A theoretical and numerical investigation of heat and mass transfer within the evaporator of a capillary pump loop is presented. In this system a wet porous structure is heated by metallic fins and the vapor resulting from the phase change is evacuated through the grooves. Owing to the high thermal resistance of the vapor zone that forms under the fins, superheating is important. Moreover as the pressure drop increases, the efficiency of the loop is reduced. To improve the efficiency of the system the authors propose to control the extension of the vapor zone allowing the vapor to escape between the whick and the fin through a small gap. With this in mind, an evaporator with a thin gap between the whick and the fin is studied. For the same power load and subcooling as in the study without gap, numerical simulation of phenomena inside the wick shows that when a gap exists the liquid vaporizes under the fin, then flows to the groove. This result has two main consequences: firstly, the wick remains liquid saturated and with the cinematic viscosity of the liquid being lower than of the vapor, the pressure drop through the evaporator is lower. Secondly, as the mean thickness of the vapor zone located between the fin and the liquid-vapor interface inside the wick decreases the thermal resistance decreases, and the superheating obviously decreases too.
Investigation and analysis of a porous evaporator for a capillary pump loop
Untersuchung und Analyse eines porösen Verdampfers im Kreislauf einer Kapillarpumpe
1996
8 Seiten, 17 Bilder, 5 Quellen
Conference paper
English
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