[TRNSYS-users] total heating rate and total cooling rate in heat pump 954

[David BRADLEY]

Enyuan,
   The total cooling rate is the sensible and latent energy being 
removed from the air stream by the active section of the heat pump. It 
is computed as the mass flow rate of air multiplied by the difference 
between the enthalpy of air leaving the heat pump and the enthalpy of 
the mixed air (return + ambient) entering the evaporator. The heat pump 
does not have any kind of economizer controls built into it. The amount 
of outdoor air being mixed with return air is simply a function of how 
you have set the outdoor air damper position input. It could be that 
your heat pump is cooling because there is no ambient air being mixed in 
and the heat pump is working only with return air. If your concern is 
that the heat pump would not operate when the ambient temperature is so 
low (because of freeze up in the condenser) then you have to be careful 
of your external data file. Performance is interpolated within the range 
of data given in the file but it is not extrapolated beyond the range. 
If the heat pump asks for cooling (because of the way you have set the 
cooling signal input and fan control signal) then the performance 
(cooling capacity and COP) will be returned for the closest ambient 
temperature found in the data file.
Regards,
  David


On 11/19/2014 14:26, Enyuan Hu wrote:
> Dear all,
>
> When I'm using a type 954 air-to-air heat pump to condition a one zone 
> building, I found that even during the winter (ambient temperature is 
> below the cooling threshold), the 'total cooling rate' output from the 
> heat pump is positive instead of being zero as expected. Can anyone 
> help me explain why? Thanks!
>
> best regards,
> Enyuan Hu
>
>
> _______________________________________________
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> TRNSYS-users at lists.onebuilding.org
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
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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