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Re: [TRNSYS-users] SDHW example TRNSYS

<I couldn't find solar collector type 539, do you mean type538?>

No, I meant Type 539, the TESS flat plate collector model.  Type 538 is the evacuated tube version of that model.

<When I check the input parameter it has minimum and maximum array flowrate.> 

Those parameter are used if you decide to put the collector into temperature seeking mode - varying the collector flow to try and keep the outlet temperature at the user specified value.

<Is it from Hottel-Whillier equation? can you please show me the equation? >

Please refer to the documentation for the Type 1 model.  It is simply solving the efficiency equation with no flow.  With no flow, the efficiency is equal to zero.  Be aware though that the Type 1 collector makes some assumptions to simplify the modeling that can cause some inconsistencies with very low flow (the no flow solution is fine).  These inconsistencies are not present with the Type 539 model which takes a much more rigorous solution approach.

 

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@tess-inc.com

On 06/07/2017 9:55 pm, Rm Chemilo wrote:

Thank you for your answers,
 
The reason I asked these question is because of the negatives values at the outlet temperature. 
 
<If you leave water inside a solar collector and there is no radiation incident upon the surface and no water flow, it will quickly degrade towards the ambient temperature.  Type1b has no mass (unlike the Tess Type 539) so it immediately decays to the ambient temperature.>
 
I couldn't find solar collector type 539, do you mean type538? When I check the input parameter it has minimum and maximum array flowrate.
 
<It solves the same energy balance as it does when there is flow.  The no-flow solution is found when the solar gains match the thermal losses from the collector (absorbed energy = losses).>
 
Is it from Hottel-Whillier equation? can you please show me the equation? 
 
Thanks.

On Tue, Jun 6, 2017 at 11:59 PM, Jeff Thornton via TRNSYS-users <trnsys-users@lists.onebuilding.org> wrote:

<Why the outlet temperature of solar collector (type 1b) same as temperature ambient when there is no mass flow rate and irradiance. As you can see in the table below, ToColl = Tambient)

If you leave water inside a solar collector and there is no radiation incident upon the surface and no water flow, it will quickly degrade towards the ambient temperature.  Type1b has no mass (unlike the Tess Type 539) so it immediately decays to the ambient temperature.

<How TRNSYS calculate the outlet temperature of the solar collector if there is no mass flow rate, but only the irradiance available?>

It solves the same energy balance as it does when there is flow.  The no-flow solution is found when the solar gains match the thermal losses from the collector (absorbed energy = losses).

 

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@tess-inc.com

On 06/06/2017 9:09 am, Rm Chemilo via TRNSYS-users wrote:

Dear all,
 
I want to ask several questions about TRNSYS example solar domestic hot water (SDHW).
 
- Why the outlet temperature of solar collector (type 1b) same as temperature ambient when there is no mass flow rate and irradiance. As you can see in the table below, ToColl = Tambient.
 
- How TRNSYS calculate the outlet temperature of the solar collector if there is no mass flow rate, but only the irradiance available?
 
Thanks.
 
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