Solar Air Heater

Advances in Solar Air Heater
Prepared by,
Hardik V. Ramani
13 MMET 16
M. Tech Mechanical Engineering
(Thermal Engineering)
Guided by,
Prof. S. V. Jain
Department of Mechanical Engineering
Nirma University
02-December-2013 A Seminar on Advances in Solar Air Heater 1

Power of Sun [1]

SOLAR AIR HEATER [12]
Location: At some where in Canada

Content..
• Principle
• Application
• Types
• Low Cost Solar Air Heater
• Effective Solar Air Heater by Roughness
• Summery
• References

Principle [7]

Description
• A conventional solar air heater is essentially a
flat plate collector with an absorber plate.
• It is a transparent cover system at the top and
insulation at the bottom and on the sides.
• The whole assembly is enclosed in a sheet
metal container.

SAH systems provide..[12]
Weather cladding
– Reduced heat loss
through
wall
– Better air quality
School, Yellowknife, Canada
Solar Collector

Examples: Canada and USA [12]
Ventilation Air Heating Systems
• Improved air quality at low cost
• Size ranges from a few m2 to 10,000 m2
• Ducts should be located near south wall
• Paybacks of 2 to 5 years typical
Apartment Building,
Ontario, Canada
Portable Classroom, Ontario, Canada
Brown Collector on Industrial
Building, Connecticut, USA

Example: Indonesia [12]
Process Heat Systems
• Normally constant flow
rate systems with very
simple controls
• Used for drying crops
that are harvested
throughout the year
Tea Drying Shelter, West Java, Indonesia

Application
• SAH provides ventilation and process air heating
• Locations throughout world have solar energy available with out
any cost.
• SAH serves as weather cladding and feeds into conventional
ventilation systems
• Efficiency and cost are the biggest barriers for any solar product.

Types of Solar Air Heater [7]

Non-Porous [5]
In this type air does
not passing through
below the absorber
plate but air may flow
above the plate.

Porous Type [5]
It has porous absorber
which may include slit
and expanded metal,
overlapped glass plate
absorber.

Advanced
Solar Air Heaters

1.Low Cost Solar Air Heater [2]

General
• Two low cost solar air heaters viz. single glazed and double
glazed were designed, fabricated and tested.
• Thermocole, ultraviolet stabilized plastic sheet, etc. were used
for fabrication to reduce the fabrication cost.
• These were tested simultaneously at no load and with load
both in summer and winter seasons along with packed bed
solar air heater.
• The efficiencies of single glazed, double glazed and packed
bed solar air heaters corresponding to flow rate of 0.02 m3/s-m2
were 30.29%, 45.05% and 71.68% respectively in winter
season.

Cost Comparison
• Single and Double Glazed Solar Air Heater are
low cost.
• Packed Bed Solar Air Heater is comparatively
30% costly than the Single and Double Glazed
Solar Air Heater.

Single Glazed Solar Air Heater

Double Glazed Solar Air Heater

Packed Bed Solar Air Heater

Tested at No Load

Tested at Load-Rise in Temperature
(During Summer Season )

Tested at Load-Thermal Efficiency
(During Summer Season )

Tested at Load-Rise in Temperature
(During Winter Season )

Tested at Load-Thermal Efficiency
(During Winter Season )

The Efficiency

The Energy gain for Flow Rate

The Bill of Material with Cost

Summery
• Single glazed low cost solar air heater gives better thermal
effi-ciency during summer while double glazing is better
during winter for all flow rates.
• For flow rate of 0.020 m3/s per m2 aperture area,the
maximum average thermal efficiency was 37.45% for single
glazed and 24.07% for double glazed solar air heater during
summer. Corresponding figures for winter were 30.29% and
45.05% respectively.

• For the same initial investment, low cost solar air
heaters collect more energy than packed bed solar
air heater.
• For flow rate of 0.020 m3/s per m2 aperture area, the
solar energy gain per unit investment was 0.13 kJ per
US$ for single glazed, 0.10 kJ per US$ for double
glazed and 0.03 kJ per US$ for packed bed solar air
heater during summer. Corresponding figures for
winter were 0.08 kJ per US$, 0.07 kJ per US$ and
0.02 kJ per US$ respectively.

Effective technique to enhance the
rate of heat transfer…..
• The Thermal efficiency of solar air heater has been found to be
poor.
• The reason behind it is low heat transfer capability between
the absorber and air flowing in the duct.
• So, by providing the artificial roughness on the underside of
the absorber plate, turbulence increase and heat trnsfer
coefficient also increase.

CFD Analysis[8]

2. Effective Solar Air Heater by
Improvement in Roughness

[3]

• It would also result in increase in friction
losses and hence greater power requirements
for pumping air through the duct. In order to
keep the friction losses at a low level, the
turbulence must be created only in the region
very close to the duct surface, i.e. in laminar
sub layer.

• The application of artificial roughness, by
using different shapes has been
recommended to enhance the heat transfer
coefficient by several investigators.

Types of shapes of Roughness [3]
• V-shaped
• Wedge shaped
• Expanded metal mesh
• Angle circular rib

Objective of Experiment [4]
• Our objective is to investigate the effect
discrete v & v-groove shaped roughness on
the absorber plate of solar air heater, on the
heat transfer coefficient and friction factor
and to compare it with smooth absorber plate
to know the actual increase in performance of
flat plate solar air collector by using this
particular artificial roughness on absorber
plate.

Basic Equation [4]
• The useful heat gain of the air is calculated as:

Where,
m’ is mass flow rate of air through the test duct
Cp is specific heat of air
Tfo is fluid temperature at exit of test duct
Tfi is fluid temperature at inlet of test duct

• The heat transfer coefficient for the test
section is:
• The Nusselt number is:

• The friction factor was determined from the
measured values of pressure drop across the
test length:
• Thermo hydraulic performance
hp= (Nu /Nus) / (fr/fs)1/3

OBSERVATION TABLE [4]
S. Reynolds Inlet Average Average Average Heat Convectiv Nusselt Friction Thermo
No. no. temperatu outlet air plate transfer e heat no. Factor hydraulic
(Re) re of air temperatur temperatu temperat Q (Watt) transfer (Nu) (f) performa
(ti) OC e (toav) OC re (tfav) OC ure (tpav) coffecient nce
OC (h) W/m2-
oK
1 5387 34.00 46.00 40.00 72.28
136.80
14.12 22.57
0.032 0.5
2 7604 33.50 44.00 38.75 70.48
169.00
17.75 28.37
0.0275 0.69
3 9315 33.00 42.00 37.50 66.00
178.00
20.81 33.23
0.025 0.853
4 10788 33.00 41.00 37.00 63.00 182.00 23.33 37.26 0.023 1.0
5 12051 32.00 39.50 36.00 61.20 191.30 25.26 40.37 0.022 1.1
6 13211 31.50 39.00 35.2 60.00 209.00 27.80 44.40
0.021 1.07

EXPERIMENTAL RESULTS [4]

SUMMERY
( 1 ) In the entire range of Reynolds number, it is
found that the Nusselt Number increases,
attains a maximum value for v groove
roughened plate and increases with increasing
roughness geometry.
( 2 )On increasing the roughness on the plate
the friction factor also increase.

( 3 )The value of the friction factor reduces
sharply at low Reynolds Number and then
decrease very slightly in comparison to low
Reynolds Number.
The experimental values of the heat transfer of
the v groove Roughness absorber plate has been
compared with smooth plate. The plate having
Roughness geometry v groove, gives the
maximum heat transfer

REFERENCES

1. The Solar Thermal Air Heating and Cooling Association
(STA), http://solarairheating.org.au/
2. R.S. Gill, Sukhmeet Singh, Parm Pal Singh, Low cost solar
air heater, Energy Conversion and Management,2012
3. M.K. Mittala, Varuna, R.P. Saini, S.K. Singal, Effective
efficiency of solar air heaters having different types of
roughness elements on the absorber plate, Elsevier,
Energy 32 (2007) 739–745, September 2005
4. Manash Dey Effect of Artificial Roughness on Solar Air
Heater: An Experimental Investigation, Int. Journal of
Engineering Research and Application Vol. 3, Issue 5,
Sep-Oct 2013, pp.88-95
5. Sukhatme S.P., "Solar Energy: Principles of Thermal
Collections and Storage", Tata McGraw-Hill, New Delhi
2003.

6. Rai G.D., "Non-Conventional Energy Sources ", Khanna
Publishers Delhi,1999
7. RREA Rural Renewable Energy Alliance, www.rreal.org
8. Akpinar Ebru Kavak, Kocyigit Fatih. Energy and exergy
analysis of a new flatplate solar air heater having different
obstacles on absorber plates. Appl Energy 2010;87:3438–50.
9. Akpinar Ebru Kavak, Kocyig˘it Fatih. Experimental
investigation of thermal performance of solar air heater
having different obstacles on absorber plates. Int Commun
Heat Mass Transfer 2010;37:416–21.
10. Ramadan MRI, El-Sebaii AA, Aboul-Enein S, El-Bialy E.
Thermal performance of a packed bed double-pass solar air
heater. Energy 2007;32:1524–35.
11. Bansal NK, Uhlemann R. Development and testing of low
cost solar energy collectors for heating air. Sol Energy
1984;33:197–208
12. Rate Screen International www.ratescreen.com

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