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[TRNSYS-users] R: Air-air heat pump: performance data files

Hi David,

in my heating performance data, the normalized capacity and power values depend on outdoor temperature until -19 °C. My minimum ambient temperature is aroud -5 °C.

During the simulation I have the following warning, repeated for several hours:

“the referenced unit has called the psychrometrics routine with humidity ratio above the saturation humidity ratio for the given dry bulb temperature. The air was assumed saturated at the given dry bulb temperature and the humidity ratio set for this condition.”

This error is referred to the type 960.

Could be this the problem of a constant COP during the heating simulation?

Really thank you.

 

Best regards,

 

Jacopo

 

Da: David BRADLEY
Inviato: lunedì 6 febbraio 2023 16:10
A: TRNSYS users mailing list at OneBuilding.org
Cc: Jacopo Valente
Oggetto: Re: [TRNSYS-users] Air-air heat pump: performance data files

 

Jacopo,

 It may be that the evaporator temperatures in the default heating performance file do not correspond with the range of evaporator temperatures that are occurring during your simulation. Type954 is able to interpolate within the range of temperatures (and flow rates, etc.) that is given in the file. However, it cannot extrapolate beyond the range of numbers given. If you have COP values for ambient temperatures from 5C to 20C in the data file but the ambient temperature in your weather data is consistently below 5C then the COP corresponding to 5C would always be returned. Have a look in your *.log file; if the data file is often being accessed with temperatures above or below the range there will be a warning written there.

kind regards,

 David

 

On 2/4/2023 11:54 AM, Jacopo Valente via TRNSYS-users wrote:

Dear all,

 

i’m using the type 954 to model an air-to-air heat pump. Analyzing the results of my simulation, the COP is almost constant during the heating working. I’m using the default performance data file. The problem is only for the heating working, while the COP varies for the cooling working.

I can suppose there is some problem with the default heating performance data.

Can u help me please?

 

I try to attach an image of COP curve:

 

Thanks.

 

Best regards,

 

Jacopo Valente



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