Abstract
The results of experimental research of heat exchange under the nucleate boiling of refrigerants R404a, R407c and R410a on the tubes with capillary-porous coating are presented. Experimental studies were carried out with the aid of an experimental installation in conditions of a large volume at pressures of saturation pн = 0.9–1.4 MPa and densities of the heat flux q = 5–35 kW/m2. For the first time the criterion equation for the calculation of the intensity of heat transfer during evaporation of ozone safe refrigerants on surfaces with high thermal conductivity sintered capillary-porous coating was obtained. Experimental data are summarized satisfactorily in a wide range of parameters of the porous layer, i.e. the pressure (pн = 0.9–1.4 MPa) and heat loads (q = 5–35 kW/m2). The ratio makes us possible to calculate the heat transfer coefficients within ±20 %. The dependence can be used in engineering calculations of the characteristics of the heat exchangers of the evaporative type. The coefficient of heat transfer during boiling of refrigerants on the investigated surfaces with the sintered capillary-porous coating, 4 times higher than on a smooth one and 1.5 times higher than on the finned surface, that allows us to come to a conclusion about the advantage of porous coatings. Boiling in capillary-porous coating leads to a decrease in weight and size of the installations due to the heat exchange intensification and the size of the tubes smaller as compared to the size of the finned ones.
Highlights
Одним из наиболее эффективных способов интенсификации теплообмена при кипении является применение пористых металлических покрытий
The dependence can be used in engineering calculations of the characteristics of the heat exchangers of the evaporative type
The coefficient of heat transfer during boiling of refrigerants on the investigated surfaces with the sintered capillary-porous coating, 4 times higher than on a smooth one and 1.5 times higher than on the finned surface, that allows us to come to a conclusion about the advantage of porous coatings
Summary
В которых изучалось влияние поверхностных эффектов на кипение, однако результаты их недостаточны для построения обоснованных обобщений, а многие выводы противоречивы. Цель данной работы – экспериментальное исследование процесса теплообмена при кипении смесевых озонобезопасных хладагентов R404a, R407c и R410a на высокотеплопроводных порошковых спеченных капиллярно-пористых покрытиях; установление обобщенных зависимостей для определения коэффициентов теплоотдачи и влияния на них различных факторов, определяющих интенсивность теплоотдачи при фазовых переходах в аппаратах холодильных и теплонасосных установок
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