Thermodynamic analysis of alternative refrigeration cycles driven from waste heat in a food processing application

In this paper, the performance comparison of a waste heat driven Organic Rankine Cycle (ORC) powered Vapour Compression Refrigeration (VCR) system and a waste heat driven NH3–H2O Absorption Refrigeration (AR) system were carried out through modelling and simulation using IPSEpro PSE simulation tool. The simulation result shows that at the given design constraints, the ORC driven VCR system gives a better COP and second law efficiency than the AR system. Also at the breakeven pressure ratio (pressure ratio at which the COP of both system is the same) the ORC driven VCR system also gives a better second law efficiency than the AR system. However, at pressure ratios higher than the breakeven point, performance behaviour seems to contradict the well known notion that systems with low irreversibility should be more efficient that those with high irreversibility. This is a paradox and might be as a result of high number of thermal systems in the AR system. However, the trend in the COP and Φ obtained for each of the systems conforms to expectation (i.e. increase in COP leads to decrease in Φ).