Guidelines for Modeling Projecting Fenestration Products

Date Published
01/1998
Publication Type
Journal Article
Authors
LBL Report Number
LBNL-40707
Abstract

Heat transfer patterns in projecting fenestration products (greenhouse windows, skylights, etc.) are different than those with typical planar window products. The projecting surfaces often radiate to each other, thereby invalidating the commonly used assumption that fenestration product interior surfaces radiate to a uniform room air temperature. The convective portion of the surface heat transfer coefficient is also significantly different from the one used with planar geometries, and is even more dependent on geometry and location. Projecting fenestration product profiles must therefore be modeled in their entirety. This paper presents the results of complete cross section, variable film-coefficient, 2-D heat transfer modeling of two greenhouse windows using the next generation of window specific heat transfer modeling tools. The use of variable film-coefficient models is shown to increase the accuracy with which simulation tools can compute U-factors. Simulated U-factors are also determined using conventional constant film coefficient algorithms. The results from both sets of simulations are compared with measured values.

Journal
ASHRAE Transactions
Volume
104, Part 1
Year of Publication
1997
Place Published
San Francisco, CA
Custom 1
<p>Windows and Daylighting Group</p>
Organizations
Research Areas
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