error at Condensor ttd_u value. But the values obtained shouldnt cause the error ? Or am i wrong somewhere in understanding ?

[ronitd07]

Hello,

While running a heatpump simulation I get below error

Invalid value for ttd_u: ttd_u = -1.6613626246231092 below minimum value (0) at component condenser.
Invalid value for ttd_min: ttd_min = -1.6613626246231092 below minimum value (0) at component condenser.

On checking my temperature values for refrigerant and water
Refrigerant condenser input temp : 104.18
Refrigerant condenser output temp : 90.10863737537642
Sink Water in temp : 60.35
Sink Water out temp : 96.77

In my knowledge ttd_u is hot_in temperature - cold_out temperature
So in my case it should be 104.18 - 96.77 which is positive. from where do I get the error of ttd_u -1.66

If can someone help.

Thanks,
Ronit

[fwitte]

Hi @ronitd07,

the definition of the Condenser component is a bit different in that context. The component comes from steam power plants, where the upper terminal temperature usually indicates temperature difference between condensing temperature and cold side temperature exit, disregarding potential desuperheating. I recommend you use the MovingBoundaryHeatExchanger instead, also see the tutorials on the heat exchangers here: https://tespy.readthedocs.io/en/main/advanced_tutorials/heat_exchangers.html#tutorial-heat-exchanger. This shows the differences between the different classes.

Best

[ronitd07]

Hi @fwitte

Thanks for your help and clarification. But I also need to use subcooling at the end of my condensor which I was using with Condensor component but subcooling is not available with MovingBoundaryHeatExchanger I guess as i get an error that it has no attribute subcooling.

Thanks,
Ronit

[fwitte]

The MovingBoundary has no inbuilt constraint for the condensing fluid outlet. You can specify td_bubble=10 to the outlet connection, that will impose 10 K sub cooling.

[ronitd07]

thanks