Heat Transfer and Flow Characteristic of Sinusoidal Wavy Microchannel Heat Sink With Different Phase Shift

Abstract

Microchannel heat sinks (MCHS) are promisingly utilized to remove large heat flux from microelectronic devices. However, the velocity and thermal boundary layers grow continually in a straight microchannel. As a result, the performance of the microchannel degrades. Disrupting the formation of the boundary layer can enhance the performance of MCHS. One approach to achieve that goal is to develop a wavy channel rather than a straight microchannel (s-MCHS) which hinders the continual growth of boundary layers due to its waviness. Numerous researches suggested that wave amplitude increment and wavelength decrement enhanced the chaotic advection and better coolant mixing. Thus, heat transfer and pressure drop were increased in the MCHS. Although wavelength and wave amplitude in a wavy MCHS (w-MCHS) significantly impact heat transfer performance, the phase shift (θp) between two wavy walls in an MCHS also affects the flow and heat transfer characteristics. When the upper and lower sinusoidal walls are in different phases, the cross-sectional area of the MCHS varies. So, the cross-sectional flow area variation creates an adverse pressure gradient in the MCHS. which causes more flow reversal and better coolant mixing, resulting in improved thermal performance. The current study aims to study the flow and heat transfer characteristics in w-MCHS for three different phase shifts, θp = 0, π/2, π, under laminar flow conditions. Re ranges from 300 to 800 in the study. w-MCHS with phase shift, θp = π/2, π always shows higher Nusselt number (Nu) than s-MCHS and w-MCHS with phase shift, θp = 0. An increase in surface area due to phase shifts, θp = π/2 and θp = π in wavy MCHS, is negligible and the enhancement in heat transfer of phase-shifted w-MCHS is caused by interruption, reinitialization, and reattachment of boundary layers. In the current numerical study, Nu was found to increase with the phase shift and found 7 times higher than s-MCHS at phase shift, θp = π for wavelength (λ) = 3.5 mm. Besides higher heat transfer and better coolant mixing, the phase shift in wavy MCHS causes increased shear stress and pressure drop due to chaotic flow in wavy MCHS.