Numerical Analysis of Vapour Absorption Refrigeration System with different Refrigerant Absorbent Pairs

Vapour absorption refrigeration systems (VARS) offer a promising alternative for cooling applications driven by thermal energy. This study presents a numerical and comparative thermodynamic analysis of three ammonia-based refrigerant pairs: ammonia–water (NH₃–H₂O), ammonia–lithium nitrate (NH₃–LiNO₃) and ammonia–sodium thiocyanate (NH₃–NaSCN). A mathematical model based on mass and energy balances of the major cycle components was developed and implemented in MATLAB. The effects of generator, condenser, absorber and evaporator temperatures on the coefficient of performance (COP) were investigated. Under the selected reference conditions, the COP of NH₃–H₂O, NH₃–LiNO₃ and NH₃–NaSCN were 0.616, 0.624, and 0.639, respectively, with NH₃–NaSCN exhibiting the highest performance. At a generator temperature of 100 ˚C, the COP reached approximately 0.650 for NH₃–NaSCN, compared with 0.635 for NH₃–LiNO₃ and 0.630 for NH₃–H₂O. For NH₃–H₂O, COP increased from 0.608 to 0.622 as generator temperature increased from 50 ˚C to 100 ˚C, while it decreased from 0.660 to 0.578 as condenser temperature increased from 15 ˚C to 45 ˚C. Furthermore, increasing evaporator temperature from −15 ˚C to 15 ˚C, COP increased from approximately 0.604 to 0.624 for NH₃–H₂O. Overall, NH₃–NaSCN demonstrated the highest thermodynamic performance among the investigated refrigerant pairs.