Natural convection heat transfer of nanofluid in a cavity under an inhomogeneous electric field.

Highlights • The natural heat transfer of nanofluids was investigated under electric field. • The electric field forces can reduce a strong electric convection. • In the absence of gravity, the EHD effect on heat transfer is significant. • In the existence of gravity, the EHD effect on heat transfer is limited. Abstract Natural convective heat transfer of nanofluid consisted of transformer oil and Al 2 O 3 nanoparticles in a cavity under a non-uniform high electric field intensity was experimental investigated. The main objective is looking for a coupling enhanced method by nanofluid and electric field. It is found that when the effect of gravity is ignored, the electric field forces applied on the working fluids induce an electric convection and thence induce significant heat transfer enhancement. This enhancement effect increases rapidly with the increase of electric field intensity, the nanoparticles mass concentration of nanofluid and the heat flux. When the effect of gravity exists, a coupled convection is caused by both gravity and electric field force together. For pure transformer oil, the influences of electric field force and gravity on the heat transfer almost offset each other. However, for nanofluid, the impact of the electric filed force is dominant. The study results revealed the enhanced mechanism of natural convection heat transfer of nanofluid under electric field and provided some useful technical support for practical application. [ABSTRACT FROM AUTHOR]