Effect of Boiling Condition on Vapor Concentration during Boiling of Liquid Mixture

点击翻译按钮获取中文摘要

Recently, the utilization of the non-azeotropic working fluid in the cycle is developing for achieving high performance liquid-vapor two-phase cycle and for the various usage of the working fluid. It is important to clarify the characteristic of the vapor-liquid phase change process of the mixtures. The objective of the study is to clarify the effect of the boiling condition of liquid mixture in the nucleate boiling process on the composition of the generated vapor. The vapor concentration measurement was carried out in the bulk vapor layer in the saturated pool boiling process of water-ethanol and ethanol-acetone mixtures from the thin heated wires. Two kinds of measuring method ; the dew-point method by using the dew-point measurement and the known liquid-vapor equilibrium relation, and the laser light absorption method by using the property of infrared light absorption to the vapor of hydrocarbon were adopted. As the result, it was clarified that the vapor concentration in the bulk … More vapor layer which was generated by the nucleate boiling was in equilibrium with bulk liquid and was independent on the boiling conditions such as the degree of surface superheat and liquid layer height etc. Next, the change of the generated vapor temperature was measured in order to clarify the variations of the temperature and concentration change of vapor in the process of the bubble generation and departure. The vapor bubble, which was created on heating surface, had comparatively large degree of superheat. The selective condensation was occurred and the temperature also lowered in the process of the departure of the bubbles. As a result, the vapor in the bubbles attained to be in equilibrium with the bulk conditions almost at the height of 3-5 mm from the heating surface. Moreover, the temperature change of vapor bubble was determined by the elapsed time from the vapor bubble generation. Thus, it was clarified that the concentration of vapor layer existed in equilibrium with the bulk state in the system in which the steady boiling and condensation was occurred. Less