Simulation-oriented multi-criteria efficiency optimization of a solar energy-based waterheater system for use in marine vessels

This paper aims to design and develop thermodynamic model and a multi-criteria performance optimization of adirect-expansion solar-assisted heat pump water heater (DX-SAHPWH) system to supply hot water for marinevessels throughout the whole year. After the validation of the thermodynamic model, the performance of theDX-SAHPWH is analyzed for use in marine vessels in Bandar Abbas zone. Then, a parametric study isconducted to identify how various design parameters may affect the performance of the DX-SAHPWH system.In the current investigation, the effects of design parameters including solar radiation intensity, ambient airtemperature, outlet water temperature of the condenser, solar collector area, compressor speed, length of tube inthe condenser, external diameter of the tube in collector plate, fin thickness, and thermal conductivity ofcollector plate on the performance of the DX-SAHPWH are investigated. Besides, single and bi-criteriaoptimizations are carried out using genetic algorithm(GA) to obtain the optimal solutions of design parameters,where the coefficient of performance (COP) and the solar collector efficiency (SCE) are selected as two fitnessfunctions. The optimal solutions achieved from the bi-criteria optimization process will be given as Paretofrontier. The final optimum solution from the available solutions on the Pareto optimal frontier is selected usingdecision-making methods, such as LINMAP, TOPSIS, and Shannon’s Entropy. The comparison of single and bicriteriaoptimization results illustrate that the bi-criteria optimization method yields more proper results thansingle ones, mainly because of the lower deviation index from the ideal solution. The results of bi-criteriaoptimization show that SCE decreases ۱.۶% compared to the initial model while the COP increases close to ۲۰%that makes the optimum solution more desirable compared to the single ones. Moreover, the performance of theoptimized DX-SAHPWH system is compared with the initial model in each month of the year. The resultsindicate that the performance of the optimized DX-SAHPWH is highly improved so that the working hours ofthe system decrease close to ۱۰۹ hours compared to the initial model during the whole year.