Master Dissertations

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End date: 2019Subject: search.filters.subject.Liquefied Natural Gas

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    Design of small scale liquefaction cycle for natural gas
    (Indian Maritime University, Kolkata Campus, 2019-06-19) Gupta, Nishit; Eswara, Arun Kishore
    Liquefied natural gas is found to be the most economical mode of transportation for distances covering more than 3500 miles. The boiling point of natural gas is 111 .7 K at atmospheric pressure and falls under the category of cryogenics. The process has components such as compressor, heat exchanger, expansion valve, insulating material, storage tank and pipes. The liquefaction of natural gas is achieved by processing natural gas in the liquefaction cycle. There are many parameters affecting the cycle such as compressor efficiency, heat exchanger effectiveness, ambient temperature, friction losses in pipes and insulating materials. In this thesis, some of the above mentioned parameters are considered while some parameters are neglected or assumed appropriately. It is observed that out of the existing cycles such as simple Linde-Hampson cycle, Pre-cooled cycle, Claude cycle and Kapitza cycle, each cycle has its own benefits and drawbacks. The fraction of liquefaction is found maximum for simple Claude cycle while the work required also reduces due to expansion of the high pressure gas through reciprocating expansion engine. The iterative procedure to find the configuration of each cycle is explained in the thesis and can be used with minimum bare inputs. An experimental setup can be built through these configurations and better study can be performed. To obtain the results, residue in the iterations is taken to 0.1 for temperature, pressure and mass flow rate both. In the Claude cycle, for mass flow rate of 1.02 kg/sec and the pressure ratio of 40, the fraction of liquefaction is found 0.0646 while in the kapitza cycle, for mass flow rate of 1.35kg/sec and the pressure ratio of 40, the fraction of liquefaction is found as 0.040. It is found that, the pressure required to liquefy the gas is not practical in the case of Linde-Hampson cycle. Further, it is found that Claude and Kapitza cycle can be used for experimental purpose.
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    Piping design for LNG liquefaction systems
    (Indian Maritime University, Kolkata Campus, 2019-06-20) Gupta, Satya Vart
    Liquefied Natural gas is the future of the energy sector, as it is a source of clean energy. The liquefaction of natural gas is achieved at 111.67 K temperature, 1 atm; which is a cryogenic temperature. The cryogenic flow needs special attention because fluid, as well as material of the pipe, behave differently at cryogenic temperature. Two-phase flow is another critical point in the liquefaction of natural gas. The objective of this thesis work is to select the material of the pipe, calculate frictional losses in the pipe, and pressure drop in the pipe through which the cryogenic fluid flows. The frictional loss in the pipe mostly depends on Reynolds number, Roughness factor, and phase of flow. As the Reynolds number increases, the friction factor increases in a greater value. As the time lapses, corrosion and erosion factor plays a key role in frictional pressure drop. As there is an increment in pipe diameter, the pressure drop due to friction or frictional losses decrease but by virtue of that the weight of the piping system increases which is an unfavourable condition from an economic point of view. The flow in pipe encounters different forms of fluid in the liquefaction cycle of natural gas i.e. liquid phase flow, Gas phase flow and mix flow of liquid and gas. The Liquid flow and gas flow in a pipe are mainly deal with the Colebrook equation. Two-phase flow is a critical phenomenon in the liquefaction cycle. The pipe sizes mentioned in the result can be used for experimental setup. It is found that the corrosion factor is 0.3 and 3 mm respectively for a period of 30 years. Also, it is found that, there exists two phase flow after the joule Thomson expansion device. While selecting the pipe size, it has been observed that the thickness of the pipe greatly depend on internal pressure of the flowing fluid.