Influence of nanoparticle size and gap size on nucleate boiling using HFE7100

In this study the effect of the deposition of maghemite (γ-Fe2O3) nanoparticles on a horizontal heated copper surface during the nucleate boiling of HFE7100, at atmospheric pressure and saturation temperature, was investigated, using two nanoparticle diameters (10 nm and 80 nm). Two main conditions are considered: unconfined and confined boiling. In the later, the gap size is 0.1 mm. The results showed an enhancement in the heat transfer coefficient (HTC) of around 55% for the surface nanostructured with the smaller nanoparticles compared to the surface without deposition. The results for the larger nanoparticles showed a decrease in the HTC of around 29% compared to the case without deposition. For the confined cases, as a general trend, the HTC increased when the gap size decreased, mainly for lower heat flux.