[bldg-sim] Overhead Radiant Heaters

[Jon Maxwell]

I think you're on the right track.  I don't have a paper to offer, just an
opinion that I have loosely correlated with field observations.  Reduce the
temperature for two reasons:  (1) People are comfortable at a lower
temperature with radiant than convection heating.  So reduce your modeled
inside setpoint a couple of degrees on account of that.  (2) Radiant
delivers major stratification-related savings as well.  With a 40- to 50-ft
ceiling and forced air heat, you might have to maintain 90F air at ceiling
in order to have 70F air at the 5-ft high thermostat.  That means the
average inside temperature is 80F even if the setpoint is 70F.  Radiant
won't have that problem.  So that would be another 10F reduction on the
average inside temperature.

Third, by eliminating the aforementioned stratification you will reduce the
stack effect-driven infiltration.  This can have a measurable effect on the
heating load if your building is not pressurized with a lot of OA.

Fourth, check your candidate equipment rated efficiencies.  Depending on
venting and burner types a radiant heater can be more efficient than a
convection unit.

Jon Maxwell
Aspen Systems

----- Original Message ----- 
From: "Mike Tillou" <miket at etcgrp.com>
To: <bldg-sim at gard.com>
Sent: Friday, October 28, 2005 10:04 AM
Subject: [bldg-sim] Overhead Radiant Heaters


Hi all,

I am currently modeling an overhead radaiant heating system in a large
industrial building.  The application is similar to a Public Works
garage, large overhead clearence (50' center height), insulated metal
building, space doesn't have to be heated but they need heating for
employees at the ground level.

I plan on using DOE2.2 because I don't have the budget for using a more
appropriate modeling tool.

Does anyone have good ideas about how to approach this using a DOE 2.2
model?

My initial thoughts have focused on reducing the space temperature
setpoint but how much is appropriate 2 degrees , 5 degrees or 10 degrees
?   Are there any papers or articles that discuss air temp vs mean
radiant temp of the surrounding mass while using overhead radiant
heaters?

Many thanks in advance for any help/guidance that can be offered.

Mike


Michael Tillou, PE
etc Group, Inc.
PO Box 7, Williamstown, MA 01267
ph. (413) 458-9870 fx. (413) 458-9875
www.etcgrp.com





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