| The Arctic Channel has promoted economic development and caused extensive research on polar ships by scholars from various countries.Heat exchange tubes are the key to the stable operation of marine equipment,as the "Human blood" is inseparable from the "Heart".When a ship is sailing in a polar region,the low-frequency periodbased vibration caused by the ship’s power plant operation and continuous ice-breaking stamping causes the flow field in the heat exchange pipe to change.In addition,the small hard ice crystal particles and seawater form seawater-ice crystals during operation.The phase flow solution is pumped into the central cooling system,which has a certain effect on the fluid flow and heat transfer in the heat exchange pipe,and then affects the safety of the ship’s power system.Therefore,studying the flow and heat transfer characteristics of seawater-ice crystal two-phase flow in heat exchange pipe under vibration conditions provides guidance for the safe navigation and piping system design of polar ships.Due to the complex characteristics of flow and heat transfer in heat transfer tubes under vibration conditions,this paper aims at the horizontal-horizontal（H-H）elbow widely used by ships as a physical model to simplify the wall vibration to a sinusoidal function vibration.Using the Fluent of Euler-Euler model,Turbulence model,Wall function model,UDF dynamic grid technology is used to load different vibration conditions,and the phase-to-phase heat and mass transfer model written by UDF is used to study the phase transition of ice particles,and analyze seawater-ice crystal two-phase flow under vibration conditions in heat transfer tubes Non-isothermal flow and heat transfer characteristics.The main conclusions are as follows:1)Set up an experimental platform for seawater ice crystal flow and heat transfer,and verify the accuracy of the experimental system through the empirical formula of pressure drop;determine the change in the flow resistance of the pipeline under different vibration conditions,and compare the experimental results with numerical simulation values.Within this range,the validity of the numerical model of vibration and interphase heat and mass transfer is verified.2)Research shows that the flow friction losses of ice crystal particles in the tube are mainly mechanical friction and viscous friction.Under other conditions,the pressure drop gradually increases at a frequency of 0～50Hz.In the range of amplitude0～1mm,the pressure drop increases first and then decreases.The pressure drop is greatest at 0.3mm,but the vibration is higher than the static effect on the pressure drop..The pressure drop of seawater ice crystal two-phase flow gradually increases with the increase of flow velocity and particle size,and increases linearly with the ice content at the inlet.The numerical results are consistent with the experimental values and theoretical formula trends.3)There is a phase change in the ice crystals during the flow,and a significant layering phenomenon occurs due to the difference in density.Applying vibration will weaken the concentration distribution of ice crystals,and the phenomenon of aggregation on both sides will occur after the frequency is 40 Hz.With the increase of ice content,flow velocity and ice crystal particle size,the concentration tends to be symmetrically distributed,with IPF <5% and particle size <0.2,no ice crystal particles were present at the exit.The angle velocity increases with the increase of the amplitude,ice content,velocity,and particle size.The shrinkage of the section and the secondary flow cause the outside velocity of the elbow to be greater than the inside velocity.In order to avoid ice blocking in the bend,the critical speed should be higher than 0.4m/s.4)The temperature and average mass transfer rate of seawater-ice crystal twophase flow continued to increase,but the growth rate was slower at the corners.Under vibration conditions,bend angle disturbance and heat flow,the temperature in the tube increases with the increase of vibration,ice content and heat flow density,and decreases with the flow velocity and particle size.As the ice particles gather on the inside of the curved tube,As a result,the mass transfer rate inside the elbow is high,and a large amount of ice particles are melted.Relative to static conditions,the application of vibration frequency and amplitude promotes a heat transfer coefficient increase of approximately 12%. |
