[TRNSYS-users] Simulating an existing installation using a water-water heat pump

[David BRADLEY]

Metkell,
   Typically the sign of Q is used to determine whether it is a heating 
load or a cooling load. Cooling loads should cause a rise in temperature 
of course so I think that with your equations below you'd want q to be 
negative so that dT comes out negative and T2 comes out greater then T1.

   The answer to your second question depends a bit on the heat pump 
technology that you are modeling. A single stage heat pump will not 
provide a constant supply temperature. Single stage heat pumps have a 
constant speed compressor and so essentially run at capacity whenever 
they are on. Type927 models such a heat pump. Recently heat pumps with 
variable speed compressors have become more common. These devices often 
try to maintain a constant supply temperature by modulating the speed of 
the compressor.
Kind regards,
  David


On 2/19/2014 06:51, metkell yebiyo wrote:
> Dear TRNSYS Users,
> I am using a water-water heat pump (Type 927) to simulate an existing installation.
> I have the heating and cooling demand profiles of the building, therefore I use an equation with the formula Q=m*Cp*?Tto calculate the returning temperature of the fluid (T2) in the load loop for each time step.
> Flow rate = 6.8 l/s
> Cp = 4.18
> dT= (Q*3600)/(Flowrate_to_Load*Cp)
> T1 = Constant
> T2 = T1-dT
> Q = heating or cooling load
> 1. when calculating dT how do I differentiate between the heating and cooling data?
> 2.Should the return temperature (T1) from the heat pump be constant or is there another way of calculating the return temperature?
> For the load loop the only components I use are the heat pump, one equation and a single speed pump.
> Thank you in advance.
> Regards,
> Metkel Yebiyo BEng (Hons), MSc
> CEREB PhD Researcher - Ground Source Heat Pumps
> Room T615
> Department of Urban Engineering
> Faculty of Engineering, Science and the Built Environment
> London South Bank University,
> 103 Borough Road,
> London SE1 0AA
> Tel: +44 (0)20 7815 7639
> E: yebiyom at lsbu.ac.uk <mailto:yebiyom at lsbu.ac.uk>
>
>
>   
>
>
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> TRNSYS-users at cae.wisc.edu
> https://mailman.cae.wisc.edu/listinfo/trnsys-users

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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
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d.bradley at tess-inc.com

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