Thermodynamic analysis of an air source ejector assisted compression-absorption-resorption refrigeration system

Abstract

The vapour absorption-resorption cycle has an additional degree of freedom than the conventional vapour absorption cycle. This additional degree of freedom allows the flexibility to operate the system at lower cycle high-pressure and low-pressure values. However, the coefficient of performance (COP) of the system decreases with decreasing the operating pressures and with increasing the absorber temperatures. In this study, a novel air source ejector assisted ammonia-water compression absorption-resorption refrigeration system is proposed, in which an ejector replaces a throttle valve in the absorption-circuit to boost the absorber pressure, and a compressor is integrated to compress the ammonia vapour from the desorber pressure to the absorber pressure. The performance of the proposed system is evaluated and compared with that of the conventional absorption refrigeration system. A parametric analysis is performed to study the effect of different feasible compression ratios on the system performance, ejector pressure ratio, and the heat input to the generator. For a certain high-pressure value, the cycle low-pressure is varied in the feasible range and the system COP is calculated in relation to the high-pressure value and the ejector pressure ratio. Furthermore, the effect of the generator and the absorber temperatures on the performance is studied in relation to the desorber temperature. The results indicate that for the same operating conditions, the conventional absorption heat pump has a COP of 0.43, while the proposed system can attain a maximum COP of 0.61. The COP increased with increasing ejector pressure ratio and increasing compressor compression ratio. For a certain generator and absorber temperature, the COP increased with increasing desorber temperature. And for a certain desorber temperature, the COP first increased to attain a maximum value and after that remained constant with increasing generator temperature.