[Equest-users] MRT in eQUEST

[Alex Krickx]

Vikram,

Thanks for correcting me - I mixed up the terminology. I guess the point I was trying to make was, although MRT will vary throughout the zone at each point in space - is it unfair to take a representative point (say, at the center of each zone) and calculate the MRT at that point? In a perimeter zone during summer the MRT would be hotter closer to the window, and cooler closer to the core, so taking a central point would seem reasonable. What seems difficult to me would be to take the surface temperatures (which I am now assuming from your response we CAN retrieve from eQUEST), calculate the solid angles and figure out to automate the process for every zone...

I take your point that this is an average for the zone. My gut says as long as you're not averaging across a whole floorplate that this methodology would be sound. I don't mean to be contrary, I'm just interested in learning what the software is capable of.

Regards,
Alex Krickx


Alex Krickx
Building Energy Specialist
[cid:image001.jpg at 01CB1924.2045BF30]
1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124

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From: Sami, Vikram [mailto:Vikram.Sami at perkinswill.com]
Sent: Thursday, July 01, 2010 1:40 PM
To: Alex Krickx; Grando, John; equest-users at lists.onebuilding.org
Subject: RE: MRT in eQUEST

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 01CB1924.2045BF30]
1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124

Warning: The information contained in this e-mail may be privileged attorney-client communications or attorney work product and/or proprietary and confidential.  If the reader of this message is not the intended recipient then you have received it in error and any review, distribution or copying of this message is prohibited and you are to notify us immediately by reply e-mail and delete the original message immediately.



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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