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Experimental study of a two-phase ejector for CO2 transcritical refrigeration system

Haberschill Philippe, Nehdi Ezzeddine, Kairouani Lakdar, Elakhdar Mouna Abouda

Archives of Thermodynamics

2021

Vol. 42, no 4

217--246

The geometry and operating parameters have an important influence on the performance of ejectors. The improvement of the refrigeration cycle performance and the design of the ejectors for the compression energy recovery requires a detailed analysis of the internal ejector working characteristics and geometry. To this aim, an experimental investigation of an ejector refrigeration system is conducted to determine the effect of the most important ejector dimensions on ejector working characteristics and system performance. Different dimensions of ejector components are tested. The influence of the ejector’s geometrical parameters on the system performance was analysed. The experiments with respect to the variation of ejector geometry such as the motive nozzle throat diameter, the mixing chamber diameter and the distance between the motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. The experimental results show that the performance (entrainment ratio and a compression ratio of the ejector) increases significantly with the position between the primary nozzle and the mixing chamber. A maximum entrainment ratio of 57.3% and a compression ratio of 1.26 were recorded for the different parameters studied. The results obtained are consistent with experimental results found in the literature.

Optimization of absorption refrigeration systems by the method of computational experiment design

Iffa Ridha Ben, Kairouani Lakdar, Bouaziz Nahla

Archives of Thermodynamics

2019

Vol. 40, no 1

85--102

The objective of this work is to present an energy analysis of different absorption refrigerating systems operating with diverse refrigerants. Also is applied the method of experimental design to optimize configurations proposed by the absorption pairs used and the operating conditions. Both acceptable coefficient of performance and low operating generator temperature are scrutinised. Therefore, a computer program is developed. An investigation of the thermodynamic properties is presented. Results show the coefficient of performance evolution versus respectively the evaporator temperature, temperature of condensation and generator temperature. A particular interest is devoted to the intermediate pressure effect on the performance of different systems. In order to better converge in the selection of the configuration and the refrigerant, which can ensure a high coefficient of performance associated to relatively low operating generator temperature the plan of experiments has been developed, taking in account all parameters influencing the system performance and the function of operating temperature. Results show that the refrigerating machine containing a compressor between the evaporator and the absorber has a coefficient of performance quite acceptable and that it can work at low generator temperature for about 60°C and using the NH3/LiNO3 as refrigerant.