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Re: [TRNSYS-users] How to get constant outlet temperature from heat pump

Amirezza,

1) Most times you don't try and get a constant outlet temperature out of a heat pump (unless you have a variable speed heat pump) - you simply charge the storage tank using an on/off controller that watches the tank temperature and then you use a tempering valve on the load side to deliver the correct temperature water; bypassing some of the return water from the load around the tank and mixing with a fraction that goes through the tank.

2) I don't see any pipes in your flow loops.  Please consider adding them to allow for some thermal capacitance in the loops which will help control the system and provide more reasonable results.

 

Jeff

 

---
Jeff Thornton
President - TESS LLC
3 N. Pinckney Street, Suite 202, Madison WI USA 53703
Office: (608) 274-2577  Fax: (608) 278-1475
www.tess-inc.com
E-Mail: thornton@tess-inc.com

On 07/29/2021 2:46 am, Amirreza Heidari via TRNSYS-users wrote:

Hello,

 

I have a heat pump (type 938) that supplies hot water to two tanks, one for space heating and the other for domestic hot water. Because the return temperature of the hot water is varying a lot (from 50 C to 90 C), the outlet temperature of hat pump also varies a lot. I am designing a control method that only works based on turning ON and OFF the heat pump and supply pumps to adjust the temperature of building and hot water tank. The variations of heat pump outlet temperature has made the control process much more complicated and less efficient. I can use an auxiliary heater at the outlet of heat pump to make sure a constant outlet temperature, but this kind of heaters are not very energy efficient and I would avoid using them as much as possible. Is there any other way to make sure that my heat pump would produce a constant outlet temperature regardless of inlet temperature?

 

Thanks

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--------------------------------------------------------------------------------------------------------------------------------------------------
Amirreza Heidari
Department of Energy Engineering
Sharif University of Technology
Tehran-Iran
E-mail address:

heidari@energy.sharif.edu

amirrezaheidarysbu@gmail.com

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