Heat Transfer In Tube Bundles Research Articles

The interaction between cross-flow induced vibration and convection heat transfer in tube bundle at subcritical Reynolds number

This work numerically investigates the interaction between flow-induced vibration (FIV) and forced convection heat transfer in tube bundle with a pitch ratio of 1.5 at subcritical Reynolds number (Re = 5 × 103-3 × 104). The range of reduced velocity is 0.53 ≤ Vr ≤ 2.71. The mass-damping parameter of coupling system is 0.07. The three-dimensional refined FIV simulation considering fluid viscous damping has been validated by the literature experiment to capture three continuous FIV mechanisms, namely turbulence-induced vibration, vortex-induced resonance and fluidelastic instability. The heat transfer and pressure drop in tube bundle are validated by the experiment. The coupling of Navier-Stokes equations, energy equations and vibration equations is solved by under-relaxation algorithm. The results of vibration response, the change of damping for the coupling system, flow field and temperature field, heat transfer and pressure drop are presented and delineated in this paper. The results show that for the low velocity turbulence-induced vibration, the interaction between FIV and flow heat transfer is negligible due to the weak fluid–solid interaction. In vortex-induced resonance region, the wall heating makes each row tube be out of phase by affecting the vortex shedding and reduces the positive feedback of resonance, which reduces the amplitude. The wall heating reduces the damping of coupling system, which causes an earlier transition from vortex-induced resonance to fluidelastic instability and a faster increase of amplitude in fluidelastic instability. In both vortex-induced resonance and fluidelastic instability, the vibration of tube bundle dominates the vortex shedding by the natural frequency, and further dominates the change of heat transfer. The best performance of enhanced heat transfer induced by FIV is located in vortex-induced resonance region, in which the time–space averaged Nusselt number is increased by 8.83%. Due to the redistribution of flow field and the elimination of deflective flow pattern, compared with vortex-induced resonance, the increasing ratio of heat transfer induced by FIV is lower and the increasing ratio of pressure drop induced by FIV is higher in the fluidelastic instability.

Numerical study of local heat transfer in tube bundle in pulsating flow

Forced pulsating flows enhance the heat transfer of various heat exchange equipment; however, such flows remain poorly understood. A numerical simulation was used to study how the position of a cylinder in a tube bundle affects the heat transfer during pulsating flow. The tubes of the tube bundle were arranged in an in-line order with the same relative pitch of 1.4. The Reynolds number and Prandtl number had constant values of 1500 and 4.03, respectively. The pulsating flow exhibits a reciprocating asymmetrical character. The pulsation amplitude related to the cylinder diameter was in the range from 0.1 to 0.4, and the pulsation frequency was in the range from 0.2 to 0.8 Hz. The numerical simulation results indicated that the heat transfer of the cylinder in the tube bundle was affected by the row number. With pulsating flow, the heat transfer of the cylinder in the first row had a minimum value, whereas the maximum heat transfer was observed in the last row. The effect of the position of the cylinder along the flow in the tube bundle decreases with increasing pulsation intensity. The maximum heat transfer enhancement of 51% was observed in the first row at a frequency of 0.8 Hz and amplitude of 0.4.

Experimental investigation of tube diameter and inclination angle on steam condensation accompanying with air in tube bundles

Steam condensation accompanying with air is an important thermal-hydraulic phenomenon in reactor containment. Condensation outside tubes is an important method to remove heat out of the containment under an accident. Most of the previous studies have been conducted on single tube and vertical plates, where the findings may not reflect the heat transfer in tube bundle well. The experimental studies were firstly carried out based on 3 × 3 tube bundle with diameters of 12–19 mm and inclination angles of 0–90° in the parameter range of pressure 0.2–1.6 MPa, air mass fraction of 12.1–75.2% and wall subcooling of 28.3–114.1℃. The results indicate that the effect of diameter and inclination angle in the tube bundle varies significantly in different pressure ranges. When the pressure is less than 0.8 MPa, the condensation heat transfer coefficient (CHTC) generally increases with decreasing tube diameter and inclination angle. The CHTC of the heat transfer tube with a tube diameter of 12 mm and an inclination angle of 0° increased by a maximum of 29% compared to that of the heat transfer tube with a tube diameter of 19 mm and an inclination angle of 90°. When the pressure is 0.8–1.6 MPa, the overall CHTC decreases as the diameter of the tube decreases, and the maximum reduction is about 20%. It decreases first and then increases with the decrease of the inclination angle, and the CHTC is the smallest when the inclination angle is about 60°.

Large-Eddy Simulations of Heat Transfer in the Tube Bundle

The tubular heat exchangers are widespread in the oil industry, therefore, the numerical simulation of the flow around a tube bundle is important. In this article, the LES method is used to study heat transfer in a ten-row in-line tube bundle in cross-flow. LES Smagorinsky, LES WALE and LES WM techniques in the numerical simulation were used. The Reynolds number Re was 2400, and the Prandtl number Pr was 7.33. The streamwise spacing-to-diameter ratio of the tube bundle was 1.3, transverse was 2.6. The local heat transfer characteristics of the eighth row are compared with the experimental data. The best agreement with the experimental data was obtained using the LES WALE and LES WM techniques.

A numerical study of heat transfer in the in-line tube bundle under pulsating fluid flow conditions

Shell-and-tube heat exchangers are widely used in different industries. Even a small increase in the efficien-cy of shell-and-tube heat exchangers can lead to significant energy savings. One of the ways to improve the efficiency of shell-and-tube heat exchangers is the use of pulsating flows for the enhancement of heat ex-change. Despite the fact that heat transfer in the tube bundle cross flow in steady-state conditions has been studied quite well, there is limited data on heat transfer in pulsating flow, which means that the problem of finding regularities of heat transfer with pulsating flows in tube bundles is still important. The work employs the incompressible Reynolds averaged Naviere-Stokes (URANS) equations and the continuity equation. Heat transfer is described by the convective heat transfer (Fourier-Kirchhoff) equation. The calculations are performed using Ansys Fluent. A numerical study has been conducted of the effects of forced asymmet-rical pulsating flow on heat exchange in in-line tube bundle cross-flow conditions. In the numerical experi-ment the Reynolds number Re ranged from 1000 to 2000, the relative pulsating amplitude A/D – from 1 to 2, the Strouhal number Sh – from 0,77 to 1,51, the Prandtl number and the duty cycle had fixed values: Pr = 7,2,  = 0,25. The relative transverse and longitudinal pitch was s1,2/D = 1,3. It has been found that pulsating flows lead to the enhancement of heat transfer in the whole range of the studied operating parameters. An increase in A/D and Sh leads to bigger Nusselt number Nu. An increase in the Re number leads to a de-crease in the Nu ratio in pulsating and steady flow conditions. The general correlation obtained based on the numerical study results can be used to predict heat transfer in a pulsating flow in the range of the studied geometric and operating parameters. More research is needed to predict heat transfer in a wider range of operating parameters and with other tube bundle configurations.

CFD simulations of convective heat transfer in actively heated tube bundle

Active heating is used as a flow assurance technique to prevent the huge temperature drop of crude oil while transporting from wells to facilities, which creates a friendly environment for hydrate formation and solid depositions. In the present study, convective heat transfer in tube bundle with three internal tubes was investigated through computational fluid dynamics simulation. A three dimensional model for existing bundle was developed. The model described the heat transfer occurring inside the bundle, aiming to heat up or at least maintain the production fluid temperature. The heat transfer from heating pipe to the whole bundle can be visualized through the temperature contours and the temperature gradient at the outlets. The effect of heating medium temperature and flow velocity are studied in the developed model.

Empirical heat transfer correlations of tube bundles under pulsating flows

In this paper, the influence of the parameters of pulsations on the heat transfer in tube bundles was considered. An analysis of the influence of the parameters of pulsations on heat transfer was carried out by empirical correlation. A new empirical correlation is proposed for calculation of external heat transfer in under of pulsating flow in tube bundles with different configurations. The maximum deviation of the empirical correlation with the data of the numerical experiment was 16.9%.

Thermo-Hydraulic Performance Evaluation, Field Synergy, and Entransy Dissipation Analysis for Hexagon-Like and Circular-Like Pin Finned Tube Bundles

ABSTRACTIn this paper, a comprehensive thermo-hydraulic performance evaluation for air flow across the hexagon-like and circular-like staggered pin finned tube bundle heat transfer surfaces has been numerically carried out by adopting the performance evaluation plot of enhanced heat transfer techniques oriented for energy-saving. In addition, the simulation results have also been analyzed from the viewpoints of field synergy principle and entransy dissipation extreme principle. The results indicate that the heat transfers are all enhanced based on identical pressure drop for the hexagon-like and circular-like pin finned tube bundles within the inlet velocity range from 1 m/s to 10 m/s studied. Moreover, the circular-like pin finned tube bundle offers the lowest friction factor increase ratio for the same Nusselt number increase ratio. Furthermore, the synergy between velocity and fluid temperature gradient has been proved again, having inherent consistency with the dissipation of entransy.

The evaluation of energy efficiency of convective heat transfer surfaces in tube bundles

When evaluating the effectiveness of the heat exchange surfaces in the main considered characteristics such as heat flow (Q, Watt), the power required for pumps (N, Watt), and surface area of heat transfer (F, m2). The most correct comparison provides a comparison “ceteris paribus”. Carried out performance comparison “ceteris paribus” in-line and staggered configurations of bundles with a circular pipes can serve as a basis for the development of physical models of flow and heat transfer in tube bundles with tubes of other geometric shapes, considering intertubular stream with attached eddies. The effect of longitudinal and transverse steps of the pipes on the energy efficiency of different configurations would take into account by mean of physical relations between the structure of shell side flow with attached eddies and intensity of transfer processes of heat and momentum. With the aim of energy-efficient placement of tubes, such an approach opens up great opportunities for the synthesis of a plurality of tubular heat exchange surfaces, in particular, the layout of the twisted and in-line-diffuser type with a drop-shaped pipes.

Application of field synergy principle for optimization fluid flow and convective heat transfer in a tube bundle of a pre-heater

The big problems facing solar-assisted MED (multiple-effect distillation) desalination unit are the low efficiency and bulky heat exchangers, which worsen its systematic economic feasibility. In an attempt to develop heat transfer technologies with high energy efficiency, a mathematical study is established, and optimization analysis using FSP (field synergy principle) is proposed to support meaning of heat transfer enhancement of a pre-heater in a solar-assisted MED desalination unit. Numerical simulations are performed on fluid flow and heat transfer characteristics in a circular and elliptical tube bundle. The numerical results are analyzed using the concept of synergy angle and synergy number as an indication of synergy between velocity vector and temperature gradient fields. Heat transfer in elliptical tube bundle is enhanced significantly with increasing initial velocity of the feed seawater and field synergy number and decreasing of synergy angle. Under the same operating conditions of the two designs, the total average synergy angle is 78.97° and 66.31° in circular and elliptical tube bundle, respectively. Optimization of the pre-heater by FSP shows that in case of elliptical tube bundle design, the average synergy number and heat transfer rate are increased by 22.68% and 35.98% respectively.

ТеплообміН пучкіВ труБ З рівнорозвиненоЮ поверхнеЮ

Наведено результати експериментальних досліджень конвективного теплообміну шахових пучків труб з рівнорозвиненою поверхнею в діапазоні зміни чисел Рейнольдса від 5000 до 70000. Запропоновано узагальнену залежність для розрахунку конвективних коефіцієнтів тепловіддачі таких пучків. Показано, що коефіцієнт Сq при числі Рейнольдса в рівнянні подібності залежить від геометричних характеристик пучків та труб.

The effect of flow pulsation on drag and heat transfer in an array of heated square cylinders

Laminar 2-D pulsating flow through homogeneous linear arrays of heated square tubes is simulated for pulsation frequencies of 0–80 Hz for tube diameter-based Reynolds numbers from 50 to 200. The objective is to examine the effects of flow pulsation on drag and heat transfer in heat exchanger tube bundles. Cycle-averaged and maximum drag coefficients, as well as the instantaneous and cycle-averaged Nusselt numbers are reported for each of the ten rows of tubes in the simulated array. The results show that flow pulsations can enhance heat transfer in tube bundles, and the level of enhancement increases with pulsation frequency and mean flow Reynolds number. A wake interference effect has been observed which significantly amplifies the drag on the leading rows and reduces and instantaneously reverses the sign of the drag force on the tubes located in the wake region. Cycle-average drag coefficients decreased with increasing Reynolds number and porosity, and were only a weak function of pulsation frequency. Peak drag coefficients were found to decrease with increasing Reynolds number and porosity, but increase with frequency approximately linearly. Empirical correlations are presented for a tube bundle with 64% porosity that relate maximum and cycle-average drag coefficients as well as Nusselt numbers to the Reynolds number and frequency.

An asymptotic approach to generalizing the experimental data on convective heat transfer of tube bundles in crossflow

Based on the analysis of experimental data the universal methods of calculating convective heat transfer of smooth and finned tube bundles in the crossflow have been developed over the ranges of geometric characteristics covering all practical needs at the Reynolds number Re = 3 × 10 3…1 × 10 5. The distinctive feature of the methods proposed is that the generalized similarity equation of convective heat transfer takes into account the dependence of the Reynolds number exponent on tube pitch characteristics in a bundle. This has allowed the mechanism of heat transfer and hydraulic performance in tube bundles to be taken into utmost consideration and the asymptotic character to be given to the generalized dependence. In turn, this has permitted one to show the presence of maximum of heat transfer intensity and also to cover limiting combinations of pitches, at which differences in staggered and in-line arrangements of tubes are leveled, i.e., practically the restrictions on the ranges of tube pitch characteristics of bundles can be removed.

Experimental investigation of in-line tube bundle heat transfer process to vertical downward foam flow

Usage of two phase flow as a coolant allows to reach more intensive heat transfer process. This paper presents the results of the investigation of the heat transfer between the in-line tube bundle and statically stable aqueous foam flow. The flow of the foam was generated at the top of the experimental channel and crossed down the tubes of the bundle (the diameter of the tubes was 0.02 m; horizontal and vertical distances between the centers of the tubes – 0.03 m). This investigation allowed determining the dependence of the heat transfer intensity of the tubes to foam flow on the volumetric flow rate and volumetric void fraction of the foam. The influence of tube position in the bundle on the intensity of heat transfer was found in this experimental study: the intensity of the heat transfer between the middle tube and the downward foam flow was determined to be higher comparing to the intensity between the tubes in both sideways of the bundle and the downward foam flow. The results of investigation showed that an average heat transfer intensity of the tubes of in-line bundle to downward without any turning foam flow was higher than that in the case of the downward after 180° turning foam flow. The results of this experimental study were generalized using the empirical equation between heat transfer coefficient from one side and the volumetric flow rate and volumetric void fraction of the foam from the other side.

Analysis of staggered tube bundle heat transfer to vertical foam flow

In general heat transfer intensity between solid surface and coolant (fluid) depends on three main parameters: heat transfer coefficient, size of heat exchange surface and temperature difference between surface and fluid. Sometimes the last two parameters (surface size and temperature difference) are strictly limited due to the process or technological requirements, and only increase of heat transfer coefficient is allowed. Simplest way offering sufficient increase in heat transfer rate (heat transfer coefficient as well) is to go from the laminar fluid flow regime to the turbulent one by increasing flow velocity. In many cases it helps despite such disadvantages like more complicated fluid supply system, rise of fluid flow mass rate and growth of energy usage for pumping. But in some cases, for example, in space application, in nuclear engineering, etc. there is not allowed to use high flow velocity of coolant – gas (due to vibration danger) or to apply high mass rate of coolant – liquid (due to limitation concerning weight or mass). One of the possible solutions of that problem could be the usage of two-phase flow as a coolant. An idea to use such two-phase coolant for heat removal from the solid surface is not new. Boiling liquid (water especially), gas flow with liquid droplets and other two-phase systems are widely used for heat and mass transfer purposes in various industries like food, chemical, oil, etc. An application of such two-phase coolants has lot advantages; high value of heat transfer coefficient is one of the most important. Unfortunately nothing is ideal on the Earth. Restrictions on vibration, on coolant weight (or mass rate); necessity to generate two-phase flow separately from the heat removal place; requirements on very low coolant velocities and other constraints do not allow using such type of two-phase coolant for purposes which were mentioned above (space application especially). As a possible way out can be usage of the statically stable foam flow produced from gas (air) and surfactant solutions in liquid (water). Our previous investigations [J. Gylys, Hydrodynamics and Heat Transfer under the Cellular Foam Systems, Technologija, Kaunas, 1998] showed the solid advantages of that type of two-phase coolant, including high values of heat transfer coefficient (up to 1000 W/m 2 K and more), low flow velocities (less than 1.0 m/s), small coolant density (less than 4 kg/m 3), possibility to generate foam flow apart from the heat removal place, etc. This article is devoted to the experimental investigation of the staggered tube bundle heat transfer to the vertical upward and downward statically stable foam flow. The investigations were provided within the laminar regime of foam flow. The dependency of the tube bundle heat transfer on the foam flow velocity, flow direction and volumetric void fraction were analyzed. In addition to this, the influence of tube position in the bundle was investigated also. Investigation shows that the regularities of the tube bundle heat transfer to the vertical foam flow differ from the one-phase (gas or liquid) flow heat transfer peculiarities. It was showed that the heat transfer intensity of the staggered tube bundle to the foam flow is much higher (from 25 to 100 times) than that for the one-phase airflow under the same conditions (flow velocity). The results of the investigations were generalized using criterion equations, which can be applied for the calculation and design of the statically stable foam heat exchangers with the staggered tube bundles.

Influence of Vertical Foam Flow Liquid Drainage on Tube Bundle Heat Transfer Intensity

The results of an experimental investigation of staggered tube bundle heat transfer to upward and downward moving vertical foam flow are presented in this article. It was determined that a dependency exists between tube bundle heat transfer intensity on foam volumetric void fraction, foam flow velocity and direction, and liquid drainage from foam. In addition to this, the influence of tube position of the bundle on heat transfer was investigated. Experimental results were summarized by criterion equations, which can be applied in the design of foam type heat exchangers.

Characteristic Features of Heat Transfer of Tube Bundles in a Cross Water–Air Flow and a Three-Phase Fluidized Bed

Characteristic Features of Heat Transfer of Tube Bundles in a Cross Water–Air Flow and a Three-Phase Fluidized Bed

The generalized Lévêque equation and its practical use for the prediction of heat and mass transfer rates from pressure drop

Based on the generalized Lévêque equation (GLE) a new type of analogy between pressure drop and heat transfer has been discovered, that may be used in the cross corrugated channels of chevron type plate heat exchangers, in packed beds, in tube bundles, in crossed rod matrices or in many other spacewise periodic arrangements. Experimental data on heat transfer in tube bundles in crossflow, both inline, and staggered arrangements, had been recently tested in greater detail. Using an empirical correlation for pressure drop in these arrangements from the literature that has been successfully tested against a large number of experimental pressure drop data, heat transfer data collected earlier could be very well represented from the pressure drop correlation and the GLE. The data for staggered bundles have been shown to be in better agreement with this new method, than with the existing empirical heat and mass transfer correlations. Somewhat larger deviations for inline tube bundles had been found at lower Reynolds numbers. Here a simple and physically reasonable correction function of Re is presented, which leads to a better agreement for the inline bundles, too. Additionally, it can be shown for a number of literature data on tube bundles and on crossed rod matrices that the agreement with the GLE prediction is even better if original pressure drop data from the same sources are available in place of a pressure drop correlation. The method results in reasonable heat or mass transfer predictions from frictional pressure drop, which may be widely used in chemical engineering applications.

Investigation on the bundle effects of boiling heat transfer in tube bundle using nitrogen bubble simulation

Investigation on the bundle effects of boiling heat transfer in tube bundle using nitrogen bubble simulation

STGEN computer program methodology and application to the steam line break tests in the RD-12 steam generator

A computer model for calculating a U-tube stream generator response to a main stream line break accident is presented. The stream generator is nodalized into three regions: riser, steam drum, and downcomer. Mass and pressure (temperature) are the main state variables representing each region. Models for steam drum swelling, tube bundle heat transfer, liquid subcooling, void fraction distribution and two-phase flow in the various flow connections are all formulated based on the state variables of the regions. The model was tested in a series of experiments carried out with the steam generator RD-12. Comparison between the experimental data and code predictions are discussed for small and large breaks. The model correctly predicts the major quantitative trends and many of the quantitative features. This includes global system variables such as the pressure variations as well as local variables such as quality, void fractions, liquid levels, and dryout level.