[TRNSYS-users] COP Type 941 Ait to water Heat Pump

[Paris Pasqualin]

Hi Miriam,

You could read the 06-HVACLibraryMathematicalReference.pdf in the documentation of the TESS Models which shows all the calculations for Type941.

Best regards,
Paris Pasqualin
From: TRNSYS-users <trnsys-users-bounces at lists.onebuilding.org> On Behalf Of trnsys-users at lists.onebuilding.org
Sent: 21 March 2022 12:02
To: TRNSYS users mailing list at OneBuilding.org <trnsys-users at lists.onebuilding.org>
Cc: miriam di matteo <dimatteo.1585179 at studenti.uniroma1.it>
Subject: [TRNSYS-users] COP Type 941 Ait to water Heat Pump


Dear all users,

About the Type 941 (Trnsys v.17):

  *   First: can you confirm if I understand its functioning? I use it only for heating, at the moment.
  *   Second: I believe that the values of the COP it isn’t correct, or I don’t understand it. The COP trend depends on the external files with the heating performance data, is it? In this file I have:
Capacity increases when the entered water temperature decreases and the air temperature increases ( <Tin,w and >Tin,a → >Capacity)
Power increases when the entered water temperature increases and the air temperature decreases ( >Tin,w and <Tin,a → >Power)
So the COP increases when the entered water temperature decreases and the air temperature increases ( <Tin,w and >Tin,a → >COP). But the simulation gives opposites results. The external files are wrong? or I misunderstand the Type functioning?
I tried to calculate the COP with excel and the results come out as per the provision, therefore different from TRNSYS' results.

About the first question:

I know as Parameters:

  *   Specific Heat of Liquid Stream
  *   Blower Power (pb)
  *   Total Air Flowrate (Fa,d)
  *   Rated Heating Capacity (qh,d)
  *   Rated Heating Power (ph,d)

and as Input:

  *   Inlet Liquid Temperature (Tin,w)
  *   Inlet Liquid Flowrate (Fin,w)
  *   Inlet Air Temperature (Tin,a)
  *   Inlet Air Humidity Ratio
  *   Inlet Air % Relative Humidity
  *   Heating Control Signal

and as external files

  *   Heating and cooling catalog data for the capacity and power as a function of entering the water and air temperature (fc=f(Tin,a;Tin,w) and fp=f(Tin,a;Tin,w))

So when the simulation running:

  1.  The Type 941 reads the air and water entering temperature (Tin,w and Tin,a)
  2.  Interpolates the heating performance file and multiplies this “performance factor” by HP Rated capacity and power. (fc(Tin,a;Tin,w) and fp(Tin,a;Tin,w))
  3.  So obtain Capacity and Power as a function of entering the water and air temperature by each time step. (qh(t)=fcqh,d and ph(t)=fpph,d)
  4.  Calculates the COPh as a ratio between qh(t)/(ph(t)+pblower) , i put paux=0

Is it correct??

Thank you in advance,
Regards,
Miriam Di Matteo
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