Analysis of Heat Transfer in Several Media

Analytical solutions to three heat transfer problems, each involving more than one medium, are obtained by using some exact and approximate methods. I. In particular, for the analysis of nucleate boiling at a solid surface, a single bubble is simulated by a point source (or a sink) of liquid. A solution of the boundary layer type is obtained for a constant point sink, and it is used to estimate the microlayer thickness, a quantity useful in determining some features of latent heat transfer due to vapor flow within the bubble. II. The thermal effects of droplets condensing on, or evaporating from, a solid surface are analyzed by solving the steady heat-conduction equation for a spherical segment droplet on a semi-infinite solid with suitable boundary and interface conditions. Expressions for the temperatures, the over all heat flow and the lifetime of an evaporating droplet are obtained. From these expressions, the effects of the solid properties and the contact angle are predicted. III. Estimates of long-time thermal contact resistances are obtained by considering the transient thermal response of two semi-infinite bodies in contact over (1) a circular disk; and (2) a series of identical, equally spaced strips. The unsteady heat equation is solved by using suitable interface conditions with each solid being at an initially uniform but different temperature. The solution is valid for large values of the Fourier number.