Simulation study of the combination of absorption refrigeration and ejector-expansion systems

Recently, in refrigeration industry the use of efficient dual-evaporator refrigeration systems has been paid a lot of attention. These systems sound even more interesting when they are a combination of different kinds of conventional refrigeration systems. In this paper three thermally driven chillers consisting of absorption refrigeration and ejector-expansion transcritical cascade CO2 cycles are proposed and investigated thermodynamically. The systems are called “hybrid dual-evaporator” cycles. The absorption cycle in the systems is either the single-effect or double-effect series-flow or double-effect parallel-flow cycle for each of which a solar collector is considered to supply the required heat in their generator. The performances of hybrid dual-evaporator systems are analyzed and optimized, using the Engineering Equation Solver and applying the principles of conservation of mass and energy as well as the exergy balance to each component of each system. Results indicate that combing the double-effect parallel absorption refrigeration system with ejector-expansion system gives the highest coefficient of performance among the other configurations. However, a combination of single-effect absorption refrigeration system with ejector-expansion cycle may be preferred due to its less complexity and reasonable exergy efficiency. Results also reveal that at optimum generator temperature of 72.92 °C the coefficient of performance and exergy efficiency of hybrid dual-evaporator with single-effect absorption are 1.182 and 0.2564, respectively. In addition, it is observed that increasing the cooling capacity ratio from 1 to 6 results in increases of the coefficient of performance and exergy efficiency of configurations by up to 36.32% and 11.5% respectively.