This article deals with an urgent issue - that of the deficit of natural energy resources, ways of their sustainable utilization and the need to find new alternative energy sources. It proposes a way to improve the efficiency of energy usage as well as to save energy in a mechanical ventilation system through the heat recovery of ventilation emissions by platetype waste heat exchangers. Schemes of steam-curing the supplied air in ventilation systems featuring waste heat recovery and partial recirculation of exhaust air in a cold season have been developed for the dining halls of the canteen at Lipetsk State Technical University. This paper relies upon the results of microclimate parameter analysis in the scenarios of using the proposed scheme and the current direct-flow scheme of supplied air treatment in cold and transitional seasons. It provides conclusions on the possibility to attain optimum parameters of air inside the serviced rooms in case of implementing the scheme of steam-curing the supplied air with the recovery and circulation. The research also involved an appraisal of feasibility of using heat recovery installations in air ventilation systems.
For practical applications, the description of processes occurring during the flow of two-phase gas-liquid mixtures requires a simple physical and mathematical model that describes the behavior of a two-phase medium in the entire range of phase concentrations changes and in a wide range of pressure changes. Problems of this kind arise in various branches of industry and technology. In the space industry, one often has to deal with the movement of various gases in rocket nozzles, consider the combustion, condensation of various vapors on the nozzle walls and their further impact on the velocity sublayer at the nozzle wall. The large acoustic effect arising from the engines affects the gas-liquid mixture in the nozzles of rocket engines. In the metal industry, metal cooling occurs with the help of nozzles in which the emulsion mixture is supplied under high overpressure. But this is only a short list of applied issues in which one has to deal with a problem of this type. The paper presents the results and directions of study of the problems of two-phase dispersed gas-droplet flows in the nozzles. The main methods of investigation of two- phase heterogeneous flows are described. The main characteristics of heterogeneous two-phase flows in the nozzles, which were confirmed by experimental results, are presented. The calculation of the air-droplet flow in the Laval nozzle is given. The technique, which is based on integral energy equations for two-phase dispersed flows, is described. The main problems and questions concerning the further description and studying of two-component flows are stated.
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