Thermal and hydrodynamic behavior of suspensions comprising nano-encapsulated phase change materials in a porous enclosure

Abstract

Nano-encapsulated phase change materials (NEPCMs) are known to enhance the thermal characteristics of fluids; therefore, there is a rising interest in employing these materials in future thermal control systems. This paper investigates hydrodynamic and thermal characteristics of nanofluids, NEPCMs mixed in the host liquid, in glass balls as a porous structure. The geometry is a two-dimensional porous square cavity in which the left boundary is hot, the right boundary is cold, and the horizontal ones are considered to be insulated. The NEPCMs are composed of polyurethane (PU) as shell and nonadecane as a core. The impact of different non-dimensional parameters, such as Darcy number, 10−5 ≤ Da ≤ 10−1, porosity, 0.4 ≤ ɛ ≤ 0.9, Stefan number, 0.2 ≤ Ste ≤ 100, fusion temperature, 0 ≤ θf ≤ 1, and volume fraction of the NEPCMs, 0 ≤ ϕ ≤ 0.05, is studied on the flow and heat transfer characteristics. It is shown that the volume fraction of NEPCMs is directly proportional to the strengthening of the heat transfer rate in such a way that applying 5% volume fraction of NEPCMs could enhance the heat transfer up to 20.1% and 14.1% at θf = 0.5 in comparison to the cases of pure fluid and NEPCM mixture with no core-phase change, respectively. The effect of non-dimensional fusion temperature on the rate of heat transfer is also found to be noticeable. The maximum average Nusselt number emerges at θf = 0.5, which is the optimum fusion temperature.