Heat and mass transfer processes in two phase HeII/vapor

Modeling heat and mass transfer characteristics of two phase He II is discu ssed. The case considered assumes that the channel flow is one-dimensional and stratified, with mass exchange between the two phases. Two specific exa mples are considered in some detail. The first is the heat and mass transfe r characteristics for small liquid flow rate. Use of several simplifying as sumptions allows the problem to be reduced to solution of a one-dimensional ordinary differential equation. The result is a non-dimensional expression for the liquid level or void fraction along the channel. A set of dimensio nless parameters are defined that establish the relative contributions of v apor mass transport and counterflow in the He II. The model also predicts t he temperature profile and vapor mass flow rate. The second case concerns t he flow of liquid under nearly isothermal conditions with relatively small vapor mass flow rate. Under these conditions, the flow may be modeled using classical hydrodynamics taking into consideration the unique characteristi cs of the He II. Results of these models are compared to experimental data for heat and mass transfer in a two phase He II/vapor how. (C) 2000 Elsevie r Science Ltd. All rights reserved.