Study On Calculation Method Of LN₂ Injected Into LNG Road Tanker

Injecting LN₂ into LNG road tanker will not only reduce the quality of LNG,but also change the temperature and pressure of the LNG tank,which may bring about safety hazards.In this paper,temperature and pressure changes are studied and a calculation method of LN₂ injected into LNG road tanker is put forward.The calculation model of the temperature and pressure of LNG with LN₂ is established,it shows that the temperature of LNG in tank reduces rapidly after filling,and improves slowly in transportation.The calculation method of LN₂ injected into LNG road tanker is established so that the amount of LN₂ can be calculated based on the raw LNG components,initial temperature and pressure,tank vehicle parameters,transportation time and terminal pressure.The numerical simulation of bottom filling is carried on which is likely to be the way of filling procedure.The process of mixed liquid nitrogen can be divided into four stages:filling process,the static mixing process after filling cut-off,the boost caused by evaporation after filling cut-off,the improvement of temperature and pressure during the transportation.It shows that LNG and LN₂ are homogeneous mixing in the end of the static mixing process after filling cut-off,and vertical temperature gradient of storage tank is close to zero,but the temperature of the front part slightly higher than that of the behind,and the pressure rises to 192 kPa suddenly,then the temperature and pressure increase slowly during transportation.The simulation result is almost same to calculation model,which shows that the calculation model can figue out the the amount of LN₂ correctly in LNG tank.The calculation software of LN₂ amount is edited,which can judge whether LN₂ is injected into LNG road tank and how many.