This article presents the results of investigations of new heat pump refrigerants that provide a high-effi ciency working cycle of heat pump. These refrigerants are mixtures of a few cooling agents, and they are more environmentally friendly than the traditional ones. The mixture components used are С 3 F 8 and SF 6 (R218/R846). The specifi c diff erences in these refrigerants used in the heat pump thermodynamic cycle are shown, and their benefi ts are presented. The infl uence of the recuperative heat exchanger characteristics on the effi ciency of heat pump operation was investigated by numerical and physical modeling. Investigations were carried out on the experimental facility of the Department of Theoretical Basics of Heat Engineering at the National Research University "Moscow Power Engineering Institute". The experimental facility was modernized by replacing the tubular (double-pipe) heat exchanger by a plate heat exchanger. This upgrading was made to decrease the fl ow resistance and increase the heating temperature at the compressor inlet for the refrigerant mixtures described above. Thermal testing of the plate heat exchanger was conducted. The effi ciency of the plate heat exchanger as compared to the tubular one is shown. KEY WORDS: heat pump, coolant, recuperator, heat exchanger, energy effi ciency, coeffi cient of performance International Journal of Energy for a Clean Environment 210 Sukhikh et al.

This article studies the drying characteristics of granules of hydrophobic polymers. The hydrodynamics of a bed of PET granules has been studied taking into account the process of dust formation. On the basis of the data obtained, restrictions on the velocity gas movement through the granulate bed have been revealed to reduce dust formation at the same time preserving the quality of drying. The refined dependence of the hydraulic resistance of the bed of granules on the velocity of the gas has been obtained.

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In this article, drying characteristics were studied for polyethylene terephthalate (PET) granules. For data analysis, a modified quasistationary method was used. The values of the reduced time and the hydrodynamic intensity index were obtained for the generalized drying curve of the entire drying process in the temperature range from 120 to 185°C. The duration of the first drying period of PET granules was determined for all experiments.