ISSN Online: 2377-424X
ISBN Print: 0-85295-345-3
International Heat Transfer Conference 10
A BOUNDARY-LAYER MODEL FOR TURBULENT FREE CONVECTION IN OPEN AND PARTIALLY DIVIDED ENCLOSURES
摘要
A mechanistic model for thermally driven turbulent free convection in open and partially divided enclosures is proposed. The model consists of the boundary-layer
equations for flow over two opposing vertical
walls; one warm and the other cool, and energy
and mass conservation for the enclosure core. For partially divided enclosures, mass and energy conservation for two-way flow through an aperture (orifice) connecting two cores is included. The boundary layer equations are reduced to one-dimensional form by
integral methods and solved by Runge-Kutta integration. The core and aperture equations are written in finite differences and, using relaxation, solved simultaneously with the boundary layers. The eddy diffusivity in the
core equations is determined by comparing with data but is approximately a factor of 40 larger than molecular. Because of the quasi one-dimensional approach taken in this model, the solution for a typical case is obtained
within a minute on a 486 personal computer;
much less than solving the complete Navier-Stokes
equations.
Temperature and heat transfer distributions are presented and compared with data of others. Agreement between test-cell and predicted core temperatures is found to be good. Predicted mean Nusselt numbers are generally within 10 percent of the experimental values; often within the band of experimental uncertainty. Orifice coefficients for the aperture range from 0.05 to 0.5 for apertures starting at an enclosure boundary. The coefficient is found to decrease with increasing aperture size.
Temperature and heat transfer distributions are presented and compared with data of others. Agreement between test-cell and predicted core temperatures is found to be good. Predicted mean Nusselt numbers are generally within 10 percent of the experimental values; often within the band of experimental uncertainty. Orifice coefficients for the aperture range from 0.05 to 0.5 for apertures starting at an enclosure boundary. The coefficient is found to decrease with increasing aperture size.