[bldg-sim] Radiant Heating/Cooling

sjudson at noresco.com sjudson at noresco.com
Tue Apr 13 05:31:49 PDT 2004


I am curious how you modelled the performance of the gas fired radiant tube
heating. My experience has been that conventional load calculation and
simulation techniques do not work well with these systems.


-----Original Message-----
From: Jon Maxwell [mailto:jmaxwell at aspensys.com]
Sent: Monday, April 12, 2004 11:46 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] Radiant Heating/Cooling


I have modeled the savings for radiant systems for unvented low intensity
gas fired radiant tube heating systems in high bay warehouses and
manufacturing facilities in particular by:

    1. Reducing the setpoint dry bulb temperature a few degrees because
human comfort with radiant heating is reached at a lower ambient than with
convection heating systems.  I am certain that comfort research supports
this.
    2. Reducing the setpoint temperature a few more degrees because there is
less floor-to-ceiling temperature stratification. With the desired
temperature at belly button level, radiant systems will have a lower average
temperature floor-to-ceiling than unit heaters overall.
    3. Reducing the amount of infiltration, due to reduced stack effect, due
to reduced temperature stratification
    4. Increasing the heating system combustion efficiency slightly due to
having no intermediate media such as air or water between the combustion air
and the space to be heated and lack of venting.

While I cannot cite studies to validate the adjustments or quantify them
generally (though I have rules of thumb based on ceiling height), such an
approach has predicted savings roughly in the right ballpark, close enough
to make a do/don't do decision at least.

Would love to be able to cite rigorous research that proves or disproves my
approach.

Jonathan B. Maxwell, PE
Senior Engineer
Aspen Systems Corporation
710 Park Place
College Station, TX 77840
(979) 764-6779 wk
(979) 764-7810 fax
(979) 575-1281 mobile
jmaxwell at aspensys.com
www.OPUSPOWER.com
www.aspensys.com

----- Original Message ----- 
From: "Chris Jones" <cj at cr-jay.ca>
To: <BLDG-SIM at gard.com>
Sent: Monday, April 12, 2004 6:25 AM
Subject: [BLDG-SIM] Radiant Heating/Cooling


In your research with radiant heating cooling savings, have you found any
energy "savings" that can be attributed directly to the use of the radiant
system vs other systems (air supply in particular).  For example, I have
seen some papers that note that the heating setpoint can be relaxed while
still maintaining thermal comfort with a radiant system.


At 10:47 07/04/2004, you wrote:
>Dear All,
>
>For those interested in the simulation of radiant heating/cooling systems,
>IRC has developed a semi-analytical model for integration in energy
>simulation software that use the one-dimensional numerical modeling to
>calculate the heat transfer within the building construction assemblies.
>
>The model combines the one-dimensional model of the energy simulation
>software with a two-dimensional analytical model.  The advantage of this
>model over the one-dimensional one is that it accurately predict the
contact
>surface temperature of the circuit-tubing and the adjacent medium, required
>to compute the boiler/chiller power, and the minimum and maximum
>ceiling/floor temperatures, required for local moisture condensation
>(ceiling cooling systems), thermal discomfort (heating floor systems) and
>controls.  The model predictions for slab-on-grade heating systems compared
>very well with the results from a full two-dimensional numerical model.
>
>The model was implemented in the Canadian software HOT3000 and the UK
>software ESP-r as a plant component. The implementation of this model in
the
>ESP-r program offers additional flexibilities to the radiant system
designer
>community, mainly:
>·       Designers can use any control algorithm possible in ESP-r with the
>new plant component (e.g.., use the flux or temperature control, and
compare
>their performance).
>·       Designers can specify any number of radiant surfaces of the
building
>fed by the same or different heat source.
>·       Designers can size realistic radiant systems, and get realistic
>energy consumption (from the source side) and cost.
>
>
>A copy may be downloaded from:
>Laouadi, A. "Development of a radiant heating and cooling model for
building
>energy simulation software," Building and Environment, 39, (4), April,  pp.
>421-431, Apr, 2004
>(NRCC-46099)
><http://irc.nrc-cnrc.gc.ca/fulltext/nrcc46099/>
>
>
>Thanks
>
>Dr. Abdelaziz (Aziz) Laouadi
>Research Officer
>Indoor Environment Research Program
>Institute for Research in Construction
>National Research Council of Canada
>1200 Montreal Road, Building M-24
>Ottawa, Ontario, Canada, K1A 0R6
>Tel.:  (613) 990 6868;  Fax:  (613) 954 3733
>Email: Aziz.Laouadi at nrc-cnrc.gc.ca
>Web: http://irc.nrc-cnrc.gc.ca/ie/light/skyvision/
>
>
>You received this e-mail because you are subscribed
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Chris Jones, P.Eng.
14 Oneida Avenue
Toronto, ON M5J2E3
Tel. 416 203-7465
Fax. 416 946-1005

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