Experimental Study on Subcooled Pool Boiling in Microgravity Utilizing the Drop Tower Beijing (NMLC)

摘要

A temperature-controlled pool boiling (TCPB) device was developed to perform pool boiling heat transfer studies at both normal gravity and microgravity. A platinum wire of 60 μm in diameter and 30 mm in length was simultaneously used as heaters and thermometers. The heater resistance, and thus the heater temperature, was kept constant by a feedback circuit. The fluid was R113 at 0.1 Mpa and subcooled by 24 nominally for all cases. The results of the experiments at both normal gravity and microgravity in the Drop Tower Beijing were presented. Nucleate and two-mode transition boiling were observed. For nucleate boiling, the heat transfer was slightly enhanced, namely no more than 10% increase of the heat flux was obtained in microgravity, while the bubble pattern is dramatically altered by the variation of the acceleration. For two-mode transition boiling, about 20% decrease of the heat flux was obtained, although the part of film boiling was receded in microgravity. A scale analysis on the Marangoni convection surrounding bubble in the process of subcooled nucleate pool boiling was also presented. The characteristic velocity of the lateral motion and its observability were obtained approximately. The predictions consist with the experimental observations.