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Vol. 28 (2025 year), No. 3, DOI: 10.21443/1560-9278-2025-28-3

Zhukov A. V. , Golubeva O. A.
The occurrence of a heat exchange crisis of the first kind on a verticalsteam-generating pipe during the evaporation of salt solutions

A heat exchange crisis of the first kind occurs on the steam-generating tube of the evaporator during an abrupt transition from nucleate boiling to film boiling, when a steam film is formed along the heat-exchange surface, worsening the heat transfer conditions. The studies have been conducted on saline solutions of sodium chloride with a dry matter concentration of 5–11 % with a uniform step of 2 % (5, 7, 9, 11 %) under three heating modes of the steam-generating tube established during the previous research stages. During the experiments, the current strength and voltage in the heating coil circuit, as well as the temperature of the heated surface, have been determined. A heat exchange crisis of the first kind is recorded using thermal imaging photography during an abrupt change in the tube surface temperature. Thermal images have been processed using software corresponding to the model of the thermal imager used. Based on the thermal profiles of the heat exchange surface of the steam-generating tube, the occurrence of a heat exchange crisis of the first kind in the middle and lower parts of the steam-generating tube is confirmed. The critical temperature of salt solutions increases both with an increase in the solution concentration under conditions of a constant heating mode and with an increase in the heating density at a constant concentration. The conducted study of the processes of evaporation of salt solutions under various experimental conditions contributes to the development of new scientific and practical approaches to the study of the crisis of heat exchange of the first kind.

(in Russian, стр.7, fig. 6, tables. 1, ref 9, AdobePDF, AdobePDF 0 Kb)