Abstract
In this paper, a hybrid ejector single-effect lithium-bromide water cycle is theoretically investigated. The system is a conventional single-effect cycle activated by an external steam-ejector loop. A mathematical model of the whole system is developed. Simulations are carried out to study the effect of the major parameters of the hybrid cycle on its performances and in comparison with the conventional cycle. The ejector performance is also investigated. Results show that the entrainment ratio rises with steam pressure and condenser temperature, while it decreases with increasing generator temperature. The effect of the evaporator temperature on ejector performance is negligible. It is shown also that the hybrid cycle exhibits better performances than the corresponding basic cycle. However, the performance improvement is limited to a specific range of the operating parameters. Outside this range, the hybrid system behaves similar to a conventional cycle. Inside this range, the COP increases, reaches a maximum, and then decreases and rejoins the behavior of the basic cycle. The maximum COP, which can be as large as that of a conventional double-effect cycle, about 1, is obtained at lower temperatures than in the case of single-effect cycles.
Highlights
Cooling and air conditioning are essential for small scale and large industrial process applications
We investigate the evolution of the COP of the hybrid cycle with the steam generator temperature and the main factors of the cooling machine, i.e., desorber, condenser, and evaporator temperature
We can proceed to the simulations of the proposed hybrid cycle with some confidence
Summary
Cooling and air conditioning are essential for small scale and large industrial process applications. While systems applying the vapor-compression technique use environmental harmful refrigerants (FCC, FCHC, etc.), absorption technique for production of cold is based on environment friendly working fluids, namely, aqueous lithium bromide solutions with water as refrigerant or water-ammonia mixtures with ammonia as refrigerant Investigations indicate that COP of the combined configuration are greater or equal to that of single-effect cycles, but reached at lower generator temperatures. Experimental studies [15] show that this combined cycle is 3060% more performant than conventional absorption cycles and almost reaches the COP of double-effect systems. The new cycle worked as a conventional double-effect cycle Another configuration was studied with an ejector coupled to vapor generator [21,22,23]. The behavior of the entrainment ratio as ejector performance criterion is investigated for various primary and secondary flow pressure and backpressure
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