Heat transfer and fluid dynamics in miniature two-phase heat transfer systems

For the first time a comprehensive study of the processes of heat transfer and hydrodynamics during evaporation and condensation in closed miniature two-phase systems was carried out. The regularities of the influence of geometric and regime factors on the thermal resistance and maximum heat fluxes of miniature heat pipes, thermosyphons and pulsating capillary heat pipes are revealed. The physical model of heat exchange processes in the conditions of limited space at application as heat carriers of ordinary liquids and nanofluids is developed and presented. The nature of the influence of the main factors on the heat transfer processes is revealed. Dependences for calculation of heat transfer intensity in heat exchange zones of miniature thermosyphons are obtained. The mechanism of pulsation phenomena in miniature thermosyphons is revealed and the influence of regime and geometric factors on the range of occurrence of such pulsations is revealed. New approaches for intensification of vaporization processes in the evaporation zones of miniature heat exchangers are presented and their designs with different heat transfer characteristics are given. The results of the study of the interaction model in annular two - phase systems and the determination of the conditions for maintaining the stability of the film flow during countercurrent motion of gas and liquid in vertical channels with a mesh coating are presented. According to the results of research, current samples of cooling systems based on miniature two-phase systems with characteristics exceeding the best foreign analogues have been developed and manufactured.