Elastic Tube Bundle Research Articles

Optimizing Baffle Height in Improved Elastic Tube Bundle Heat Exchangers

To clarify the optimal matching relationship between the inlet velocity Uin and baffle height, based on the improved elastic tube bundle (I-ETB) heat exchanger, the vibration characteristics and comprehensive heat transfer performance (HTP) of I-ETBs inside the heat exchanger under various Uin were analyzed numerically. The results show that there is an optimal baffle height coefficient hc, which matches the specific Uin. When Uin is 0.1 m/s, 0.4 m/s, 0.7 m/s, and 1.0 m/s, the corresponding optimal hc is 0.70, 0.82, 0.87, and 0.73, respectively. It is evident that as Uin increases, the optimal hc initially increases but subsequently decreases. Note that, in the design of heat exchangers, it is very important to customize the baffle height according to the operating conditions. Through the comprehensive evaluation of different cases, within the calculation range of this paper, it is finally concluded that the heat exchanger configuration of case I (Uin=0.1 m/s, hc=0.70) can achieve the best comprehensive HTP.

Vibration-Enhanced Heat Transfer Analysis and Improvement of Spiral Elastic Tube Heat Exchanger

Using the fluid–solid coupling approach in fluid-induced vibration studies, the effect of flow-induced vibration on a heat exchanger is investigated. This paper analyzes the impact of flow parameters for shell fluid on heat transfer characteristics enhanced by the vibration of a spiral elastic tube bundle (SETB). Improvement schemes for heat exchangers are also proposed, and they are studied and compared. The results show that there is a positive correlation between the inlet velocity and the heat transfer coefficient of the SETB heat exchanger. As the inlet velocity rises to 0.9 from 0.3 m/s, the Nusselt number of the hollow SETB heat exchanger under vibration conditions is increased by 153.10, 45.55, and 26.73% sequentially. The vibration generated by impacting the elastic element during fluid flow can improve the Nusselt number effectively. As the flow velocity increases to 0.9 from 0.3 m/s, the flow-induced vibration enhances the Nusselt number of the hollow SETB heat exchanger by 2.13, 1.53, 1.05, and 0.89%. When the inlet flow velocity of fluid is in the range of 0.3–0.9 m/s, under the same flow velocity, same pressure drops, and same pumping power conditions, the performance of the improved heat exchanger is greater than that of the SETB heat exchanger before the structural improvement.

Numerical study on lead–bismuth cross-flow induced vibration in the elastic tube bundle

The physical properties of liquid lead–bismuth eutectic fluid are quite different from that of water or air. It needs to be verified whether the cross-flow vibration mechanism and the empirical prediction model of fluidelastic instability in conventional media are applicable to lead–bismuth. In this work, for an in-line elastic tube bundle with pitch ratio P/D = 1.5, the flow excitation of lead–bismuth at 200 °C is studied and compared with that of water in uncoupled flow field. Then, two cases of lead–bismuth flow-induced vibration with different mass-damping parameters are simulated and studied by fully coupled numerical simulation considering fluid viscous damping. The tube bundle experiences the process from turbulence-induced vibration in low flow velocity to fluidelastic instability in high velocity. The results of flow excitation show that the pressure coefficient distribution of the front row tube in lead–bismuth is basically consistent with that in water, while the inconsistency of the pressure coefficient distribution for the back row tube is caused by the bi-stable deflective flow. The results of lead–bismuth flow-induced vibration show that, in fluidelastic instability, the vibration of tube bundle and the vortex shed from tube bundle are dominated by the frequency close to the first wet modal frequency of tube bundle. The different deflective directions of lead–bismuth and water, caused by bi-stable characters, have less effect on the onset of fluidelastic instability. The instability points of lead–bismuth agree with the experimental results of other media and the Connors prediction model considering fluid viscous damping. The prediction model is suggested to predict the onset of fluidelastic instability induced by lead–bismuth cross-flow in the tube bundle.

Mechanism Analysis of Forced Induced Wave Evaporation Heat Transfer by Liquid Film outside Elastic Tube Bundle

Mechanism Analysis of Forced Induced Wave Evaporation Heat Transfer by Liquid Film outside Elastic Tube Bundle

Numerical study on the effect of baffle structure on the heat transfer performance of elastic tube bundle heat exchanger

To make up for the research gaps in the existing literature on the effect of baffle structural parameters on the vibration and heat transfer of elastic tube bundle (ETB) heat exchangers, and improve the comprehensive heat transfer performance (HTP) of heat exchangers, based on an improved elastic tube bundle (I-ETB) heat exchanger used in previous studies, using the bi-directional fluid-structure interaction calculation method, the effects of the baffle structure improvement (height and curvature) on the comprehensive HTP of the I-ETB heat exchanger at different inlet velocities (Uin) were numerically studied. The results show that: while the height factor increases from 0.70 to 0.80, the vibration amplitude of I-ETBs decreases maximum by 10.05 %, and the heat transfer coefficient (h) of I-ETB increases maximum by 5.50 %. Increasing the baffle height improves the comprehensive HTP while suppressing the vibration of the I-ETBs. While the baffle curvature is 10°, the vibration of I-ETBs is the most intense, with the amplitude of the I-ETBs improving maximum by 10.79 %. The Nusselt number per unit pressure drop Nu/ΔP and performance evaluation criteria PEC and JF (a dimensionless number related to Colburn factor j and Fanning friction factor f) values of the heat exchanger all reach the maximum while the baffle curvature is 10°. The increase of baffle curvature has a positive effect on the vibration-enhanced HTP of the I-ETBs, and when the curvature is 10°, the comprehensive HTP of the heat exchanger is better.

Vibration and Heat Transfer Study on Elastic-Tube Heat Exchange with Curved Baffle

A heat exchanger with a curved baffle for an elastic-tube bundle (ETB) is designed to effectively improve the performance based on a common ETB heat exchanger, and this paper systematically studies its vibration and heat transfer characteristics under different inlet velocity and structural parameters. The results indicate that the ETB vibration characteristics increase significantly with an increasing velocity, and the average amplitude of the ETB at 0.7 m/s is 4.51 times higher than that at 0.1 m/s. Similarly, the heat transfer performance subsequently decreases, but the average heat transfer coefficient of the ETB is significantly increased with the increase of the inlet velocity. When the long axis increases from 45 to 75 mm, the vibration intensity of the ETB decreases sharply, and the x direction and the total vibration Aa decrease by 43.4 and 51.5%, respectively. At the same time, the heat transfer coefficient of the ETB and its growth rate decrease by 3.9 and 45.6%. Additionally, the baffle curvature has little impact on the vibration and heat transfer performance. The difference between the average heat transfer coefficient and the total vibration amplitude of the ETB for different baffle curvatures is less than 5%.

Numerical research on vibration and heat transfer performance of a conical spiral elastic bundle heat exchanger with baffles

To improve the comprehensive heat transfer performance of elastic tube bundle heat exchangers, four heat exchanger schemes were proposed based on a conical spiral elastic tube bundle heat exchanger, in combination with an arrangement of pulsating baffles and heat transfer elements. The four heat exchanger schemes include two without baffle, one with the same direction baffles and one with opposite direction baffles. Using a calculation method of bidirectional fluid-solid coupling, the influences of the vibration and heat transfer performance for the four exchanger schemes at various Reynolds numbers were studied. The results display that the two schemes with baffles can enhance the regularity of the fluid movement and the hierarchy of the temperature field distribution. The average amplitudes of the conical spiral elastic tube bundles in the four heat exchanger schemes are increased by 107%, 117%, 1785%, and 1935%, respectively, when the Reynolds number is increased in the range of 1000–9000. The performance evaluation criteria of conical spiral elastic tube bundles in the four heat exchanger schemes are increased by 1.89%, 2.68%, 5.71%, and 5.84%, respectively. The schemes with the pulsating baffle installed in heat exchangers can improve the heat transfer performance. Especially, the installation direction of the baffle will affect the comprehensive heat transfer performance of heat exchangers, which has important significance in engineering application.

Research on the heat transfer performance of an improved elastic tube bundle heat exchanger under fluid-induced vibration

The heat transfer performance (HTP) of an improved elastic tube bundle (IETB) was analyzed using a bi-directional fluid-structure interaction calculation method. The vibration-enhanced HTP of heat exchangers with different inlet velocities (Uin) and row number N were studied. The results show that the amplitude gradually increases as the Uin increase with a maximum increase of 309.98%. The amplitude with fixed shell side length (FL-heat exchanger) is generally higher than that with variable shell side length (VL-heat exchanger) under different row numbers. The average amplitude of the three directions increased by 4.55%, 11.54%, and 7.41%, respectively. The heat transfer coefficient (h) is directly proportional to Uin, and the comprehensive HTP gradually decreases with the increase of Uin. With the increase in the row numbers, h generally showed a downward trend. For the VL-heat exchanger, h decreases as the row number increases, which increases from N=6 to N=9, and h decreases by 13.85%. For the FL-heat exchanger, h first increases and then gradually decreases. The comprehensive HTP also maintained the same trend. Compared VL-heat exchanger and FL-heat exchanger, reducing the spacing between tube rows increases heat transfer per unit volume, leading to improved comprehensive HTP of the IETB heat exchanger.

Numerical analysis of vibration response of elastic tube bundle of heat exchanger based on fluid structure coupling analysis

Abstract A tube bundle heat exchanger is a typical heat exchange equipment that exchanges heat between two fluids with different temperatures. Through this equipment, one fluid can be cooled down and another fluid can be heated up to meet their respective needs. The equipment is widely used in chemical, petroleum, pharmaceutical, energy, and other industrial sectors, and is one of the indispensable and important equipments in chemical production. To improve the heat transfer performance and service life of the heat exchanger, a numerical analysis of the vibration response of the elastic tube bundle in the heat exchanger based on fluid–structure coupling analysis is proposed. Using the weak coupling method of fluid–structure coupling, the vibration response of multiple rows of elastic tube bundles induced by shell side fluid in a heat exchanger with different tube row spacing and different tube row numbers is studied numerically, and the effects of shell side fluid and tube side fluid on the vibration response of elastic tube bundles are compared and analyzed. The results show that the maximum relative error of monitoring point amplitude is 43.36% when H = 40 mm and 10.17% when H = 70 mm. For connection IV, the maximum relative error of monitoring point amplitude is 31.71% when H = 40 mm and 24.08% when H = 70 mm. This is because when H is small, the interaction between rows of tube bundles is strong, so the amplitude changes violently with the number of the tube bundle. The step-by-step calculation strategy of rough calculation and actuarial calculation proposed in this article can greatly reduce the calculation time and improve the calculation efficiency.

VIBRATION AND HEAT TRANSFER STUDY ON IMPROVED ELASTIC BUNDLE HEAT EXCHANGER

The comprehensive performance of an improved elastic tube bundle heat exchanger (IETB) was studied by varying its structural parameters (diameter and wall thickness). The influence of the structural parameters on the vibration and heat transfer properties of IETBs at different inlet velocities (u<sub>in</sub>) was studied. The results show that the average amplitude of IETBs maximum increase was 41.67% and the average heat transfer coefficient (HTC) maximum increase was 46.47% as the u<sub>in</sub> value increased from 0.3 m/s to 0.5 m/s. As the diameter increased from 8 mm to 12 mm and the wall thickness increased from 1.2 mm to 1.8 mm, the average amplitude of IETBs maximum decreased by 98.18% and 11.73%, respectively, and the heat transfer intensity of vibration enhancement decreased by 10.69% and 15.83%, respectively. According to the performance evaluation criteria analysis, when the wall thickness was constant at 1.5 mm, the comprehensive performance of the IETB heat exchanger with a diameter of 8 mm was better than that at other diameters. When the diameter was constant at 10 mm, the IETB heat exchanger with a wall thickness of 1.2 mm had a better comprehensive performance than those with other wall thicknesses.

Numerical Analysis of Flow-Induced Vibration of Heat Exchanger Tube Bundles Based on Fluid-Structure Coupling Dynamics

According to the needs generated by the industry, there is an urgent need to investigate the flow vibration response law of the elastic tube bundle of heat exchangers subjected to the coupling effect of shell and tube domain at different inlet flow velocities. In this paper, based on the continuity equation, momentum equation, turbulence model, and dynamic grid technology, the vibration response of the elastic tube bundle under the mutual induction of shell and tube fluids is studied by using pressure-velocity solver and two-way fluid-structure coupling (FSC) method. The results show that the monitoring points on the same connection block have the same vibration frequency, while the vibration amplitude is different. Monitoring point A is the most deformed by the impact of fluid in the shell and tube domain. When the inlet velocity( v shell = v tube = 0.15 , 0.4, 0.5 m/s) of shell and tube is low, the amplitude of tube bundle vibration in the Y direction is greater than that in X and Z direction, and the tube bundle produces periodic vibration in the vertical direction. The vibration equilibrium position of the tube bundle along the shell flow direction gradually moves up with the increase of the inlet velocity. The amplitude in the Y -direction of the elastic bundle decreases with the increase of shell-side and tube-side velocity. The relationship between the vibration amplitude in the Y direction and the entrance velocity is a linear function.

Analysis of the effect of baffles on vibration and heat transfer characteristics of elastic tube bundles

For improving the performance of heat exchangers by effectively utilizing the flow-induced vibration, a presence baffle elastic tube bundle heat exchanger, is proposed according to the absence baffle elastic tube bundle heat exchanger. Heat transfer and vibration characteristics of them at different velocities, using flow-solid coupling calculation, are studied and compared. The results show that baffle can improve flow uniformity of shell-side fluid and fully excites the elastic tube bundle vibration to improve its heat transfer performance. When inlet velocity becomes 1.0 m/s from 0.7 m/s, the maximum amplitude of two monitoring points on elastic tube bundle increased by 25.40% and 25.92% for absence baffle elastic tube bundle heat exchanger and by 42.44% and 42.97% for presence baffle elastic tube bundle heat exchanger; in non-vibration and vibration conditions, average heat transfer coefficient of the elastic tube bundle increased by 32.46% and 30.48% for absence baffle elastic tube bundle heat exchanger and by 31.16% and 31.36% for presence baffle elastic tube bundle heat exchanger. Compared to absence baffle elastic tube bundle heat exchanger, heat transfer performance and vibration-enhanced heat transfer of presence baffle elastic tube bundle heat exchanger are generally improved. And at low flow velocities, the improvement is more significant.

Research on enhancement of heat transfer by vortex-induced vibration of heat exchange tube bundles with elastic joints

In the field of fluid-induced vibration enhanced heat transfer in heat exchangers, the elastic tube bundle structure currently cannot reach the ideal state of fluid-induced vibration enhanced heat transfer and is prone to fatigue failure. In response to this problem, this article proposes to make full use of the shell-side fluid vortex-induced elastic tube bundle vibration to achieve the purpose of enhancing heat transfer, and innovatively design heat transfer tube bundles with elastic joins that can adapt to large-amplitude vibration and be not damaged by structural fatigue. Here, the dynamic modal characteristics and the fluid–solid coupling vibration heat transfer characteristics of the single heat transfer tube bundle with elastic joints are studied by numerical calculation. The results show that the low-order modes of this tube bundle include one-dimensional mode, two-dimensional mode, and three-dimensional mode. When the flow velocity is 0.1 m/s≤ u≤ 0.2 m/s, the fluid vortex-induced tube bundle produces a two-dimensional vibration response with a maximum amplitude of 9.2 mm. At the same time, the tube bundle vibration enhances heat transfer significantly. When the flow velocity u= 0.12 m/s, compared with the static circle tube under the same working condition, the heat transfer coefficient is increased by 11.8%. When the flow velocity u > 0.2 m/s, the fluid can stimulate the three-dimensional vibration response of the tube bundle, but the circular tube vibration no longer has the function of enhancing heat transfer. The research in this article will enrich the development of fluid-induced vibration enhanced heat transfer theory and promote its engineering application.

Numerical research on vibration-enhanced heat transfer of improved elastic tube bundle heat exchanger

Based on the traditional elastic tube bundle (ETB) heat exchanger, an improved elastic tube bundle (IETB) heat exchanger with ETB structure upgraded and baffles installed was proposed to study its comprehensive heat transfer performance. The influence of inlet velocity and baffles installation on IETBs vibration and heat transfer features were studied. Numerical results show that the IETB heat exchanger has obviously improved the comprehensive heat transfer performance. The average amplitude of out-of-plane vibration and the heat transfer features of IETBs is significantly elevated by increasing inlet velocity and installing baffles. With the inlet velocity increased and baffles installation, the average amplitude of out-of-plane vibration of IETBs is improved maximum by 616.19% and 26.06%, the average heat transfer coefficient (HTC) is improved maximum by 97.89% and 23.24%, and the performance evaluation criteria (PEC) of IETBs is improved maximum by 3.45% and 2.06%, respectively. In addition, while the installation of the baffles can restrain the total vibration of IETBs (maximum reduction, 4.60%), it can strengthen the heat transfer capacity of IETB heat exchanger.

Experimental and numerical study on heat transfer enhancement by Flow-induced vibration in pulsating flow

The combination of flow-induced vibration and pulsating flow has a greater potential to enhance heat transfer. This study aims to investigate the effect of flow-induced vibration using pulsating flow generated by a vortex generator on the heat transfer enhancement of planar elastic tube bundle (PETB) in three kinds of flow fields. Water was utilized as working fluid to study the vibration characteristic and heat transfer of PETB comprehensively in a laminar flow using the experimental platform of flow-induced vibration and two-way fluid structure interaction (FSI) calculation. Vibration results found that the main vibration frequency of PETB in three flow fields was mainly concentrated in 24–25 Hz and the vibration amplitude was most obviously affected by the pulsating flow, leading to an amplitude reduction of 18.5% and 51.75% in coupled flow, 62.2% and 59% in steady flow. The difference in constrain support caused the local vibration displacement on No.3 tube showing a trend of first decreasing and then increasing and the local vibration displacement on No. 4 tube presenting a gradually increasing trend. Findings indicated that there was the same variation trend between the vibrational Reynolds number and heat transfer enhancement. The pulsating flow enhanced the vibration intensity of PETB, resulting in a increase in the turbulence kinetic energy and variation in the vorticity patterns. As a result, the passive heat transfer enhancement using the flow-induced by pulsating flow was obtained with a heat transfer coefficient increase of 28%, 25% and 19.5% in pulsating flow, coupled flow and steady flow, respectively. The maximum difference in local heat transfer was obtained at the position near the big connecter, where the local heat transfer coefficients in pulsating flow and coupled flow were 11.4% and 2.8% higher than that in steady flow, respectively.

Numerical Simulation of Flow-Induced Vibration of Three-Dimensional Elastic Heat Exchanger Tube Bundle Based on Fluid-Structure Coupling

The reliability of the heat exchanger tube bundle not only affects the economic efficiency of production but also relates to the normal development of production safety and health. To study the flow-induced vibration of tube bundles, a three-dimensional finite element model of heat exchange tubes and watersheds inside and outside the tubes was established to explore the flow-induced vibration characteristics of tube bundles and analyze the natural frequencies of single-span and multispan heat exchange tubes. Considering the randomness of the effective support between the tube bundle and the support plate of the heat exchanger, the natural frequency and vibration mode of the four-span tube with failure of the tube bundle support are analyzed. On this basis, the vibration caused by the two-way coupling flow between tube and tube outflow is calculated. Finally, the flow-induced vibration characteristics of the five-tube bundle with two different pitch-diameter ratios are analyzed. The calculation results show that the error between the calculated natural frequencies and the theoretical values is less than 3%, and within the allowable error range, the natural frequencies of the same order decrease with the increase of the number of support failures. The vibration frequencies of single-span and multispan tube bundles are consistent with the lift and drag frequencies, the vibration displacement curves show typical Strouhal modes, and the amplitude increases with the increase of fluid velocity. Vibration displacement curves of symmetrical spans of multispan tube bundles are similar in shape and amplitude. With the increase of tube bundle spacing, the vibration characteristics become more obvious.

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

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

Improved tube structure and segmental baffle to enhance heat transfer performance of elastic tube bundle heat exchanger

• Three novel elastic tube bundle heat exchangers were proposed. • The thermohydraulic performance of four heat exchangers were compared. • The vibration-enhanced heat transfer of four heat exchangers were compared. • A novel heat exchanger with superior thermohydraulic was obtained. Based on conventional elastic tube bundle heat exchangers, three novel elastic tube bundle heat exchangers were proposed by improving the tube bundle structure and adding segmental baffles in the heat exchanger to obtain a better comprehensive heat transfer effect. The heat transfer performance and vibration-enhanced heat transfer performance of conventional elastic tube bundle heat exchanger without baffles (CETB-NB), improved elastic tube bundle heat exchanger without baffles (IETB-NB), conventional elastic tube bundle heat exchanger with baffles (CETB-HB) and improved elastic tube bundle heat exchanger with baffles (IETB-HB) were compared qualitatively and quantitatively by numerical simulation. Numerical results show that improving the tube bundle structure and adding baffles in the heat exchanger can remarkably enhance the vibration-enhanced heat transfer performance and heat transfer capability of the heat exchanger. At the same inlet velocity, the vibration-enhanced heat transfer capability of the CETB-NB, IETB-NB, CETB-HB and IETB-HB are increased by 2.55%, 6.53%, 5.09% and 7.96% respectively. In the inlet velocity range of 0.1–1.0 m/s, compared with the CETB-NB, the heat transfer capacity of the IETB-NB is improved by 8.44%, 6.91%, 5.50% and 2.41%, respectively. Compared with the CETB-HB, the heat transfer capacity of the IETB-HB is improved by 5.14%, 4.21%, 4.03% and 2.14%, respectively. At the same inlet velocity, the pressure drop of the heat exchanger is IETB-HB, CETB-HB, IETB-NB and CETB-NB from largest to smallest. Considering the heat transfer and pressure drop of the heat exchanger comprehensively, the IETB-HB has obvious advantages in vibration-enhanced heat transfer performance and thermohydraulic performance.

Study on Vibration and Heat Transfer Performances of a Modified Elastic Tube Bundle Heat Exchanger

Based on the bi-directional fluid-structure coupling method, the vibration and heat transfer performances of a modified elastic tube bundle heat exchanger are studied. The vibration frequency and amplitude of tube bundle are compared between different directions and tube row spacing. Furthermore, the Nusselt number of tube bundle are studied in vibrational and non-vibrational cases. The numerical results represent that the vibration amplitude of tube bundle is the largest in the z direction, which is 7.25 times that in the y direction (direction of the smallest amplitude). In the calculation scope, the vibration frequency and amplitude promote with tube row spacing. From 50 mm to 90 mm spacing, the vibration frequency and amplitude increase by 21.88% and 10.65%, respectively. The Nusselt number under the fluid-induced vibration increases up to 11.67% compared with non-vibration. Besides, the Nusselt number of tube bundle in the middle part is lower than that at the two ends. Within 50-90 mm interval, the enhanced heat transfer effect rises along with tube row spacing. The rising rate of the Nusselt number increases by 52.4%. in the range of computation.

Analysis of the Effect of Baffles on Vibration and Heat Transfer Characteristics of Elastic Tube Bundles

Analysis of the Effect of Baffles on Vibration and Heat Transfer Characteristics of Elastic Tube Bundles