[TRNSYS-users] Air-based PVT-Type 50

[David BRADLEY]

Ali,

  The problem with just changing the fluid specific heat is that the 
model still won't take into account the impact of the latent heat of 
vaporization that occurs in air as it passes through the collector. If 
you're going to approximate an air-based collector using Type50 you at 
least need to put a psychrometrics component (Type33) after the 
collector and pass it the collector outlet temperature and the 
collector's /inlet /humidity ratio since the absolute humidity won't 
change across the collector as the working fluid heats up. The Type33 
will correct the exiting air state when the collector is heating the 
working fluid. Correcting the air after calculating the collector 
performance isn't ideal. You also have to be concerned about flow 
through the collector when there isn't enough solar energy to heat up 
the working fluid. If the fluid is cooling down instead of heating up 
(and it certainly can unless your controls specifically prevent it) and 
it cools down enough that it drops below the dewpoint temperature then 
water is going to condense out of the air as it passes through. Again 
the Type33 will correct the outlet air state and account for the 
condensation energy but again, it will only correct it after the fact 
and the correction won't impact the collector's performance.

  A preferable solution would be that if you have access to it there are 
a number of air-based PV/T models available in the TESS Electrical library

kind regards,

  David


On 05/25/2021 09:05, Ali Shahrouzian via TRNSYS-users wrote:
>
> Hi,
>
> I’m modelling an air-based PVT system for heating application. Do you 
> think I could use the type 50 as an air-based PVT collector if I 
> specify the fluid thermal capacitance of 1 (kJ/kg.K) instead of 4.19?
>
> Thanks in advance
>
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI  53703 USA

P:+1.608.274.2577
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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