1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 5, May (2014), pp. 102-106 © IAEME
102
EXPERIMENTAL STUDY OF A SOLAR AIR HEATER
Durgesh Kunvar Yadav, Dr. Ajeet Kumar Rai, Vivek Sachan
MED, SSET, SHIATS-DU Allahabad-211007 (U.P.) India
ABSTRACT
In the present work, a solar air heater is designed, fabricated and its performance is evaluated
in the forced convection mode in the Allahabad climatic condition. Solar air heater is a simple
device, which captures the solar energy. Production of hot air by using solar air heater is a renewable
energy heating technology used to process heat generation or space heating. Aluminium Absorber
plate of size 1.12 m2
is painted black to absorb maximum insolation. The performance of the system
is evaluated for the different mass flow rates of 0.023, 0.031, 0.038 and 0.046 kg/s. A maximum
instantaneous efficiency of 85% is obtained with the minimum mass flow rate of 0.023 kg/s.
INTRODUCTION
The solar air heater device intercepts solar radiation, converts this radiation to the heat in air
and delivers the hot air for use. The main components of a solar air heater is an absorber plate, one or
more channels for the flowing air, insulation for the bottom and lateral sides of the solar collector
and one or more transparent covers. The use of a blower is optional for the air supply.
Solar air heaters are devices that utilize solar radiation for a variety of purposes. This heated
air can be used in several applications such as drying agricultural products, space heating and air
conditioning, water heating, industrial process heating and spraying operations.
The primary disadvantage of these systems is the low heat transfer coefficient compared to
systems that use liquid as the working fluid. This is the result of low heat transfer coefficient
between the absorber plate and the air. Low heat transfer coefficients lead to low thermal efficiency
of solar air heaters. For many years researchers have studied the enhancement of heat transfer
coefficients of solar air heaters. To increase the efficiency of such a system, various configurations
and designs have been proposed [1,2]. Satcunanathan and Deonarine [3] have suggested that the heat
loss can be reduced by using two pass solar air heater. Whillier [4] carried out experiments on the
conventional air heater consists of an absorbing plate, a rear plate, insulation below the rear plate,
transparent cover on exposed side, and the air flows between the absorbing plate and rear plate.
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2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
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Ranjan et al. [5] refers to an air heater with flow above the absorber which consists of an absorber
plate with a transparent cover at the top and insulation at the bottom. The cover and the plate provide
the passage for the air. Solar radiation, after transmission through the cover, is absorbed by the
absorber plate. Sodha and Bansalt [6] have studied an air heater with flow on both sides of the
absorber assuming that equal flow occurs both above and below the absorber plate and the heat
transfer coefficient between the absorber plate and the air stream is same on either side. Yousef and
Adam [7] have investigated the effect of mass flow rate, flow channel depth and collector length on
the system thermal performance and pressure drop through the collector with and without porous
medium.
The present work is undertaken with the objective to investigate the performance of a solar
air heater with different mass flow rate of air.
EXPERIMENTAL SETUP
A Solar Air Heater was constructed to determine the efficiency of solar air heater in forced
convection mode. A flat-plate collector (single pass) consists of a absorber plate of size 1.21m
X0.92 m, made up of galvanized Iron and cover plate of transparent plastic sheet. Silica is used to
hold the sheet in place. Air is used as a heat exchanger medium. Absorber plate is painted black to
absorb maximum insolation. Insulation is placed below the absorber plate to reduce the heat loss
from the system. Fig. 1 shows the photograph of the solar air heater.
The experimental setup was located at Solar Energy Laboratory in the Mechanical
Engineering department of SHIATS, Allahabad. The experiments were conducted in the month of
May 2014. The experiments were carried between the hours of 08:30 and 17:00 every day. The
system is insulated from its base and two sides to prevent heat losses through the surroundings. Air is
supplied to the system with the help of a fan. The flow rate of the fan is controlled and manipulated
by a fan regulator. Solar intensity is measured by solarimeter (SURYAMAPI). Wind velocity is
measured by anemometer. The temperature at the different points of the system is measured by J-
type thermocouples.
Fig 1: Experimental Setup of a Solar Air Heater

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 5, May (2014), pp.
Thermal Efficiency
The thermal efficiency of the solar air heater (
Where m =mass flow of air in kg/s
Cp= specific heat of air in kJ/kgK
Tout-Tin= Temperature difference between outlet air temperature and inlet air temperature
A = area of the heater which captures maximum insolation in m
Ib = intensity of solar radiation in W/m
RESULTS AND DISCUSSION
System was fabricated and experimentation were done for the different mass flow rate of air.
Solar intensity was measured by solarimeter for four consecutive days in a month and variations a
shown in fig 2 for different mass flow rate of air. Since solar intensity was almost same for all days,
inlet temperatures are also equal which is shown in fig
Fig 2: variation of solar intensity with time of the day at different mass flow ra
Fig 3: shows that the variation of inlet temperature with time of the day at different mass flow rate
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
6499(Online) Volume 5, Issue 5, May (2014), pp. 102-106 © IAEME
104
The thermal efficiency of the solar air heater (η) is given by the following expression
= specific heat of air in kJ/kgK
= Temperature difference between outlet air temperature and inlet air temperature
A = area of the heater which captures maximum insolation in m2
.
= intensity of solar radiation in W/m2
.
System was fabricated and experimentation were done for the different mass flow rate of air.
Solar intensity was measured by solarimeter for four consecutive days in a month and variations a
for different mass flow rate of air. Since solar intensity was almost same for all days,
inlet temperatures are also equal which is shown in fig 3.
variation of solar intensity with time of the day at different mass flow ra
shows that the variation of inlet temperature with time of the day at different mass flow rate
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
© IAEME
) is given by the following expression:
= Temperature difference between outlet air temperature and inlet air temperature
System was fabricated and experimentation were done for the different mass flow rate of air.
Solar intensity was measured by solarimeter for four consecutive days in a month and variations are
for different mass flow rate of air. Since solar intensity was almost same for all days,
variation of solar intensity with time of the day at different mass flow rate
shows that the variation of inlet temperature with time of the day at different mass flow rate

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 5, May (2014), pp.
Fig 4: Variation of outlet temperature with time of the day at different mass flow rate
Fig. 4 shows variation of outlet temperature with time
It is observed that outlet temperature is higher with lower mass flow rate of 0.023 kg/s. A maximum
temperature gain of 28% is observed with a lower mass flow rate of 0.023 kg/s whereas 27% gain is
observed with highest mass flow rate of 0.046 kg/s. Fig.
difference between inlet and outlet is dominant for lower mass flow rate maximum time throughout
the day.
Fig 5: Variation of temperature difference between outlet temperature an
time of the day at different mass flow rate
CONCLUSION
The fabricated solar air heater is very simple and easy to fabricate with locally available low
cost materials. The air temperature obtained from the system was noteworthy. The
instantaneous temperature of the air coming out from the system was 67
rate of 0.023 kg/s. The average daily efficiency of 45% is observed at this mass flow rate. The
average daily efficiency of 55% is calculated at higher
temperature difference of 12 degree is obtained in both the cases.
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
6499(Online) Volume 5, Issue 5, May (2014), pp. 102-106 © IAEME
105
Variation of outlet temperature with time of the day at different mass flow rate
of outlet temperature with time of the day at different mass flow rate.
It is observed that outlet temperature is higher with lower mass flow rate of 0.023 kg/s. A maximum
temperature gain of 28% is observed with a lower mass flow rate of 0.023 kg/s whereas 27% gain is
hest mass flow rate of 0.046 kg/s. Fig.5 shows that variation of temperature
difference between inlet and outlet is dominant for lower mass flow rate maximum time throughout
Variation of temperature difference between outlet temperature and inlet temperature with
time of the day at different mass flow rate
The fabricated solar air heater is very simple and easy to fabricate with locally available low
cost materials. The air temperature obtained from the system was noteworthy. The
instantaneous temperature of the air coming out from the system was 670
C at a minimum mass flow
rate of 0.023 kg/s. The average daily efficiency of 45% is observed at this mass flow rate. The
average daily efficiency of 55% is calculated at higher mass flow rate of 0.046 kg/s. whereas average
temperature difference of 12 degree is obtained in both the cases.
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
© IAEME
Variation of outlet temperature with time of the day at different mass flow rate
of the day at different mass flow rate.
It is observed that outlet temperature is higher with lower mass flow rate of 0.023 kg/s. A maximum
temperature gain of 28% is observed with a lower mass flow rate of 0.023 kg/s whereas 27% gain is
shows that variation of temperature
difference between inlet and outlet is dominant for lower mass flow rate maximum time throughout
d inlet temperature with
The fabricated solar air heater is very simple and easy to fabricate with locally available low-
cost materials. The air temperature obtained from the system was noteworthy. The maximum
C at a minimum mass flow
rate of 0.023 kg/s. The average daily efficiency of 45% is observed at this mass flow rate. The
mass flow rate of 0.046 kg/s. whereas average

5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 5, May (2014), pp. 102-106 © IAEME
106
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