A study of convective heat transfer and pressure drop phenomena in curved microchannels

The research conducted in this paper was based on numerical simulation analysis that investigated the relationships between convective heat transfer and pressure drops and the flow patterns between conventional straight channels and curved microchannels. The main goal is to thoroughly investigate thermo-fluidic phenomena in curved microchannels and to determine the optimal design for the curved microchannel cooling system. Commercial numerical software (ESI-CFD) was used to simulate all cases studied in this paper. The computer simulated results were compared with actual experimental results to evaluate its accuracy. Six cases of different dimensions were studied. Results obtained from this study showed that when the dimensions of curved microchannels are smaller than 40 μm in height, conventional macro fluidic theory can still be used, since the numerically simulated results are in good agreement (<6% difference) with those obtained experimentally. Hydraulic diameter is the factor affects the pressure drop. Larger hydraulic diameter causes smaller pressure drop while smaller hydraulic diameter results in higher pressure drop. Secondary flow patterns and Nusselt numbers are also illustrated in this paper. When the Dean number is lower than 400, the pressure drop of fluid in 40 μm height models is similar to that found in straight microchannels. For the velocity profiles in the curved microchannels, the main stream is at the center of the curved microchannel first. But it is gradually offsets to the outer wall when the mass flow rates increases. The centrifugal force due to the curve geometry is the main reason that results in the shifting of the main flow toward the outer wall of the microchannel.