Research Of Flow Distribution Characteristics Of Supercritical Carbon Dioxide In The Microchannel Parallel Flow Gas-cooler

As growing along with the energy conservation and emissions reduction, environmental friendly, it has become a research hotspot to look for alternative to replace the refrigerants which cause environmental damage and greenhouse effect. As a natural working substance, CO2 has the extremely broad application prospect especially under supercritical condition, the flow and heat transfer performance is very good.Research in the field of heat transfer of supercritical carbon dioxide is rich both at domestic and abroad, but the application of parallel flow supercritical CO2 flow of air cooler study is less. Numerical simulation, orthogonal experiment design and experimental study are applicated compossitive in this paper. And internal flow distribution characteristics of parallel flow of supercritical carbon dioxide air cooler is analyzed, the main research contents and results are as follows:(1) Physical properties of supercritical carbon dioxide area is obtained in this paper through software of REFPROP and sums up the parameters changes with temperature curve.It finds that the change trend are same basically, the most dramatic change is near the critical point. At a certain temperature, the greater the pressure, the bigger the value of corresponding;but under a certain pressure, with the increase of temperature, the curve is flat gradually.(2) The numerical simulation combined with orthogonal experimental design method are used in this paper to study flow distribution characteristic of gas cooler.Several important factors which affect the internal flow distribution are listed first,such as:combination depth of flat tube and header pipe, length of flat tube, flat tube row number, tube space, diameter of microchannel, number of microchannel hole, and select number of levels and examining index, orthogonal table, make sure different combinations second, a total of 24 groups, establish and calculate the overall air cooler model respectively in the ANSYS software, then the results show that in terms of the total flow mal distribution, the influence of various factors to primary and secondary are as follows:space of flat tube<number of microchannel hole<row number of flat tube<combination depth<length of flat tube<diameter of microchannel;in terms of inlet and outlet pressure drop,the factors of primary and secondary are as follows:combination depth<length of flat tube<space of flat tube<number of microchannel hole<row number of flat tube<diameter of microchannel.According to the comprehensive balance method,the total flow maldistribution is the main consideration within the scope of the parameters in this paper, the optimal combination is that combination depth is 0.4,length of flat tube is 200 mm, row number of flat tube is 8,space of flat tube is 9.0 mm,microchannel diameter is 0.6 mm, number of microchannel is 9,in consideration of both indicators of the total flow maldistrubiton and pressure drop.(3) Effect of different types of collector tube on microchannel overall flow distribution are comparative analysized, the results show that flow distribution of the structure of the header pipe for type D microchannel is most uniform among the different structure. The equivalent diameter of 13.3 mm type D tube is more suitable to improve flow distribution performance compared with the different equivalent diameter of D type header pipe.And internal flow distribution is analysized in the condition of different inlet pressure,inlet temperature and inlet the mass flow rate.The results show that the pressure and temperature have little impact on the uniformity of flow distribution and although mass flow rate is different, the curve trend are same basically, the increase of inlet mass flow rate, the total flow maldistrubition also has a tendency to rise.(4) The experiment scheme is established and a set of microchannel air-cooling experiment device is designed,measure according to the experimental principle.Each row of the flow inside the micro channels is measured when the inlet flow of 18 1/h,28 1/h,38 1/h,respectively,and the numerical simulation results are agree with the expetiment, which prove the accuracy and reliability of the results of numerical simulation.