The Mathematical Description Of Liquid-phase Mass Diffusivity And Experimental Validation

Holographic interferometer has become a generally accepted and the most effective method today in the study of transport phenomena, it has been widely applied to precise, qualitative and quantitative measurement of various physical parameters in fluids such as velocity, temperature, concentration and density etc. with the advantages of high sensitivity and accuracy, large capacity of information, non-instructive and feasible to make instantaneous measurement and visualization instantaneous measurement and visualization in overall insight into the whole process. The molecular diffusivity in liquid phase is one of the most important dynamical parameter for describing mass transfer. Due to the lack of satisfactory theoretical model to predict liquid diffusivity, it necessitates to exploit a novel and accurate experimental technique in order to meet the need of practical utilization and validate theory.First,based on a lot of references, the author summarized and compared the merit and shortcoming of the predecessor. Digital image holographic interferometer is used to measure the mass diffusion coefficient of fluid.Second,based on studying tradition optical experiment system, a digital image holographic interferometer and a new system of diffusion cell are designed and constructed for the measurement of mass diffusion coefficient. The new diffusion cell makes the interface of diffusion samples clearer. The honeycomb on the under side of diffusion cell and a new method of inject liquids are designed, and it reduces the confusion when injecting. According to the design of diffusion cell, a temperature control system using circular waters is designed, and it makes the experiment processed under the precision of±0.1K.Based on the Second Fick Law, a mathematical model of mass diffusion was established by using the principle of diffusion process in semi-infinite plate. The maximum interference fringes parameters were determined with experimental method of Laser holographic interference, and the mathematical description of liquid-liquid mass diffusion coefficient was obtained. The maximum value of interference fringes produced by sucrose solution at a concentration of 0.10mol·L^-1 diffusing to water was measured at 15℃, and the mass diffusion coefficient of sucrose solution was calculated.The error is 3.67% and the standard deviation is 0.378 comparing to the values in other papers. The result demonstrates the accuracy of the diffusing formula using for the interference fringes maximum point, provides a beneficial reference to the research of mass diffusion coefficient theory for new refrigerants, which is urgently required in chemical engineering application.