[TRNSYS-users] Doubt on the codes of some TESS Unglazed collector models

[Jeff Thornton]

Javier, 

It's the net long wave radiation on the collector surface - not the long
wave radiation from the collector surface to the sky. It's taken
directly from the standards for modeling un-glazed solar collectors. 

Jeff 

---
Jeff Thornton
President - TESS LLC
22 N. Carroll Street, Madison WI USA 53703
Office: (608) 274-2577 Fax: (608) 278-1475
www.tess-inc.com
E-Mail: thornton at tess-inc.com

On 01/05/2018 2:45 pm, Javier Vega via TRNSYS-users wrote: 

> Hi TRNSYS users, 
> 
> I was just checking the codes of Type 553 and Type 1290 (Unglazed Solar Collector models) and something grabbed my attention. When both models do the Net Long Wave Radiation Balance, they do the following: 
> 
> !Account for the long wave losses from the collector surface 
> T_ambient_K = T_ambient+273.15 
> T_sky_K = T_sky+273.15 
> Sigma = 3.6*5.67d-08 !Stefan Boltmann constant 
> Net_Longwave = Sigma*(T_ambient_K**4.-T_sky_K**4.)*Emissivity/Absorptance 
> 
> That is a copy/paste of Type 553. 
> 
> Why the Net Long Wave is defined with the Ambient Temperature and not with the Collector Average Temperature? It doesn't make sense to me. Is there something I'm uderstanding wrong? 
> 
> Bests of wishes, 
> 
> Javier Vega Benavente 
> Universidad de Concepción, Chile. 
> 
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