[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

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*ΔT to 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@lsbu.ac.uk




        

        

        
 

        

      

      

      

      

      
_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@cae.wisc.edu
https://mailman.cae.wisc.edu/listinfo/trnsys-users


    

    

    
-- 
***************************
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@tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com