Numerical analysis for enhancing transferred heat in porous counter flow heat exchanger

Abstract

The numerical analysis is accomplished to simulate the heat transfer in double tube heat exchanger with and without porous media by utilizing ANSYS FLUENT 14.1. A geometry system is used to predict the heat transfers and pressure drop characteristics of the flow. Alumina (2.5mm diameter) as a porous media were added in to: inner tube (IP), outer tube (OP) and both tube of heat exchanger (IOP) were tested with the variation of hot and cold fluid inlet temperature, mass flow rate ratio (mr) to evaluate their influence on effectiveness of heat exchanger, Nusselt number, number of heat transfer unit. The evaluating has been performed in the steady-state. Water was used as a working fluid in a double tube heat exchanger. The study was conducted at the hot and cold water mass flow rates between ( 0.0166 - 0.0833kg / s), ( 0.05-0.116 kg/s) respectively. The inlet temperatures of cold and hot water were (20, 25 °C), (47, 55 °C) respectively. Noted from results that adding pad of porous increases effectiveness of the heat exchanger and the increasing rate of transferring heat as mass flow rate ratio increases and the highest value are obtained when alumina is in double pipe. Effectiveness decreases with increase in mass flow rate ratio but increases when using alumina as a porous media and the better value is obtained when alumina is in IOP, IP, OP and NP respectively. Effectiveness increased as the NTU increases.