The Heat And Mass Transfer During Composition-varying Evaporation Of Binary Mixture

Energy-saving and environmental requirements of the mixing refrigerants as current optimal alternative refrigerants get more and more extensive research and application. Because of temperature sliding phenomenon of mixture refrigerants or refrigeration unit reasons such as leaking, the mixture refrigerant composition changing will affect unit performance during operation of the system. For added refrigerants components to keep the mixtures excellent performance, it is necessary to calculate the amount added components.The research on component changes of mixtures in evaporation process is essentially solution of the thermal physical characteristics, such as heat transfer coefficient and specific heat. The problem is therefore estimation of thermal physical characteristics of mixtures by easily measured parameters such as temperatures or pressures and so on. For binary azeotropic mixtures, taking the alcoholic solution for example, based on the condition that the pressure of component first derivatives is zero at the azeotropic point, the Newton's method is used to calculate the pressure extremum, thus obtains the composition of the azeotropic mixtures. For binary non-azeotropic mixtures, one-dimension transient heat transfer model is established by using Levenberg-Marquardt method. Measured by test transient temperature data to predict the temperature in linear relationship with the heat conduction coefficient of thermal physical parameters, then the characteristic parameters of binary non-azeotropic mixtures during evaporation process are obtained.This paper discussed the thermal physical features of the mixtures changing during evaporation, comparing the differences in research method between binary azeotropic mixtures and non-azeotropic mixtures. It provided analysis and calculation in detail from theory and method of test. Some reference value of the theory and data in test will be applied in the future mixture refrigerants research or actual application.