Research of mixing and heat transfer performance of liquid nitrogen foam generator with SK spoiler
In order to enhance the mixing and foaming performance of the liquid nitrogen foam generator and mitigate the is-sue of ice blockage,the numerical simulation was conducted followed by experimental validation to study the mixing and heat transfer characteristic of SK spoiler.Through the numerical simulation and comparative analysis of different liquid nitrogen flow velocity,spacing,and shape parameters of the cone spoiler and SK spoiler,the outlet nitrogen volume fraction,coefficient of variation,and temperature along the way were studied.Additionally,the effects of aspect ratios,number of units,and spac-ing on mixing homogeneity were compared using the range analysis for factor effects.The results show that the SK spoiler,compares to the cone spoiler,significantly improves the gas-liquid mixing and heat transfer performance by introducing the swirling flow to disrupt flow stratification,resulting in an 83％reduction in the coefficient of variation.Furthermore,as the flow rate of liquid nitrogen increases,the local sub-freezing conditions within the pipe can lead to ice blockage,suggesting the maximum flow rate ratio ranging from 1∶33 to 1∶50.With the increase in the distance between liquid nitrogen jet and spoi-ler,the vaporization rate of liquid nitrogen decreases,leading to the corresponding reduction in the outlet nitrogen volume frac-tion and velocity,and the effect is better under 10 mm spacing.Under the spoiler length of 300 mm,the mixing homogeneity increases first and then decreases with the decrease of spoiler aspect ratio,while the pressure loss gradually increases.Com-prehensively considering the pressure loss and mixing homogeneity,the optimal aspect ratio is 0.75,and the aspect ratio has a significant impact on the coefficient of variation.The research results can provide guidance for the design of liquid nitrogen foam generator and enhancing the foaming performance.
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