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Thermal Analysis of Effect of a Compartment Fire on Window Glass. September 1, 1988-August 31, 1989.


pdf icon Thermal Analysis of Effect of a Compartment Fire on Window Glass. September 1, 1988-August 31, 1989. (707 K)
Joshi, A.; Pagni, P. J.

NIST GCR 90-579; NISTIR 4449; 23 p. June 1990.

U.S./Japan Government Cooperative Program on Natural Resources (UJNR). Fire Research and Safety. 11th Joint Panel Meeting. October 19-24, 1989, Berkeley, CA, Jason, N. H.; Cramer, D. M., Editor(s)(s), 233-252 pp, 1990.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB90-244468

Keywords:

glass; windows; mathematical models; radiation; thermal stresses; vents; thermal analysis

Abstract:

Glass breaking in fires is an important practical problem since a window acts as a wall prior to breaking and as a vent after breaking. As Emmons explained, windows break in fires due to thermal stress from the differential heating of the central portion and the shaded edge. If the depth of shading around the edge is much greater than the glass thickness, one can assume that the edge remains at its initial temperature. This paper determines the surface temperature history, [equation] of the glass. The temperature at breaking is when [equation] where [equation] and [equation] both give the strain at breaking in tension. The glass coefficient of linear thermal expansion is alpha, the glass modulus is epsilon and sigma b is its tensile strength. Typical property values suggest the range of 50 deg C-100 deg C for the breaking T. Here the transient, one-dimensional (into the glass normal to the pane), inhomogenous (in-depth radiation absorption) energy equation is solved using an innovative Laplace Transform technique suggested by Baum. Time varying equations are solved numerically by using the trapezoidal rule for numerical integration and Newton-Raphson's method for determining the roots on non-linear equations. Results are presented for typical values of the governing dimensionless parameters.