SEDL / STP / STP1116-EB / STP16357S

Combined Conduction, Radiation Heat Transfer and Mass Transfer in Fibrous Attic Insulations

Gorthala, R
University of MississippiFlorida Solar Energy Center, UniversityCape Canaveral, MSFL

Roux, JA
University of MississippiFlorida Solar Energy Center, UniversityCape Canaveral, MSFL

Fairey, PW
University of MississippiFlorida Solar Energy Center, UniversityCape Canaveral, MSFL

Pages: 16    Published: Jan 1991

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Abstract

A numerical model to study heat transfer in an attic insulation has been developed. This model comprises combined conduction, radiation, and moisture transport. The one-dimensional energy equation, radiative transport equation and species equations for liquid H²O and vapor H²O were solved simultaneously. A control volume based finite difference method was used to solve the energy equation and the species equations. A quasi-analytical technique (method of discrete ordinates) was used in solving the radiative transport equation. Standard fiberglass insulations with and without a foil radiant barrier were modeled. Heat transfer results were compared with the experimental data measured at the Florida Solar Energy Center. Predicted heat fluxes agree with measured fluxes quite well. All the cases studied with moisture present were also studied for the dry cases (no mass transfer) and the results were compared. Results with moisture being included indicate that heat transfer from the attic into the house decreases for fiberglass insulations during summer as compared to dry insulation.