Performance investigation and numerical evaluation of a single-effect double-lift absorption chiller

Abstract

This study deals with innovative integrated absorption refrigeration systems. This cycle could be useful for converting low-temperature energy sources into useful outputs like cooling. The Single Effect Double Lift Absorption Chiller (SE-DL AC) was introduced and energetically evaluated. A detailed modeling based on the first law of thermodynamics is built to investigate the performance of this novel system. This model was initially validated considering a reference SE-DL AC from the Hitachi company with a nominal cooling capacity of 106.1 kW. This system is compared to a conventional single-effect absorption chiller while maintaining the same operating parameters and boundary conditions in both configurations to ensure a fair comparison in terms of the internal and external baseline operating conditions. A parametric study of the driving hot water inlet temperature, the solution mass flow rate, the effectiveness of the solution heat exchanger, and internal and external temperatures on the Coefficient of Performance (COP), Cooling capacity (CC), and Glide Temperature (ΔT) are conducted. The final results demonstrate that the cooling production capability of the SE-DL is increased by an average of about tenfold when compared to the conventional SE AC at a thermal source temperature of 88.7 °C and an inlet hot water mass flow rate of 1 kg/s. The COP results produced under the same operating conditions are quite similar. The cooling generation capability of the SEDL is, on average, 10 times greater than that of the traditional SE AC. This explains that the SEDL-AC is well suited for a wide range of low-temperature heat sources (e.g., solar energy). Furthermore, the SE-DL AC enables efficient use of low-grade heat with a high glide temperature in the driving heat stream of about 10 times (36 °C instead of 3.5 °C). This large temperature difference exemplifies that the SE-DL AC absorption chiller is an alternative for extracting as much heat as possible, thereby improving cold production.