滴状凝縮法による凝縮係数の評価 : エチレングリコールおよび水の凝縮係数

抄録

The purpose of the study is to obtain the experimental data on condensation coefficient for a future molecular-scale clarification of the mechanism of vapor-liquid phase transformation. Condensation coefficients of ethylene glycol and water were investigated by the dropwise condensation method based on the fact that the heat-transfer coefficient depends on an interfacial heat-transfer coefficient. Assuming the value of condensation coefficient, the heat-transfer coefficient can be calculated for the measured drop-size distribution. It should coincide with the actually measured heat-transfer coefficient, so that the condensation coefficient can be determined. To improve measurement accuracy, the effects of constriction resistance and of Knudsen number on the heat-transfer coefficient are considered. It is concluded that the condensation coefficients are 0.17∼0.45 for ethylene glycol at pressures between 0.24 and 1.57 kPa and 0.35∼0.7 for water between 1 and 3.5 kPa.