Force And Stress Analysis Of Tube Bundles In Elastic Tube Bundle Heat Exchanger

Heat exchanger is the basic equipment of heat exchange, and is widely used in electricity, petroleum and chemical industries, etc. Elastic tube bundles are in the form of a composite curved beam and cantilever beam, changed the traditional rigid fixation form of tube in tube-shell type heat exchanger and make full use of vibration to strengthen heat transfer. Elastic tube bundles can use flow-induced vibration to realize the passive heat transfer enhancement. But there are still phenomenons like uneven vibration of multipul row elastic tube bundles, which causes parts of tube bundles not obvious on heat transfer enhancement, parts of tube bundles occurring fatigue damage and other problems. Therefore, using fluid force incent and control elastic tube bundles to achieve the desired vibration, and reach the purpose of matching heat transfer enhancement of vibration tube bundles and fatigue life, have the important theoretical and practical value. Based on the issues of uneven force and vibration of tube bundles in elastic tube bundle heat exchanger, the force rule and stress distribution of elastic tube bundles under the action of shell-side flow are studied, and the support-side structure of elastic tube bundle and the structure of elastic tube bundle are improved. In this paper, the main research work are summarized as follows.(1) Finite element model of single row elastic tube bundle heat exchanger was set up. Based on the sequential solution of the fluid-structure interaction coupling method, the force of different locations on single row elastic tube bundles were simulated by combining ANSYS Workbench and CFX. Every point force of single row elastic tube bundle under the same working condition, the same point force of single row elastic tube bundle under different working conditions were analyzed, and get the force distribution along the tube bundle and the discipline of force changing with the time of elastic tube bundle. The force distribution of elastic tube bundle along tube bundle is uneven. Each position’s force of elastic tube bundle is periodic in every direction. Along with the rising of the shell-side flow velocity, force amplitude of elastic tube bundles increases.(2) The finite element model of multiple rows of elastic tube bundles heat exchanger was established. Force analysis of multiple rows of elastic tube bundles were simulated under the shell-side flow velocity. The influences of tube row spacing and shell-side flow velocity on force of multiple row elastic tube bundles were investigated. Tube row spacing on the force of elastic tube bundle has a certain influence. Each row of elastic tube bundle in heat exchanger is mainly affected by the force of longitudinal flow. Under low shell-side flow velocity, the force of each monitoring point on the free end of elastic tube bundle is different on law. Along with the rising of shell-side flow velocity, the force of free end on elastic tube bundle trends to a single changing rule. The amplitudes of free end on each row tube bundle are different, the amplitude of free end on tube bundle of the flow coming side of shell-side is larger.The frequency and amplitude of vibration acceleration on free sides of four row tube bundles were tested under different shell-side flow velocity. The changing rule of simulated value of the acceleration vibration amplitude of elastic tube bundle’s free sides are the same as changing rule of experimental value.(3) The stress condition of elastic tube bundles in the shell-side flow under actual working conditions was analyzed. The influences of shell-side flow velocity on maximum stress were investigated. Along with the rising of the shell-side flow velocity, maximum stress of tube bundles also increase. When the shell-side flow velocity is larger, the maximum stress of tube bundle at the flow coming side is bigger than the maximum stress of tube bundle far from the flow coming side.(4) The support sides structure of elastic tube bundles and the structure of elastic tube bundle were improved on design, so the maximum stress on support sides of elastic tube bundles and elastic tube bundle reduced obviously.