Effect of Channel Size on Heat Transfer and Pressure Drop in Thin Slabs Minichannel Heat Exchanger

Abstract

The effect of circular channel diameter on convective heat transfer and pressure drop behaviors in thin slabs minichannel heat exchanger is studied using a three- dimensional computational fluid dynamics ( ) modeling. De-ionized water and air are considered as working fluids and aluminum as slab material for the particular interest of the current study. In this study, four different channel diameters of 0.25, 0.5, 0.75, and 1 are considered. Investigation is evaluated for the liquid side Reynolds number of 100, 400, 700, 1000, and 1300. The simulations are performed with parallel processing of 8 CPUs using a finite volume method based commercial code. Three-dimensional double precision pressure-based absolute velocity formulation with parallel processing is employed. The constant temperature of 76 for water inlet and 14 for air inlet are considered for all cases in this study. The effects of channel diameter over liquid-side temperature drop, heat transfer coefficient, pressure drop, and Nusselt number are analyzed and reported in this paper. Results show that the changes in the pressure drop decreases with increasing channel diameter and decreasing Reynolds number; however, for higher diameter and lower Reynolds number, it is found to be negligible. For a constant Reynolds number, the heat transfer coefficient of water increases and the Nusselt number decreases with the increase of ⁄ . However, the Nusselt number of water is observed to be higher than that of the theoretical prediction because the flow in the current study is neither hydrodynamically nor thermally fully developed before the entrance and through most of the channel length.