Evaluating the efficiency and effectiveness of non-Newtonian fluid flow in a double-pipe heat exchanger with porous medium via numerical simulation

Abstract

In the present work, the convection heat transfer and pressure drop of the turbulent flow based on a non-Newtonian fluid were numerically investigated in a double-pipe heat exchanger with various porous rings by considering the inner tube under constant heat flux. The solution of 0.1% and 2% mass carboxy methyl cellulose in deionized (DI) water water was used as the base non-Newtonian fluid. The fluid flow and heat transfer in this study were modeled by using the RNG K-ε turbulent viscosity with the enhanced wall treatment. The non-Newtonian power-law method was used in ANSYS Fluent software to resolve the flow within the numerical solution domain in the double pipe. Furthermore, the thermal performance of the heat exchanger, and the effects of the geometry, number, thickness, and height of the porous rings at the various Reynolds numbers were studied. According to the results, using non-Newtonian fluid had a significant effect on the average Nusselt number and pressure drop which were increased by up to 40.1% and 10 times, respectively. The annular tube possessing six porous rings at Re = 4,000 and height = 2 mm, thickness = 6 mm, applying non-Newtonian fluid can improve the efficiency of the system by up to 11.25%. It also found that by increasing the porous thickness, the Nusselt number increased by up to 56.3% at its maximum. The results have demonstrated a satisfactory level of agreement with experimental and correlation data by comparing them with existing data in similar literature.