[TRNSYS-users] pump mass balance error

[David BRADLEY]

David,

  I did not take the time to run the project but there are two issues 
that need to be resolved.

The first is the 1-hour time step; I would guess that part of the 
problem is non convergence due to the long time step. The pump on the 
hot water side of the absorption chiller has a flow rate of 58000 kg/h 
and the tank is 5m3. That means that in each time step, the tank volume 
turns over a bit more than 11 times. The flow rate on the collector loop 
is 20000 kg/h causing another 4 turnovers in each time step. I would 
start by reducing the time step to about 5 minutes.

  The other issue is that you have two devices in the collector loop 
that are both trying to set the flow rate in that loop. Type110 is being 
controlled by an on/off differential controller but your collector is 
also set up in Pump Control Specification mode 2 (an input), which means 
that the collector model is modulating its own flow in order to deliver 
a specified outlet temperature.

kind regards,

  David


On 11/03/2020 11:17, David Redpath (Staff) via TRNSYS-users wrote:
> Hi,
>
> I'm trying to simulate a system with a single effect absorption chiller (project file attached) however I keep getting an error saying pump mass balance failed, is there a way of calculating the correct mass balance. Any help gratefully appreciated. Thanks
>
> David
>
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
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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