Thermal and hydraulic performance of microencapsulated phase change material slurries in a microchannel heat sink

Abstract

The distinctive capability of Phase Change Materials (PCMs) to store and release thermal energy during the phase change process makes them important materials for tackling the energy efficiency-related challenges faced by modern compact energy systems. In this context, the present study explores the thermal and hydraulic performance of microencapsulated phase change materials (mPCMs) with a specific melting point of 37°C within a microchannel heat sink (MCHS) operating under convective heat transfer conditions. Various performance parameters, including the thermal boundary layer (TBL), bulk fluid mean temperature, wall temperature, the local and average Nusselt numbers (Nu), the pressure drop (ΔP) across the MCHS, and the performance evaluation factor (PEF), were investigated under varying mass concentrations (5–15 %) and inlet velocities (0.55–1.20 m/s) of the mPCMs. The increase in the Nu and ΔP was found to be 21 % and 16.7 %, respectively, at an inlet velocity of 1.2 m/s and a mass concentration of 15 %. The PEF was found to reach a maximum value of 1.29 for a mass concentration of 10 % and an inlet velocity of 1.2 m/s. The PEF is a quantity that balances the gains achieved in heat transfer with the associated penalties due to the increase in pressure drop. These pressure drop penalties typically occur due to an increase in the viscosity of the slurry due to the rise of the mass concentration of the mPCMs. Parametric sensitivity analysis for key thermophysical properties, confirmed the robustness of the CFD model under ±10 % variations. The significant improvement in the thermal performance of the mPCM slurry underscores its potential for heat transfer and thermal energy storage in modern energy systems. Integrating mPCMs with microchannel heat exchange systems will enhance the energy efficiency of modern thermal energy storage and heat transfer systems and reduce operational and maintenance costs.

Keywords: Heat transfer enhancement, Hydraulic performance, Microchannel heat sink, Phase change material, Performance evaluation factor