[bldg-sim] Overhead Radiant Heaters

[Fred Porter]

All;
Be afraid of any savings computed using a lower space temperature. See 
ASHRAE Transactions 89-17-5 which showed no savings of IR tube heating 
compared to unit heaters and measured very high stratification in the 
space. While the MRT for employees at floor level can be equivalent at 
lower floor level air temperatures, these heaters seem to convect 
considerable heat up from the heater, leadng to high temps at the 
ceiling and perhaps no difference in bulk average room air temperatures 
that define the majority of heat losses in these spaces due to door 
infiltration. If air is exfiltrating at the ceiling at other times, the 
nice warm air will be the first to go. Some of the heaters will probably 
be installed with reflectors tilted to direct heat from heaters at the 
outer edge. Intuitively this greatly increases the upward convected 
fraction of heat output. The slab is also warmed which may lead to 
increased losses, though better comfort. The savings that can be shown 
via methods in ASHRAE Systems(?) are based on theoretical perfect 
distribution of heat from the tube, and no increased losses at the 
ceiling or slab.
Fred

Mike Tillou wrote:

> 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_* <file://www.etcgrp.com>*
> *
>
>
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-- 
Fred W. Porter
Senior Engineer
Architectural Energy Corp.
2540 Frontier Ave. Suite 201
Boulder CO 80301
email: fporter at archenergy.com
fax: 303-444-4304

office: 303-444-4149 x225
mobile: 303-748-4536


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