The Setting Bases of Working Pressure in LNG Systems and Orthogonal Experiment Design of Heat Exchangers
|School||Harbin Institute of Technology|
|Course||Refrigeration and Cryogenic Engineering|
|Keywords||LNG Mixed refrigerant cycle Working pressure Orthogonal experiment design Numerical simulation|
Liquid natural gas (LNG) has obvious advantages in storing and transporting natural gas. Compared to LNG technology in western nations, the LNG technology in China which is a new technology and developing rapidly have a shorter history and a big technology gap. There are lots of scattered and remote natural gas resources in China, which haven’t been utilized for limits of kinds of conditions, and our purpose of researching small plants of gas liquefaction is no other than to utilize these natural gas resources. Based on thermodynamics, here the simulation and optimization of the process of mixed refrigerant cycle (MRC) for small scale gas liquefaction plants have been researched.In this thesis first the history and trends of LNG technology in the world is presented, and the principle of liquefaction technology is introduced. Based on the investigation of different liquefaction technology chosen by plants of natural gas liquefaction over the world, the choosing principles for liquefaction process are presented here too. The author chooses the P-R equation to calculate the phase equilibrium properties of LNG liquefaction, and builds mathematic models for equipment modules in the liquefaction cycle, which consists of compressor、throttle valve、multi-flow heat exchanger. Considering the characteristics of natural gas resource, the author presents three flow process of mixed refrigerant cycle for small scale gas liquefaction plants, simulates and analyses the whole process based on the two steps before. Finally, the author chooses the process of turn round heat exchange mixed refrigerant cycle with propane precooling.In this thesis the working pressure analyze of turn round heat exchange mixed refrigerant cycle with propane precooling has been discussed. The author especially analyses the setting bases from the factors including: low working pressure refrigerant, high working pressure refrigerant, storing pressure. The author optimizes the process, using the minimum power of the compressor as the aim function.In this thesis, the orthogonal experiment design of the plate-fin heat exchanger which is important equipment in the liquefaction process has been done. The?result is carried out by the MATLAB programming .The optimum design Scheme is found by?visual analysis methods of orthogonal experiment design. Factors affecting degree are evaluated by variance analysis methods of orthogonal experiment design. The passage design model of local heat load balance is adopt. The author analyses which is The best passage arrangement.Finally, In this thesis, The header structure Fluid field distribution of Plate-fin heat exchanger is simulated using the commercial CFD code FLUENT. When the nozzle ratio and depth ratio is different,we can simulate different results. The simulated results show that the header structure has a large effect on fluid field.