Heat Transfer during Evaporation/Boiling of Horizontal Layers of Liquid at Low Pressure

In this work, experimental data on the heat transfer in a horizontal layer of liquid are obtained for wide ranges of the layer height and reduced pressure. Explosive boiling-up of liquid at low reduced pressures, when significant fluctuations of the pressure, heating surface temperature, and heat flux were observed, is considered. For this condition, the problem of determination of the temperature head is analyzed, as well as uncertainties of its measurement. The experimental data obtained at different layer heights and pressures were compared with the known calculation formulas derived for determination of the heat transfer coefficient during nucleate boiling for analysis of the range of applicability of these formulas. It is shown that at low reduced pressures, the experimental data are generalized well by Yagov’s formula, and the experimental data obtained at moderate reduced pressures at nucleate boiling are generalized well by Gogonin’s formula. Both formulas were obtained for pool boiling. With the help of Pioro’s formula in which we corrected the coefficients and exponents at the Prandtl number and heat flux, we managed to summarize the experimental data over the entire range of the reduced pressure and the liquid layer height.