Modelling temperature and concentration polarization phenomena in ultrafiltration of non-newtonian fluids under non-isothermal conditions

Model for concentration polarisation (CP) and temperature polarisation (TP) in ultrafiltration process of non-Newtonian fluid has been developed, The model is applicable for plate and frame channels. The proposed solution is based on the following assumptions: (1) flow is to be laminar, incompressible and steady-state (2) fluid properties are independent of applied pressure and time under shear; (3) no slip at the wall; (4) the field of apparent viscosity has non-isotropic configuration, (viz., depends on local shear rate); The paper covers pseudoplastic and dilatant time-independent flow; (5) input approximations for temperature and concentration profile have parabolic configuration. Transport expressions for viscous, temperature and diffusion boundary layers are the core of the model. Integrating these equations over the control volume has been carried out. Proposed solutions give correlations between tangential fluxes of mass and heat and degree polarisation (degree of CP and degree of TP). It permits us to analyse the influence of parameters of hydrodynamic and concentration field, physical properties geometry of channel and on tangential distribution of TP and CP degree. The presented solution can be segmented and built into a complex algorithm of membrane processes. The solution does not contain digital integration. The paper includes developed algorithm, array of calculated data and graphical visualisations of solutions. (C) 2001 Elsevier Science B.V. All rights reserved.