Modeling and Design of Micro Groove Falling Film Evaporators

Abstract

In the present study, heat transfer in a falling film micro groove evaporator has been simulated by an analytical model. The flow and thermal fields were divided in two regions, i.e. macroscopic flow inside the groove and the microscopic flow where intensive evaporation takes place at the thin film interline region. For the micro region model, pressure in the liquid film was expressed as a sum of surface tension and disjoining pressure effects. The film thickness profile was obtained by solving the 4th order differential equation by Runge-Kutta method. Then, this micro region model was combined with the macro region model. Macro region model solves one dimensional bulk flow inside the groove with gravitational effect taken into account. Constant curvature of the liquid vapor surface was assumed for the macro flow. It is shown that the gravitational force is essential for providing the liquid to wide range of heat transfer area. Thus, diverging branch evaporator is investigated. It is demonstrated that this concept has large potentiality for improving the performance of the micro groove falling film evaporator.