Study Based On The Digital Image Holographic Interferometry Measurement Of Liquid Mass Diffusion Coefficient

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. The theory of digital image holographic interferometer and it's application in the experiment of mass diffusion coefficient measurement are discussed in this paper.(1) 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.(2) Theoretical analysis foundation for holography reconstruction, namely, Fourier transform theory is presented. The fundamental theory of the recording and reconstruction of optical holography and digital holography were represented in details. With the diffraction theory of angular spectrum, frequency domain algorithm in object field reconstruction is discussed.(3) 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.(4) By starting with the optical holography experiment, the author completes designing the experiment in which the holographic interferometry hologram is recorded with CCD.The achieved approach of digital holography was introduced. The program of digital processing holographic images is written by MATLAB, and the interference pattern is clearly reconstructed.The mass diffusion coefficients of KCL aqueous solution at temperature 291.8K, 294.7K, 298.8K, 299.8K, 305.4K, 308.5K and 315.2K and at condensation 0.33mol·L-1 were measured to verify the accuracy and reliability of the system. Compared with the data from literature, the measurement results show that the absolute average of relative deviations is 1.3%. The mass diffusion coefficients of saccharose aqueous solution at temperatures ranging from 288.15K to 338.15K and at condensation 0.1mol·L-1 were also measured. The system can provide a new effective method for measuring the mass diffusion coefficient of new refrigerants and new fuels.