[TRNSYS-users] Direct Expension Solar Assisted Heat Pump System

Candy He candyhe at graduate.hku.hk
Wed Jul 18 08:10:39 PDT 2007

Dear all,

I am trying to model a direct expansion solar assisted heat pump system and I am wondering whether I can build up the system in TRNSYS 16.1? In this system, the solar collector is serpentine and is also used as the evaporator of the heat pump, with the refrigerant evaporating from the liquid to the vapor. Do we have the expansion valve module in TRNSYS library? Can the compressor module in TRNSYS be used to compress the refrigrant rather than air? Can the vertical storage tank module be used in the case that the refrigrant is circulating inside the heat exchanger? Thanks in advance.

Best Regards,

Candy He
Research Assistant
City Univercity of Hong Kong
  ----- Original Message ----- 
  From: Jeff Thornton 
  To: Julian Demetz ; trnsys-users at engr.wisc.edu 
  Sent: Tuesday, May 15, 2007 1:56 AM
  Subject: Re: [TRNSYS-users] Solar Assisted Heat Pump System

  "Since I'm using Trnsys for the first time I have some questions about modelling the heat pump: 
  Which Type (also from TESS-Library) should I use to model the heat pump? " 

  I would recommend using Type 504 from the TESS libraries - it was written for exactly this type of situation. 

  "How can I control the input # 5 "Heating control function" of type 20? Is it calculated internally or has it to be connected with an Output from the solar collector (Output # 1, Type1b, "Outlet Temp"??)." 

  It's not calculated internally and should not be connected to the solar collector. This input is used to turn the heat pump on and off and should be connected to some device that is sensing the heating demand (the load the heat pump is meeting) - likely a thermostat, aquastat, or equation. You'll also need a controller and some valves to control the flow of water across/around the heat pump. I've attached a simple schematic that may help you set it up. 


  Jeff Thornton 
  President - TESS, LLC 

  2916 Marketplace Drive - Suite 104 
  Madison WI 53719 USA 

  Phone: 608-274-2577 
  Fax: 608-278-1475 
  E-mail: thornton at tess-inc.com 
  Web: www.tess-inc.com 


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