Application of an Evolution Program for Refrigerant Circuitry Optimization | NIST

Increased concerns about climate change have emphasized the importance of airconditioning and refrigeration systems with a high coefficient of performance (COP). The effectiveness of heat exchangers significantly influences the vaporcompression system’s COP. Evolutionary algorithms provide an opportunity to optimize engineering designs of heat exchangers beyond what is typically feasible for humans. This paper presents a summary of our past and most recent work with finned-tube heat exchangers using an evolutionary program, Intelligent System for Heat Exchanger Design (ISHED), which optimizes refrigerant circuitry. The experiments with ISHED included evaporators and condensers working with refrigerants of vastly different thermophysical properties and heat exchangers exposed to non-uniform air distributions. In all cases, ISHED generated circuitry designs that were as good as or better than those prepared manually. Further simulations showed that the COP ranking of R600a, R290, R134a, R22, R410A, and R32 in systems with optimized heat exchangers differed from the ranking obtained using theoretical cycle analysis. In the system simulations, the high-pressure refrigerants overcame the thermodynamic disadvantage associated with their low critical temperature and had higher COPs than the low-pressure refrigerants.