Thermal Transport and Flow Dynamics of Viscoplastic Nanofluids in Ventilated Enclosures Using a Two-Phase Numerical Framework

A numerical study on the mixed convection of nanofluid, modelled as a Bingham plastic fluid, in a ventilated enclosure has been conducted, considering the relative slip velocity between the fluid and nanoparticles. The enclosure, with heated walls, is ventilated by an inlet on one vertical wall for cold fluid injection and an outlet on the opposite vertical wall for fluid outflow. This study utilizes a two-phase model for the nanofluid to examine the thermal performance of the viscoplastic nanofluid within the ventilated enclosure and assesses the impact of yield stress on the flow field. The governing equations are numerically solved using a control volume approach. Heat transfer analysis is performed by evaluating the average Nusselt number, entropy generation, cup mixing temperature, and average pressure drop between the inlet and outlet of the enclosure. Slip mechanisms resulting from Brownian diffusion and thermophoresis lead to a higher heat transfer rate, distinguishing the results from those of the homogeneous model. The effects of key governing parameters, including Reynolds number, Richardson number, nanoparticle bulk volume fraction, nanoparticle diameter , and the Joule heating parameter, are determined. In all cases, the enhancement in heat transfer due to nanoparticle inclusion is found to be greater than the increases in entropy generation and pressure drop. While the yield stress of the Bingham plastic fluid adversely affects heat transfer, it promotes thermal mixing. This study provides valuable insights into the behaviour of viscoplastic nanofluids in ventilated enclosures, with implications for optimizing heat transfer and flow characteristics in practical applications.