Study On Pressure Drop Characteristics Of Fluid In Spiral Tube For Coil-wound Heat Exchanger

Coil-wound heat exchangers are a highly efficient heat transfer equipment and are widely used in the chemical and energy sectors.In the design and operation of wound tube heat exchangers,the structural parameters of the tube-side spiral wound tube bundle have an important influence on the heat transfer performance and fluid mechanical properties of the heat exchanger.The pressure drop of the fluid in the tube side spiral bundle is an important parameter of the heat exchanger performance.The structure of the tube side spiral bundle is complex and involves a variety of structural parameters such as tube diameter,winding diameter,winding angle and pitch.To address the uncertainty of the fluid pressure drop inside the spiral wound tube bundle on the tube side of the wound tube heat exchanger with the change of the structural parameters of the tube bundle itself,a simplified spiral wound single tube on the tube side of the wound tube heat exchanger was used as the object of study,and the numerical simulation of the fluid flow in multiple spiral wound tube models with water as the medium and a certain tube length and different structural parameters was carried out using FLUENT software.The flow characteristics and pressure drop characteristics of the fluid in the spiral wound tube were analysed under different working conditions.Firstly,a single spiral winding tube model was established by Solidworks,a 3D modelling software,and numerical simulations were carried out by Computational Fluid Dynamics(CFD)software to calculate the fluid flow in a spiral winding tube with circular cross-section under laminar and turbulent flow conditions.The effect of different structural parameters and changes in the physical properties of the medium on the fluid flow regime and flow characteristics inside the spiral-wound tube is investigated.The pressure drop of the fluid in the spiral wound tube is compared with different structural parameters using a single variable control method,and the sensitivity of different parameters to the pressure drop is analysed.The velocity field,velocity vector,in-plane flow line and pressure drop in different angular cross-sections are compared with each other.The velocity and pressure fields in the spiral-wound tube are also compared and analysed in terms of the velocity and pressure changes along the tube course when the spiral-wound tube is in laminar and turbulent flow under different operating conditions.The velocity and pressure variations of the fluid in the shaped spiral tube along the flow line in different directions of the coordinate axis are compared and analysed.The research shows that: the influence of tube diameter and winding diameter on fluid flow is greater,the influence of pitch and spiral angle on fluid flow is smaller,at the same pitch,the greater the spiral angle,the faster the rotation speed of the fluid in the tube;the flow velocity of the medium inside the tube has a greater influence on the pressure drop of the fluid inside the spiral winding tube,the greater the flow velocity the greater the pressure drop;the larger the tube diameter,the smaller the flow velocity,the smaller the pressure drop;the smaller the winding diameter,the greater the flow velocity The smaller the winding diameter,the higher the flow velocity and the lower the pressure drop;the smaller the winding diameter and the higher the flow velocity,the higher the pressure drop;the change in pitch has little effect on the pressure drop and can be ignored;the fluid density and viscosity also affect the pressure drop,and it should be noted that these parameters are interrelated and cannot be considered separately.In addition,the three cross-sectional shapes of the spiral winding tube in the fluid in the laminar flow,turbulence will appear in the phenomenon of secondary flow,and shaped cross-sectional spiral winding tube in some conditions have better flow performance.In practice,spiral wound tubes with appropriate flow rates and structural parameters should be selected to meet the design and operational requirements of the heat exchanger.The results of the study can be used as a reference for the design and optimisation of coil-wound heat exchangers and as a reference for the study of other similar tube types.