Performance analysis and optimum design of a heat exchanger for waste heat recovery

Abstract

Enhancement in performance of heat transfer is one of the most significant issues for a heat exchanger in waste heat recovery systems. In design of the heat exchanger, increases of the heat transfer area and the heat transfer coefficient have been generally considered until now. On the other hand, a practically-designed heat exchanger has not often provided enough performance in terms of the heat transfer due to restrictions of installation space of the system and pressure drop of working fluid. Especially, in the waste heat recovery system for internal combustion engines, it is necessary to pay attention for a design of exhaust system because high-pressure drop of exhaust gas has considerable effect on combustion in the engine. In this study, the mathematical models which can estimate heat transfer rate of the heat exchanger and the pressure drop of exhaust gas has been defined. The mathematical model has roughly validated by comparison with CFD. And then, the optimum design of the heat exchanger has been considered for the solution of a trade-off problem between the heat transfer rate and the pressure drop of exhaust gas based on a genetic algorithm coupled with the mathematical model. Moreover, the benchmark experiment has been carried out with some prototypes of heat exchanger based on the optimum calculations, and the validation study of the mathematical model has presented by the comparison with the experiments. The methodology of the optimum design for the exhaust gas heat exchanger has been mentioned from these results.

Keywords

• waste heat recovery
• heat exchanger
• optimum design
• mathematical model
• genetic algorithm