 Open Access
 Total Downloads : 6346
 Authors : D. Bhandari , Dr. S. Singh
 Paper ID : IJERTV1IS6129
 Volume & Issue : Volume 01, Issue 06 (August 2012)
 Published (First Online): 30082012
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Performance Analysis of Flat Plate Solar Air Collectors With and Without Fins
PERFORMANCE ANALYSIS OF FLAT PLATE SOLAR AIR COLLECTORS WITH AND WITHOUT FINS
D. Bhandari1 , Dr. S. Singp
1M. Tech Scholar, 2Associate Professor
Department of Mechanical Engineering,
Bipin Tripathi Kumaon Institute of Technology, Dwarahat, Almora, Uttarakhand (India) 263653
Abstract
The present work involves a comparative study of performance analysis of different types of flat plate solar air heaters. A MATLAB program code is generated to carry out the whole analysis. The effect of mass flow rates, inlet temperature and intensity of solar radiation on the performance of solar air heaters is also investigated in the present study. The three types of solar air heaters used for the analysis are: Conventional solar air heater, double glazing single pass solar air heater and double pass solar air heater with internal fins.
Keywords: Conventional single pass solar air heater, Double pass solar air heater, Internal fins, Thermal efficiency, MATLAB.

Introduction
Humans have always used the rays of the sun to gather their energy needs. In the energy needs of today with increasing environmental concern, alternatives to the use of nonrenewable and polluting fossil fuels have to be investigated. One such possibility is solar energy, which has become increasingly popular in recent years. Various types of solar energy systems for agricultural and marine products have been reviewed [4]. One of the most important components of a solar energy system is the solar collector. Solar air collectors are simple, cheap and most widely used. Solar collectors can be used
for drying, space heating, solar desalination, etc. Extensive investigations have been carried out on the optimum design of conventional and modified solar air heaters, in order to search for efficient and inexpensive designs suitable for mass production for different practical applications. The researchers have given their attention to the effects of design and operational parameters, type of flow passes, number of glazing and type of absorber flat, corrugated or finned, on the thermal performance of solar air heaters (Ratna et al. [10]; Ratna et al. [11]; Choudhury et al. [1]; Karim and Hawlader,
[8] ). They concluded that for shorter duct lengths and lower air mass flow rates, the performance of the two pass air heaters with a single cover is most costeffective as compared to the other designs. Helal et al. [6] studied energetic performances of an integrated collector storage solar water heater. The systems shows little cost, simplicity and simpler to be installed on the roof of the building. Fudholi et al.[3]Where,
Solving these equations we get
+
(1)
(2)
(3)
(4)
conducted an experimental study on a forced convective doublepass solar air
collector with fins in the second channel.
The experiments were conducted by changing the parameters that influence the
thermal efficiency of the collector. Ho et
al. [7] experimentally investigated a new
(5)
(6)
(7)
(8)
device of inserting an absorbing plate to divide a flatplate channel into two channels with fins attached and external recycling at the ends, resulting in substantially improving the heat transfer efficiency. The present work deals with comparing the performances of flat plate solar air heaters with and without fins using MATLAB computer software.

Mathematical Model

Conventional Solar air heater
The steady state energy balance conditions for the various parts of conventional flat plate solar air collector is given as
+ (9)
Mean fluid temperature is calculated by using the formula
which on substituting terms by relevant gives
(10)

Double Glazing Solar air heater
The steady state energy balance conditions for the various parts of conventional flat plate solar air collector is given as
+
(1)
(2)
(3)
Solving these equations we get
(5)
Where,
(6)
Solving these equations we get
(4)
(7)
(8)
(5)
(9)
(7)
(8)
(10)
Mean fluid temperature is calculated by using the formula
+ (9)
(10)
which on substituting terms by relevant gives

Double Pass Solar air heater with internal fins
The steady state energy balance conditions for the various parts of conventional flat plate solar air collector is given as
+ (12)

Empirical relations
Where
And,
(1)
(3)
(4)
For calculating the above parameters we need to find out the overall heat transfer coefficients and dimensionless numbers such a Reynolds number and Nusselt number.
An empirical equation for the loss coefficient from the top of solar collector to the ambient Ut was developed by Klein
Nomenclature hw Convective heat transfer coefficient between glass cover and ambient, W/m2K
Ap
Surface area of the absorbing plate,m2
p
Convective heat transfer coefficient between the absorber plate and the air stream, W/m2
Af
Total surface area of fins,m2
p
Convective heat transfer coefficient between the bottom plate and the air stream, W/m2
Afb
Total crosssectional area of fins,m2
L
Length of collector, m
B
Width of the air tunnel in the solar collector,
I0
Intensity of solar radiation, W/m2
m
Cp
Specific heat of air at constant pressure,
Ks
Thermal conductivity of material of fins,
J/kgK
W/mK
De
Equivalent diameter of the air tunnel, m
Ta
Ambient temperature, K
F
Efficiency factor of the solar air heater
m
Mass flow rate, m/s
FR
Heat removal factor for the solar air heater
N
Total number of fins
H
Height of the air tunnel in the solar air
Nu
Nusselt number
collector, m
R
Remixing ratio
Tfm
Mean fluid temperature, K
Re
Reynolds number
Ti
Inlet air temperature, K
T
Thickness of fin, m
Tbm
Mean bottom plate temperature, K
Ut
Loss coefficient from the top of absorbing plate to the atmosphere, W/m2K
Tpm
Assumed mean temperature of absorber plate, K
w1
Distance between fins, m
T0
Fluid outlet temperature, K
w2
Height of fins, m
Qu
Useful heat gain per unit time, W
V
Wind velocity, m/s
p
Emissivity of absorber plate
X
Axis along the flow direction, m
b
Emissivity of bottom plate
Efficiency of solar air collector
f
Fin efficiency
Density of air, kg/m3
Stefan Boltzman Constant
Transmittance of glass cover
Dimensionless quantity
Absorptivity of the absorbing plate
Âµ
Absolute viscosity of fluid , Ns/m2
Tpm
Calculated value of mean absorber
temperature, K
plate T
Difference between assumed and calculated
values of mean absorber plate temperature, K
Glass Cover Absorber
Insulation Bottom Plate
L
Figure1: Conventional Solar Air Heater
Glass Cover
Absorber
Insulation Bottom Plate
Figure2: Double glazing solar air heater
Glass Covers
Ab
sorber
Insulation Recycling Channel
Figure3: Double pass solar air heater with internal fins
[14] following the basic procedure of Hottel and Woertz [5] ,The convective heat transfer coefficient hw for air flowing over the outside surface of the glass cover depends primarily on the wind velocity. V. McAdams [15] obtained experimental result as
Where,
(1)
(2)
(3)
Reynolds number is calculated by using the following relation
(4)
And, Nusselt number is calculated by using following relation


Computational Solution
(5)
It provides an interactive environment with hundreds of builtin functions for technical computation, graphics and animation. It
The whole analysis is carried out with the help of MATLAB R2009b. MATLAB is a software package for highperformance numerical computation and visualization.
also provides easy extensibility with its own highlevel programming language. The name MATLAB stands for MATrix LABoratory.
Figure4: Schematic diagram of double pass internally finned solar air heater
Input Parameters
S.No.
1
Input Parameter
Width of the air tunnel, m
Magnitude
0.6
2
Length of the collector, m
0.6
3
Thermal conductivity of fin, W/mK
386
4
Mass flow rate, m/s
0.01, 0.015, 0.02
5
Solar radiation intensity, W/m2
950, 1100
6
Thickness of fin, m
0.001
7
Emissivity of glass cover
0.94
8
Emissivity of absorber plate
0.95
9
Absorptivity of absorbing plate
0.95
10
Transmittance of glass cover
0.0875
11
Stefan Boltzmann Constant, W/m2K4
5.67×108
12
Air velocity, m/s
1
13
Height of fins, m
0.013
14
Distance of fins, m
0.025
15
Ambient temperature, K
283
16
Number of fins
24

Algorithms
The MATLAB programme algorithm with respective notations and formulae for the three types of solar air heaters described above are given below. Algorithm is the
step by step indication of execution of any program. Algorithm is very essential to understand the flowchart of any programme.

Algorithm for the MATLAB programming of Conventional and Single pass double glazing solar air heaters

START

Assume any arbitrary value of Tpm.

Enter input value of Cp, Âµ, K, Ti , Io, H, Ks, B, W1, W2, t, n, V, , , p , g

Set initial value of m =0.01
,T

Find out the value of required parameters ( Ut , F, FR , Qu ) and hence the value of u, v and
pm
T . Here u= { m,T
o, }, v={m} and T=T
pmT
pm

If value of T lies in the range of {1,1} then display the value of u as optimized otherwise display the value of v as not optimized

Increase value of m by 0.005, if value of m is less than 0.03 go to STEP 4.

When the whole loop is completed notice the values which are not optimised to find such values again go to step 2 and repeat the whole steps further until all of the values get optimised.

END


Algorithm for the MATLAB programming of Double pass internally finned solar air heater

START

Assume any arbitrary value of Tpm.

Enter input value of Cp, Âµ, K, Ti , Io, H, Ks, B, W1, W2, t, n, V, , , p , g

Set initial value of m =0.01

Set initial value of R=1 .
,T

Find out the value of required parameters ( Ut , F, FR , Qu ) and hence the value of u, v and
pm
T . Here u= { m,T
o, }, v={m} and T=T
pmT
pm

If value of T lies in the range of {1,1} then display the value of u as optimized otherwise display the value of v as not optimized

Increase value of R by 1 , if value of R is less than 3 go to STEP 5 else go to NEXT STEP.

Increase value of m by 0.005, if value of m is less than 0.03 go to STEP 4.

When the whole loop is completed notice the values which are not optimised to find such values again go to step 2 and repeat the whole steps further until all of the values get optimised.

END
3.1 Flow charts
Flow charts for the MATLAB programming for the three types of solar air heaters are illustrated below. The first flow chart corresponds to conventional and
single pass double glazing solar air heater while the second one corresponds to double pass internally finned solar air heater.
Figure5: Flow Chart for the Conventional and single pass double glazing solar air heaters
Figure6: Flow Chart for the Double pass internally finned solar air heater




Results and Discussions
The effects of the air inlet temperature and incident solar radiation on the collector efficiency of the conventional, double glazing single pass and double pass solar air heaters with the fins attached have been investigated computationally. As evident from the results, it is clear that the efficiency of all the three types of solar air heaters increases with the increase in mass flow rate and decreasing fluid inlet
pressure. The remixing ratio also has a tremendous effect on the efficiency of double pass finned solar air heater and the efficiency increases with the increase in the value of remixing ratio R. Similarly it is clear from the results obtained that the value of mean absorber plate temperature Tpm and fluid outlet temperature To decreases with the increase in mass flow rate.
45
40
35
30
25
Efficiency ,
20
15
Ti=293K
Ti=288K
10
5
0
0
0.005
0.01 0.015
0.02
0.025
0.03
0.035
Mass flow rate, m'(kg/s)
Figure7: Graph of conventional solar air heater for Io=950W/m2
10
5
0
0
0.005 0.01 0.015 0.02 0.025 0.03 0.035
Mass flow rate, m'(kg/s)
Ti=293K
Ti=288K
20
15
Efficiency,
45
4035
30
25
Figure8: Graph of conventional solar air heater for I0 = 1100 W/m2
40
35
30
25
Efficiency, 20
15
Ti=293
Ti=288
10
5
0
0
0.005 0.01 0.015 0.02 0.025 0.03 0.035
Mass flow rate, m'(kg/s)
Figure9: Graph of double glazing single pass solar air heater for I0=950 W/m2
40
35
30
25
Efficiency, 20
15
Ti=293K
Ti=288K
10
5
0
0
0.005 0.01 0.015 0.02 0.025 0.03 0.035
Mass flow rate, m'(kg/s)
Figure10: Graph of double glazing single pass solar air heater for I0=1100 W/m2
70
60
50
40
Efficiency ,
30
20
R=1
R=2 R=3
10
0
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
Mass Flow rate , m' (kg/s)
Figure11: Graph of double pass finned solar air heater for Io=950W/m2 and Ti=288 K
60
50
40
10
0
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
Mass flow rate, m'(kg/s)
R=1
R=2 R=3
20
Efficiency, 30
Figure12: Graph of double pass finned solar air heater for Io= 950 W/m2 and Ti = 293K
70
60
50
40
Efficiency,
30
20
R=1
R=2 R=3
10
0
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
Mass flow rate, m' (kg/s)
Figure13: Graph of double pass finned solar air heater for Io= 1100 W/m2 and Ti = 288K
70
60
50
40
efficiency,
30
20
R=1
R=2 R=3
10
0
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
Mass flow rate, m'(kg/s)
Figure14: Graph of double pass finned solar air heater for Io=1100W/m2 and Ti=293K
The improvement of collector performance for Conventional solar air heater
S.NO 
Io= 950W/m2 
Io= 1100W/m2 

Ti (K) 
m (kg/s) 
(%) 
Tpm(K) 
To(K) 
(%) 
Tpm (K) 
To (K) 

1 
293 
0.01 
23.88 
366.54 
301.08 
23.75 
376.79 
302.29 
2 
0.015 
29.43 
360.29 
299.64 
29.32 
369.69 
300.66 

3 
0.02 
33.58 
355.57 
298.69 
33.50 
364.30 
299.56 

4 
0.025 
36.79 
351.59 
297.98 
36.84 
360.14 
298.78 

5 
0.03 
39.47 
348.56 
297.45 
39.50 
356.47 
298.16 

6 
288 
0.01 
25.04 
365.19 
296.47 
24.77 
375.48 
297.69 
7 
0.015 
30.86 
358.75 
294.97 
30.59 
368.21 
295.98 

8 
0.02 
35.17 
353.73 
293.96 
34.96 
362.72 
294.85 

9 
0.025 
38.51 
349.52 
293.21 
38.36 
358.12 
294.02 

10 
0.03 
41.29 
346.29 
292.61 
41.15 
354.44 
293.38 
The improvement of collector performance for double glazing solar air heater
S.NO 
Io= 950W/m2 
Io= 1100W/m2 

Ti (K) 
m (kg/s) 
(%) 
Tpm(K) 
To(K) 
(%) 
Tpm (K) 
To (K) 

1 
293 
0.01 
20.94 
358.06 
300.09 
20.84 
367.16 
301.16 
2 
0.015 
25.77 
352.52 
298.82 
25.73 
361.06 
299.72 

3 
0.02 
29.33 
348.19 
297.97 
29.37 
356.28 
298.76 

4 
0.025 
32.11 
344.69 
297.35 
32.23 
352.43 
298.05 

5 
0.03 
34.39 
341.89 
296.89 
34.53 
349.19 
297.52 

6 
288 
0.01 
22.12 
356.87 
295.49 
21.88 
366.03 
296.57 
7 
0.015 
27.17 
350.93 
294.14 
26.98 
359.52 
295.05 

8 
0.02 
30.89 
346.30 
293.23 
30.75 
354.45 
294.03 

9 
0.025 
33.84 
342.73 
292.59 
33.71 
350.36 
293.29 

10 
0.03 
36.21 
339.74 
292.09 
36.10 
346.94 
292.72 
The improvement of collector performance for double pass finned solar air heater for R=1
S.NO 
Io= 950W/m2 
Io= 1100W/m2 

Ti (K) 
m (kg/s) 
(%) 
Tpm(K) 
To(K) 
(%) 
Tpm (K) 
To (K) 

1 
293 
0.01 
29.26 
347.03 
303.17 
30.11 
355.03 
304.81 
2 
0.015 
35.23 
339.49 
301.19 
36.32 
346.79 
302.50 

3 
0.02 
40.41 
334.01 
299.85 
41.63 
337.36 
300.38 

4 
0.025 
45.38 
330.51 
297.67 
46.42 
334.86 
298.59 

5 
0.03 
49.43 
327.06 
295.28 
50.64 
331.52 
296.84 

6 
288 
0.01 
31.88 
345.04 
298.81 
31.56 
353.08 
300.38 
7 
0.015 
38.19 
337.09 
296.63 
37.99 
344.31 
297.94 

8 
0.02 
42.93 
331.24 
295.22 
42.81 
337.76 
296.33 

9 
0.025 
47.89 
227.74 
294.59 
47.57 
333.67 
295.17 

10 
0.03 
51.67 
224.96 
293.61 
51.45 
330.18 
294.76 
The improvement of collector performance for double pass finned solar air heater for R=2
S.NO 
Io= 950W/m2 
Io= 1100W/m2 

Ti (K) 
m (kg/s) 
(%) 
Tpm(K) 
To(K) 
(%) 
Tpm (K) 
To (K) 

1 
293 
0.01 
34.77 
341.52 
304.79 
34.72 
348.86 
306.62 
2 
0.015 
40.78 
333.64 
302.22 
40.89 
340.05 
303.71 

3 
0.02 
45.81 
328.21 
300.59 
46.08 
333.93 
301.86 

4 
0.025 
49.87 
324.47 
298.54 
50.43 
327.63 
299.75 

5 
0.03 
52.87 
321.37 
296.31 
54.14 
324.18 
297.81 

6 
288 
0.01 
36.60 
339.13 
300.41 
36.51 
346.66 
302.28 
7 
0.015 
42.91 
330.85 
297.71 
42.78 
337.30 
299.20 

8 
0.02 
47.73 
325.13 
295.99 
47.89 
330.83 
297.25 

9 
0.025 
51.67 
321.56 
293.60 
52.04 
326.71 
295.75 

10 
0.03 
54.87 
318.34 
291.21 
56.31 
323.49 
293.62 
The improvement of collector performance for double pass finned solar air heater for R=3
S.NO 
Io= 950W/m2 
Io= 1100W/m2 

Ti (K) 
m (kg/s) 
(%) 
Tpm(K) 
To(K) 
(%) 
Tpm (K) 
To (K) 

1 
293 
0.01 
38.79 
337.72 
305.82 
38.82 
344.62 
307.84 
2 
0.015 
44.69 
329.78 
302.88 
44.83 
335.60 
304.48 

3 
0.02 
49.54 
324.47 
301.07 
49.88 
329.77 
302.38 

4 
0.025 
53.46 
320.73 
299.56 
54.74 
325.63 
300.65 

5 
0.03 
56.76 
317.21 
297.87 
58.54 
322.93 
298.23 

6 
288 
0.01 
39.94 
335.07 
301.48 
39.94 
342.03 
303.52 
7 
0.015 
46.73 
326.74 
298.39 
46.88 
332.68 
300.12 

8 
0.02 
51.89 
321.16 
296.48 
51.93 
326.26 
297.81 

9 
0.025 
55.86 
317.76 
294.45 
56.64 
324.45 
295.24 

10 
0.03 
58.71 
314.86 
292.86 
59.89 
321.84 
293.62 
Conclusion
From the analysis of various types of solar air heaters viz conventional , double glazing single pass and double pass finned solar air heaters, it is concluded that for the same mass flow rate, double pass finned solar air heater is having the highest efficiency.
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