Effects of condensate film flowing on condensation heat and mass-transfer deterioration on some regions within water-recovery module consisted of micro-porous ceramic membranes

Abstract

Heat-transfer deterioration is a thermal phenomenon existing one or multiple wall temperature fluctuation along the flowing direction on porous heat-transfer surface. Effects of condensate film on deterioration phenomenon for non-condensation heat-transfer process has been reported in the literature, but for condensation process is seldom proposed and specifically researched. Here, the condensation heat and mass-transfer characteristics on micro-porous ceramic membrane module is investigated experimentally and numerically, with absolute humidity of artificial flue gas, inlet temperature of cooling water, volume flux of cooling water covered the ranges of 0.6375–0.6845 kg/m3, 294.4–297.2 K, 0.32–0.41 m3/s, respectively. Sudden temperature fluctuation and collapsing water-recovery efficiency are observed nearby 1/3 region of the ceramic membrane module, which corresponds to the fact that remaining condensate film induces large thermal resistance because of the low thermal conductivity of the gas-like phase, and causes fluctuation of temperature gradient (i.e. condensation heat-transfer deterioration) on membrane surface. It is found that, condensation-regime transition range decreases to 0.763–0.781 at 1/3 region of membrane module, which results in a more remarkable permeation hysteresis effect and a more dominant capillary condensation process. The present findings of this paper are helpful to optimize the design parameters and operation conditions of micro-porous ceramic membrane modules.