Investigation of sub-cooling methods for discharged liquid nitrogen jet from injector

One of the problems in the experiment of breakup cryogenic liquid jet is the state of discharged cryogenic liquid jet from injector. In some applications, it is necessary jet to be in the sub-cooled condition. However, at atmospheric condition, the discharged cryogenic liquid jet becomes two-phase. In the present article, the methods for sub-cooling of the liquid nitrogen jet are investigated and a simple method to achieve this goal is used. With this method, which is based on holding at low pressure, a sub-cooled liquid nitrogen jet with a temperature of about 7 K lower than the saturation temperature was obtained. Then, the behavior of the liquid nitrogen jet at high pressure and atmospheric pressure is evaluated. High speed camera was used to observe the behavior of the jet. The speed of liquid jet is changed from 12 m/s to 34 m/s according to the Reynolds number from 90000 to 260000. When the liquid nitrogen jet is discharged into the environment under standard conditions, the jet becomes two-phase and expands. The larger the injector pressure difference, the greater the expansion of the jet; So that in the pressure difference of 6 and 13 bar, the diameter of the jet is 1.5 and 3.3 times the diameter of the injector, respectively. In the test speed range, under the conditions provided for the liquid and the environment, the breakup of the sub-cooled liquid jet leads to the production of very small droplets that are consistent with the expectation of such a liquid.