Performance Test of A Solar Air Heating Collector Using an Aluminum
Screen Absorber
This is a side by side heating performance test comparing a solar air
heating collector that uses two layers of aluminum screen for the absorber
to a backpass collector that uses a solid sheet absorber with all the
airflow behind the absorber plate.
Construction of the screen collector is covered
here...
Back to the Solar Air Heating Collector test
program home..
Test Setup
The screen vs backpass collector test was done using the same ducting and
blower setup as for the other tests. The blowers were Elicent AXC
125Bs.
Flow rates were measured using the
Big Bag technique.
Flow rates used ranged from 2.3 cfm/sf up to 3.3 cfm/sf.
The plot above shows the logged inlet and outlet temperatures for the
screen collector (black) and the backpass collector (red). These can
NOT be used directly to compare performance as the flow rates for the two
collectors were not exactly equal for the testing. In order to get a
comparison of heat output for the two collectors at a given time, the
product of the flow rate times the temperature rise must be compared for
each collector. The table below gives this comparison for several
times during the testing. For example, in the time period around 10:30
am it looks from the termperature plot like the two collectors about tied,
but in fact, while the temperature rise is about the same, the screen
collector air flow is 2.7 cfm/sf vs 2.4 cfm/sf for the backpass collector --
a 13% difference in flow rate and heat output.
In general, the screen collector output is about 7 to 13% greater than
the backpass collector.
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Screen Absorber vs Reference Backpass Collector Solar Air Heating
Collector Test |
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Janary 11, 2011 |
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| specific heat |
0.24 |
BTU/lb-F |
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| Col Area |
32 |
sqft |
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| Air Density |
0.061 |
lb/cf |
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| Bag Vol |
53.8 |
cf |
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Reference Collector |
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Screen Collector |
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Summary |
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F |
F |
F |
fpm |
fpm |
sec |
cfm |
cfm/sf |
BTU/hr |
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F |
F |
F |
fpm |
fpm |
sec |
cfm |
cfm/sf |
BTU/hr |
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| Time |
Sun |
Tamb |
Tgar |
Tin |
Tout |
dT |
Vin |
Vout |
Fill Time |
Flow Rate |
Flow/sf |
Ref Heat Out |
Efic |
Tin |
Tout |
dT |
Vin |
Vout |
Fill Time |
Flow Rate |
Flow/sf |
Scrn Heat Out |
Efic |
Hscrn/Href |
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9:51 |
725 |
0.2 |
50 |
55.9 |
95.6 |
39.7 |
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810 |
42 |
76.9 |
2.4 |
2680 |
0.36 |
55.8 |
94.9 |
39.1 |
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805 |
37.2 |
86.8 |
2.7 |
2980 |
0.41 |
1.112 |
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10:12:46 |
864 |
4 |
51 |
57.2 |
105 |
47.8 |
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810 |
42 |
76.9 |
2.4 |
3227 |
0.37 |
58.4 |
105 |
46.6 |
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805 |
37.2 |
86.8 |
2.7 |
3552 |
0.41 |
1.101 |
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10:34:16 |
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5 |
52 |
58.7 |
110.7 |
52 |
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810 |
42 |
76.9 |
2.4 |
3511 |
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59.9 |
111.6 |
51.7 |
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805 |
37.2 |
86.8 |
2.7 |
3941 |
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1.123 |
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11:24:26 |
962 |
8.4 |
55 |
58.7 |
117 |
58.3 |
350 |
805 |
42.4 |
76.1 |
2.4 |
3899 |
0.40 |
60.1 |
124.6 |
64.5 |
371 |
680 |
43.4 |
74.4 |
2.3 |
4214 |
0.43 |
1.081 |
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12:03:06 |
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8 |
56 |
59.7 |
116.8 |
57.1 |
350 |
805 |
42.4 |
76.1 |
2.4 |
3819 |
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61.1 |
125.2 |
64.1 |
371 |
680 |
43.4 |
74.4 |
2.3 |
4188 |
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1.097 |
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1:10:16 |
836 |
6.4 |
58 |
62.6 |
110.9 |
48.3 |
360 |
812 |
42.9 |
75.2 |
2.4 |
3192 |
0.38 |
63 |
114.3 |
51.3 |
380 |
683 |
42.9 |
75.2 |
2.4 |
3391 |
0.40 |
1.062 |
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1:31:46 |
821 |
8.1 |
58 |
63.2 |
108.5 |
45.3 |
360 |
810 |
42.8 |
75.4 |
2.4 |
3001 |
0.36 |
63.6 |
101.3 |
37.7 |
510 |
1006 |
30.13 |
107.1 |
3.3 |
3548 |
0.43 |
1.182 |
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2:00:06 |
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8 |
58 |
63.3 |
104.6 |
41.3 |
360 |
810 |
42.8 |
75.4 |
2.4 |
2736 |
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63.9 |
95.2 |
31.3 |
510 |
1006 |
30.13 |
107.1 |
3.3 |
2946 |
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1.077 |
Note that after this test was completed and Scott and I discovered how well this
simple simple collector did compared to the reference (backpass) collector,
as well as its low pressure drop, we decided to start using this screen collector for the reference collector
in the rest of the tests.
Gary April 12, 2011
