Numerical Analysis For The Thermal Response Of Liquefied Gas Tanks Subjected To Fire Environment

In recent years, release, fire and explosion accidents of liquefied gas in vessel happen more and more frequently due to considerable use of liquefied gas in industry and daily life as fuel, which can cause severe loss of human life and property. In many countries, therefore, great attention is paid to such accidents and a lot of experimental and numerical research works are carried out especially about the thermal response behavior of liquefied gas subjected to fire engulfment. Owing to the transitoriness and complexity of tank explosion, it is very difficult to investigate the mechanism of these fire and explosion accidents of liquefied gas completely only by experimental research. Accordingly, numerical simulating research has being carried out in this research field, i.e. analyzing physical phenomena based on experiments, setting up relevant physical models and mathematical models and modeling by computer imitate technique, and great progress has been made. Among these researches thermal response simulation of a liquefied gas tank exposed to a fire, mechanism of these fire and explosion accidents of liquefied gas are very important to avoid these accidents.The differential equations and the relevant boundary conditions that describe the thermal response of a liquefied gas tank subjected to a fire are built according to mass conservation, energy conservation and combined with research findings of the entire world. These equations including tanks wall and medium in the tanks form mathematic models for the thermal response of a liquefied gas tank subjected to accidental fire conditions.A finite difference method is adopted to calculate mathematic models for the thermal response of a liquefied gas tank. The difference equations are built using a direct method for inner nodes of tank wall and using conversation of energy for boundary nodes. The transient temperature distribution of tank wall is solved using an implicit finite scheme. The temperature, density and mass variety of medium in tanks are calculated by lumped-heat-capacity method.The numerical analysis system for the thermal response of a liquefied gas tank subjected to accidental fire conditions is developed using object oriented and visual C++ Builder including the design of the main interface and drawing of simulating curves. And the relevant database is set up using Microsoft Access database to store modeling results and famous experiment conditions of the world. This software can simulate the thermal response process of a liquefied gas tank in condition of different fire environment, different shape of tank and different medium filling ratio.Comparison of simulation results and experimental results from HSE (Health and Safety Executive, UK) shows that the simulation results are consistent with the experimental results. Therefore, the physical models, the mathematical models, the. numerical methods and the program design of the numerical simulation system are proved to be reasonable.The thermal response of a tank in different conditions is simulated and the primary factors that affect the thermal response of a tank are analyzed. Several protective measures are put forward based on current conditions in which liquefied gas is used. The advantages and disadvantages of these measures are analyzed in detail. It is very helpful for the safe transportation and design of liquefied gas tanks...