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 andrntranscritical cycles due to its high compactness and high mechanical strength. From a designer's point ofrnview, given an air-side area and faced area, there are many options to design the refrigerant circuitry andrnaspect ratio of a MCHX. The paper presents numerical studies about the influence on the MCHX'srnperformance of these design parameters for a gas cooler working with CO_2 under transcritical pressures.rnA technique to improve the MCHX effectiveness is to cut the fins along the middle section betweenrnneighboring tubes. Following same methodology as was used in previous study, the paper analyzes thernimprovement by cutting fins for different gas cooler layouts. A key point of the paper is that thernparameters analyzed can only be assessed by models which take into account heat conduction betweenrntubes otherwise their effects would be hidden. Results illustrate some general design recommendations inrnorder to maximize effectiveness of gas coolers working in similar conditions. Improvement on gas coolerrneffectiveness by cutting fins depends on the gas cooler layout, ranging from an optimum value for arnspecific configuration to negligible for other configurations.