Design characteristics of corrugated trapezoidal plate heat exchangers using nanofluids

Abstract

In this paper, fully developed turbulent flow and heat transfer behavior in trapezoidal channels using nanofluids are numerically studied. This study evaluates the effects of four different types of nanoparticles, Al2O3, CuO, SiO2 and ZnO, with different volume fractions (0-4%) and diameters (20-80nm) under constant heat flux (6kW/m2). The effects of geometrical parameters (wavy amplitudes, longitudinal pitch) of the trapezoidal channel on the thermal and flow fields are also examined. The results indicated that SiO2 has the highest Nusselt number among the nanofluids. Enhancement of heat transfer increases with particle volume concentration, but a slight increase in pressure loss with decreasing nanoparticle diameter is also observed. When nanofluids are used in a forced convection, 10% increase in average Nusselt number is observed for nanoparticles with a diameter of 20nm and at 4vol.%. Analysis of the flow and heat transfer in a corrugated trapezoidal channel is made based on the comprehensive evaluation factor J/f. The optimum (J/f) enhancement shows that the CuO nanofluid, lower concentration ratio of nanoparticles, trapezoidal height of 2.5mm and a longitudinal pitch of 6mm are the most desirable parameters for saving energy. Using nanofluids with a corrugated channel can improve the thermal performance because it can lead to more compact heat exchangers.