Power spectra of pressure pulsations in the processes of evaporation/boiling of a liquid at low pressures

Abstract

This paper presents experimental data on pressure fluctuations during evaporation/boiling of a thin liquid film under conditions of reduced pressure. The experimental data were obtained as a result of studying heat transfer on a smooth horizontal surface in a wide range of changes in the height of the liquid layer. Using the fast Fourier transform, the power spectra of pressure pulsations versus frequency were obtained. It was found that the power spectra of pressure pulsations differ depending on the mode of evaporation/boiling in the system.

Influence of liquid layer height on evaporation/boiling heat transfer under low pressure conditions

“…This fact effect to the decreasing of the number of active centers of vaporization, resulting in the increasing of temperature head. It was shown in [18,[20][21][22] that with a significant decreasing in pressure, the heat transfer mechanism changed, at pressures below 10 3 Pa no nucleate boiling is observed, and structures in the form of "funnel" and "craters" are formed in the liquid layers. "Funnels" are depressions in a thin layer of liquid with a hemispherical bottom.…”