<p>This analysis examines the boiling and condensation processes of heat carriers and presents the calculated heat transfer coefficients for these processes, which were incorporated into FloEFD simulations. Additionally, this study uses FloEFD solutions to model the circulation of the vapor-water mixture within the first cooling circuit of a&#xa0;cylindrical crystallizer with an evaporative-condensation cooling system. The calculations were performed using the adopted average coefficients, the dimensions of the first circuit elements, and the crystallizer design. The mass concentration of the heat carrier, the temperature of the mixture, the wall temperatures, and the velocity of the mixture circulation were determined for an average applied heat flux density of 1 MW/m². These calculations provide information for the modernization of the crystallizer, which aims to eliminate non-uniform cooling around the perimeter of the cylindrical steel billet. The highest vapor velocities, reaching 2–3 m/s, occur in the steam line, while the highest condensate velocities occur in the condensate line.</p>