[TRNSYS-users] Water/Water Heat pump with Storage tank

[David BRADLEY]

Fahri,
   This is a problem in actual heat pump systems, not a problem in your 
simulation. I have seen two approaches. You can either store very hot 
water (60C or so) in the tank and then use valves to mix some of the 
water that returns from the floors with some of the hot water that is 
being stored in the tank (supplied by the heat pump) so that the actual 
supply temperature is lower than the stored water temperature (maybe 
28C). Or you can store water in the tank at your distribution (supply) 
temperature of 28C. In this case, a thermostat sits watching the tank 
temperature and turns on the heatpump when the tank drops below the set 
point. Of course the heat pump still delivers 60C water to the tank but 
it then turns off as soon as the thermostat in the tank sees that the 
temperature has risen back above 28C
Best,
  David


On 6/27/2012 10:06, Fahri Avci wrote:
> Hi everybody,
>
> I'm new in Trnsys and i work on my bachelors Thesis. I have a problem 
> with my water-water heat pump(type 668) and my stratified storage 
> tank(type 4e).
> I try to heat my building model to room temperature(20°C) with floor 
> heating and the heat pump. Between the two components, i have a 
> storage tank.
>
> Now the problem is that my heat pump provides a high load temperature 
> but in fact i don't need a high temperature because a floor heating 
> system doesn't
> need a high inlet temperature. Unfortunately type 668 doesn't have a 
> parameter where i can set the outlet temperature. The only thing i can 
> do is to reduce the
> parameter "boiling point" of water in my storage tank less than 100°C  
> to have a moderate heat pump outlet temperature but i think it doesn't 
> make sense because
> the boiling point of water is about 100°C. Now i wonder how i can 
> control my heatpump to heat the water to the desired temperature. I 
> guess the high temperature is depending
> to the boiling point of the storage, i think the heat pump always try 
> to reach this point of temperature.
>
> Thank you for your helps,
>
> Best Regards,
>
> Fahri Avci
>
> TUM München
> Lehrstuhl Energiewirtschaft und Anwendungstechnik
> Arcisstraße 21 München
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

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



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