Investigation On Thermal Flow Characteristics Of Seawater Ice Slurry In Seawater Heat Exchange Pipe Of Ice Area Ship

According to the arctic research datas of“Yong Sheng”route,the seawater system of the ship sailing behind the icebreaker is extremely easy to inhale the seawater ice slurry fluid formed by seawater and ice crystals.Compared with the case of only seawater,the presence of ice crystal particles will affect the flow and heat transfer of the fluid in the heat transfer pipe of the seawater system to a certain extent,which will affect the stability of the ship's power system operation.Therefore,exploring the flow and heat transfer characteristics of seawater-ice crystal solid-liquid two-phase flow in heat exchange pipe has important guiding significance and practical value for the safe navigation of polar ships and related system design.In view of the above objectives,a comprehensive experimental platform for seawater ice slurry flow and heat transfer is built,which facilitates an intuitive understanding of the seawater-ice crystal two-phase flow slurry physical scene and provides experimental data support for the reliability of the established numerical model.Based on particle fluid dynamics,considering the solid-liquid characteristics of seawater-ice crystal two-phase flow,an Euler-Eulerian two-fluid model suitable for seawater-ice crystal two-phase flow is established.By compiling the UDF program,the interphase heat and mass transfer model is embedded in the Euler-Eulerian two-fluid model in FLUENT to investigate the flow and heat transfer characteristics of the seawater-ice crystal two-phase flow during non-isothermal flow in the pipe.The results show that the friction loss of ice crystal particles mainly includes viscous friction and mechanical friction during flow.Therefore,the flow pressure drop of seawater-ice crystal two-phase fluid increases with the increase of inlet ice packing factor?IPF?and velocity.The flow friction coefficient decreases with the increase of Re and inlet IPF.And the numerical calculation value is in good agreement with the experimental value and the theoretical formula calculation value.The phase change characteristics of ice crystals have a significant effect on the flow pressure drop.The phase change characteristics of ice crystals have a more significant effect on the pressure drop when the velocity is low.The concentration field and velocity field show a symmetric distribution trend with the increase of inlet velocity and IPF.Larger diameters of ice crystal particle lead to a non-uniform distribution of ice crystal velocity fields and concentration fields.In addition,experimental and numerical results show that the non-isothermal flow of seawater-ice crystal two-phase fluid in the pipe is divided into three flow patterns:pseudo-homogeneous flow,heterogeneous flow and moving bed.The safety critical speed to avoid moving beds was 0.9 m·s^-1.In the inlet section of the thermal flow development,the thermal boundary layer is thin,the local average heat transfer coefficient is high,and then decreases rapidly along the flow direction,and is nearly constant in the fully developed region.In the range of IPF=0³0%and U=1.0³.0m·s^-1,the local average heat transfer coefficient increases first with the increase of inlet velocity and IPF.Increasing the inlet IPF does not always enhance heat transfer.The local average heat transfer coefficient of the seawater-ice crystal two-phase flow is increased by about 1.54 times relative to the single-phase flow.The mass transfer rate of ice crystals and the distribution characteristics of fluid temperature in the pipe are affected by the distribution of the ice crystals.Due to the high number of ice crystals at the top of the pipe,the contribution of ice crystal phase transformation to heat transfer enhancement in this region is increased,resulting in a significantly lower temperature at the top of the pipe than at the bottom.