Study Of Diffusion Coefficient And Viscosity

Transport properties are widely used in chemical industry. Diffusion coefficients and viscosity are very important data for chemical engineering process. These two kinds of data are mostly obtained from experiments and semi-theoretical methods. There are still no effective theory to describe them well. In this work, we study mutual diffusion coefficients of non-associate fluids. Also, with free volume theory, this work studies relationship between transport properties and excess entropy. Theoretical and semi-theoretical models are created to calculate diffusion coefficients and viscosities for no-associated fluids.This work expands the function of self-diffusion coefficients to inter-diffusion coefficients for Lennard-Jones(LJ) chain fluids. Compared with real fluid mixture, the AAD (average absolute deviation) of the predicted coefficients for the mixture of 11 n-alkanes and 5 multi-atomic molecules are 4.81% and 5.12%, respectively, which are better than results of RLJ model. This work makes good result with no adjustment parameters, the precision is sufficient for industry.Base on free volume theory, this work generates viscosity from excess entropy. With this method, viscosities of hard sphere fluid model, hard sphere chain fluid model, LJ fliud model are calculated, relationship between viscosity and diffusion coefficient is also studied. Results fit MD data very well, The hard sphere chain fluid model is used to get viscosity data of n-alkanes, the results fit experiments well. LJ fluid model is derived from hard sphere model. With LJ fluid model, we calculate the viscosities of real fluids under different circumstance.