[TRNSYS-users] Capacity of buffer tank

[David BRADLEY]

Dear Zhe,
   In order for the simulation to be numerically stable, the buffer tank 
must be large enough to hold at least one time step of liquid. So the 
answer to your question depends upon the rated flow rate of the pump in 
the loop and on the time step that you have chosen. In the actual 
system, there is liquid volume contained in the piping network. I would 
recommend that you determine how much liquid volume there is (knowing 
the inside diameter and length of each pipe section), then create a 
buffer tank of equivalent size and reduce your time step accordingly.
Kind regards,
  David


On 11/28/2012 11:07, Zhe Li wrote:
>
> Dear David,
>
> Thanks for your time.
>
> As we discussed before, due to the fact that the current air-water 
>  heat pump (Type 941) is a single stage heat pump, a buffer tank is 
> used to prevent overheating when a imposed thermal load is employed. 
> Even though the desired system is not working with a buffer tank, this 
> does solve the original problem I had. However, I have discovered a 
> new problem. What would be the right capacity of this buffer tank to 
> built into in order to simulate the actual system (system without 
> using buffer tank)? I have tried to simulate using varies capacity 
> tank ( from 0.3m^3 to 1m^3 ) as the buffer tank, the electricity 
> consumption can be different as much as 5% which it is significant as 
> far as I am concerned.
>
> Also, I understand there is an auxiliary heater built into the 
> air-water heat pump component. Would you recommend to use this 
> auxiliary heater or use an external heater built into the circuit 
> where after the buffer tank which makes it more realistic?
>
> Hope I have explained the problem clearly.
>
> Thank you very much.
>
> Zhe Li
>
>
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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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