Elastic Tube Bundle Research Articles

Numerical Research on Vibration-Enhanced Heat Transfer of Elastic Scroll Tube Bundle

Based on a new type of elastic scroll tube bundle (ESTB) heat exchanger, the influence of shell-side fluid inlet velocity and tube bundle constraint condition on the enhanced heat transfer performances are researched by a two-way fluid–solid coupling calculation method. Numerical results show that the average heat transfer coefficient (HTC) increases with the shell-side fluid inlet velocity increases when the single group of scroll copper tubes is unconstrained. Within the range of calculated parameters in this paper, the maximum increase of average HTC is 140% under vibration conditions, and the maximum increase of average HTC is 216% under nonvibration conditions. The average HTC decreases as the number of constraints increases under vibration conditions, and the maximum decrease is 42.69%. The average performance evaluation criteria values are greater than 1.00, so the overall heat transfer performance of the ESTB heat exchanger is better.

Research on Heat Transfer Enhancement of Vortex-Induced Vibration of Side-by-Side Double Tubes

The fluid-induced vibration heat transfer enhancement technology has great potential, because it can effectively improve the heat transfer efficiency without consuming additional energy. A reasonable design of the elastic heat exchange tube bundle structure is the key to the engineering application of this technology. In this paper, the effects of flow velocity and the center distance on the characteristics of vortex- induced vibration heat transfer in side-by-side double circular tubes are studied. We demonstrate that, when the center distance is no more than (outer diameter), the interference effect of the flowfield around the two tubes is greater, and the amplitude of the double tube is small. However, with the increase of , the flowfield interference decreases. Within the scope of this paper, two modes of vibration are obtained: in-phase vibration and out-of-phase vibration. When and , the fluid vortex-induced elastic supported side-by-side double circular tubes’ vibration can enhance heat transfer. Especially, when , the heat transfer enhancement effect is the strongest, reaching 14.5%. However, when , the heat transfer enhancement effect is not obvious. The research on the heat transfer characteristics of fluid flowing around the static double tube shows that when the distance is small, the flow velocity around the static tubes is larger, resulting in a higher surface average heat transfer coefficient, and as the distance increases, the heat transfer coefficient decreases.

Calculation of the Vibration Parameters of Steam-Generator Tube Systems to Validate the Vibration Strength and Lifetime

A mathematical model of the vibrations of an elastic tube bundle in a crossflow is considered. The model is applicable to predict the reaction of the tube bundle components under the action of the vortex and hydroelastic excitation mechanisms considering the intermediate supports placed with gaps between them and the tube components—the presence of the gaps is a necessary precondition for assembling the structure. The impact of the tubes–intermediate supports is taken into account by the oblique impact model with the normal and tangential components of the reaction force of the supports. The proposed mathematical model was implemented in the Matlab programming environment. The parameters of the induced vibrations of the steam-generator-tube model such as the frequency content and the root-mean-square (rms) values of the vibration-induced displacements and accelerations were calculated. The dependences of the above parameters on the design and operating characteristics were studied.

Analysis on Fluid-Induced Vibration and Heat Transfer of Helical Elastic Tube Bundles

The study on fluid-induced vibration of helical elastic tube bundles (HETBs) to enhance heat transfer is of great significance in industrial production and energy utilization. The fluid-induced vibration response and the heat transfer property of a HETB heat exchanger were analyzed by using a two-way fluid–solid coupling method. The vibration frequency, displacement amplitude, and heat transfer coefficient were computed while considering varying entrance velocities and helix diameters. Numerical results demonstrate that the middle of the HETB vibrates the most violently, and the vibration is mainly in the vertical direction. There are a large number of vortices in the gaps between the tubes and the inner cavity of the heat exchanger. The vibration amplitude and heat transfer coefficient of the HETB increase significantly when the entrance velocity or helix diameter increases. The effect of vibration-enhanced heat transfer improves with the increase in entrance velocity. The mean value of the heat transfer coefficient at the upper side of the HETBs is 2.205 times that at the lower side.

An empirical correlation for the heat transfer enhancement of planar elastic tube bundle by flow-induced vibration

This work aims to establish an empirical correlation for predicting the heat transfer enhancement of planar elastic tube bundle by flow-induced vibration in the Reynolds number range of 100–600. The effects of tube wall thickness, tube pitch and tube row spacing on the heat transfer enhancement were investigated using a two-way fluid structure interaction calculation. Results demonstrated that the vibrational Reynolds number played a dominant role in heat transfer compared to the Reynolds number. The value of the heat transfer enhancement decreased with the increase of tube wall thickness, up to 43.4% in the range of 0.75–1.5 mm, and increased with the increase of tube pitch, up to 101.4% in the range of 20–30 mm. It was observed that the heat transfer enhancement was more sensitive to the change in the tube pitch. The value of the heat transfer enhancement increased with the tube row spacing in the range of 40–60 mm and kept almost stable in the range of 60–70 mm. It was denoted that the maximum critical value of the tube row spacing was enlarged to 6D owing to the flow-induced vibration. At last, an empirical correlation was obtained for predicting the heat transfer enhancement of planar elastic tube bundle by flow-induced vibration, which integrated the effects of the vibrational Reynolds number and Reynolds number.

Experimental study on effect of tube arrangement mode on heat transfer characteristics of a new type of elastic tube bundle

Constant heat flux heat transfer test bed is built, and experimental study on external heat transfer characteristics of a new type of elastic tube bundle is conducted, obtaining overall and local heat transfer performance of the elastic tube bundle at different Re numbers. The results show that, within the experimental parameter range, the external heat transfer coefficient of elastic tube bundles with different tube arrangement modes generally tends to reduce with fluid pulsation frequency, and increase with fluid Re number. Comparing different tube arrangement modes, it is found that overall heat transfer performance of tube bundles ranks in this order: bilateral distribution-staggered arrangement > unilateral distribution-staggered arrangement > unilateral distribution-in line arrangement.

Benefits of SiMusCP, a musculoskeletal modelling decision making procedure, on hamstring lengthening outcomes: a retrospective study

This work aims to establish an empirical correlation for predicting the heat transfer enhancement of planar elastic tube bundle by flow-induced vibration in the Reynolds number range of 100–600. The effects of tube wall thickness, tube pitch and tube row spacing on the heat transfer enhancement were investigated using a two-way fluid structure interaction calculation. Results demonstrated that the vibrational Reynolds number played a dominant role in heat transfer compared to the Reynolds number. The value of the heat transfer enhancement decreased with the increase of tube wall thickness, up to 43.4% in the range of 0.75–1.5 mm, and increased with the increase of tube pitch, up to 101.4% in the range of 20–30 mm. It was observed that the heat transfer enhancement was more sensitive to the change in the tube pitch. The value of the heat transfer enhancement increased with the tube row spacing in the range of 40–60 mm and kept almost stable in the range of 60–70 mm. It was denoted that the maximum critical value of the tube row spacing was enlarged to 6D owing to the flow-induced vibration. At last, an empirical correlation was obtained for predicting the heat transfer enhancement of planar elastic tube bundle by flow-induced vibration, which integrated the effects of the vibrational Reynolds number and Reynolds number.

Experimental study on effect of fluid impingement location on heat transfer characteristics of a new type of elastic tube bundle

A constant heat flux heat transfer test bed is built, and experimental study on external heat transfer characteristics of a new type of elastic tube bundle is conducted, obtaining overall and local heat transfer performance of the elastic tube bundle at different Re numbers. The results show that, the heat transfer performance for fluid entirely impacting on the free end of tube bundle is better than that of fluid completely entering from heat exchanger inlet. Besides, the greatest heat transfer performance occurs at the condition fluid entirely impinging on the small end of tube bundle. Similar heat transfer characteristics occur when fluid impinges on the big / small free end respectively, namely lower heat transfer coefficient for the fixed end and the big free end, and highest heat transfer coefficient for the small free end, the reason for which might be the differences of velocity and vibration characteristics for fluid around the tube bundle at different locations.

Design and application of a new distributed pulsating flow generator in elastic tube bundle heat exchanger

In order to realize reasonable and effective excitation of the vibrations in heat exchanger, a new distributed pulsating flow generator (DPFG) is proposed. The pulsating flow frequencies and intensities of different branch pipes of the DPFG are studied. Based on the vibration test bed, the vibration characteristics of the elastic tube bundles (ETBs) are tested. In addition, the heat transfer performances (HTPs) of the ETBs are numerical studied under different flow-induced conditions. The results indicate that the pulsating flows with substantially the same frequency and intensity can be generated in all branch pipes of the DPFG based on the appropriate sizes of vertical pipe and horizontal pipe. For the ETBs suffer the pulsating fluid and shell-side fluid, the ETBs have two vibration frequencies, i.e. the constant frequency and variable frequency. The constant frequency is caused by the shell-side fluid, and the variable frequency is caused by the pulsating fluid. In addition, the DPFG not only greatly improves the vibration intensities and uniformity of the ETBs, but also greatly improves the HTPs.

Vibration Response and Stress Analysis of Planar Elastic Tube Bundle Induced by Fluid Flow

Flow-induced vibration plays a positive role on heat transfer enhancement. Meanwhile, it is also a negative factor for fatigue strength. Satisfying the fatigue strength is the primary prerequisite for heat transfer enhancement. This paper numerically studied the flow-induced vibration of planar elastic tube bundle based on a two-way fluid–structure interaction (FSI) calculation. The numerical calculation involved the unsteady, three-dimensional incompressible governing equations solved with finite volume approach and the dynamic balance equation of planar elastic tube bundle solved with finite element method combined with dynamic mesh scheme. The numerical approach was verified by comparing with the published experimental results. Then the vibration trajectory, deformation and stress contour of planar elastic tube bundle were all studied. Results show that the combined movement of planar elastic tube bundle represents the agitation from inside to outside. The vibration of out-of-plane is the main vibration form with the typically sinusoidal behavior because the magnitude of displacement along the out-of-plane direction is the 100 times than the value of in-plane direction. The dangerous point locates in the innermost tube where the equivalent stress can be utilized to study the multiaxial fatigue of planar elastic tube bundle due to the alternating stress concentration. In the velocity range of 0.2‒3 m/s, it is inferred that the vibration amplitude plays a role on the stress response and the stress amplitude is susceptible to the fluid velocity. This research paves a way for studying the fatigue strength of planar elastic tube bundle by flow-induced vibration.

Numerical analysis of shell-side flow-induced vibration of elastic tube bundle in heat exchanger

The responses of the flow-induced vibration of an elastic tube bundle subjected to the shell-side cross flow are investigated in this paper. The weak coupling method and the fluid solid interface are used to solve the fluid-structure interaction problem with consideration of the geometry and physical natures. The effects of the shell-side fluid flow velocity and the structural parameters on the flow-induced vibration are discussed. Numerical results demonstrate that the vibration frequency and amplitude at the monitor points increase with the increase of the shell-side water inlet velocity in all directions. The wall thickness and the external diameter of the elastic tube bundle have significant effects on the responses of the flow-induced vibration. The structural parameters affect the vibration frequency and amplitude, and the vibration equilibrium position in the water flow direction. The vibration frequency decreases with the increase of the tube external diameter. In addition, the vibration in the water flow direction has a lower equilibrium position when the elastic tube bundle has a larger wall thickness or smaller external diameter.

Numerical study on the heat transfer enhancement and fatigue life by flow-induced vibration

In order to analyze the heat transfer enhancement and fatigue life by flow-induced vibration comprehensively, this study investigated the shell-side flow in planar elastic tube bundle heat exchanger based on a two-way fluid structure interaction using the finite volume approach and finite element method combined with a dynamic mesh scheme. This numerical approach was verified by comparing with the Zhukauskas's empirical correlation and the published experimental results. Comprehensive analysis was conducted in fatigue life and heat transfer combined with the effect of tube wall thickness, tube pitch and vibrational Reynolds number. Results indicate that the vibration amplitude is considered to depend more strongly on structural parameters because the average fluctuation 81.85% and 19.55% occur in vibration amplitude and frequency. Vibrational Reynolds number, a combination of amplitude and frequency, dominates the heat transfer enhancement resulting in the minimum heat transfer coefficient ratio 1.08 and the maximum heat transfer coefficient ratio 1.29. It is deduced that the heat transfer enhancement is obtained in the premise of satisfying the fatigue strength of tube bundle in the appropriate vibrational Reynolds number range 147–780 for the planar elastic tube bundle studied in the present paper.

Numerical investigation on the heat transfer enhancement mechanism of planar elastic tube bundle by flow-induced vibration

This work numerically investigated the heat transfer enhancement mechanism of planar elastic tube bundle by flow-induced vibration based on a two-way fluid structure interaction model. The unsteady, three-dimensional incompressible Navier-Stokes equation was solved with finite volume approach and the dynamic equilibrium equation of tube bundle was solved with finite element method combined with dynamic mesh scheme. Then the heat transfer performance was studied according to the field synergy principle. Synergy angle and Nusselt number were studied qualitatively and quantitatively from overall and local perspectives. Results show that improvement of field synergy and oscillating relative velocity are two crucial factors for heat transfer enhancement. Among which, the improvement of field synergy plays a dominated role on heat transfer enhancement. At the water velocity 0.15 m/s, the overall average Nusselt number is increased by 6.5%, and the overall average field synergy is improved by 6.01% with the tube vibration within the sub-millimeter level. In view of the shell-side geometry and vertical arrangement of tube bundle, the flow-induced vibration is conducive to the heat transfer enhancement of top tube bundle. The maximum heat transfer augmentation of 11.43% occurs around the fifth row tube bundle, and the maximum improvement of field synergy is 10.9% around the third row tube bundle.

A study of the enhanced heat transfer of flow-induced vibration of a new type of heat transfer tube bundle—The planar bending elastic tube bundle

Based on the idea of fully using flow-induced transverse vibration to enhance heat transfer, this paper proposes a new type of elastic heat transfer element—the planar bending elastic tube bundle. This elastic tube bundle has a large heat transfer area per unit volume and a small gap between the transverse and longitudinal stiffness. The inherent characteristics are numerically studied. The results showed that the natural vibration forms of the elastic tube bundle include the longitudinal vibration forms and the transverse vibration forms, and the two types of vibration modes appear alternately. In addition, the characteristics of flow-induced vibration and heat transfer are researched. Because the first two orders of the natural vibration modes are longitudinal vibration and transverse vibration, respectively, and the two vibration frequencies are low and similar, at the low flow velocity, the cross flow could induce the elastic tube bundle vibration along the three-dimensional directions. Along the X and Z axis directions, the two monitoring points A and B have the same vibration amplitude value and phase, whereas in the Y axis direction, the two monitoring points have a 180-degree phase difference, which is determined by the first-order and second-order natural vibration forms. The range of amplitudes of monitoring points A and B is from 2.3mm to 5.3mm, in agreement with the amplitude range of the heat transfer enhancement by flow-induced vibration. The effect of heat transfer enhancement of flow-induced tube bundle vibration is obvious. With the increase in flow velocity, the influence of tube vibration on heat transfer enhancement decreases greatly. Within the scope of this research, compared with the heat transfer of the still tube bundle in the same condition, the average heat transfer coefficient of the flow-induced planar bending elastic tube bundle vibration is 2.64 times that of the static tube bundle.

Numerical investigation on heat transfer performance of planar elastic tube bundle by flow-induced vibration in heat exchanger

This study numerically investigated the heat transfer enhancement of planar elastic tube bundle by flow-induced vibration based on a two-way fluid structure interaction (FSI) model in the range of inlet velocity 0.2–0.5m/s. This two-way FSI calculation involved the unsteady, three-dimensional incompressible Navier–Stokes equation solved with finite volume approach and the dynamic equilibrium equation of tube bundle solved with finite element method combined with dynamic mesh scheme, which was verified by comparing with the published experimental results. Then the Nusselt number of the circumference of tube, local position, single tube and the overall tube bundle was presented. The performance evaluation criterion (PEC) was selected to study the heat transfer performance of planar elastic tube bundle. Results show that vibration frequency dominates the heat transfer enhancement at the local position near the mass-block. In the middle of tube bundle, vibration amplitude plays a significant role on heat transfer enhancement. Therefore, the average heat transfer enhancement of 12.97% and 4.58% at the middle two tubes is higher than that of 5.37% and 2.4% at the innermost and outermost tubes when the inlet velocity is 0.2m/s and 0.5m/s, respectively. In the range of inlet velocity 0.2–0.5m/s, flow-induced vibration contributes to enhancing the heat transfer of planar elastic tube bundle at low inlet velocity, resulting in the heat transfer enhancement of 8.26%, 6.07%, 5.67% and 3.91% respectively. Compared to the mechanical vibration strengthening heat transfer technology, flow-induced vibration plays an advantage on energy conversion to improve heat transfer. PEC indicates that the higher inlet velocity is sometimes more acceptable to obtain a higher heat transfer coefficient in the industry production.

Numerical investigation on synthetical performance of heat transfer of planar elastic tube bundle heat exchanger

This paper studied the synthetical performance of heat transfer in the shell-side of planar elastic tube bundle heat exchanger using numerical simulation. The temperature distribution in shell-side was studied. The relation of average heat transfer coefficient, pressure drop and comprehensive heat transfer performance were also discussed considering varying Reynolds number and geometry parameters. Results demonstrate that the temperature distribution provides a possibility to improve heat transfer by arranging the tube bundle layout to produce a fully heated fluid within full-scale shell-side. For the effect of geometry parameter, tube pitch has a greater effect on heat transfer compared to the tube-row spacing. However, Reynolds number dominates the heat transfer and fluid flow in shell-side. As a result, a prediction correlation of average Nusselt number is developed based on Reynolds number using the multiple-regression analysis of MATLAB software. A quite outstanding comprehensive heat transfer performance can be obtained in the case of tube pitch 20mm. However, the high Reynolds number is more acceptable in the industry to enhance the heat transfer rate without considering the heat transfer difference caused by geometry parameter.

Numerical analysis on shell-side flow-induced vibration and heat transfer characteristics of elastic tube bundle in heat exchanger

Based on the sequential solution of bi-direction fluid-structure coupling method, the shell-side flow-induced vibration responses and the heat transfer characteristics of the elastic tube bundles in heat exchanger have been investigated in this paper. Taking into account the meshing convenience and computing efficiency, appropriate meshing strategy and step calculation method have been proposed. Effects of shell-side water inlet velocity on the flow-induced vibration responses and heat transfer characteristics of the elastic tube bundle have been discussed. The results indicate that the mainly vibration of each tube bundle induced by the shell-side fluid is the out-plane vibration. The vibration amplitudes of the two stainless steel blocks are basically consistent when the shell-side fluid inlet velocity is lower, and the vibration amplitude of the stainless steel block III is more intense when the shell-side fluid inlet velocity is higher. In addition, the heat transfer coefficient of each elastic tube bundle has increased significantly at low flow rate (or low Reynolds number) when the shell-side flow-induced the elastic tube bundle vibration.

Numerical investigation of heat transfer characteristic of fixed planar elastic tube bundles

Planar elastic tube bundles are a novel approach to enhance heat transfer by using flow-induced vibration. This paper studied the heat transfer characteristic and fluid flow in both tube-side and shell-side using numerical simulation. Two temperature difference formulas were used to calculate convective heat transfer coefficient and the results were verified by theoretical analysis and experimental correlations. The effect of Reynolds number on overall convective heat transfer coefficient and pressure drop in tube-side and shell-side were studied. The comparison of the secondary flow in planar elastic tube bundles and conical spiral tube bundles were conducted. The external flow field and local convective heat transfer around the periphery of fixed planar elastic tube bundles subjected to the cross fluid flow were also analyzed. The results show that the energy consumption efficiency should be taken into account in the forced heat transfer process conducted by adjusting the fluid flow. The secondary flow varies depending on the fluid flow state and the geometry of tube. Hence, it is deduced that the heat transfer enhancement is obtained because the thermal boundary layer in the deformed planar elastic tube bundles caused by flow-induced vibration is damaged by the disordered secondary flow. In addition, the convective heat transfer capability of outside the two intermediate tube bundles is enhanced because of the effect of irregular and complex fluid flow affected by the role of curved tubes on both sides.

A comprehensive comparison on vibration and heat transfer of two elastic heat transfer tube bundles

Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bundle were comprehensively compared in the condition of the same shell side diameter. The natural mode characteristics, the effect of fluid-structure interaction, the stress distribution, the comprehensive heat transfer performance and the secondary fluid flow of the two elastic tube bundles were all concluded and compared. The results show that the natural frequency and the critical velocity of vibration buckling of the planar elastic tube bundle are larger than those of the conical spiral tube bundle, while the stress distribution and the comprehensive heat transfer performance of the conical spiral tube bundle are relatively better.

Research on Vibration and Heat Transfer Characteristics of an Optimized Structure of Elastic Tube Bundle

Combined with the structure and operating characteristics of the original type, an optimized structure of elastic tube bundle is proposed. The mechanical properties of the end region of the elastic tube bundle are derived theoretically, and researches are carried out on the vibration and heat transfer characteristics by adopting the method of combination of experiment and numerical simulation. The results show that there exist noticeable improvements for the optimized structure in the four aspects as follows: 1. the bending moment endured in the end section is only 0.159 times of the original tube bundle; 2. the natural frequency is lower than that of the original type; 3. the mean heat transfer coefficient of which is 26% higher than that of the original one; 4. the heat transfer area per unit volume increases by 24.7%. Furthermore, a comprehensive analysis is made on heat transfer performance improvement of the optimized structure