Numerical analysis of heat transfer and flow characteristics of supercritical CO₂-cooled wavy mini-channel heat sinks

In today's world, thermal management in the components of new electronic and electromechanical technologies has become one of the most critical challenges in this realm. Generally, there is a high heat flux generating part in these instruments, so a robust heat dissipation or cooling system is required to guarantee their reliability and lifetime. Recently, miniature heat sinks have attracted the attention of many researchers, and the performance of air- and liquid-cooled heat sinks having wavy miniature channels has frequently been investigated. However, the heat transfer and flow characteristics of these cooling systems utilizing critical or pseudocritical carbon dioxide (CO₂) as the coolant have not been investigated yet and are still an unclear subject. To fulfill this gap, 3D simulations are carried out to scrutinize the thermal and hydraulic characteristics of CO₂ flow inside a wavy mini-channel heat sink at a uniform heat flux of 1000 kW m⁻². This study also aims to explore the effects of specific design factors, including wave amplitude (w_a) and wavelength (w_l), at different inlet temperatures (from 305 to 310 K) and mass fluxes (500–2000 kg m⁻² s⁻¹) of the CO₂ flow. The simulations start with the validation of the numerical results with the available experimental data, in which the deviations lie within ±2%. The results endorse that replacing the straight mini-channels with the wavy ones can enhance the thermal performance of the heat sink by an average of 1.86 times associated with an average pressure drop increment of 1.58 times. The maximal heat transfer coefficient of 8.58 times is obtained at the lowest inlet temperature of 305 K, whereas the maximal pressure drop of 5.65 times is observed at the highest inlet temperature of 310 K. The results suggest that larger wave amplitudes and smaller wavelengths contribute to the larger heat transfer coefficient values. However, these factors become less influential when the inlet temperature increases. Imposing a lower inlet temperature can significantly improve the overall performance. A maximal performance index of 4.41 is obtained for a model with w_a = 1.0 and w_l = 5 mm at the inlet temperature of 305 K.