Performance Of Ejector Refrigeration System Research Articles

Impact of primary nozzle area ratio on the performance of ejector refrigeration system

This paper proposes an experimental investigation to demonstrate the impact of the primary nozzle area ratios on the ejector performance in an R141b ejector refrigeration system. The experimental refrigerator was tested based on the alternative testing method in which the generator temperature and condenser pressure were held constant for particular test cases. Three primary nozzles were studied which had identical throat diameter but different nozzle area ratios which produced different exit Mach numbers. Three primary nozzles were equipped with one mixing chamber with throat diameter of 9 mm. With the alternative testing method, two critical evaporator temperatures were found, the lower and upper critical evaporator temperatures. It was also found that the change in the nozzle exit Mach number and the primary fluid mass flow rate (using different generator temperatures) had significant impact on these two critical points which affected the entire ejector performance. The primary fluid expansion coefficient (Cprimary), which is key to indicate the limited range of the working condition, was introduced. It indicates the expansion wave formation which has significant impact on two critical points. Hence, the proper value of Cprimary under various primary nozzle area ratios was determined for this present work.

Experimental investigation of an ejector refrigeration system using R-134a

In the present study, the performance of ejector refrigeration system is investigated using R-134a as working fluid. Six ejectors of different geometries are used to experimentally evaluate the coefficient of performance, cooling capacity, pressure lift and critical condenser pressure for fixed generator and evaporator temperature, while varying the condenser temperature. It is observed that an optimum area ratio of the ejector is required to obtain better performance and is found that a higher value of area ratio gives maximum COP for the specified conditions but for a lower value of critical condenser pressure. The critical condenser pressure for the ejector of area ratio 10.08 comes out to be 778.9 kPa whereas it is 916.72 kPa for the ejector of area ratio 6.451 while working at generator and evaporator temperature of 80 °C and 15 °C respectively. Further, the ejector having a shorter length of constant area section is found to excel. It is also concluded that for lower evaporator pressure, higher pressure lift is obtained from the same ejector.

Thermodynamic investigation of a booster-assisted ejector refrigeration system

In order to improve performance of ejector refrigeration system, a booster is added before an ejector to enhance secondary flow pressure, which is called a booster assisted refrigeration system. Based on mass, momentum and energy conservation, a 1D model of ejector for optimal performance prediction was presented and validated with experimental data. A detailed study of working characteristics of the booster assisted ejector refrigeration system was carried out and compared against conventional ejector refrigeration system and compressor based refrigeration system, on the basis of first and second laws of thermodynamics. Effects of booster outlet pressure on COPth based on thermal energy and COPw based on work input, and also on entrainment ratio and area ratio of ejector were studied. The exergy destruction rates were also computed and analyzed for components of the booster-assisted ejector refrigeration system. Ways to reduce exergy destruction were discussed.

Experimental analysis on the effect of internal heat exchanger in transcritical CO 2 refrigeration cycle with two-phase ejector

The performance of CO 2 ejector refrigeration system needs further improvement to make CO 2 more viable than traditional harmful refrigerants. In this research, the effect of internal heat exchanger (IHX) in the performance of ejector refrigeration system was analyzed experimentally and compared with conventional expansion refrigeration system. Experiments were performed at different operating pressure and temperature for the cases of without IHX, 30 cm IHX and 60 cm IHX. The results showed that IHX significantly increased the coefficient of performance (COP) of ejector system. At the conditions used in this research, the ejector system with 60 cm IHX provided the maximum COP improvement of up to 27% compared to similar conventional system. The motive nozzle’s inlet condition had significant effect on the performance of ejector system. The results also confirmed the presence of considerable amount of liquid refrigerant at separator’s gas outlet of ejector system which was deemed possible in our previous research.

Experimental determination of the optimum performance of ejector refrigeration system depending on ejector area ratio

The performance of the ejector refrigeration system using ejectors with cylindrical mixing chamber is studied at operating conditions with choking in the mixing chamber. The condenser pressure is chosen so that the secondary flow choking can occur even in the ejector with the smallest area ratio. In the present study, the performance of the constructed system is determined by using six configurations of ejector and R-123 as working fluid in the system. The study is performed over a range of the ejector area ratio from 6.5 to 11.5 at the compression ratio 2.47. In the studied range, the experimental coefficient of performance of the system rises from 0.29 to 0.41, as the optimum generator temperature increases from 83 to 103 °C. Similar results were also found in the parametric study when the efficiencies of the nozzle and diffuser are taken as 0.90.

Experimental investigations on ejector refrigeration system with ammonia

A vapor ejector refrigeration system has been designed and developed to operate with ammonia. In this paper, performance of ejector refrigeration system has been experimentally studied with three different area ratio ejectors by varying operational parameters namely generator, condenser and evaporator temperatures. Effect of non-dimensional parameters like compression ratio, expansion ratio and area ratio on the system performance is studied. Entrainment ratio and coefficient of performance of the system increase with increase in ejector area ratio and expansion ratio and they increase with decrease in compression ratio.