Impact of tortuous geometry on laminar flow heat transfer in microchannels

Abstract

An experimental investigation of the hydrodynamic and heat transfer characteristics of water flowing through tortuous microchannels for Reynolds numbers ranging from 50 to 900 has been carried out. The microchannels have semi-circular cross-sections (diameter 2mm) and follow zigzag or sinusoidal pathways consisting of at least five repeating units. Conjugate heat transfer simulations in a straight channel are carried out to understand the complex thermal behaviours present in the current experimental design and to validate the experimental approaches. The integrated measurements of fluid flow and heat transfer offer capabilities for characterising the thermohydraulics of wavy microchannels. Experimental results show that significant heat transfer enhancement is achieved in wavy channels compared with the equivalent straight channel, although an increased pressure-drop penalty is also observed. A detailed flow dynamics study shows that the flow recirculation and secondary flow structures (Dean vortices) induced by the bend help to increase the heat transfer rates. The impact of geometrical parameters on flow and heat transfer performance is assessed. In addition, the stackability of channels on a plate structure is considered. Zigzag channel configurations which provide high heat transfer intensification, are well suited for the use in compact plate heat exchangers due to their significant heat transfer enhancement, as well as good stackability.