[Equest-users] MRT in eQUEST

[Sami, Vikram]

The surface property is really a surface temperature (not MRT). MRT<http://en.wikipedia.org/wiki/Mean_radiant_temperature> is not really a surface property of a single surface - its the average of radiant fluxes acting on a point in space. The point is the fluxes are a result of the view factors (solid angles) of the surfaces from that point - which is precisely why you cannot have a single MRT for a zone.

Vikram Sami, LEED AP
Sustainable Design Analyst
1382 Peachtree St. NE, Atlanta, GA 30309
t: 404-443-7462    f: 404.892.5823       e: vikram.sami at perkinswill.com   www.perkinswill.com<http://www.perkinswill.com/>
Perkins+Will.  Ideas + buildings that honor the broader goals of society


From: Alex Krickx [mailto:akrickx at seriousmaterials.com]
Sent: Thursday, July 01, 2010 4:33 PM
To: Sami, Vikram; Grando, John; equest-users at lists.onebuilding.org
Subject: RE: MRT in eQUEST

I read John's question as asking: can you get the MRT for each surface? - perhaps I misread it. I would assume, though, that if you could get it for each surface, than you could calculate the PMV of each zone. Your end result would show that zone A had -4 and B had +4 and they wouldn't be averaged together. This approach would understand and provide results that back up Vikram's point that a space near a façade will experience different MRT than a core zone. Is that not possible in eQUEST?

Regards,
Alex Krickx


Alex Krickx
Building Energy Specialist
[cid:image001.jpg at 01CB193B.ADF328B0]
1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124

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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Sami, Vikram
Sent: Thursday, July 01, 2010 1:17 PM
To: Grando, John; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] MRT in eQUEST

John,

I'm guessing you wouldn't be doing this analysis on a project unless you were concerned about thermal comfort issues from skin related stimuli.

So if you had a PMV of +4 in one zone and -4 in another would you say that on average everyone in your building is comfortable?

Calculating MRT in a lumped node simulation program is kind of like that - an average MRT for a zone is often misleading. For example - a room with a large west window in the summer time will have a much higher MRT for someone sitting next to the window than for someone sitting near an interior wall on the other side - especially if there is direct sunlight in the room. Similarly - in winter - proximity to a north window might result in a much lower MRT than for someone sitting near the core.
Bottom line - you pick the tool that's appropriate to the analysis. You really want a full-field solution tool (like a CFD program or a thermal software like RADtherm) to perform comfort analyses like this.


Vikram Sami, LEED AP
Sustainable Design Analyst
1382 Peachtree St. NE, Atlanta, GA 30309
t: 404-443-7462    f: 404.892.5823       e: vikram.sami at perkinswill.com<mailto:vikram.sami at perkinswill.com>   www.perkinswill.com<http://www.perkinswill.com/>
Perkins+Will.  Ideas + buildings that honor the broader goals of society


From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Grando, John
Sent: Thursday, July 01, 2010 3:36 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] MRT in eQUEST

Hello All,

I have to calculate the PMV for a zone and I did the analysis already in eQUEST.  I need the mean radiant temperature though to perform this calc.  I am pretty sure that MRT is not an output variable so I'm guessing I need to calculate the wall temperatures and do it myself.  Has anyone tried to do this before?  I didn't find anything in the archives or in the DOE22 manual.  Thanks.


John Grando LEED AP| Mechanical Engineer




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