Design of Performance Test System for Water-Water and Carbon Dioxide Compressed Air Microchannel Heat Exchanger

Abstract

As a new type of heat exchanger with compact structure and efficient performance, microchannel heat exchangers have good application prospects in industries with strict requirements such as energy and power, petrochemical, aerospace, and other industries. Therefore, exploring the performance and heat transfer characteristics of microchannel heat exchangers is of great significance. This article designs a performance testing system that can simultaneously explore the enhanced heat transfer inside the pipeline of water water and carbon dioxide compressed air microchannel heat exchangers. The variable working fluid circuit design is used to analyze the factors that affect the enhanced heat transfer. The Control variates is used to control the heat transfer conditions, explore the difference of heat transfer performance between different working fluids under different flow rates, inlet temperatures and other conditions, and analyze the heat transfer performance of different channel types by comparison method. The results indicate that when the hot water flow rate range is 2.063×10-5~2.556×10-5m3/s, Re<2320, and under the same flow rate conditions, the Nu of the 3.6 mm inner diameter microchannel is significantly higher than that of the 6.6 mm inner diameter microchannel. When the inlet flow range is 2.063×10-5~2.556 ×10-5m3/s, the Reynolds number and Nusselt number in the pipeline increase with the increase of inlet flow. In the carbon dioxide compressed air heat transfer experiment, when the flow rate range is 2.810×10-4~3.182×10-4m3/s, the Nusselt number and convective heat transfer coefficient of the 3.6mm inner diameter microchannel are always greater than the Nusselt number and convective heat transfer coefficient of 6.6mm. When the pipe diameter is the same, the water water microchannel heat exchanger has better heat transfer performance and smaller pressure drop compared to the carbon dioxide compressed air microchannel heat exchanger.