CFD Simulation Study on the Air Side of a CO2 Evaporator in a Motor Train Unit Air Conditioning System

At present, China’s high-speed rail is in a period of rapid development. Most the refrigerants used Chinese motor train units at this stage are still R134a and R407c, which have an impact on environment. In response to environmental protection concept green travel, it great significance study air conditioning system using CO2 refrigerant. Using CFD simulation analysis technology, heat transfer performance side finned tube evaporator unit studied. We select outlet temperature, pressure drop, factor, resistance factor as objective function, addition, monitoring points set up flow channel monitor turbulent field pipe wall pressure. Our research shows that cooling capacity can reach 29.76 kW, meet exchange required unit. order obtain better structure conditions effect, structural optimization was conducted. The results demonstrate several trends: (i) With augment inlet velocity, increases effect improves; when ve > 2.2 m/s, continuing weak. (ii) Following appropriate reduction diameter tube, wind reduced improved. (iii) enlargement fin spacing, motion be fully developed, there peak change area optimal spacing between 1.6 mm 1.7 mm; time, average kinetic energy larger dissipation rate smaller. These provide reference for practical application refrigerant