[Equest-users] loop to loop heat pump for preheat coils

[Maryanne Mason]

Alper

 

The main problem I see with your approach is that you are essentially
putting the heat pump in series with the district cooling plant. eQuest
currently will not do series chillers. However, if you have the option to
split the plant cooling load so that the heat pump and district plants are
parallel, you should be able to use the loop to loop model.

 

I have modeled a similar system using canal water instead of return water
from cooling coils. A loop to loop heat pump model assumes that your heat
source goes through one of two heat exchangers instead of going directly
into the chiller. 

 

In your case, the evaporator loop would be a local loop between the heat
exchanger and chiller, while your condenser loop would be the LTHW loop
serving the dedicated outdoor air units. You would also need a ground loop
heat exchanger of the "Lake/Well" type connected to your heat source (CHR)
loop.

 

Since you probably have no heat exchanger, just specify the evaporator loop
with similar conditions to the cooling coil return water.

 

I have attached a copy of the schematic to help clarify the operation -
Figure 34 most closely resembles your situation.

 

 

 

Regards,

 

MaryAnne Mason 
Mechanical Engineer 
Process Infrastructure 
  
Ausenco Sandwell 
1016B Sutton Drive, Suite 100 
Burlington ON L7L 6B8 
Canada 
  
T   +1 905 319 1698 
F   +1  905 319 1801 
E    <mailto:maryanne.mason at ausencosandwell.com>
maryanne.mason at ausencosandwell.com 
W   <http://www.ausenco.com/> www.ausenco.com 

 

Regards

 

 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Fred Betz
Sent: Thursday, October 21, 2010 3:06 PM
To: Alper Erten; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] loop to loop heat pump for preheat coils

 

Alper,

 

To my knowledge there is no way to do this within eQuest. 

 

What we do is output the hourly loads to a spreadsheet and apply them to
heat pumps or heat recovery chillers in TRNSYS. 

 

There is a lot of leg work required to setup a functioning system including
controllers, inputting performance maps, etc.

 

This has worked very well for us in several HP and HRC applications. If this
is for a LEED project, it must be documented separately as an exceptional
calculation.

 

Fred

 


Fred Betz  PhD., LEED AP 
Sustainable Systems Analyst

 

AEI | AFFILIATED ENGINEERS, INC.  
5802 Research Park Blvd. | Madison, WI  53719

P: 608.236.1175 | F: 608.238.2614  
 <mailto:fbetz at aeieng.com> fbetz at aeieng.com  |   <http://www.aeieng.com/>
www.aeieng.com  

 

 

From: Alper Erten [mailto:Alper.Erten at BuroHappold.com] 
Sent: Thursday, October 21, 2010 2:02 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] loop to loop heat pump for preheat coils

 

Hi all,

 

I am trying to simulate a heat pump which will recover heat from chilled
water return pipes to provide preheat for the dedicated outdoor air units in
a cooling dominated building. This is my first time trying to model heat
recovery with heat pumps, so I appreciate any help with it.

 

The chilled water system is a district cooling plant which I modeled using a
chilled water meter. The heat pump would be in operation only when there is
a cooling demand and will be providing heat for LTHW loop which will have
preheat coils attached to it. The remaining heating is done via electric
resistance heating coils of the air side system which i modeled as a
constant volume single zone system.

 

I am not sure if this the correct way but I am trying to use a loop-to-loop
heat pump with default library performance curves; but couldn't figure out
which loop types are appropriate for it? This heat pump type seems to
require a condensing water loop which is not present in the actual building
design, do I still have to create one in the model? Also the regular
condensing water loop is not appropirate to be attached to a loop-to-loop
heat pump. Does this have to be a lake/well loop?

 

I am also trying to simulate a similar type of heating for the domestic hot
water. In the actual system, service water is preheated to an intermediate
temperature via heat pumps that recover heat from the chilled water loop
return and the secondary stage heating is done via electric resistance water
heaters. Is it possible to model this in Equest? 

 

Thanks in advance,

Alper Erten, PE, LEEDAP

 

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