Re: [TRNSYS-users] Cpc - type 74_ variation of acceptance angle

[Arian Bahrami <arianbhm@yahoo.com>]

Hi,

The type 74 is based on constant aperture area not based on absorber area. So when you increase the half acceptance angle when the aperture area is fixed it means that the CPC performance approachs flat plate performance so you got higher output. The notation you are using here is when the absorber area is fixed and as GCR increases when the absorber area is fixed, the output would be higher due to the fact the aperature area would be higher in this case.

Arian 


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On Monday, September 30, 2019, 9:44 AM, Aditi Garg via TRNSYS-users <trnsys-users@lists.onebuilding.org> wrote:

Dear all

I am working with type 74 (cpc-solar collector). I am using it in a small circuit for water heating purpose. I had tried to vary the half acceptance angle parameter for cpc (30-65 degrees). Theoretically, with an increase in half acceptance angle value, the geometrical concentration ratio (GCR) will decrease and related by correlation, GCR=1/SIN (half acceptance angle).

Now, the results indicate that with an increase in half-acceptance angle, the collector outlet temperature is increasing. However, it also means that with decreasing GCR, the temperature is increasing. This contradicts the theoretical fact that temperature increase with an increase in GCR.

Besides, in the mathematical reference given in volume-4, page 552, the correlation for useful heat gain, the overall heat loss coefficient (UL) is also not divided by GCR. Generally, in concentrating collectors, the heat losses are divided by GCR.

Any help regarding this doubt will be appreciated.

Thanks

Best regards

Aditi

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