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[TRNSYS-users] Type 695 (variable speed pump) : mass balance check failed



Hi, 

Please check the appended screenshot to see how my TRNSYS project looks like (note that this screenshot is zoomed in the loop I am having problems with). 
In my project, a variable speed pump flow rate is set with a control function. A tempering valve controls the pump entering temperature according to a set temperature (read from an external file). It is a very common system. 

However, the problem is the following : mass balance check fails across the pump (warning messages + I have checked the results and indeed, it occurs during most of the timesteps). The difference between input and output flow rates can be as large as 100%. On the other hand, mass balance is checked when control signal is 0 or 1 (rated flow rate). Connections are set as it follows :

-  Tee piece outlet temperature / flowrate --> pump inlet temperature / flowrate
- Pump outlet flowrate --> valve inlet flowrate    
- Valve inlet temperature from external file
- Valve set temperature from external file 
- Pump control signal from external file

Please feel free to ask for more information about the project.

Thanks in advance for your help,

Have a good day,


Regards,

--
Damien CASETTA
INSA Lyon / Génie Energétique et Environnement
ENERTECH / Cabinet SIDLER
26160 Félines sur Rimandoule
Tél & Fax : 04 75 90 18 54
Courriel : damien.casetta@gmail.com
Site : www.enertech.fr

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