Entropy generation analysis on thermo-hydraulic characteristics of microencapsulated phase change slurry in wavy microchannel with porous fins

Abstract

• Combined design enables smaller temperature gradient and more uniform temperature. • Larger h m and lower ΔP can be concurrently gained in wavy MCHS with porous fins. • Thermal entropy is three orders of magnitude larger than the frictional entropy. • Thermal entropy increases with heat flux but the frictional entropy is opposite. • Lower irreversible losses can be achieved at the cost of higher power consumption. Recent advancement in micro/nano-scale electronic systems, the need for efficient heat dissipation has become more rigorous, and traditional thermal management solutions are facing enormous challenges. In this study, a novel combined design of wavy microchannel heat sink (MCHS) with porous fins and microencapsulated phase change material (MPCM) suspension is developed and numerically studied to achieve a balance between flow and heat transfer behaviors. The equivalent heat capacity method is adopted to deal with the phase change process of microcapsule particles in steady and laminar states, and the Brinkman–Darcy–Forchheimer model based on the volume-averaged method is employed to characterize the fluid flow in porous fins. A three-dimensional solid-fluid conjugate model is established based on the finite-volume method to investigate the effects of different coolant types (water and MPCM suspension), geometric parameters (wavy amplitude, wavelength, and channel width ratio), and working conditions (inlet flow velocity, heat flux, and slurry concentration) on the thermo-hydraulic properties and entropy generation of wavy MCHS. The results reveal that the combination of porous fins and MPCM suspension presents smaller temperature gradient and more uniform temperature distribution than conventional design. Larger heat transfer coefficient and lower pressure drop can be simultaneously obtained in wavy MCHS with porous fins than in solid fin configuration. The thermal entropy generation is three orders of magnitude larger than the frictional entropy generation, and the Bejan number is close to 1 for different microchannel configurations. Thermal entropy generation increases with increasing heat flux but the frictional entropy generation decreases. Lower irreversible losses can be achieved at the expense of greater pumping power consumption caused by increasing inlet velocity and suspension concentration. The superior effect of wavy MCHS with porous fins using MPCM suspension as coolant has been observed in all cases.