| With the continuous development of the economy,the demand for energy has increased sharply,the contradiction between the energy consumption and environmental protection has become increasingly prominent.The shell-and-tube heat exchangers are widely used in the process industry due to the solid structure,strong adaptability,and simple operation.The development of new high-efficiency heat exchangers is always the focus of research.Based on the research of the twisty flow heat exchanger,this paper analyzes the fluid flow uniformity in the shell side,and proposed a new tube bundle support structure,using a combination of theoretical analysis,numerical simulation and experimental research to study the shell side performance.The main research contents and conclusions are as follows:1.Use the velocity standard deviation to characterize the uniformity of the fluid flow in the shell side,analyze the influence of the structural parameters of the twisty flow heat exchanger on the uniformity,and compare with the different support structures.The results showed that:with the increase of the arrangement spacing of the baffle,the increase of the inclination angle and the decrease of the arrangement width,the fluid flow is more uniform,and the inclination angle of the baffle by range analysis has a greater impact on the uniformity of the flow.2.Combining the installation and manufacturing process of the trapezoidal baffle and the change of shell side flow pattern,the U-shaped baffle support structure is proposed;multiple baffles are evenly arranged in the circumferential direction as a group,and arranged at equal intervals along the tube length.The shell-side fluid is divided into multiple oblique flows through the baffle,and the whole present a spiral flow pattern,uniformly scouring the heat exchange tube bundle,so that the shell-side fluid conducts heat transfer under a low flow resistance environment.3.The overall structure model of the U-shaped baffle heat exchanger was established,the average velocity,pressure drop,and dimensionless temperature change laws at different working conditions and measurement position were analyzed.The results showed:the fluid between the second baffle to the last baffle in the shell side is the fully developed section of the U-shaped baffle heat exchanger,and the fully developed section is independent on the working conditions.4.The period whole cross-section models of the twisty flow heat exchanger and the U-shape baffle heat exchanger were established,and study on the change of the shell side performance under the same pumping conditions.The results showed that:compared with the twisty flow heat exchanger,the pressure drop of the U-shape baffle heat exchanger is reduced by 45%-49.6%,the heat transfer coefficient is reduced by 10.5%-15.4%,the uniformity is increased by 2.4%-4.0%,and the overall performance is increased by 6.6%-22.1%,and the velocity and pressure gradient field have better synergy of U-shape baffle heat exchanger.The effects of the structure parameters and arrangement of the U-shape baffles on the shell side performance were discussed.The results showed:The effects of the structure parameters and arrangement of the U-shape baffles on the shell side performance were discussed.The results showed that the angle and folded arrangement of the baffles has a significant affect,the pitch of the baffles has a moderate effect,and the width and rotation arrangement of the baffles has a less significant effect;from the perspective of the fluid streamline distribution in the shell side,with the increase of the angle,spacing,and width of the baffle,the streamline continuity is better.When the baffle is folded arrangement,the continuity is the worst,but there will be greater pressure drop and higher heat transfer coefficient.5.Design and build a shell-and-tube heat exchanger cold model experimental platform,make a plexiglass experimental model.Using LDV to measure the velocity at different positions in the shell side,the results showed that the numerical simulation and the experimental measurement data in a good agreement,the error is within the allowable range of the project,and the accuracy and reliability of the numerical simulation methods and results are verified. |
