Air heat pump units (HPUs) for space heating are used more widely than geothermal ones, mainly due to lower installation costs. The main disadvantages of geothermal installations are their low productivity and coefficient of performance (COP). In this work, a multistage heat pump unit with an air source was modeled, which lead to reduce in the energy consumption of the compressors in all of the HPU stages at an ambient temperature of -30 ° C and a heating temperature from 20 ° C to 65 ° C. Wherein, the COP of the modeled multistage HPU in all modes is 20% higher in comparison with a two-stage HPU considered in the literature review. In addition, the influence of the decrease in the ambient temperature on the increase in the energy consumption of the first stage of a multistage HPU was presented in this work.
The article describes the features developed by the authors of the profiling method of the piston skirt, provides the main parameters that affect the lubrication conditions of the piston skirt and the magnitude of mechanical losses. In computational studies, the basic formulas are given for determining the thickness of the oil layer in a piston skirt - cylinder sleeve conjunction to assess the nature of friction. To determine the deformations, the finite element method is used on the spatial model of the piston. To verify the finite element model, a stand for experimental studies was developed. The article describes the developed stand, the methodology and results of experimental studies of the stress-strain state of the two-piece piston skirt obtained at this stand and a comparative analysis of the results of the calculated and experimental studies of the stress-strain state of the two-piece piston skirt of a diesel engine. The research results showed that the developed stand can be used to verify mathematical models for calculating the stress-strain state of the piston skirt in the pilot production of internal combustion engine pistons to accelerate and reduce the cost of the piston design development process, as well as the results of experimental studies obtained at the stand, can be used as initial data for the developed mathematical model of the dynamics of the movement of the piston and the profiling of the piston skirt.
Currently, much attention is paid to improving the efficiency of energy generating facilities through the use of secondary energy resources. This article presented a cogeneration turbine in the general energy scheme with a heat pump installation. During the winter period, due to the increased consumption of heat energy, heat-generating turbines, by closing the regulating diaphragm, are switched to full steam extraction mode from the low-pressure flow part to heat the supply water. In this case, the last stages of the turbine are transferred to the ventilation mode with the release of heat due to the vortex flows on the blades of the low pressure part. In order to obtain additional heat energy for network water, the article considers the option of using secondary energy resources with the help of a heat pump unit operating in a steam turbine plant scheme. All necessary calculations of thermodynamic modeling were carried out according to the EES heat pump, the program working as part of a cogeneration turbine, and the results were obtained of increasing the efficiency of using secondary energy resources with various refrigerants.
The increase in the cost of fuel and energy resource and the deterioration of the environment from the combustion of traditional fossil fuel, have led to a great interest in energy-saving technology by using secondary energy resources in the thermal energy of industrial, housing and communal services using heat pump units in Russia and abroad. This paper analyzes the well-known two-stage heat pump units, and reveals their advantages in comparison with single-stage. The modeling of a highly efficient multistage vapor compression heat pump unit is proposed. Moreover, a method for calculating a multistage heat pump unit with a high coefficient of performance is presented. In addition, an example of calculating the thermodynamic cycle of a four-stage heat pump unit is presented. The influence of the number of stages on the increase in coefficient of performance in relation to a single-stage heat pump unit, the effect of the temperature difference between the temperature of the high-potential heat source and the temperature of the low-potential heat source on the coefficient of performance were analyzed. In addition, the influence of the initial value of the temperature of the high-potential heat source before heating during the course in the heat pump unit on the value of coefficient of performance for a different number of stages is analyzed under the condition of a constant difference between the heating temperature of the high-potential heat source at the outlet of the heat pump unit and the temperature of the low-potential heat source.
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