Full Description

Recent work has been conducted to characterize the air-side heat transfer and pressure drop performance of heat exchangers with slit and louver fins and tube diameters ranging from 3-5 mm (0.12-0.2 in). These newly developed correlations have been implemented into a heat exchanger simulation tool to predict the performance of heat exchangers with varying designs and operating conditions. An optimization study was conducted using a Multi Objective Genetic Algorithm (MOGA) technique to vary key parameters of the heat exchanger designs in order to optimize performance.

In this sample case study, the outdoor unit of a 1-ton residential split AC system is optimized to minimize air-side pressure drop and raw material costs while maintaining equivalent capacity. Minimization of charge and coil volume are also achieved through optimization.The design space of the study is comprehensive, including not only the number and dimensions of tubes and fins, but also the variation of the fin surface geometry details (e.g. slit height, number of slits, etc.) across the range of the correlations. This is the first optimization study of this type presented for slit and louver fin heat exchangers with tube outer diameters from 3-9.52 mm (0.12-0.375 in).

Findings indicate the potential for significant cost savings when replacing the baseline 9.52 mm (0.375 in) tubes with smaller diameter tubes. Current results show that the optimal designs with 9.52 mm tubes have material costs on the order of twice as much as the optimal designs with 5 mm (0.2 in) tubes for equivalent performance. To some extent, the results also indicate diminishing returns as the tube size continues to decrease below 5 mm. From this effort, additional analyses can be conducted with different objective functions and constraints including minimization of charge or volume or optimizing a system of a different capacity and configuration.

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