Термодинамічний аналіз комбінованої компресорно-ежекторної холодильної машини

Abstract

This paper presents the results of thermodynamic analysis of the hybrid mechanical compression-ejector cooling machine (MC-ECM). The technological scheme of the MC-ECM represents two independent systems working on separated cycles: a mechanical compression refrigerating machine (MCRM) and an ejector cooling machine (ECM). MCRM is the two-stage refrigerating machine with R744, in which heat dissipation is carried out at transcritical temperatures. ECM is the ejector refrigeration machine with two-stage generation, which is a utilization machine in relation to the MCRM. The ECM’s working fluid is R601b, which belongs to the group of natural refrigerants. Utilization of high-temperature heat, which is a direct discharge of MCRM, helps to increase the energy efficiency of MCRM and reduce the consumption of external cooling medium. It is proved that the achievement of the maximum MC-ECM’s efficiency is possible only with a certain combination of key parameters that ensure the maximum efficient use of heat regeneration between the cycles of MCRM and ECM. These parameters are the pressure of R744 in the gas cooler p_GC, the generating temperature t_G in the first and second stages of the ECM’s generator and the evaporating temperature t₀^E in the evaporator ECM. The basis for the study was the energy analysis of the MCRM and ECM cycles, both separate and integrated into the system due to common characteristics. The results of calculations of the hybrid cooling system for evaporating temperatures from –30 °C to 0 °C using refrigerant R601b in the ejector cooling cycle show that COP_MCRM rea­ches 1.88-3.62 for high COP_ECM, equal to 0.41-0.51. The relative increase in СОР compared to the usual two-stage cycle of MCRM with R744 is 25.4-30.3%. The introduction of the hybrid mechanical compression-ejector cooling machines on environmentally friendly working fluids is a promising area of commercial refrigeration equipment improvement