HEAT TRANSFER IN A SINGLE VERTICAL TUBE CONDENSER-SUBCOOLER

Abstract

A model for a vertical a condenser-subcooler is described. It is based upon tests performed with: - a monotubular pyrex condenser equipped for flow visualisation, - two metallic monotubular condensers-subcoolers (a steel one and a copper one) heavily equipped with measurement devices. Visualisation tests have shown that there is a sharp discontinuity between the condensation zone and the lower part of the tube. In this region (the flooded zone), the condensate completely fills the tube section. The limit between these two zones is stable in time and space. The model is built on the following assumptions: - the liquid film reaching the interface between the condensation and the flooded zones develops a hydrodynamical behaviour compared to a wall jet, - in the flooded zone, a mixed convection phenomenon occurs. Longitudinal temperature profiles measured along the tube axis are adequately described by selected correlations. Generally the new, simple model gives a better agreement than previous correlations, especially in the flooded zone; in some cases, the improvement for design reaches 100%.