Boiling of liquid in a mini channel on smooth, rough and porous surfaces

Abstract

A series of experiments were conducted to study the effect of the heater coating on the frequency of formation of steam bubbles and on heat exchange during boiling in the channel. Three different surfaces were used: 1) smooth, 2) rough and 3) porous. It was found that at relatively low heat fluxes, the specific frequency of bubble formation on a rough surface is higher than on a smooth one. However, with an increase in the heat flux, the difference in the frequency of bubble formation on rough and smooth surfaces practically disappears. At the same time, bubble formation on a porous surface occurs with almost 3 times the frequency, compared to both smooth and rough in the entire range of heat fluxes (up to 500 W/cm2). The obtained results can explain the recorded fact of a significant increase in the heat transfer coefficient and the critical heat flux on a porous surface.