Award Date

1-1-1996

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Committee Member

Samir Moujaes

Number of Pages

98

Abstract

A two-dimensional finite element model is developed to simulate the thermal performance of a residential attic. The attic is ventilated using an evaporative cooler for the occupied space which vents its exhaust air into the attic. The attic is also ventilated by outside air introduced at the perimeter(soffit) of the attic ceiling and is exhausted at the ridge of the roof; The thermal effects of an installed Attic Radiant Barrier System (ARBS) on the underside of the roof are also investigated. The model is steady state in nature using different solar insolation fluxes and ambient temperatures as driving functions at several discrete hourly values during the day. A ({dollar}k-\varepsilon{dollar}) turbulent model has been used to describe velocity and thermal distributions in the attic. Several recirculation zones have been observed in the attic which seem to suggest the existences of convective cells. Also the effect of lowering the emissivity on the underside of the roof was investigated. This emissivity reduction seems to raise the temperature on the underside of the roof and increase the average bulk temperature of the air leaving the attic while reducing the net heat flux passing through the ceiling insulation. Variations of temperatures have been shown to exist at the edges of the inclined surfaces and insulation especially at the locations of inlet and outlet vents of the attic. Finally, the model will give some correlations, and be compared with the existing correlations, of the length averaged convective heat transfer coefficients on the underside of the inclined surfaces of the roof due to the combined forced and natural flow over these surfaces. (Abstract shortened by UMI.).

Keywords

Attic; Barrier; Dimensional; Element; Finite; Heat; Model; Residential; System; Transfer

Controlled Subject

Mechanical engineering; Civil engineering

File Format

pdf

File Size

2314.24 KB

Degree Grantor

University of Nevada, Las Vegas

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