Study On Vibration Response Of Conical Spiral Elastic Tube Bundle Induced By Distributed Pulsating Flow

The elastic tube bundle utilizes fluid-induced vibration to achieve passive enhanced heat transfer,which has a good application prospect in the heat exchanger.Under the same conditions,the fatigue strength and heat transfer efficiency of conical spiral elastic tube bundles are higher,which have certain advantages in elastic tube bundle heat exchangers.The induction and control of the elastic tube bundle vibration is an important guarantee for heat transfer enhancement of tube bundle on the premise of a certain fatigue life.Distributed pulsating flow can induce and control the vibration of elastic tube bundles,which has been verified in the planar elastic tube bundle heat exchangers.In this paper,structural parameters design and simulation analysis of conical spiral elastic tube bundle and its pulsating flow generation device were carried out.The numerical analysis of the vibration response of the tube bundle under the shell-side flow field and the coupled flow field in the heat exchanger was carried out,and the vibration response of the conical spiral elastic tube bundle under the coupled flow field was tested by constructing the experimental device.The research work is of great significance to the excitation and control of the elastic tube bundle vibration and the design of the conical spiral elastic tube bundle heat exchanger.the main work of this paper is as follows:(1)The conical spiral elastic tube bundle was designed,then the geometric model was built.The intrinsic characteristics and harmonic response of the tube bundle were simulated and analyzed,which provided a basis for the choice of pulsating element size in the distributed pulsating flow generating device.Natural frequencies of the conical spiral elastic tube bundle decrease with the inner tube fluid-solid coupling,which further decrease under the inner and outer tube fluid flow-solid coupling,the low-order natural frequency decreases greatly.The excitation frequency of pulsating flow should be close to the natural frequency of the conical spiral elastic tube bundle to enhance the vibration amplitude of the tube bundle.(2)The distributed pulsating flow generating device was designed,then the geometric model and simulation analysis model of internal flow field were established.The effects of parameters such as the longitudinal dimension of the pulsating element and the inlet flow velocity on the pulsating flow frequency and intensity were analyzed.At the same inlet flow velocity,pulsating flow intensity of the same branch tube in the distributed pulsating flow generating device increases first and then decreases as longitudinal dimension of the pulsating element increases,while the frequency decreases first and then increases.The relative variation of the frequency and intensity of the pulsating flow generated in each branch pipe of the distributed pulsating flow generating device is small,so the uniformity of pulsating flow is good.(3)The fluid-solid coupling analysis model of the shell-side flow field and the conical spiral elastic tube bundle in the heat exchanger was established,and the vibration response of the tube bundle under different inlet flow rates was simulated and analyzed.The amplitude of the conical spiral elastic tube bundle is greatly affected by the shell inlet flow velocity while its vibration frequency is less affected.At the same inlet flow rate,the amplitude of each conical spiral elastic tube bundle increases first and then decreases from the top to the bottom,and the vibration uniformity of each conical spiral elastic tube bundle is poor under the shell-side flow field induction.(4)Simulation model of the conical spiral elastic tube bundle coupled with pulsating flow field and shell-side flow field was established,and the vibration response of the conical spiral elastic tube bundle in the heat exchanger induced by the coupled flow field was numerically analyzed.The effect of the distributed pulsating flow generating device on exciting vibration of each row of tube bundles was analyzed and experimental study was carried out.The vibration uniformity of each conical spiral elastic tube bundle is better under the induction of the coupled flow field.The distributed pulsating flow generating device can generally achieve the excitation and control of the tube bundle vibration effectively,and improve the vibration intensity of the tube bundle while enhancing the vibration uniformity of each conical spiral elastic tube bundle.