| As is now well known, petroleum and natural gas are indispensable important energy sources in the economic development of all countries at present. The economic competition among all countries becomes more and more impetuously. Whether the oil and gas system is perfect not only affects the sustainable development stratagem of the country economic construction, but also is the important factor of restraining the balance and development of domestic area economy.The basic component of natural gas is methane (CH4). Natural gas is mainly used as fuel except for being used as cheap raw chemical material, it is a kind of high quantity fuel, having high calorific value, and its combustion products less pollute the environment. At present, it is one of the energy sources with the least social effects of pollution and regarded as "clean fuel". Like other energy sources, the producing area of natural gas is not often at the place where the industries centralize, the producing and sale area are often separated by the oceans, especially for the development of the offshore gas, we must resolve the transportation problem. As the volume of liquefied natural gas (LNG) is only 1/625 of its original one. It becomes one of the main modes of transporting the offshore gas. Lots of natural gas need liquefying, and turn into LNG, then being transported by LNG carriers. As for the transportation temperature of cryogenic liquid cargo is -162癈, LNG carrier is unheard-of ship with high technology, high difficulty and high additional value. The technology of LNG carrier has been fairly advanced abroad.Developing the large ships with high technology and high additional value has become the focus of the world ship market competition. China has become the large shipping country, however, its shipping industry hasn't had practical experience of managing and transporting LNG, and has no one LNG carrier. It is blank in producing, storing and transporting LNG in China. The Ministry of Communications of the People's Republic of China has ranked the project-"designing and making engineering of ships with high technology and performance" as one of the twelve large engineering projects with high technology,and ranked LNG carrier as one of the main new ships in the projects. In the "fifteenth plan" of the Ministry of Communications, it said that oceangoing and coastal ships would be developed in the direction of macro-scale operations technology and specialization. The emphasis is developing liquefied gas carriers, especially is the LNG carriers, large bulk carriers, large oil tankers, container ships and ro ro vessels.The transportation and storage of LNG is one the pivotal technology of developing and using natural gas. The security and economical efficiency of the transportation and storage are very important. In the present paper, I have analyzed the main method of liquefying natural gas, the types and design principles of liquefied gas carriers, the technical characteristics of LNG carriers and the cargo hold types of LNG carrier. I have studied and compared some typical thermal insulation structures of cargo hold, brought forward the train of thoughts of designing and applying heat pipe as the thermal insulation of cargo hold and it is a new kind of thermal insulation technology. I have analyzed and studied the other new thermal insulation according to thermodynamics, which is vapor insulation system. In the present paper, according to the economical efficiency of LNG carriers' operating, I have made a thermodynamic research to the precooling process of cargo hold, gained the precooling way and rule, calculated the thermal load when the precooling is finished, gained the calculation method for the precooling temperature of MOSS type cargo hold and the program, analyzed and studied the temperature changing rule of cargo hold. I have validated the theoretical calculation result with the real ship data, it showed that the research is valid and real, and the error is in the permitted range.This thesis is the first research in this... |
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