Experimental Investigation And Numerical Simulation On Fluid Flow And Heat Transfer In Submergerd Combustion Vaporizer

With the adjustment of the national energy strategy,LNG(refered to Liqufied NaturalGas)imports increased year by year,the coastal LNG receiving terminal was completed.The SCV(referred to Submergerd Combustion Vapoeizer)as the core vaporizing equipment of LNG receiving terminal has become the focus of academic research.The utility model relates to a new heat exchange equipment which is developed by adopting the technology of immersion combustion and multiphase flow,and the trans critical heat transfer technology.Compared with the developed countries,there is a big gap between the level of research and design of SCV in our country,at present,China's SCV is imported from Japan or Germany.In order to get rid of the design,construction and technical blockade of foreign contries,it is necessary to research and develop the domestic SCV.Therefore,the following works were carried out as folloes:(1)An unabridged and visual experimental apparatus was designed and built,and the internal flow field was studied.The results show that the liquid inlet duct near the water bath and prone to icing phenomenon;direct contact heat transfer between the shell of high temperature flue gas and water bath,formed across the bundle of gas-liquid two-phase flow and heat transfer form unique flow;water bath in induced by high temperature flue gas through the cofferdam form a unique circulation effect,effectively enhance the convective heat transfer.(2)For safety reasons,the tube-side is replaced by liquid nitrogen instead of LNG.Experimental study on heat transfer characteristics and pressure drop characteristics of SCV under different working conditions was carried out.The results show that the rate of initial water level and the flue gas quantity affected gas within the cofferdam;high temperature flue gas heat carried by vaporization of cryogenic fluid basically meet the required heat,the stable operation of the system when the water temperature and remained constant;direct contact heat exchange between flue gas and water bath,water bath temperature and the outlet temperature of the flue gas balance is SCV;the shell side pressure drop is mainly affected by the initial water level;according to the experimental data,the correction formula of SCV Zhukasuskas convection heat transfer coefficient dimensionless correlation,in order to provide reference for the engineering design.(3)The numerical model of supercritical fluid flow and heat transfer of SCV serpentine heat exchanger was established.The liquid nitrogen in the tube was replaced by LNG,and the physical properties of liquid nitrogen were calculated according to the linear interpolation function of Fluent.The effects of inlet velocity and inlet pressure on the flow and heat transfer across the critical fluid are investigated by numerical simulation.The results show that the direction of flow,the local convective heat transfer coefficient increases first and then decreases,when the temperature of liquid nitrogen to your pseudo critical temperature,the local convection heat transfer coefficient reaches the maximum value;the tube inlet mass flow is large,the local convection heat transfer coefficient is larger;the tube inlet pressure is high,the local convection heat transfer coefficient the peak value is small;the fluid in the pipe flows in a pipe section,in the two heat transfer coefficient of local convection will mutate.On the basis of this study,the Dittus-Boelter formula is modified to obtain the correlation of flow and heat transfer in SCV tube.The research results of this paper provide a theoretical basis for the localization of the submerged combustion vaporizer,which is of great significance in engineering application.