Energy and exergy analyses of a two-stage vapour compression refrigeration system

Abstract

SUMMARYIn this paper exergy analysis of two-stage vapour compression refrigeration (VCR) system has been carried out with an objective to evaluate optimum inter-stage temperature (pressure) for refrigerants HCFC22, R410A and R717. A thermodynamic model based on the principles of mass, energy and exergy balances is developed for this purpose. The computed results illustrate the effects of evaporation and condensation temperatures, isentropic efficiencies of compressors, sub-cooling of refrigerant and superheating of suction vapour on optimum inter-stage saturation temperature (pressure). The optimum inter-stage saturation temperatures (pressures) for HCFC22 and R410A are proximate to arithmetic mean of evaporation and condensation temperatures (AMT) when assuming superheating of suction vapour and non-isentropic compression processes in low-pressure and high-pressure compressors. The optimum inter-stage saturation temperatures (pressures) for HCFC22 and R410A are near to geometric mean of evaporation and condensation temperatures (GMT) when it is assumed that cycle involves the effects of sub-cooling, superheating of suction vapour and non-isentropic compression of the suction vapour. The optimum inter-stage saturation temperature (pressure) for R717 is close to GMT irrespective of sub-cooling, superheating of suction vapour and non-isentropic compression in the cycle. The efficiency defects, computed corresponding to optimum inter-stage temperature in condenser is higher in comparison to the other components. Finally, it is deduced that R717 is a better alternative refrigerant to HCFC22 than R410A in two-stage VCR system.

Energy and exergy investigation of a novel double effect hybrid absorption refrigeration system for solar cooling

“…However, combined cycles of vapor compressioneabsorption refrigeration system can provide high COP. Several works on combined cooling system or absorption refrigerator (mainly on the cooling performance analysis and optimization) have been carried out (Lee SF and Sherif SA, 2001; Arora and S.C. Kaushik, 2009) [4,5]. In general, performance analysis of these systems is investigated using energy analysis method, based only on the first law of thermodynamics (energy balance) by means of the coefficient of performance (COP).…”

Comparative analysis of thermodynamic performance of CO 2 cascade refrigeration system assisted with expander and mechanical subcooling

“…6 However, after the Kigali amendment was passed, many refrigerants could not be used, and the ultimate solution maybe using natural refrigerants. 10 However, it is worth noting that R717 cannot be used as a direct evaporative refrigeration system for personnel operations and mobility, and it is banned as a refrigerant in residential areas and supermarket refrigeration systems in some countries. 7,8 At present, natural refrigerants have been used for air conditioning, freezing, and refrigeration.…”

“…10,31 Therefore, it is necessary to adopt a reliable technical scheme to meet the requirements of low evaporation temperature. 10,31 Therefore, it is necessary to adopt a reliable technical scheme to meet the requirements of low evaporation temperature.…”

“…R717 has been used in industrial refrigeration and large cold storage systems for more than 260 years. 10 However, it is worth noting that R717 cannot be used as a direct evaporative refrigeration system for personnel operations and mobility, and it is banned as a refrigerant in residential areas and supermarket refrigeration systems in some countries.…”

“…In the low-temperature applications where the evaporation temperature is limited in a range of −30°C and − 55°C, such as rapid freezing, single-stage refrigeration cycles adopting CO 2 are generally not economical, since the high-pressure difference between evaporator and condenser or gas cooler will cause the volumetric TABLE 1 Previous research on transcritical CO 2 single-stage refrigeration system efficiency of the compressor to be low and the coefficient of performance of the system to be decreased. 10,31 Therefore, it is necessary to adopt a reliable technical scheme to meet the requirements of low evaporation temperature. For the low-temperature applications, two-stage compression systems and cascade refrigeration systems (CRSs) can be used.…”