermal design 3 has the lowest observed
average room temperature, which is roughly 299K. With a
magnitude of roughly 309.69K, the generic design (without
a geothermal mechanism) produces the greatest average
room temperature. The rate of mass flow decreases with the
inclusion of a geothermal process.
Key Words: CFD, Comfort thermal, naturally ventilated,
solar chimney
1. INTRODUCTION
1.1 VENTILATION
In any closed environmental system, ventilation involves
the input and outflow of air. There may or may not be an
air purification component. To control interior humidity,
remove impurities, and maintain a reasonable
temperature, a structure must have proper ventilation.
Inhaled air quality has a big impact on how comfortable
people are and how productive they are.
Humans need at least 1.2 litres of air to breathe per
second, however more is preferable for comfort. This
allows for appropriate O2 circulation and CO2 dilution.
Proper ventilation helps sustain temperature in cases of
extreme heat gains. The following factors affect a
building's thermal comfort and interior air quality.
1.2 Natural ventilation (1.1.1)
Natural ventilation involves the circulation of air via
apertures like windows and doors. To allow air to flow, an
intentional aperture has been made. The pressure
differential between inner and exterior air is what causes
air to move. The natural ventilation may be influenced by
wind or by temperature.
Building quality and thermal comfort are determined by
the following elements.
1. Positive pressure and negative pressure are produced in
a ventilation system powered by the wind. Building
pressure is positive on the windward side and negative on
the leeward side. Air flow is caused by the pressure
difference between these two areas.
2. In ventilation systems driven by temperature, a high
temperature creates a stacking effect. The building's
interior air temperature rises as cooler exterior air enters
at a faster rate. As a result, cool air is brought in from the
outside, causing airflow.
1.3 Mechanical ventilation (1.1.2)
Mechanical fans are used throughout the mechanical
ventilation process. These mechanical fans are installed on
ducts, walls, ceilings, or both. These mechanical fans' main
function is to make it easier for air to enter and leave the
area. When the weather is warm and muggy, infiltration is
used. A constructive pressure system places the room
under positive pressure, and the room air escapes through
envelope leaks or other openings. A negative pressure
system places the room under negative pressure, and the
room air is made up by sucking air in from the outside. [6].
The mechanical ventilation system should be balanced
"where air supply and exhausts have been evaluated and
changed to satisfy design standards." [6].
2. PROBLEM FORMULATION
The present work is concerned with carrying out two-
dimensional simulations on an solar roof chimney,
through which air flows. The inlet and outlet is defined of
length
Figure 5.2 Schematic of inclined solar chimney [9]

3. MESHING
The model is meshed using fine sizing and brick elements.
The growth rate is set to 1.2, inflation is set to normal and
number of layers set to 5. The meshed model of
computational domain is shown in figure 5.4 below.
Figure 5.4 Meshing of inclined chimney
Without a geothermal mechanism, an inclined solar
chimney
The findings from a CFD analysis of an inclined solar
chimney without a geothermal mechanism are discussed
in this section.
Figure 6.1 Temperature plot of an inclined solar chimney
without a perforated plate.
The temperature map created by CFD analysis is shown in
Figure 6.1. The plot shows that the temperature is higher
close to the absorber plate and the glass. Heat is dispersed
throughout the domain by radiation. The investigation
made use of multiband spectral modelling with Monte
Carlo radiation modelling. The room has a higher
temperature in the corners than it does in the centre.
Convective heat transfer caused by airflow in the dark
blue zones is to blame for this.
Figure 6.2 Velocity vector for inclined solar chimney
without perforated plate
The velocity vector plot is shown in Figure 6.2. Two places
where vortex development is shown in the plot. The
bottom left corner is the first zone, and the top right
corner is the second zone. The area where air flow is
straight from entrance to exit is where convective heat
transfer is greatest. This kind of air flow raises
temperatures in vortex zones, as seen in Figure 6.1.
Figure 6.3 Radiation intensity of inclined solar chimney
Figure 6.3 depicts the radiation intensity plot. Due to the
direction of incident radiation, the map reveals a higher
intensity of magnitude 436.4 W/m2 in the regions near
the incidence glass surface and in the bottom right corner.

Figure 6.4 Eddy viscosity for inclined solar chimney
without perforated plate
Figure 6.5 without a perforated plate, turbulence eddy
dissipation for an inclined solar chimney
The temperature is lower in sections where the air flow
vectors are straight (without swirl) than in parts where
the air flow vectors are swirled or turbulence is induced.
The same can be seen in the eddy viscosity plot, which
exhibits high values in places with high air turbulence.
Figure 6.6 Turbulence kinetic energy for inclined solar
chimney without perforated plate
Turbulence's kinetic energy is greatest near the exit and
near the absorber plate and glass surface where sunlight is
incident. Figure 6.7 depicts the pressure plot. Suction
(negative pressure) is depicted on the pressure plot in the
region between the glass (on which the sunrays are
incident) and the absorber plate.
Table 6.2: Temperature and heat transfer table
Geometry
Details
Inlet
Temp
(K)
Outlet
Temp
(K)
Temperatur
e Difference
(K)
Average
temperat
ure (K)
Without
geothermal
300 310.33 10.33 309.69
With
geothermal
design 1
295 310.67 15.67 300.41
With
geothermal
design 2
295 311.16 16.16 299.42
Table 6.4: Heat extracted
Geometry
Details
Average Mass
Flow
(Kg/s) * 10-5
Temperature
Difference
(K)
Heat
extracted
(Joules)
Without
geothermal
8.23488 10.33 .854
With
geothermal
design 1
5.78872 15.67 .911
With
geothermal
design 2
5.78872 16.16 .939
The heat extraction comparison among 3 different design
configurations is shown in figure 6.26 below. The
comparison graph shown highest heat extraction rate for
geothermal design 2 followed by geothermal design 2 and
minimum heat extraction is observed for generic design.

Figure 6.26: Heat extraction comparison
4. CONCLUSION
1. With and without the use of a geothermal
mechanism, the solar chimney's CFD analysis is
carried out using ANSYS CFX. It looks at radiation
intensity, average room temperature, and airflow
rate.
2. Moving away from the left glass, where solar
radiation is incident, reduces the average
radiation intensity in the room. Radiation levels
are lowest at the room's centre.
3. With a magnitude of roughly 299K, geothermal
design 3 has the lowest average room
temperature.
4. A magnitude of roughly 309.69K is recorded for
the generic design (without a geothermal system)
as the greatest average room temperature.
5. With the addition of a geothermal mechanism, the
mass flow rate decreases. Despite the fact that the
cooling obtained is more than with a generic
design.
6. Geothermal design 2 extracts the most heat, while
generic design extracts the least.
7. Geothermal design 3 achieves the highest in-room
cooling, whereas generic design achieves the
least.
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0.8 0.85 0.9 0.95
Without geothermal
With geothermal design 1
With geothermal design 2
Heat extracted
Heat extracted

Computational fluid dynamic analysis of solar chimney design

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