Preliminary Design of the Two-Phase Ejector under Constant Area Mixing Assumption for 5 kW Experimental System

4th International Conference on Advances on Clean Energy Research (ICACER) -- APR 05-07, 2019 -- Univ Coimbra, Coimbra, PORTUGALWOS: 000503744000002Ejector expansion refrigeration cycle is the modification of the vapour compression refrigeration cycle with the implementation of a two-phase ejector and a vapour-liquid separator to improve the cycle performance. in this study, main geometrical parameters of an ejector, i.e. diameters of the motive nozzle throat, motive nozzle outlet, suction nozzle outlet, and constant area mixing section are calculated in order to provide the preliminary design aspects at various operation conditions. the thermodynamic model of the ejector is established with reference to constant-area mixing assumption. the equations are solved in Matlab (R). the environmentally-friendly refrigerants, R1234yf and R1234ze(E) from the hydrofluoroolefins (HFOs) and R134a which is about to be phased out by the F-gas Regulation are used in the analyses. When compared to the previous literature findings, the current research aims to compare the dimensions of a twophase ejector to be used in anexperimental system having 5 kW coolingcapacity for these three refrigerants.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [116M367]The authors would like to acknowledge the support of the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant No: 116M367

Investigation of the Liquid-Vapor Separator Efficiency on the Performance of the Ejector Used as an Expansion Device in the Vapor-Compression Refrigeration Cycle

WOS: 000509108300006Ejector expansion refrigeration cycle with reference to the constant pressure mixing theory is investigated to display the effects of the liquid-vapor separator efficiency on the performance, entrainment ratio, and area ratio at various operation conditions. Reversible ejector assumption is used for the highest theoretical performance limit, whereas efficiency of the liquid-vapor separator and all ejector components is added to the model to calculate more realistic performance improvement potentials. R1234yf and R1234ze(E) having low global warming potential values are used in the analyses. Zero-dimensional thermodynamic models are constructed applying the conservation equations between the inlets and outlets of the refrigeration cycle and ejector components. Percentage performance decrease is higher when the mixing section and the separator efficiency is added to the model at higher condenser temperatures compared with the lower evaporator temperatures according to the investigated operation ranges. Vapor and liquid separation efficiency affects not only the performance but also the design of the ejector although it is an external component since it has influence on the area ratio and entrainment ratio. Finally, the difference between the percentage performance improvement of the reversible ejector cycle and the realistic ejector cycle including the separator and ejector components efficiencies is as high as 35% at the highest investigated condenser temperature for R1234yf.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [116M367, 10.13039/501100004410]Scientific and Technological Research Council of Turkey (TUBITAK) (Grant No. 116M367; Funder ID: 10.13039/501100004410)

THERMODYNAMIC PERFORMANCE OF THE TRANSCRITICAL REFRIGERATION CYCLE WITH EJECTOR EXPANSION FOR R744, R170, AND R41

WOS: 000459361300010For more than a decade, there is a great demand for finding environmentally-friendly refrigerants obeying the global warming potential value restrictions of the tough environmental legislation. Among the candidate working fluids, R744 (carbon dioxide or CO2), R170 (ethane), and R41 (fluoromethane) are selected to be investigated parametrically in this paper. Performance comparison is made for these three working fluids individually in both transcritical (supercritical) refrigeration cycle and modification of this cycle with ejector expansion. As the first step, the effects of the gas cooler outlet temperature, evaporator temperature, and evaporator outlet superheat temperature difference on the overall performance and percentage expansion losses are investigated within a specific gas cooler pressure range. Evaporator outlet superheat temperature difference is found to be the least effective parameter on the performance; hence, secondly, the transcritical ejector expansion refrigeration cycle is analyzed considering only evaporator temperature and gas cooler outlet temperature based on the same gas cooler pressure ranges. Thermodynamic models are constructed in Matlab (R) and the ejector equations for the ejector expansion refrigeration cycle are established with reference to constant pressure mixing assumption. Comparisons of the performance, percentage expansion losses, and performance improvement potential through the implementation of the ejector instead of the expansion valve among these three refrigerants having low critical temperatures represent the main objective of the paper in order to make contributions to the previous researches in the literature.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [116M367]The authors would like to acknowledge the support of the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant No: 116M367