Non-newtonian flow modelling based design of plate heat exchangers

Abstract

Plate heat exchangers (PHEs) are widely used in food industries for processing liquid products, because of their high thermal effectiveness, ease of maintenance and cleaning, high heat exchange rate and demand of relatively small floor area.  As many food products are non-Newtonian fluids, particularly pseudoplastic in nature, it is important to study nature of their flow and heat transfer characteristic in PHEs.  Aqueous solutions of carboxymethylcellulose (CMC) at different weight concentrations (0.2%, 0.4% and 0.6%) and 25 ≤ N_Re,_gen ≤ 250 and at different inlet temperatures (50°C, 60°C and 70°C) were considered as operating conditions.  Using data obtained, relations between dimensionless numbers (N_Nu, N_Pr and N_Re,gen) were established.  Pressure drop across inlet and outlet of PHE was measured for each run and correlations between friction factor and generalized Reynolds number were established for different concentrations.  To study flow pattern of CMC fluid through narrow gap between two plates, simulation was carried out using FLUENT 6.3 software by supplying actual experimental conditions.  Theoretical method is suggested for predicting temperatures of fluids after each pass of PHE.