THERMODYNAMIC ENERGY EFFICIENCY OF HEAT TRANSFORMATION IN THE HEAT PUMP CYCLE "WATER-WATER"

Currently, at the current stage in the field of application of heat pumps in heat supply systems, it is promising to use low-potential heat from natural sources. The purpose of the work is to study the thermodynamic energy efficiency of heat transformation in the "water-water" heat pump (HР) cycle, the working agent of which is propane. A thermodynamic analysis of the energy efficiency of the use of modern heat pump technologies for the heat supply system when using natural, ecologically clean energy sources was performed. Factors that directly affect the energy efficiency of HР “W-W” have been identified, and the features of the operation of a water HР have been evaluated. Increasing the energy efficiency of a water HР depends not only on the perfection of the HР operation cycle and the choice of the HР working agent, but also on the process of heat transformation in the heat pump cycle. The results of the thermodynamic calculation of the energy efficiency indicators of the operation of the water heating plant using the natural energy source of water are presented. The energy efficiency of the water HР cycle, which implements the reverse thermodynamic Carnot cycle using a low-potential water heat source, is shown. The heat pump cycle "W-W" is accompanied by minimal losses when throttling the liquid working agent propane, and also solves the problem of useful heat use to increase the temperature of the coolant, which is heated for heat supply. A thermodynamic and exergy analysis of the energy efficiency indicators of the water HР with the environmentally safe agent propane (R290) was performed. The energy efficiency of the water HР cycle is estimated by the heat transformation coefficient HР (COP), which is calculated to be 3.72. The thermodynamic efficiency of the water HР in heat supply systems is considered using the exergy efficiency, it is 44 %. A comparative analysis of the thermodynamic energy efficiency of a water-based heat pump with other heat pumps operating on low-potential natural heat sources, such as ground and air, was conducted. For a ground-based heat pump, the coefficient of thermal transformation (COP) of the heat pump is 3.53, for an air-based heat pump 3.37. The thermodynamic efficiency of a ground-based heat pump is 40 %, for an air-based heat pump 36 %. Therefore, the thermodynamic energy efficiency of a water-based heat pump, based on the comparative thermodynamic analysis, is higher than the use of ground and air heat pumps in heat supply systems. Therefore, the use of water НР in heat supply systems is more appropriate in comparison with air and ground НР. Bibl. 42, Fig. 2, Tab. 1.