[TRNSYS-users] solar collector drainback

[Jeff Thornton]

We have been modeling solar hot water systems for years and we never
model the physical draining of the solar collector and pipes. We include
a drainback tank for the additional losses that it provides and set up
controls to mimic the operation of a drainback system. We allow the pump
to run a bit longer after it turns off in order to fill the drainback
tank (variable volume tank Type 39) with fluid to it's "drainback
volume". At start-up of the pump, we "throw away" the fluid returning
from the collector and return line using a diverting valve until the
drainback tank reaches it's "operating volume". While this isn't
perfect, developing pipe and collector models that deal with both air
and water filled sections would be difficult. Besides, the amount of
energy that we are talking about is usually very small when compared to
the total amount of collected energy over the year. 

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 11/04/2013
9:11 am, Pascual Ortiz, Carol wrote: 

> Dear all, 
> 
> I would also
like to simulate the drain-back of a flat plate collector but I do not
know how to do it. So far, I simulated the FPC using the type 1b but now
I do not know how can I simulate the drain-back, because if the inlet
flow rate of the collector is zero kg/h also the outlet flow rate will
be zero. I think that I should change the type 1 for another one, but I
do not know which is the type that I should use, could you give me a
clue, please? 
> 
> Thank you in advance, 
> 
> CAROL PASCUAL 
> 
>
Energía Térmica/Thermal Energy 
> 
> DIVISIN DE ENERGA Y MEDIO AMBIENTE/

> 
> ENERGY AND ENVIRONMENT DIVISION 
> 
> TECNALIA 
> 
> Área Anardi,5

> 
> Laida Bidea, Edificio 204 
> 
> E-20730 Azpeitia - Gipuzkoa
(Spain) 
> 
> T 902 760 000* 
> 
> M 667119581 
> 
> T +34 946 430 850
(International calls) 
> 
> carol.pascual at tecnalia.com [1] 
> 
>
www.tecnalia.com [2] 
> 
> [3] 
> 
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Links:
------
[1]
mailto:carol.pascual at tecnalia.com
[2] http://www.tecnalia.com/
[3]
http://www.tecnalia.com/pulseraverde/
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