Numerical studies on the hydraulic and thermal performances of microchannels with different cross-sectional shapes

Abstract

This paper numerically investigates the hydraulic and thermal performances of water flow in microchannels with three different channel cross-sectional shapes of rectangle, ellipse and isosceles triangle by solving the 3-D steady and conjugate heat transfer model. Two different microchannel size limitations are applied; one limitation is constant microchannel cross-sectional area and the other one is constant microchannel perimeter. The present work finds that both the hydraulic resistance and convective heat transfer coefficient of microchannel with given cross-sectional shape decrease as the increasing microchannel hydraulic diameter. Among the three shaped microchannels with the same hydraulic diameter under each size limitation, the triangular-shaped microchannel has the smallest hydraulic resistance and the smallest convective heat transfer coefficient; however, for the elliptical- and rectangular-shaped microchannels, there is a switching hydraulic diameter to distinguish their hydraulic and thermal performances. The rectangular-shaped microchannel has larger hydraulic resistance and larger convective heat transfer coefficient when their hydraulic diameter is smaller than the switching value, but the elliptical-shaped microchannel has larger hydraulic resistance and larger convective heat transfer coefficient when their hydraulic diameter is larger than the switching value. The present work gives the approximate correlations to determinate the switching hydraulic diameter under different size limitations.