IMPACT OF FIN CUTS AND REFRIGERANT LAYOUT ON THE PERFORMANCE OF A MICROCHANNEL GAS COOLER WORKING WITH TRANSCRITICAL CO_2

摘要

Microchannel heat exchangers (MCHX) play an important role in topics about charge reduction and transcritical cycles due to its high compactness and high mechanical strength. From a designer's point of view, given an air-side area and faced area, there are many options to design the refrigerant circuitry and aspect ratio of a MCHX. The paper presents numerical studies about the influence on the MCHX's performance of these design parameters for a gas cooler working with CO_2 under transcritical pressures. A technique to improve the MCHX effectiveness is to cut the fins along the middle section between neighboring tubes. Following same methodology as was used in previous study, the paper analyzes the improvement by cutting fins for different gas cooler layouts. A key point of the paper is that the parameters analyzed can only be assessed by models which take into account heat conduction between tubes otherwise their effects would be hidden. Results illustrate some general design recommendations in order to maximize effectiveness of gas coolers working in similar conditions. Improvement on gas cooler effectiveness by cutting fins depends on the gas cooler layout, ranging from an optimum value for a specific configuration to negligible for other configurations.