Heat exchanger circuitry optimization using an enhanced integer permutation-based genetic algorithm in low-GWP reversible heat pump applications

Tube-fin heat exchangers (HXs) are key components in air-conditioning and heat pump applications. Advanced heat exchanger design optimization tools are desired to adapt to the industrial transition from conventional refrigerants to low Global Warming Potential (low-GWP) refrigerants. The performance of heat exchangers is strongly influenced by the refrigerant circuitry. This research presents an enhanced integer permutation-based Genetic Algorithm (IPGA) to optimize the circuitry of tube-fin heat exchangers. To remedy the limitation of the previous IPGA, which cannot generate designs with splitting and merging of circuits, a new chromosome, as well as new generic operators, are developed. The enhanced IPGA uses effective chromosome representations and GA operators to guarantee the chromosome (genotype) can be mapped to valid heat exchanger designs (phenotype) and incorporates real-world manufacturability constraints to ensure the optimal designs are manufacturable with the available tooling. Previous circuitry optimizations focus on improving component-level performance under a specific operating condition, i.e., the heat exchanger either works as a condenser or an evaporator. The optimal circuitry obtained under air conditioning (AC) mode cannot guarantee optimal performance when used in heat pump (HP) mode. To improve the dual-mode performance of reversible heat pumps, a bi-objective optimization problem formulation is implemented to achieve optimal system performance in both AC and HP modes. A case study using six refrigerants, i.e., R410A, R452B, R454B, R32, D2Y60, and L41a, shows that optimal heat exchangers yield up to 6.1 % energy efficiency ratio (EER) improvement under AC mode and up to 8.5 % coefficient of performance (COP) improvement under HP mode. The use of this design approach can ensure a preferable performance of reversible heat pumps during both cooling and heating modes.