Numerical study on free-surface jet impingement cooling with nanoencapsulated phase-change material slurry and nanofluid

The free-surface jet impingement technique operating with two-phase advanced coolants has recently drawn much favorable attention in cooling applications. However, numerical understanding of free surface jets along with improved realization of pros and cons associated with these advanced coolants remains a challenge. In this work, the flow and thermal performances of free-surface jet impinging on a heated copper plate are numerically investigated using water, nanoencapsulated phase-change material (NEPCM) slurry, and nanofluid as coolants. Three-dimensional continuity, momentum, and energy equations are discretized with a commercial finite volume code in accordance with a standard k-epsilon turbulence model. The volume of fluid multiphase technique is adopted in this study to model the free surface between the liquid jet and surrounding ambient air. A single-phase fluid approach is employed using existing models from other references to determine the effective thermophysical properties of NEPCM slurry and nanofluid. The predicted Nu and pressure drop calculations agreed well with the experimental data from references. Physical understanding of the effects of fluid jet inlet temperature, nozzle-to-target distance, and nanoparticle concentration is reported. The addition of both NEPCM and Al2O3 particles to water helps in improving the Nusselt number and decreases the stagnation point temperature with certain pressure drop penalty. The NEPCM slurry enhances the cooling performance of the system by improving its latent heat storage capability, whereas nanofluids improve the cooling performance by enhancing the effective thermal conductivity. The thermal performance can be further improved with increased particle concentration. The NEPCM slurry demonstrates performance superior to nanofluid working at the same particle loading. Overall, the proposed model can provide valuable guidelines for the use of advanced coolants in a free-surface jet impingement cooling system. (C) 2017 Elsevier Ltd. All rights reserved.