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In this paper, both experimental and numerical studies have been performed on the convective boiling heat transfer of the Ethanol-in-Polyalphaolefin (PAO) Nanoemulsions inside a heat exchanger of twelve 1mm diameter mini-channels that was subjected to a uniform heat flux at its outer surface. The heat transfer characteristics and the pressure drop of the Ethanol/PAO nanoemulsion was studied experimentally, meanwhile, the volume of fraction (VOF) model with Pressure-Velocity coupling based Semi Implicit Method for Pressure Linked Equations (SIMPLE) iterative algorithm is employed to simulate the same experimental conditions numeircally. The results reveal that the convective boiling heat transfer coefficient of the nanoemulsion can be greatly enhanced upon the nucleation of ethanol nanodroplets inside, in which a maximum 50% enhancement compared to pure PAO base fluid can be achieved under current test conditions. However, the thermal conductivity and viscosity of the nanoemulsions has an insignificant effect on convective boiling heat transfer coefficient based on the experimental results. The ANSYS FLUENT simulation results also agree well with the experimental data. The Ethanol-in-PAO nanoemulsion could function as a good alternative conventional working fluid in two phase heat transfer applications.

In this study, a numerical study has been performed on the two-phase heat transfer of a new nanostructured heat transfer fluid: Water-in-Polyalphaolefin (PAO) Nanoemulsion Fluid inside a mini-channel heat exchanger using ANSYS FLUENT. Nanoemulsion fluids are liquid suspensions of nanosized droplets, which are part of a broad class of colloidal dispersions. The nanoemulsion fluid can be formed spontaneously by self-assembly, in which these nanodroplets are in fact swollen micelles. To simplify the complexity of the numerical model, the nanoemulsion fluid was then treated as a homogenous fluid during single-phase and only the water vaporizes during the phase change. The volume of fraction (VOF) model with Pressure-Velocity coupling based Semi Implicit Method for Pressure Linked Equations (SIMPLE) iterative algorithm is employed to solve the continuity, momentum, energy equations in two dimensional domains. The thermophysical properties of the nanoemulsion fluid were measured and used for the current simulation. The results were verified using the experimental results and has shown good agreement. This study has demonstrated the feasibility of simplyig the simulation of flow boiling heat transfer of this new heat transfer fluid through treating it as a homogenous fluid during single-phase convective heat transfer and separating the vapor phase of the nano-micelles during flow boiling. This study has also shown that this Water-in-PAO nanoemulsion could function as a good and alternative conventional working fluid in heat transfer applications.