Optimization of Air Supply Mode on Vaporization Performance of an Air-Based Cryogenic Finned Tube Under Forced Convection
The influence of different air supply modes on the vaporization performance of a finned tube in LNG(liquefied natural gas)ambient air vaporizer was investigated by the FLUENT software,and the distribution of air physical parameters around the tube on different air supply modes i.e.,the bottom air supply and top air exhaust mode,the top air supply and bottom air exhaust mode,the side-air supply and top air exhaust mode,and the side-air supply and bottom air exhaust mode were analyzed.The vaporization process of liquefied natural gas in the tube was investigated by using the Lee model.The effects of air supply mode and air inlet velocity on the vaporization capacity of the finned tube were analyzed by considering the variation of fluid temperature in the tube.The results indicate that the low wind speed boundary layer appears around the finned tubes,and a wake range with poor heat exchange efficiency is likely to be formed on the leeward side of the tube for side air-supply modes.When the air inlet velocity increases from 2.8 m/s to 3.8 m/s,and from 3.8 m/s to 4.8 m/s,the maximum heat transfer coefficients on the air side increase by 3.92 and 2.6 W/(m2·K)respec-tively for the side-air supply and bottom air exhaust mode.The boundary layer distribution for the bottom air supply mode and the top air supply mode is uniform,and the maximum recommended air inlet velocity is 3.2 m/s because the heat transfer performance does not increase significantly with the rise on the air velocity.The vaporization performance of the finned tube on the top air supply mode is better than that on the bottom air supply mode.Among the four air supply modes,the side-air supply and top air exhaust mode is the best one to improve the heat transfer performance of the single finned tube.The forced-draft AAV(ambient air vaporizer)using the side-air supply and top air exhaust mode has a much better vaporization performance than the general AAV.
heat transferliquefied natural gasair supply modevaporization performanceambient air vaporizer
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