Heat Exchanger Tube Bundles Research Articles

Mathematical Investigation of Heat Transfer Characteristics and Parameter Optimization of Integral Rolled Spiral Finned Tube Bundle Heat Exchangers

In this study, the effects of fin tip thickness and fin root thickness of integral rolled spiral finned tube bundles on flow resistance, heat transfer performance and heat transfer and flow exergy destruction were investigated via mathematical simulation. The correlations between heat transfer and flow resistance performance were fitted with dimensionless numbers. The optimized parameters with performance evaluation criteria (PEC) as the objective were obtained using methods involving computational fluid dynamics and machine learning. The results show the effects of fin tip thickness and fin root thickness on the Nusselt number (Nu), Euler number (Eu), PEC, heat transfer exergy destruction (ExT) and flow exergy destruction (ExP) as obtained via mathematical simulation. A new mathematical correlation is proposed for predicting the Nu and Eu of integral rolled spiral finned tube bundles. Among the four optimization models tested, the random forest regression algorithm was the most accurate algorithm for PEC prediction models. In the studied range, the optimal parameters were a fin tip thickness of 2 mm and a fin root thickness of 3.5 mm. Compared with the initial parameters, when the Reynolds number was 20,380, the PEC increased by 2.53%, the ExP increased by 2.37% and the ExT decreased by 7.96%.

Experimental Analysis of Flow Induced Vibrations in Heat Exchanger Tube Bundles with P/D of 1.54 Subjected to Crossflow

This paper presents an experimental analysis of flow-induced vibrations in a heat exchanger tube bundle subjected to crossflow. The study focuses on the characterization and insights gained from the investigation. The tube bundle configuration consists of plain tubes with a single flexible tube, arranged in a squared pattern. The primary objective is to assess the flow-induced vibration behavior and identify any potential instabilities within the system. To analyze the flow-induced vibrations, various parameters were considered, including the P/D ratio (tube pitch to tube diameter ratio), which was found to be 1.54. The experiments were conducted under different flow velocities, and the vibration responses of the tube bundle were measured using suitable sensors. The results revealed that the third row of tubes in the bundle exhibited the highest level of instability compared to the other rows. This finding suggests that the positioning of the tubes within the bundle significantly influences the flow-induced vibrations. The vibrations were observed to vary with the flow velocity, indicating a strong fluid-structure interaction. It can be concluded that the squared arrangement of tubes in the tube bundle, along with the specific P/D ratio, contributes to the flow induced vibration characteristics. Understanding these effects is crucial for optimizing the design and operation of heat exchanger systems, as excessive vibrations can lead to mechanical failures and reduced heat transfer efficiency.

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.

Magneto-bioconvection flow in an annulus between circular cylinders containing oxytactic microorganisms

The present work focuses on the numerical investigations of the existence of oxytactic microorganisms on the bioconvection flow of nano-encapsulated phase change material (NEPCM) inside an annulus. The novel geometry of an annulus contains an inner wavy cylinder and an outer circular cylinder considering a rotational circular velocity of an inner wavy cylinder. The incompressible smoothed particle hydrodynamics (ISPH) method solved the dimensionless form of controlling equations. The novel annulus between the embedded circular cylinder and the outer circular cylinder can be applied in the tube bundles in heat exchangers. Further, rotation of an inner wavy cylinder in a circular cavity can be used in thermal fin's vibration and cooling of the electric devices. The effects of pertinent parameters such as a rotational frequency number ω, bioconvection Rayleigh number Rab, thermal radiation Rd, Lewis number Le, and Hartmann number Ha on the contours of oxygen concentration ϕ, temperature θ, heat capacity ratio Cr, oxytactic microorganisms N, and velocity field V as well as the average Nusselt & Sherwood numbers Nu¯ and Sh¯ are conducted. Increasing ω enhances the maximum of V by 56.6% and lowers Nu¯. The variations of Rab are enhanced the contours of N and maximized the velocity field from 0.86 at Rab=1 to 8.22 at Rab=100 due to the power in bioconvection flow. Increasing Le diminishes the strength of oxygen concentration ϕ and microorganisms N. Increasing Ha from 0 to 50 slows down the velocity field's maximum by 47.2% and enhances the value of Nu¯.

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.

Experimental estimation of equivalent loads on upward two-phase crossflow in tube bundles via Kalman filtering

Tube bundles of heat exchangers are permanently exposed to flow-induced forces, which may lead to high amplitude vibrations compromising the lifetime. In this context, Flow-induced vibration (FIV) is the most crucial dynamic issue to deal with in the design and operation of shell-and-tube heat exchangers. The experimental investigation of FIV requires determining the nature of flow-induced forces and their consequences, which are given by the characteristics of tube vibration. However, the measurement of flow-induced forces is challenging due to space restrictions within a tube bundle and their intrinsic spatially-distributed nature, often represented by equivalent point forces. The present work aims to estimate the equivalent flow-induced forces in tube bundles due to two-phase crossflow using Virtual Sensing principles. In order to do that, a device is designed and constructed to replace a tube within a normal triangular (transversal pitch to diameter ratio of 1.26) tube bundle, which is subjected to two-phase flow with void fractions ranging from 30% to 95% and a wide range of mass velocities. The device is instrumented with two couples of accelerometers and strain sensors, aligned with drag and transverse directions. The measured dynamic responses are discussed in terms of void fraction, mass velocities, and flow patterns. The results confirm the severity of FIV under Intermittent-type flow patterns. Further, the equivalent force estimation is performed via the Augmented Kalman Filter (AKF), which requires a model approximation (based on EMA techniques) and the system’s outputs. The values of the input covariance matrix are determined through the L-curve regularization method. Finally, the quality of the estimated equivalent force is tested by simulating system accelerations, whose RMS values are compared with measured data. The results suggest better acceleration predictions in the transverse direction than in the main flow direction for relatively low mass velocities and Bubbles flow pattern.

Analysis of Flow-Induced Vibrations in a Heat Exchanger Tube Bundle Subjected to Variable Tube Flow Velocity

Analysis of Flow-Induced Vibrations in a Heat Exchanger Tube Bundle Subjected to Variable Tube Flow Velocity

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.

Numerical study of different Pr number medium turbulent cross flow in staggered tube bundle

Tube bundle heat exchangers have been recognized as the most efficient means of thermal exchange. The staggered row method can enhance the performance of a heat exchanger. However, it results in a large pressure drop loss. As working media with high thermal conductivities, liquid metals can potentially replace conventional working media. In this study, for working fluids with low Prandtl number cross flowing through a staggered tube bundle, the turbulent Prandtl number model of cross flow was verified. The unsteady characteristics of the two working fluids traversing through the tube bundle were analyzed. The effects of molecular thermal diffusion on the total heat transfer capacity of the two working fluids during heat transfer were compared, along with the changes in the circumferential heat transfer characteristics of the tube bundles under different Reynolds numbers. The ζ factor was then proposed to analyze the non-uniformity in the heat transfer characteristics of a single tube. An empirical correlation describing the heat transfer non-uniformity at the fully developed region and inlet region and involving parameters such as working properties and flow state was proposed based on computational fluid dynamics data. Finally, the performance evaluation criteria(PEC) factor was used to analyze the comprehensive performance of the two heat transfer fluids. The results revealed that the comprehensive heat transfer performance of mercury was 60–70 times that of conventional working fluids.

Effect of triangular cross-sectional transverse wedge on the performance of an inline tube bundle heat exchanger

ABSTRACT In order to have a heat transfer per volume, heat exchangers have to have high overall heat coefficient. The effects of a transverse wedge on the heat transfer, the pressure drop, and the thermal efficiency factor (TEF) of air flow through a tube bundle heat exchanger was investigated. TEF increases continuously with the wedge aspect ratio (α). Form α = 0.275, 0.550, 0.758 to 1, TEF increases continuously from 1.157 to 1.84, 1.11 to 1.72, 1.05 to 1.42, and 1.02 to 1.39 for x/L = 1/3, 2/3, 1, and 0, respectively.

Investigation of deposition characteristics on tube-bundle heat exchanger with an improved ash particle model

The deposition of fly ash in the tube-bundle heat exchanger has become an urgent problem that must be resolved. During the deposition process, the fly ash particles will alter the physical properties and geometry of the heat exchange surface. A random function model combined with the dynamic mesh method is proposed to improve the existing particle deposition model. The effects of various flow velocities and particle sizes on particle deposition are analyzed. The results indicated that the total deposition mass of large particles decreases and the small particles increases as the flow velocity increases. With increasing particle size at the same flow velocity, the total particle deposition mass increases first and then decreases for in-line tube bundles. Local analysis indicates that the initial deposition occurs primarily on the windward side of the tube, with a greater number of particles deposited on the upstream tube bundles than on the downstream tube bundles.

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.

A partitioned-monolithic finite element method for thermo-fluid–structure interaction

In this study, a computational method for the coupled four-field problem of thermo-fluid–structure interaction (TFSI) using finite elements for all fields is proposed. Residual-based variational multiscale formulations are used for ensuring stable and accurate solutions of the flow as well as the temperature-transport problems. Adequate formulations for considering both the flow of gases and liquids are included in the computational method, with the most prominent representatives of each explicitly considered in the numerical examples contained in this article, that is, air and water, respectively. For air, a variable-density formulation of the Navier–Stokes equations at low Mach number, and for water, an incompressible formulation of the Navier–Stokes equations are utilized. Each of them is coupled to fully nonlinear dynamic equations for the structural field, along with the corresponding nonlinear dynamic equations for temperature transport in both fluid and solid domain. For the two surface couplings and the two volume couplings, a partitioned-monolithic strategy is pursued, in that the surface-coupled problems are solved monolithically, and the volume-coupled problems in partitioned form. On the one hand, choosing a monolithic scheme for the surface-coupled problems is particularly due to the improved performance of such a scheme compared to a partitioned scheme for FSI, as demonstrated by various studies published earlier. On the other hand, by using a partitioned algorithm for the volume-coupled problems, a potentially very large overall system of linear equations encompassing all fields can be avoided, for the time being, by splitting it up into two smaller monolithic systems. The choice is also motivated by the fact that the interaction is typically stronger for the surface-coupled fields in the applications of main interest. The computational method is applied to four numerical examples of increasing complexity, ranging from a rather simple problem of a plate which is subjected to tangential flow via channel flow with single and double elastic walls to the simplified configuration of a complex tube-bundle heat exchanger. The presented approach proves to be robust, and accurate results are obtained for all test cases. In particular, it is shown that the proposed method is capable of simulating a complex technical device such as a heat exchanger under its nominal working conditions.

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.

Experimental Investigation of a Prototype Thermal Refuge for Trout

Recent years have seen an increase in surface water temperatures in several streams and fisheries, which has a detrimental effect on cold-water species such as trout. One possibility to resolve this issue is to create localized refugia of colder water generated through active cooling. The current work focuses on a prototype thermal refugia design and field testing. Various configurations of the prototype thermal refugia were tested in a stream, which could benefit from additional refugia regions. The prototypes featured a staggered, tube-bundle heat exchanger placed inside an enclosure with an aperture. The results demonstrate that in remote locations, man-made refugia can be provided. While the base enclosure (91.5 cm × 91.5 cm × 45.8 cm) allowed for excess mixing with the warmer free stream and resulted in low performance (dimensionless temperature difference of θ¯avg= 0.07), additional modifications improved performance. By utilizing a panel or an extension, the dimensionless temperature difference quadrupled (θ¯avg= 0.26) while the average heat transfer per dimensionless temperature difference was reduced to approximately one-fifth (1.92 kWth/θ¯avg) of the base enclosure. But these configurations increased the standard deviation of the temperature differences inside the refugia due to localized cooling. The combination of the panel and the extension did not further increase the standard deviation but resulted in an even higher dimensionless temperature difference (θ¯avg= 0.55) and a lower heat transfer per dimensionless temperature difference (0.81 kW/θ¯avg). This suggests that the enclosure design can be used to achieve a desirable temperature differential while maintaining a reasonable spatial fluctuation in that temperature difference and power requirement.

Numerical study on structure optimization and heat transfer characteristic of distributed pulsating flow heat exchanger

ABSTRACT Distributed pulsating flow planar tube bundle heat exchanger (DPFPTB-HE) can improve heat transfer and have a high prospect of application in the industry. Computational fluid dynamics (CFD) software Fluent was utilized as an analysis tool, and the factors affecting heat transfer in heat exchangers were comprehensively studied based on the theory of fluid mechanics and heat transfer in this article. The local average surface Nusselt number(Nu v) evaluated the heat transfer performance. Results found that the DPFPTB-HE proposed in this paper has more uniform distribution of cold fluid in the shell domain and higher heat transfer efficiency in each layer of the tube bundle compared with the conventional planar tube bundle heat exchanger (PTB-HE). In this paper’s single-factor analysis experimental session, the study showed that with the inlet velocity increases, Nu v increases; as the length of the branch pipe increases, Nu v decreases; branch pipe diameter increases, Nu v decreases. The results obtained Nu v by applying the optimal experimental parameters selected by the Taguchi method were 7.22% larger than the maximum value in the control group. The numerical result and methodology are beneficial for providing further insight into guiding the optimization of heat exchanger structure and promoting industrial progress.

Detached-eddy simulation of the flow behavior in the shell-side of the coil tube bundle in turbulent flow

The coil tube bundle of Coil-wound heat exchanger (CWHE) is densely arranged, resulting in a complex flow domain in the shell. And Flow-induced vibration (FIV) is a common phenomenon in working situations where coil tubes are submerged in the oncoming flow. Understanding the flow and FIV characteristics of the shell-side plays a significant key in engineering issues, such as the design of coil tube bundle arrangements and safety verification of heat exchangers. This paper presented a detailed investigation of flow in the shell-side of the three-layer coil tube bundle with Detached eddy simulation (DES), whose validity was verified by comparison with the experimental results. Eight calculated cases of inlet flow rates from 0.01 m3/s to 0.15 m3/s with an interval of 0.02 m3/s were set up to determine that the flow domain of the shell-side is turbulent. The flow was found to form flow channels between adjacent layers, while variable eddy currents appeared around coil tubes. Subsequently, the gap transverse flow velocity was predicted and the calculation correlation was proposed. Furthermore, spectral and wavelet analyses were carried out to investigate the time-frequency data of fluctuating velocities in the flow, to bring to light vortex shedding frequencies and to capture St with respect to this tube bundle arrangement.

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.

Analysis of the causes of the cracking of tube bundles of 316L stainless steel Shell-and-Tube heat exchanger

In an oil field, numerous tube bundles in the reboiler at the bottom of a regeneration tower cracked and leaked after only 2.8 years of service. Analysis was conducted on the material properties, failure characteristics, and corrosion products of the cracked 316L stainless steel tube bundles, and the causes of the cracking of the tube bundles of the heat exchanger were clarified. The results indicated that the failure of the tube bundles was caused by typical stress corrosion cracking (SCC), and the cracking originated from the pitting corrosion that occurred on the exterior surface of the tube bundles. The chemical composition, metallography, and mechanical properties of the failed tube bundles met standard requirements. The synergistic effect of chloride ions and oxygen in the solution was the main cause of the SCC of the heat exchanger tube bundles.

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.