Thermodynamic modelling for absorption refrigeration cycles powered by solar energy and a case study for Porto Alegre, Brazil

The objective of this study is to develop explicit thermodynamic models for absorption refrigeration systems. The models include recent advances in calculating thermodynamic properties of ammonia-water system, the parabolic trough solar collector (PTC) model and the storage tank model. The configurations studied are the single stage cycle (SAR-C) and the generator-absorber heat exchange absorption refrigeration cycle (GAX-C). However, the procedure can be extended to other cycles or to other refrigerant-absorbent pairs. The thermodynamic model was validated with published experimental results. In terms of coefficient of performance (COP), the models of both cycles showed excellent accuracy. The average relative errors were 6.91% and 1.34%, respectively. A parametric study was performed to determine the feasible evaporation temperatures. A critical mass flow ratio was also determined. It was found that higher evaporator temperatures and lower condenser temperatures increased COP. A case study was also conducted for the city of Porto Alegre in the south of Brazil. During the summer and spring, a maximum cooling load of 18.89 kW was reached in December, while the minimum cooling load of 11.31 kW was reached in March. The system is suitable for a commercial office with a peak cooling load between 12 and 16 h.

Automated summary

The study aimed to develop explicit thermodynamic models for absorption refrigeration systems. The models included recent advances in calculating thermodynamic properties, parabolic trough solar collectors, and storage tanks. The models were validated with experimental results and showed excellent accuracy in terms of coefficient of performance (COP). A parametric study was conducted to determine feasible evaporation temperatures, and it was found that higher evaporator temperatures and lower condenser temperatures increased COP. A case study for a city in Brazil showed the system's suitability for a commercial office with a peak cooling load between 12 and 16 hours.