Design optimization of bare tube heat exchanger for the application to mobile air conditioning systems

A louver fin heat exchanger (LFHX) has been widely used as an evaporator in the mobile air conditioning system due to its high heat transfer performance. However, there is an inherent problem of the LFHX such that it is poorly drained due to the fins. This causes problems with odor, corrosion, and window fogging. The purpose of the study is to investigate a bare tube heat exchanger (BTHX) to overcome LFHX problems while maintaining heat transfer and air-side pressure drop performance. In this context, heat transfer performances for both LFHX and BTHX were measured experimentally, and the numerical model of the heat exchanger was developed and validated. Then, the geometry model of the BTHX is optimized with five independent design variables. The approximated assisted optimization method is applied with the objectives of maximizing heat transfer performance and minimizing air-side pressure drop. A global sensitivity analysis is performed to analyze the effect of design variables on output performance. A dynamic dip test was performed to evaluate the drainage performance of heat exchangers. The performance of the optimized BTHX is compared with that of the LFHX and discussed the potential of the BTHX for the application to the mobile air conditioning systems.