[TRNSYS-users] Mass blance problem with flow diverter

[Jeff Thornton]

<I have a problem with the mass balances of my system. In my proct a
flow diverter divides the waterflow into two separate pipes. .After the
flowdiverter both pipes go to their own pumps. The flow diverter is
controlled according to the ratio of mass flows produced by the pumps.
After the pumps comes heating loads. After that the waterflows are
connected in a flow mixer and the water is being heated in a heatpump.


The problem is that Trnsys gives mass balance warnings for both pumps.
When I check the mass flows of the pumps, they some times are even
larger than the rated flow of the pump.I think the problem has something
to do with the flow diverter...

Can someone give me advice how to fix
this problem and make the mass flows balanced. I have attached a
demonstrative picture of my project.>

That's a very common system in
TRNSYS and shouldn't be a problem. I'm guessing that the equation you
use to set the diverter is wrong. Try something like:


Y_Diverter=MIN(1,(Mpump1/MAX(0.001,(Mpump1+Mpump2)))) 

Mpump1 is the
flow rate from the first pump and Mpump2 is the flow rate from the
second pump. Then connect Y_Diverter to the Type 11 flow diverter
control signal input and then connect Outputs 1 and 2 from the flow
diverter to Pump2 (critical) and Outputs 3 and 4 from the flow diverter
to Pump1. 

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 09/19/2012 5:54 am, Santeri Siren wrote: 

> Dear all,
> 
> I have
a problem with the mass balances of my system. In my proct a flow
diverter divides the waterflow into two separate pipes. .After the
flowdiverter both pipes go to their own pumps. The flow diverter is
controlled according to the ratio of mass flows produced by the pumps.
After the pumps comes heating loads. After that the waterflows are
connected in a flow mixer and the water is being heated in a heatpump.

> 
> The problem is that Trnsys gives mass balance warnings for both
pumps. When I check the mass flows of the pumps, they some times are
even larger than the rated flow of the pump.I think the problem has
something to do with the flow diverter...
> 
> Can someone give me
advice how to fix this problem and make the mass flows balanced. I have
attached a demonstrative picture of my project.
> 
> best regards. 
>
Santeri Siren
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/trnsys-users-onebuilding.org/attachments/20120919/c093d7fe/attachment-0001.htm>