Computational Fluid Dynamics Analysis on the Liquid Piston Gas Compression

Wong, Lak Kin

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Computational Fluid Dynamics Analysis on the Liquid Piston Gas Compression

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Liquid piston gas compression utilizes a liquid to directly compress gas. The benefit of this approach is that liquid can conform to irregular compression chamber volume. The compression chamber is divided into many small little bores in order to increases the surface area to volume ratio. The heat transfer rate increases with increasing surface area to volume ratio. However, as the bore diameter becomes smaller, the viscous force increases. In order to maximize the heat transfer rate and to minimize the viscous force, computational fluid dynamics is used. ANSYS Fluent is used to simulate the liquid piston gas compression cycle. Having created the model in Fluent, different factors, including diameter, length, liquid temperature, and the acceleration are varied in order to understand how each factor affects the heat transfer and viscous energy loss. The results show that both viscous force and heat transfer rate increase as the diameter decreases. The viscous force increases and the heat transfer decreases as the length increases. Both the viscous force and heat transfer increase as the acceleration increases. The viscous force decreases as the liquid temperature increases. Results show that the highest compression efficiency of 86.4% is found with a 3mm bore radius and a short cylinder. The piston acceleration is advised to be below 0.5g in order to avoid surface instability problem.

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