Optimization Analysis Of Bonnet Structure And Temperature Field Of Cryogenic Valve With Drain Tray

With the rapid development of petrochemical, LNG, refrigeration industry and cryogenic industry in China, the demand quantity of cryogenic valve is more and more, as well as its performance requirements is increasingly high. When the filling seal temperature of cryogenic gate valve, ball valve, stop valve and butterfly valve is below 0℃, if the condensed water in the air is into the filling seal, it will be frozen. It not only affects the normal operation of valve stem, but also scratches the seal and makes it failure when the valve stem is moved vertically. Therefore the length of bonnet is usually extended(long neck bonnet). The extended length of bonnet can make the working temperature of filling seal bottom be above 0℃。The drain tray is welded on the face of long neck bonnet to prevent the condensed water from entering the cold-keeping layer and avoid or alleviate its corrosion. Meanwhile, the heat exchange area of natural convection between bonnet and air is enlarged and the cold loss from valve body is reduced after fixing the drain tray.Using the correlation theory transfer heat study and energy conservation principle, thermal conduction differential equation of drain tray was derived in this paper. And according to the boundary conditions of model, it obtained the temperature field of drain tray, and then the calculation method of heat dissipating capacity and efficiency of drain tray. At same time, according to the Fourier thermal conduction differential equation in the cylindrical coordinates, it obtained the differential equation of long neck bonnet and used the separation of variables to solve its general solution. After that, it used the orthogonality of Bessel function to determine undetermined coefficient so that derived the temperature field of long neck bonnet. And it simplified this function to substitute the initial condition with filling seal temperature being 0℃. Finally, the calculation model of least length of bonnet was derived.Taking the DJ41W-300 Lb P 6″cryogenic stop valve for example, the related parameters were substituted into the calculation model to solve the value of least length of long neck bonnet. Meanwhile, it used Workbench to make finite element analysis for this valve to derive the temperature field and the least length of bonnet.It utilized this mathematical model and finite element analysis to analyze the effects of some factors on the least length of the long neck bonnet, such as the material thermal conductivity, the radius, fixing quantity and spacing of drain tray, ambient temperature and so on. And it obtained the reasonable plan of shortening its least length. It provided reference for production design and theoretical research.