Heat transfer and flow of droplets in ejector diffusion chamber for liquid nitrogen ejection by low-temperature gas helium
To optimize the formation of solid particles during liquid nitrogen injection by low-temperature gas helium,mathematical models for the heat transfer and flow of nitrogen droplets and gas helium in the ejector diffusion chamber were built to analyze their characteristics and also the heat transfer mechanism of liquid nitrogen solidification.The influence of initial droplet diameter,initial gas condition and liquid-gas flow ratio on the slush nitrogen formation was emphatically studied.The results show that the solidification processes of droplet with various diameters are sig-nificantly different.Smaller droplets are easier to solidify,but heat transfer reverses in the stage of solid temperature regulation.With the increase of droplet diameter,the complete solidification dis-placement increases exponentially.The heat transfer caused by mass transfer is enhanced with the increase of gas temperature and plays a leading role in the freezing stage of large droplets.Reduc-ing the initial gas velocity and temperature is conducive to increasing the solidification rate at the outlet.The solidification rate is higher than 99％when the liquid-gas flow ratio is changed at the initial gas temperature of 30 K.However,the solid formation rate and heat transfer efficiency in-crease mainly with the increase of liquid-gas flow ratio.
slush nitrogenejectordroplet solidificationheat and mass transfer
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