[Equest-users] [Bldg-sim] Modelling air cooled heat recovery chiller in eQUEST

[Brian Fountain]

Good morning Syed,

What you are describing can be modelled in a reasonably straightforward fashion in eQUEST.

My first observation is you will have to use DOE-2.2 rather than DOE-2.3 in eQUEST.  While the heat recovery keywords are implemented in DOE-2.3, it is not recovering heat to the hot water loop in build 7175 (DOE2.3-50h).

Specifying heat recovery on a chiller – either air cooled or water cooled – is done by adding the loop that the heat will be recovered to the HTREC-LOOP keyword.  You will be prompted for what percentage of the condenser heat is available for heat recovery (i.e. is it desuperheat which might be 25% or condensing heat recovery where almost all the heat is available).

[cid:image002.png at 01D62A95.C292C2A0]


The key input on the chiller is on the Loop Attachments tab:
[cid:image004.png at 01D62A92.6D2D3780]

The MAX-RECOVER-T is the highest temperature that will be recovered.  You will likely want to set this to 120°F.  If the return water temperature of the heating loop that you are recovering to exceeds this value, you will not recover any heat to the loop.  Whether this is an issue with your DHW system will depend on the amount of recirculated water in the loop.  With no recirculation the chiller would always recover heat to the DHW loop however I can envision a situation where the recirculation flow is set too high increasing the return water to the DHW heater above the MAX-RECOVER-T preventing heat recovery.  If you are not seeing heat recovery from the chiller, you may want to create an hourly report on the loop that heat is being recovered to and look at the loop temperature returning to the plant.



Here is an example .sim where I am attempting to recover heat from an air cooled chiller to a hot water loop set at 180°F.  Not surprisingly, no heat recovery.
[cid:image005.png at 01D62A92.E1FB1A50]

By reducing the hot water loop temperature, we now see that heat is being recovered from the chiller and that the boiler load is reduced correspondingly.  This is an air cooled chiller example.

[cid:image006.png at 01D62A95.B83E4270]

I hope this helps.

Regards,

Brian


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Brian Fountain
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From: Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> On Behalf Of Syed Safiuddin Hussaini via Bldg-sim
Sent: May 14, 2020 10:35 PM
To: bldg-sim at lists.onebuilding.org; rintveld at ptrenergy.com
Subject: [Bldg-sim] Modelling air cooled heat recovery chiller in eQUEST

CAUTION: EXTERNAL SENDER
Hi All,

The building that I am modelling in eQUEST has an air-cooled heat recovery chiller wherein the rejected heat from air cooled condenser is utilized to preheat the domestic hot water to the domestic hot water heater.

Is there a workaround in eQUEST for modelling the above system configuration?

Thank You



Syed Hussaini, PE, LEED GA

Energy Engineer II

________________________________

Partner Energy

680 Knox St., Suite 150 |Los Angeles, CA 90502
D: 310-622-8851 | C: 480-512-9739 | F: 310-862-2399

www.ptrenergy.com<http://www.ptrenergy.com/> | shussaini at ptrenergy.com<mailto:shussaini at ptrenergy.com>

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