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amantino88

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Posts: 2
Reply with quote  #1 
Hi all,
I am trying evaluate the thermal condition of a a vacuum tube solar collector CPC  plant, in particular the temperature of the absorber part of the collector. I found the dry bulb air temperature (it was 6°C) and the radiation on a tilt surface that is 120 W/m^2 (it was early morning). 

Since the trasmission coefficient multiplicated for the absorption coefficient is 0,7, the absorbed radiation energy is 0,7*120=84 W/m^2.

Then I thought to use the Stefan-Boltzman low,

Eass = (5,67*10^-8)*(Tabsorber^4-Tair^4)

Where
Eass is absorbed radiation energy
Tabsorber is the temperature of the absorbe
Tair is the already measured themeperature of the air

So i found the Tabsorber since Eass and Tair were already known.

Do you think that this method could be right? I personally have some doubt since I have not considered the temperature of the glass collector face, and I have not considered the convection. 
Do you have any advice? 
Thank you so much

Garage_Hermit

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Posts: 2,239
Reply with quote  #2 
Quote:
I am trying evaluate the thermal condition of a a vacuum tube solar collector CPC  plant, in particular the temperature of the absorber part of the collector.


Bit over my head, but according to this, you are looking at 400°C or so...

https://archive.uea.ac.uk/~e680/energy/energy_links/renewables/Riffel.pdf

G_H

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amantino88

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Posts: 2
Reply with quote  #3 
Hi Garage_Hermit. first of all thank you... But I think is difficult that can reach this value of 400°C, since the stagnation temperature of my panels is 250°C and is reached only when the radiation is about 1000 W/m^2.
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