Study Of A New Mass Transfer Model Of CFD And Its Application On Distillation Tray

The first part of this paper presents the state-of-art of the application of CFD (Computational Fluid Dynamics) to the chemical engineering and analyzes the the roles of CFD and mass transfer theory played in this application. A brief introduction is given for the conventional unsolved problems of fluid dynamic field as well as a detailed description of the approaches about the scalar field theory. In the past 10 years, the application of CFD in chemical engineering results a breakthrough in the aspects of engineering technology and theoretical consideration. The use of cross-disciplinary treatment to investigate the turbulent diffusivity and mass transfer by fluid dynamics and chemical engineering theory may deepen the computational development in the field of chemical and process engineering. In this paper, a new model was developed, which considered the influence of concentration field in calculating the turbulent diffusivity. The liquid flow on the distillation sieve tray was simulated using model. The influence of mass transfer on the turbulent diffusivity was studied and the result was compared with the turbulent diffusivity data in literatures. Description of three experiments using hot film anemometer is given in rear part of this paper. They are: 1, the velocity measurement of liquid flow field of single phase tray, 2, the measurement of local gas hold-up on the tray, and 3, local characteristics analysis of two phase flow on the tray using wavelet transform. In the last experiment two turbulent time scales of turbulent flow on the tray were acquired. They are large time scale of 2~3s corresponding the influence of bubbles passing through the liquid layer on the tray, and small time scale of roughly 0.969s corresponding the influence of liquid phase. The local distribution of signal turbulent energy on the tray; the typical profiles of signal turbulent energy in the main flow region, circulation region and region near the wall were summarized. The experimental results were used to analyze the turbulent flow on the tray. The development of model dealing with the concentration field on the tray reveals that the entry of chemical engineering theory into the calculation of turbulent diffusivity is necessary. However, the application of wavelet transform in the analysis of turbulent flow on the tray could be looked as the outset of the spectrum dynamics in chemical engineering. Should the parameters needed in the scalar calculation model be obtained according the spectrum from chemical engineering experiment, the CFD and computational mass transfer would become thoroughly suitable for the use in chemical engineering!...