Experimental Study On Influencing Factors And Calculation Method Of Evaporation Rate Of Cryogenic Storage Tank

Cryogenic storage tank has the characteristics of low transportation cost,convenient operation and strong storage capacity.So it has been used in all walks of life in recent years.And the evaporation rate of the tank is the main index to test the insulation performance of the storage tank.In this paper,a cryogenic tank with nominal volume of 195 L is used,and liquid nitrogen is used as the experiment medium.The weight of the liquid and the mass flow of gas were recorded by weighing method and steam flow meter respectively.And analyzed the influence of temperature,pressure and filling rate on the evaporation rate.The main tasks are:1.Starting from the experimental purpose,through the design and selection of multi-point temperature sensors,weighing sensors,flowmeters,cryogenic storage tanks and other devices,so that a low temperature experimental system is formed.2.In paper,taking the low temperature insulated tank as the object,study the temperature field,the safe storage time,the pressure rising speed and the evaporation rate of the tank.The results show that:(1)filling cryogenic liquid exist a rapid temperature drop region,the regional temperature changes quickly in short time;(2)with different effect on tank evaporation rate,the experimental study found 0.81 full rate is the best value,when more than value of storage tanks the evaporation rate did not fall by this;(3)study significant analysis of experimental results,found that environmental temperature is the biggest effect on the evaporation rate.3.Based on the diffusion theory and three conservation equations,establish the model of LNG tank filling process of different densities are simulated,the low density of the liquid in the buoyancy force under the action of upward movement,weight density liquid distribute in the tank bottom;at the same time,establish a two-dimensional bottom heating model,and simulate the process of mixing.4.Using the linear model,exponential model,power-law model and grey model GM(n,H)to describe results of the experiment and choose the better effect model to describe the effect on low temperature tank evaporation and fitted curve formula.5.On this basis,using MATLAB to write a calculation program about cryogenic liquid evaporation rate,the program not only re-correct cryogenic tank evaporation rate which depend on environmental temperature,initial filling rate,pressure,can also accurately predict the evaporation rate of long-term storage.The study of this paper can be used to improve the storage time and reduce the waste of low temperature liquid.