Skitsko O. Heat transfer and hydrodynamics of flows in vertical channels with a phase transition under the influence of disturbing factors.

The thesis is devoted to study of heat transfer and fluid flow in channels which imitate active zone elements of heat-and-power engineering equipment. One-dimensional unsteady mathematical model of boiling two-phase flow was improved. Multi-dimensional mathematical model of two-phase flow taking into account the effects of the phase transition was developed. Results of simulation for distribution of thermophysical and hydrodynamic characteristics in vertical channel are presented which were obtained based on the above mentioned model. The variation of thermo-hydraulic parameters of flow under malfunction conditions caused by decreased flow rate of water and sharp increase in wall heat flux was analyzed. It allows determining the time period before the crisis of heat transfer of the first and second kind in vertical steam-generating channel, as well as the time during which the temperature of the fuel element shell reaches the value allowed by the design conditions. Results of calculation of the hydrodynamic flow instability in vertical channels of power equipment in the three-dimensional formulation of the problem are presented.