[Bldg-sim] Water to Water Heat Pumps (UNCLASSIFIED)

[Nick Caton]

I can probably fill in a little on the eQuest side of the coin:

 

My general understanding is that you should be able to use either Trace
or eQuest to model process efficiency which varies with the ground loop
temperature.

 

I approached this once in eQuest, and based on that experience and as I
think others have brought up, you're restricted to using a CW loop of
the lake/well type, which means you must define for the program what the
temperature behavior of the GLHX is over the year (as a schedule). 

 

Once the groundwater temps are dealt with, from there you can either use
the default loop-to-loop chiller curves in the eQuest library, or define
your own.  The three curves separately define the following:

1.       Effects of part load on the EIR  (EIR-fPLR)

2.       Effects of temperatures on the capacity  (CAP-fT)

3.       Effects of temperatures on the EIR  (EIR-fT)

 

Unlike centrifugal chillers, finding the manufacturers data necessary to
make your own custom curves in DOE2/eQuest is not a trial by fire - all
the data for the above curves may be found on a single spec sheet
without conversions, depending on who your WWHP manf is...  There are
some restrictions regarding pump quantities and behavior of the
"loop-to-loop chiller" system  - I'd advise you to carefully review the
DOE2 dictionary entry and diagrams for "Loop-to-Loop Heat-Pump" to get
an sense of how the equipment behaves and how you may need to react
accordingly to match your proposed design.

 

I'd also refer you to not miss a recent writeup/report posted to
eQuest-users by Dana Troy detailing a strategy/feasibility study to
approach multi-stack heatpumps in eQuest... something I could've used in
the afore-mentioned project.

 

Best of luck!

 

~Nicks

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Alex Chapin
Sent: Tuesday, February 22, 2011 2:00 PM
To: John.S.Eurek at usace.army.mil; trace-users at lists.onebuilding.org;
bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Water to Water Heat Pumps (UNCLASSIFIED)

 

In TRACE:

 

The help file (press F1 on any screen in TRACE) and User's Manual are
pretty helpful with how to model geothermal heat pumps, I would suggest
reading through those first. In terms of modeling the appropriate ground
loop temperatures and associated WWHP efficiency, there are a couple of
ways of doing it (see help file and User's manual for specifics). Just
keep in mind that when you create a new WWHP in the Cooling Equipment
library and define the Full Load Energy Rate and the Design Entering
Condenser Water Temperature, you need to base them on the worst case
entering loop temperatures over the year. TRACE assumes you enter the
efficiency at the hottest and coldest entering condenser temperatures
for Cooling and Heating efficiency respectively and then uses the Power
Consumed and Ambient Modification Unloading Curves to adjust the
efficiency for air-side load and change in entering loop temperature.

 

In eQUEST:

 

I'm a little rusty on eQUEST, but this is how I remember it. You can
enter the ground and well properties for your site and system which will
be the basis of entering loop temperature for the equipment as a
function of the load on the equipment over the year. eQUEST wants the
equipment efficiency at ARI conditions and then you enter the unloading
curves (see help/Documentation for more info on this). The concept here
is similar to TRACE but from what I remember it is more detailed.

 

Thanks,

 

Alex Chapin, E.I.T., LEED AP BD+C

Energy Engineer

2rw Consultants

T: 434-296-2116 ext. 305

F: 434-977-1862

 

P Please consider the environment before printing this e-mail - Thanks!

 

Message: 1

Date: Tue, 22 Feb 2011 10:37:34 -0600

From: "Eurek, John S NWO" <John.S.Eurek at usace.army.mil>

To: <trace-users at lists.onebuilding.org>

Subject: [Trace-users] Water to Water Heat Pumps (UNCLASSIFIED)

Message-ID:

      <
57E9627AE82514439A8F543A61BFDD6807D574F1 at NWO-ML3OMA.nwo.ds.usace.army.mi
l>

      

Content-Type: text/plain;     charset="us-ascii"

 

Classification: UNCLASSIFIED

Caveats: NONE

 

The EER of WWHP can vary from 11.8 to 23.3 depending on the water
temperature returning from the well field.  Can Trace model this?

 

We are designing a lot of geo-thermal heat-pumps. If we can't model the
benefit of the well-field accurately, we can't model the energy use.

 

John Eurek PE, LEED AP

Mechanical Engineer,

US Army Corps of Engineers

Omaha District CENWO-ED-DA

1616 Capitol Avenue

Omaha, NE 68102

Phone: (402) 995-2134

email: john.s.eurek at usace.army.mil

 

 

Classification: UNCLASSIFIED

Caveats: NONE

 

 

 

 

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