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From the last few years, the use of efficient ejector in refrigeration systems has been paid a lot of attention. In this article a description of a refrigeration system that combines a basic vapor compression refrigeration cycle with an ejector cooling cycle is presented. A one-dimensional mathematical model is developed using the flow governing thermodynamic equations based on a constant area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The current model is based on the NIST-REFPROP database for refrigerant property calculations. The model has basically been used to determine the effect of the ejector geometry and operating conditions on the performance of the whole refrigeration system. The results show that the proposed model predicts ejector performance, entrainment ratio and the coefficient of performance of the system and their sensitivity to evaporating and generating temperature of the cascade refrigeration cycle. The simulated performance has been then compared with the available experimental data from the literature for validation. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a theoretical thermodynamic analysis of a novel Ejector Enhanced Vapor Compression Refrigeration (EEVCR) cycle using zeotropic mixture of propane and isobutane (R290/R600a) as a refrigerant to replace R134a in domestic refrigerators/freezers. 1 D thermodynamic model for a constant area mixing ejector is used to estimate the cycle performance under the condition of optimal operating regime. The Coefficient of Performance (COP), the Volumetric Cooling Capacity (VCC), Q v and the compressor pressure ratio are studied for the novel EEVCR cycle and the results are compared to the conventional cycle using pure fluid R134a and zeotropic mixture R290/R600a. A comparative study was carried out to determine the propane mass fraction, z in the zeotropic mixture that would be a suitable replacement for R134a. The results indicated that the cycle COP and Q v could be improved by 23% and 62.71%, respectively. In addition, the cycle COP and Q v for the proposed EEVCR cycle were higher by 70% than those for a modified ejector expansion cycle. Finally, the propane mass fraction of 60% in the zeotropic R290/R600a mixture was found to have similar saturation pressure as R134a and the cycle COP and Q v were found similar to those of R134a. Highlights • An EEVCR for dual evaporator refrigeration systems using zeotropic mixture is studied. • Energy analysis of EEVCR cycle is theoretically conducted and compared with the conventional cycle. • A comparative study of the cycle parameters is performed. • The COP and Q v of the cycle can be improved by 24% and 63%, respectively. • The R290/R600a mixture with 60% propane is a good replacement for R134a in EEVCR. [ABSTRACT FROM AUTHOR]

A hybrid vapor compression refrigeration (HVCR) system, which combines a vapor compression refrigeration (VCR) system and an ejector refrigeration (ER) system, was developed. The waste heat energy from the gas cooler in the VCR system is applied as driven source towards ER system. Thermodynamic investigations on the performance of the HVCR system, using CO 2 as a refrigerant, are performed with energetic and exergetic methods, and the comparative analyses with the VCR system are conducted. Comprehensive effects of key operating parameters on the system performance are also studied. The results indicate that for the same cooling capacity, the coefficient of performance (COP) of the HVCR system shows 25% higher COP and the total mechanical power consumption is reduced by 20% than that of conventional VCR system, respectively. The performance characteristics of the proposed cycle show its application potential in cooling and air-conditioning. [ABSTRACT FROM AUTHOR]

• An energy, exergy and exergoeconomic analysis is carried out. • The refrigeration system refrigerant is Carbon dioxide. • The NCRCPC performance was found to be superior compared to other cycles. • Parametric analysis of the NCRCPC was conducted. Three different refrigeration cycles, namely the vapor compression cycle, the combined refrigeration cycle and the new combined refrigeration cycle for power and cold, are investigated. The principles of mass and energy conservation are applied to every component of the systems, and the resulted linear system of equations was numerically solved. It was found that the new proposed cycle had a lower optimum gas cooler pressure than other refrigeration cycles, and this would enhance the lifetime and safety of the system. Besides, it was found that the coefficient of performance of the new cycle is higher than that of the vapor compression and combined refrigeration cycles 110% and 50%, respectively. The exergy efficiency was approximately 78% and 58% higher than that of the vapor and combined refrigeration cycles, respectively. Furthermore, the exergoeconomic results of the new cycle showed that the total unit cost was lower by 16.6% and 13% than that for the vapor compression and combined refrigeration cycles, respectively. [ABSTRACT FROM AUTHOR]