Numerical and experimental investigation of buoyancy effects in a plate heat exchanger

This paper presents an experimental and numerical investigation of the hydrodynamic and thermal fields in a two-channel chevron-type plate heat exchanger (PHE) under mixed convection conditions. Eight pairs of experiments were performed, with water on both sides, with Reynolds number varying between approximately 100 and 400. Each pair consisted of two experiments: one with aiding mixed convection and the other with opposing mixed convection conditions. The temperature distributions on the end-plates, the outlet temperatures, the heat flux and the Nusselt number obtained in the two positions of the PHE were compared. A validation of the numerical model in this flow regime has been made in order to analyze numerically the pressure losses and the flow structure. Comparisons of the experimental data obtained for the fluid outlet temperatures, heat transfer rate and Nusselt number showed that the heat transfer is improved under aiding mixed convection conditions. The numerical data analysis shows that opposing mixed convection deteriorates the symmetry of the flow distribution inside the PHE's channels and that aiding buoyancy forces cause higher pressure losses. (C) 2012 Elsevier Ltd. All rights reserved.