HEAT AND MASS TRANSFER IN DISPERSED, 2-PHASE, SINGLE-COMPONENT FLOW

The process of heat transfer to a two-phase mixture of well-dispersed subliming particles and vapor, flowing over a heated surface, is analyzed. It is shown by a laminar boundary layer analysis that, when the surface-area per unit volume of the particle (or solid) phase is large enough, the phase change dominates the heat-transfer process and hastens the development of the thermal boundary layer. Under these conditions, the thermal boundary-layer thickness not only becomes uniform a short distance downstream from the starting point, but also is substantially less than it would be were the particle phase absent. For such systems, the equations describing the heat-transfer process can be considerably simplified and, if the physical properties of both phases are uniform, a remarkably simple solution results. For systems in which the physical properties are not uniform, a solution involving integration across the boundary layer is developed. The solutions are applicable to developing, as well as fully developed, laminar boundary layers over a flat plate; the solutions also approximate conditions in flow through a tube, provided that the tube radius is large compared to the thermal boundary-layer thickness. The predictions of this theoretical analysis agree satisfactorily with experimental results. With slight modification, the same approach may possibly be applicable for turbulent flow in the boundary layer. © 1969.