CONJUGATE HEAT TRANSFER DURING FALLING FILM EVAPORATION

摘要

An analytical solution is derived for a transient conjugate heat transfer problem in three domains: a solid wall, an evaporating falling liquid film, and a flowing gas. The physical model comprises a vertical wall, heated on one side by radiation and convection and cooled on its other side by two fluids: a falling water film at the top and by rising air from below. At a certain location along the wall the initially subcooled water film becomes saturated due to heat absorption from the wall. The water film then evaporates and eventually dries out completely further downstream, thus forming two moving fronts at the saturation and dryout lines. Making some simplifying assumptions, the problem is formulated as a set of 1-D time dependent equations. Combining the wall and coolant equations leads to a unified hyperbolic type equation, which is solved by employing Riemann's method. The present analysis is applied to assess the performance of a containment cooling system of an advanced nuclear reactor. [References: 12]