Analysis of plate heat exchangers in binary flashing cycle using low-temperature heat source

The utilization of low-temperature heat sources represents an efficient technology that has the potential to significantly reduce both energy consumption and greenhouse gas emissions. Among the various technologies that harness low-temperature heat sources, the binary flashing cycle (BFC) stands out as a promising option. The application of the BFC is highly dependent on the thermal-hydraulic performance of the heat exchangers, which underscores the critical importance of effective heat exchanger design. The popular used plate heat exchangers (PHEs) are selected as suitable candidates for BFC system. Detailed thermodynamic, hydraulic, and thermal design models for the BFC system are developed for PHEs. The effects of geometrical parameters of the evaporator and condenser on the heat exchanger area and pressure drop are investigated simultaneously. It is revealed the increments in plate width and plate number leads to an augmentation of the heat exchanger area while concurrently reducing the pressure drop. Moreover, an optimal plate space is identified, which minimizes the pressure drop. Additionally, it is observed that the evaporator and condenser exhibit superior thermal-hydraulic performance, when the corrugation angle is approximately 60 degrees. Furthermore, a multi-objective optimization approach employing Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is utilized to determine the optimal geometrical parameters. In order to classify the alternatives to the obtained Pareto front, the technique of order preference by similarity to the ideal situation (TOPSIS) is applied. It should be noted that the decision variable is influenced by the weight factor assigned to the objective function. The optimal plate width, channel spacing, plate number, and chevron angle range from 0.3-0.56 m, 3.5-5.9 mm, 20-24, 68-74 degrees, 0.20-0.75 m, 3-7 mm, 30-32, and 56-59 degrees, respectively. The study provides valuable insights for decision-makers involved in engineering application regarding the thermal-hydraulic performance of plate heat exchangers within the BFC system.