Performance evaluation of flash tank-absorption cooling cycle using two ejectors

Combining the ejector-flash tank with the single stage absorption cycle has shown potential improvement in the COP. However, the cycle is still subject for further enhancement. Addition of two ejectors in the cycle to work under low-pressure of evaporator and intermediate-pressure of flash tank could optimize the COP of the cycle. In this study, the effect of adding two ejectors has been investigated. Moreover, a new stream line between 2nd ejector and the rectifier has been created and evaluated. Energy balance analyses of the cycle before and after modification have been carried out. A computer simulation program has been developed to evaluate the performance of the cycles using ammonia-water solution as working fluid, operating under steady-state conditions. The results indicated that the overall COPs increment of the modified cycle are 11.56%, 12.42%, 13.46% and 14.05% at generator temperature of 80 °C, 85 °C, 90 °C, and 95 °C respectively. The results also showed that utilizing a part of streamlines of 2nd ejector decreased the heat power in the generator and hence increase the COP. Generator and condenser thermal loads after modification are found permanently less than that in the cycle before modification which indicates a significant enhancement of the proposed cycle. The results showed also that the proposed cycle is able to work under higher operation temperatures as same performance as the cycle before modification (with one ejector) under lower operation temperatures. So, this investigation could help to promote absorption cooling systems in locations of high temperature conditions.