Gradient Heatmetry in Study of Heat Transfer during Pool Boiling of Subcooled Water and Liquid with the Addition of Al₂O₃ Microparticles

Abstract

Heat transfer during pool boiling of subcooled pure water and water with the addition of Al₂O₃ microparticles is considered. The presented brief literature review indicates a clearly insufficient experimental base, without which it is impossible to talk about a direct dependence of the critical heat flux on the concentration of particles in a liquid. The methods used in the considered publications for studying heat transfer during boiling do not give a complete picture of the entire process and do not allow one to draw unambiguous conclusions. In the present work, the main research method was gradient heatmetry. The applied heterogeneous gradient heat flux sensors made it possible to directly obtain local the heat flux (HF) and proved to be a reliable tool in the study of phase transitions in a unsteady formulation of the problem. The article considers three temperature differences, 384, 391, and 400°C, selected based on the resource of the model (time of uninterrupted operation of the model and primary converters) and in view of the stable film boiling mode characteristic of the critical the heat flux (HF). In the entire studied range of mass concentrations of Al₂O₃ microparticles from 1 to 4%, an augmentation of heat transfer was observed during boiling of subcooled water at atmospheric pressure. The critical HF for the considered temperature differences turned out to be 3.6–5.1 times higher than for pure water. For each temperature regime, the optimal concentrations of Al₂O₃ microparticles (particles) corresponding to the maximum HF were revealed. An increase in the critical temperature in all regimes and, as a consequence, in the Heat Flux Per Unit Area is presumably due to a change in the thermophysical properties of the suspension and the perturbations introduced by these particles into the boiling process.