[Equest-users] Modeling Under Floor Air Distribution (UFAD) system & Heat Pump Chiller

Wed Jan 26 20:05:37 PST 2022

Heatpump chillers with UFAD is the system type of the very first building energy simulation model I was ever tasked with building.  Suffice to say, like most first efforts in life, that was probably the worst model I ever built… but I sure learned a lot and the challenges of modeling that system arrangement stuck with me!  I haven’t been actively practicing eQuest for a while, but I think I can offer a leg up in this instance.

The EDR guidelines Phil extracted/shared will probably forever stand as a useful and appropriate resource to reference for bridging/informing approach for energy simulation in DOE2.  It specifically addresses UFAD from an general/office occupancy perspective. Today, I draw this distinction only to point out if you are dealing with a data center, the best approach with modern DOE2.3 may look a little different than typical/office scenarios.

Also I’d add for context that the EDR guidelines were published chronologically before ASHRAE Standard 62.1 made some substantial advancements/developments in addressing thermal displacement ventilation.  I would treat the specific guidance within that EDR document as a “foundation” to be considered, understood, then tweaked to align with your present-day system designers’ considerations, calculations, and decisions around ventilation delivery.  By way of example, you can go further than suggested/prescribed by the EDR document to not only re-appropriate thermal loads, but to also create new/dedicated under-ceiling “interstitial” plenum zones (with air walls) to better simulate a situation where you can assert buoyancy effects will be in play (as opposed to perfect mixing).  I’ve taken those lessons learned and applied to simulations of other spaces without UFAD and deliberate TDV such as auditoriums, atriums, and ice hockey rinks.

That said, you are also asking about heat pump chillers.  In DOE2 terms (semantics), if I’m correctly guessing the real-world equipment is 2-pipe (there’s a hydronic loop delivering either chilled or hot water to a single coil), then in DOE2.3 terms I think you might be happy with a CHILLER of TYPE = HEAT-PUMP and CONDENSER-TYPE = AIR-COOLED.  I’d suggest review/reference at Volume 2: Dictionary > HVAC Components > CHILLER > Air-to-Water Heat-Pump (HEAT-PUMP, AIR-COOLED).   Be mindful the number of air-side systems which can attach to a circulation loop of type 2-PIPE are limited and that probably merits separate consideration against your actual equipment.

Following is a visual example I slapped together to show what that may look like in the interface if you were to define post-wizards… I’m not certain this sort of chiller arrangement is something the wizards can set up for you however, so you may need to do what I did and create the associated loop/pump/chiller manually (after wizards):
[cid:image005.png at 01D8137C.76C00DC0]

I hope some of this is helpful!

~Nick

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Nick Caton, P.E. (US), BEMP
ニック ケートン, P.E. (US), BEMP
Senior Energy Engineer
Energy Manager, Yokota Airbase
ESS - Energy & Sustainability Services
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Email
+81 . 070 . 3366 . 3317
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From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Phil Jordan via Equest-users
Sent: Thursday, January 27, 2022 2:05 AM
To: Ahmad Fraij <fraij at yahoo.com>; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Modeling Under Floor Air Distribution (UFAD) system & Heat Pump Chiller

[External email: Use caution with links and attachments]

________________________________

Hi Ahmad,

I have some guidance from the now-defunct Energy Design Resources<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.av8rdas.com%2Fenergy-design-resources.html&data=04%7C01%7CNicholas.Caton%40se.com%7C29909216f5a2458a907708d9e0ee0771%7C6e51e1adc54b4b39b5980ffe9ae68fef%7C0%7C0%7C637788136493126993%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=OkXFnZ9BGJj2K%2BIe9v2SAZ%2BBc%2BKYghbdocC03fOuFfY%3D&reserved=0> that discusses how to model underfloor air distribution in eQUEST (attached - I extracted this from a larger document to reduce the filesize); I believe this guidance is from 2006 but hopefully it still holds.

Regards,

Phil Jordan

From: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>> On Behalf Of Ahmad Fraij via Equest-users
Sent: Tuesday, January 25, 2022 4:33 PM
To: Fraij via Equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] Modeling Under Floor Air Distribution (UFAD) system & Heat Pump Chiller

EXTERNAL email. Please exercise caution. This e-mail is from a sender outside of CLEAResult. Do not click any links or open any attachments from unknown senders or unexpected email. ***************************************************
Hello Guys,

I am modeling a building, which has Under Floor Air Distribution (UFAD) system so, how to model this system in eQUEST software? I could not find a specific system called UFAD or Under Floor Air Distribution to select in eQUEST software.

Further, the building has air source heat pump chiller that provide cooling in summer and heating in winter so, how we can model heat pump chiller in eQUEST software? How can we assign the same heat pump chiller for both the chilled water loop and the hot water loop?

Your help will be highly appreciated.

Regards

Ahmad
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