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Introduction. The complexity of determining the contact surface of phases and the boundaries of the continuous structure of liquid jets complicates the calculation of phase-contact heat and mass exchange mixing apparatuses. Materials and methods. The condensation process of water steam from a steam-gas mixture on a cylindrical free-falling liquid jet is considered under counter-current movement of the steam phase within a range of flow parameters characteristic of the food industry. Results and discussion. An empirical dependence for determining the onset of jet structure destruction adequately describes the process of its structural changes and is characterized by the fact that an increase in the Reynolds number leads to an increase in the critical height of jet destruction: the jet becomes more resistant to the action of the steam flow. With an increase in the dynamic pressure of the steam flow, corresponding to an increase in the Weber number, which characterizes a sharp decrease in the dimensionless height of dispersion, the jet intensively disintegrated, was destroyed at the outflow point, and was carried away by the steam flow. An original system of dimensionless similarity numbers, based on the results of jet hydrodynamics analysis, allows for determining the temperature change along the jet's length, taking into account the geometric characteristics of mixing heat exchanger distribution devices, flow geometric dimensions, steam-liquid flow parameters, and the thermophysical properties of the media. Empirical dependencies of the heat exchange process, considering the critical height of the existence of the continuous jet structure, are recommended for use in the thermohydraulic calculations of direct phase-contact heat exchange equipment. Conclusion. The novelty of the results lies in the introduction of empirical dependencies for calculating heat exchange, considering the critical height of the existence of the continuous structure of the liquid jet.

Розроблено математичну модель теплоперенесення в циліндричних струменях рідини. В основу моделі покладено гіпотезу пригнічення турбулентності біля поверхні поділу рідина—пара поверхневим натягом. A mathematical model of heat transfer in a cylindrical jet of liquid. It is based on the hypothesis of suppression of turbulence near the interface of liquid-vapor surface tension.

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