Numerical Simulation Of Fluid-Thermal-Solid Coupling For Heat Pipe In Submerged Combustion Vaporizer

Because of it is clean and its high enthalpy,natural gas has become the main energy resource in the energy transition period of China.Gasification is an essential link in the supply chain of liquefied natural gas.The Submerged Combustion Vaporizer?SCV?is a new type of gas gasification equipment with high starting speed and high efficiency.As the key part of SCV,the heat pipes?HP?function bear the function of energy transfer.Its safety and effective operation is of great significance to the whole gasification process.Taking the SCV of a certain receiving station as the research object,the transcritical heat transfer characteristics of the HP in SCV were numerically simulated by using CH₄ instead of liquefied natural gas.At the same time,with Workbench as the platform,the fluid-thermal-solid coupling was carried out to perform thermal analysis and static structural analysis of the HP.The temperature field,stress field and deformation distribution were obtained at different working conditions.The results show that:?1?In the pseudocritical region,the flow in the HP is assumed to be mixed convection.The convection coefficient of CH₄ is remarkably increased as a result of the severe property variation,buoyancy and gravity effects.A local peak value of heat transfer coefficient?HTC?located near the pseudocritical temperature.Far from the critical point,the supercritical flow is characterized with forced convection as the effect of gravity and buoyancy is slight.Far away from the pseudocritical region,the heat transfer deteriorated along the HP where temperature gradient becomes lower.Another heat transfer performance enhanced area is in the U-pipe,where the HTC increases and then decreases sharply due to the Dean vortex.The first U-pipe has the biggest HTC which results in its thermal performance is much higher than other regions.Also,the HTC can be improved by higher pressure and larger inlet velocity.?2?The fluid-thermal-solid coupling analysis shows that the thermal stress caused by temperature load is much larger than the stress produced by pressure load.So the thermal stress plays a major role in the coupling stress of SCV HP.All the stress is not uniform in the axial,circumferential and radial distribution:influenced by temperature difference of the heat pipe wall,both the thermal and coupling stress are decrease to some level along the pipe length.The mechanical stress presents a pattern of irregular fluctuation.At the support area,there exits the maximum coupling stress,which is 207.4MPa.Consistented with the flow field,coupling stress exhibits an phenomenon of stratification at the U-pipe;In the circumferential direction,all stress fluctuate periodically;Along the radial direction,the stress on the inner wall is greater than the outer wall.The coupling stress and thermal stress first decrease and then increase from the inner to the outer wall surface,and there is a neutral layer with the lowest stress.?3?Due to the thermal deformation is much larger than mechanical one,the coupling deformation of SCV HP is mainly caused by thermal load.Along the heat pipe length,the mechanical and thermal deformation is in a relationship of weakening each other because their direction is opposite.Hence the value of coupling deformation is slightly smaller than thermal deformation,and it first increases,then decreases along the heat pipe length.The largest deformation is 4.37mm and occurs at the first U-pipe,where the deformation is mainly composed of axial and downward displacement.?4?By studying the deformation of all working condition here,the results reveals that the coupling stress exhibits significant differences when the temperature of CH₄ is higher than the pseudocritical temperature.The coupling stress increases with the increase of water bath temperature,and the coupling deformation increases correspondly.With higher operating pressure,both the coupling stress of the inner wall and the maximum deformation are larger.Increasing the inlet velocity of fluid has little influence on deformation but will make the coupling stress of HP is larger.