Enhanced thermo-hydraulic performance with two-phase flow boiling in wavy microchannel heat sink – A numerical investigation

This article demonstrates that using a wavy microchannel instead of a smooth microchannel can enhance thermal and hydraulic performance in both single and two-phase flow. Various performance parameters such as Nusselt number (Nu), friction factor (f), performance factor (PF), and enhancement factor (EF) are estimated for different wavy microchannels with varying waviness and amplitudes. The two-phase heat transfer coefficient (HTC) varies significantly with heat flux, particularly due to nucleate boiling. The heat transfer improvement with a wavy microchannel is evident with the highest values of the Nusselt number ratio (Nutp/Nusp = 2.35), PFwavy = 1.4, and EF = 1.88 achieved at specific operating conditions (heat flux = 100 W/cm2, mass flux = 188 kg/m2s, amplitude = 0.1 mm, wavelength = 1 mm). However, as mass flux, heat flux, and amplitude increase and wavelength decrease, the Nusselt number ratio Nutp/Nusp, PF, and EF decline due to the pressure drop penalty outweighing the benefits of heat transfer enhancement. The article also explores different designs of wavy microchannels for mitigating hot spots, including one with a decreasing wavelength along the flow direction and another with a shorter wavelength in the middle. However, these designs are more suitable for single-phase flow.