Heat transfer during water boiling on black silicon surfaces of different morphologies

The paper presents experimental data on the effect of morphology of the black silicon superhydrophilic surface structure fabricated by plasma-chemical etching on heat transfer during pool boiling of water. Silicon surfaces with homogeneous and hybrid microstructures are investigated. Heat transfer experiments were carried out on pre-selected microstructured surfaces with the best characteristics of capillary wicking. It is shown that the critical heat flux (CHF) for a surface with a hybrid structure is approximately three times higher than the CHF for a smooth silicon surface (660 kW/m²), reaching a value of 1914 kW/m², while the CHF for a surface with a homogeneous structure exceeds the CHF for a smooth surface by the factor of 2.4, reaching a value of 1568 kW/m². At that, the maximum recorded heat transfer coefficient (HTC) of the surface with a homogeneous capillary structure, on the contrary, is the highest (77 kW/(m²K)), almost twice exceeding the heat transfer coefficients for the unmodified surface in the region of moderate heat fluxes. The surface with a hybrid structure demonstrates a delay in boiling incipience when compared with the results for a smooth surface, but with a further increase in the heat flux it significantly exceeds the HTC for the smooth reference surface, ultimately reaching a maximum value of 45 kW/(m²K) in the pre-crisis region.