Performance of flow distribution in a microchannel parallel flow gas cooler with stepped protrusion depth header

Microchannel parallel flow gas cooler is commonly used in transcritical carbon dioxide automotive air conditioning system. To investigate the influence of the flat tube protrusion depth on fluid distribution, a numerical calculation model of microchannel parallel flow gas cooler with D-shaped header is established. With the object of even flow distribution, a novel stepped protrusion depth header is proposed. The effects of new header on the flow distribution of gas cooler were studied by numerical simulation. The results show that the flow distribution performance of gas cooler can be improved by changing the flat tube protrusion depth. Changing the protrusion depth of three groups of flat tubes simultaneously can achieve a better flow distribution performance of gas cooler than changing the protrusion depth of only one or two groups of flat tubes. When compared with the protrusion depth of all flat tubes is 0, the novel stepped protrusion depth header reduces the total flow distribution nonuniformity of gas cooler by 34–51%. The research in this paper provides a method for improving the flow distribution performance of gas coolers.