Numerical study of heat transfer in square millimetric zigzag channels in the laminar flow regime

Abstract

The present work deals with the simulation of heat transfer in zigzag millimetric channels with square cross-section of 2 mm width in the laminar flow regime. They consist of periodic zigzag units composed of straight sections and 90° bends with a curvature radius of 1.5 mm. The influences of fluid velocity and straight section length on the thermo-hydraulic performances are investigated. The results showed that by increasing the flow velocity or decreasing the straight section length between two bends, a transition from periodic flow to non-periodic flow can be observed. A thermo-hydraulic performance factor based on heat transfer enhancement and pressure drop penalty compared with a straight channel is then discussed. It is observed that the ratio of the Nusselt number in the zigzag channels to that in the straight channel is always higher than one. This ratio increases with increasing Reynolds number and values up to 6.4 are reached in the cases studied (Pr = 6.13). When the pressure drop penalty is considered in the performance factor, an enhancement is still observed with a factor up to 2.5. It is shown that non-periodic flow is not particularly interesting in terms of thermo-hydraulic performance compared with periodic flow.