Journal articles on the topic 'Bundle of tubes'
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1
Chan, A. M. C., and M. Shoukri. "Boiling Characteristics of Small Multitube Bundles." Journal of Heat Transfer 109, no. 3 (August 1, 1987): 753–60. http://dx.doi.org/10.1115/1.3248154.
Abstract:
Boiling characteristics of multitube bundles have been investigated experimentally. Small bundles of up to nine rows were used. Void fraction profiles in the test vessel, tube surface temperatures, power input to individual tubes, and critical heat fluxes were measured for different bundle arrangements and boiling conditions. The data were used to study the system hydrodynamics, bundle heat transfer coefficients, and bundle critical heat flux. The data showed that for lower heat fluxes, the heat transfer characteristics are affected by the system hydrodynamics resulting in higher heat transfer coefficients, whereas at higher heat fluxes nucleate boiling is the dominant mechanism. The data also showed that within a tube bundle, the vapor rising from lower tubes enhances the CHF characteristics of the upper tubes.
2
Deeb, Rawad. "Flow and heat transfer characteristics of staggered mixed circular and drop-shaped tube bundle." Physics of Fluids 34, no. 6 (June 2022): 065126. http://dx.doi.org/10.1063/5.0090732.
Abstract:
The purpose of this study is to clarify heat transfer and fluid flow behavior across six-row mixed tube bundles. The tube bundle consists of circular and drop-shaped cross sections in a staggered arrangement. The Reynolds number Re for the flow is varied from 1.78 × 103 to 18.72 × 103. Six cases of the mixed tube bundle were considered. The results of the mixed tube bundles were compared with those of the circular (case I) and drop-shaped ones (case II). The Ansys Fluent software package was utilized to predict the flow pattern over the tube bundles. The results of the numerical simulation showed that the cross-sectional shape of the tubes and their location in the bundle significantly affect the heat transfer and pressure drop in the bundle. Case IV (circular tubes in the first, third, and fifth rows and drop-shaped tubes in the second, fourth, and sixth rows) increases the average Nusselt number [Formula: see text] by about 1.11%–8.10% and 47.86%–49.04% compared to that of the circular and drop-shaped tube bundles, respectively. Case VII (drop-shaped tubes in the first, second, fourth, and sixth rows and circular tubes in the third and fourth rows) has the lowest friction factor [Formula: see text] compared to the other cases of circular and mixed tube bundles. Moreover, the maximum values of the thermal–hydraulic performance [Formula: see text] were achieved for case IV at Re = 1.78 × 103 and the case VII at Re >1.78 × 103, which were about 14.55% and (2.08–4.49)%, respectively, higher than those obtained for the drop-shaped tube bundle. Generalized correlations of [Formula: see text], [Formula: see text], and [Formula: see text] for the studied mixed tube bundles were predicted.
3
Honda, H., B. Uchima, S. Nozu, H. Nakata, and E. Torigoe. "Film Condensation of R-113 on In-Line Bundles of Horizontal Finned Tubes." Journal of Heat Transfer 113, no. 2 (May 1, 1991): 479–86. http://dx.doi.org/10.1115/1.2910586.
Abstract:
Film condensation of R-113 on in-line bundles of horizontal finned tubes with vertical vapor downflow was experimentally investigated. Two tubes with flat-sided annular fins and four tubes with three-dimensional fins were tested. The test sections were 3×15 tube bundles with and without two rows of inundation tubes at the top. Heat transfer measurements were carried out on a row-by-row basis. The heat transfer enhancement due to vapor shear was much less for a finned tube bundle than for a smooth tube bundle. The decrease in heat transfer due to condensate inundation was more marked for a three-dimensional fin tube than for a flat-sided fin tube. The predictions of the previous theoretical model for a bundle of flat-sided fin tubes agreed well with the measured data for low vapor velocity and a small to medium condensate inundation rate. Among the six tubes tested, the highest heat transfer performance was provided by the flat-sided fin tube with fin dimensions close to the theoretically determined optimum values.
4
Deeb, Rawad. "Effect of angle of attack on heat transfer and hydrodynamic characteristics for staggered drop-shaped tubes bundle in cross-flow." Proceedings of the Russian higher school Academy of sciences, no. 3 (December 18, 2020): 21–36. http://dx.doi.org/10.17212/1727-2769-2020-3-21-36.
Abstract:
Tube bundles can be used as a separation heat exchanger in the organic Rankine cycle power plants (ORC), while the hot gas passes over the outer surface, and the working substance ORC flows inside the tubes. A numerical study has been conducted to clarify heat transfer and hydrodynamics of a cross-flow heat exchanger with staggered drop-shaped tubes at different flow angles of attack in comparison with circular tubes of the same equivalent diameter. The study was performed for the Reynolds number Re= 1.8 103 ~ 9.4 103, the longitudinal and transverse spacing of the tubes in the bundle are the same and are equal to 37 mm. Four cases of the tube’s arrangement with different angles of attack were investigated: 0, 45, 135, and 180 angles. The article presents a literature review related to the subject of the study. A mathematical and numerical model has been developed to calculate the heat transfer coefficient of the studied staggered drop-shaped tubes bundle using the ANSYS package, taking into account the stress-strain state of the tubes. Correlations of the average Nusselt numbers and the friction coefficient for the considered bundles in terms of the Reynolds number and angle of attack were presented. The results reveal that the thermal–hydraulic performance of the drop-shaped tubes bundle with zero-angle of attack is about 1.6 ~ 1.7 times greater than the circular one.
5
Ai, Shiqin, Chao Sun, Yuechan Liu, and Yuelin Li. "Numerical Simulation of Flow-Induced Vibration of Three-Dimensional Elastic Heat Exchanger Tube Bundle Based on Fluid-Structure Coupling." Shock and Vibration 2022 (January 12, 2022): 1–17. http://dx.doi.org/10.1155/2022/8980562.
Abstract:
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.
6
Blevins, R. D., and M. M. Bressler. "Acoustic Resonance in Heat Exchanger Tube Bundles—Part I: Physical Nature of the Phenomenon." Journal of Pressure Vessel Technology 109, no. 3 (August 1, 1987): 275–81. http://dx.doi.org/10.1115/1.3264863.
Abstract:
The intense acoustic resonance resulting from gas flow across a bank of heat exchanger tubes in a duct has been investigated experimentally and theoretically. At low gas velocities, the acoustic tone emanating from tube bundles increases in proportion to the flow velocity. When the frequency approaches a bound acoustic transverse mode of the tube bundle, intense sound can result. Sound levels as high as 173 db were measured within the bundle. During resonance, the sound correlates vortex shedding from the tubes and the pressure drop increases in some bundles.
7
Wu, Zhiwei, and Caifu Qian. "Study on Behavior of the Heat Exchanger with Conically-Corrugated Tubes and HDD Baffles." ChemEngineering 6, no. 1 (January 2, 2022): 1. http://dx.doi.org/10.3390/chemengineering6010001.
Abstract:
Baffles with holes in different diameters (or HDD baffles) and conically-corrugated tubes are respectively longitudinal flow baffle and high-efficiency heat exchange tubes proposed by the author. In this paper, vibrations of tube bundles with HDD baffles and fluid flow as well as heat transfer inside conically-corrugated tubes were numerically simulated, and the heat exchanger with conically-corrugated tubes and HDD baffles was tested for the heat transfer efficiency. It is found that compared with the traditional segmental baffles, tube bundle vibrations in heat exchangers, if using the HDD baffles, can be significantly reduced. Regarding heat transfer efficiency, conically-corrugated tubes are much better than smooth tubes and even better than other high-efficiency heat transfer tubes. Compared with the traditional heat exchangers, heat exchangers constructed with conically-corrugated tubes and the HDD baffles can provide better heat transfer efficiency and less tube bundle vibration.
8
Honda, H., B. Uchima, S. Nozu, E. Torigoe, and S. Imai. "Film Condensation of R-113 on Staggered Bundles of Horizontal Finned Tubes." Journal of Heat Transfer 114, no. 2 (May 1, 1992): 442–49. http://dx.doi.org/10.1115/1.2911293.
Abstract:
Film condensation of R-113 on staggered bundles of horizontal finned tubes with vertical vapor downflow was experimentally investigated. Two tubes with flat-sided annular fins and four tubes with three-dimensional fins were tested. The condensate flow and heat transfer characteristics were compared with the previous results for in-line bundles of the same test tubes and a staggered bundle of smooth tubes. The decrease in heat transfer due to condensate inundation was most significant for the in-line bundles of the three-dimensional fin tubes, whereas the decrease was very slow for both the staggered and in-line bundles of the flat-sided fin tubes. The predictions of the previous theoretical model for a bundle of flat-sided fin tubes agreed fairly well with the measured data at a low vapor velocity. The highest heat transfer performance was provided by the staggered bundle of flat-sided fin tubes with fin dimensions close to the theoretically determined optimum values.
9
Memory, S. B., S. V. Chilman, and P. J. Marto. "Nucleate Pool Boiling of a TURBO-B Bundle in R-113." Journal of Heat Transfer 116, no. 3 (August 1, 1994): 670–78. http://dx.doi.org/10.1115/1.2910921.
Abstract:
Heat transfer measurements were made during nucleate boiling of R-113 from a bundle of 15 electrically heated, copper TURBO-B tubes arranged in an equilateral triangular pitch, designed to simulate a portion of a flooded evaporator. Five of the tubes that were oriented in a vertical array on the centerline of the bundle were each instrumented with six wall thermocouples. For increasing heat flux, the incipient boiling wall superheat of upper tubes decreased as lower tubes were activated. In the boiling region at low heat fluxes (≈ 1 kW/m2), the average bundle heat transfer coefficient was 4.6 times that obtained for a smooth tube bundle (under identical conditions) and 1.6 times greater than that obtained for a single TURBO-B tube; a similar bundle factor has been reported for a smooth tube bundle. At high heat fluxes (100 kW/m2), the average bundle heat transfer coefficient was 3.6 times that of a smooth tube bundle. Furthermore, there was still a significant bundle factor (1.22), contrary to a smooth tube bundle, where all effect of lower tubes was eliminated at high heat fluxes.
10
Fabrykiewicz, Maciej, and Janusz T. Cieśliński. "Effect of Tube Bundle Arrangement on the Performance of PCM Heat Storage Units." Energies 15, no. 24 (December 9, 2022): 9343. http://dx.doi.org/10.3390/en15249343.
Abstract:
The results of a comprehensive study on the charging and discharging of latent heat storage systems (LHSS) are presented. Multi-tube shell-and-tube units with variable layouts of tube bundles are examined. Two tube arrangements—in-line and staggered—are tested. A variable number of tubes and different tube positions in a bundle are investigated. Moreover, two pitch ratios are studied. Three commercially available substances are used as phase change materials (PCM). The results show that increasing the number of tubes reduces both the charging and discharging times. It is found that for a bundle of seven tubes with a pitch ratio s/d = 4.5, the in-line tube arrangement results in a shorter charging time, but the discharging time is shorter for a staggered tube arrangement.
11
Sadikin, Azmahani, and Norasikin Mat Isa. "Flow Separation Prediction in a Single-Phase Flow in an Inline Tube Bundles." Applied Mechanics and Materials 465-466 (December 2013): 608–12. http://dx.doi.org/10.4028/www.scientific.net/amm.465-466.608.
Abstract:
The vertical single-phase flow was studied on the shell side of a horizontal tube bundle. In the present study, CFX version 14.0 from ANSYS was used to predict the flow regimes in the two tube bundles; i.e. the 19 mm and 38 mm arranged in an in-line configuration with a pitch to diameter ratio of 1.32. The simulations were undertaken to inform on how the fluid flowed within the tube passages in different tube bundle diameter that gives different gaps between the tubes, where the fluid must pass. The results show that the maximum gaps between the tubes have no clear effect to the flow where the flow separation and re-attachment and the average velocity is the same when increasing the tube bundle. This is consistent with other published data.
12
Taylor, C. E., I. G. Currie, M. J. Pettigrew, and B. S. Kim. "Vibration of Tube Bundles in Two-Phase Cross-Flow: Part 3—Turbulence-Induced Excitation." Journal of Pressure Vessel Technology 111, no. 4 (November 1, 1989): 488–500. http://dx.doi.org/10.1115/1.3265707.
Abstract:
An extensive experimental program was carried out to study the vibration behavior of tube bundles subjected to two-phase cross-flow. Turbulence-induced excitation is discussed in Part 3 of this series of three papers. Random vibration response to turbulence-induced excitation is a significant vibration mechanism in heat exchanger tube bundles subjected to two-phase cross-flow. The vibration responses of centrally located tubes in four tube bundle configurations subjected to air-water cross-flow was measured. The results are presented in the form of a normalized forced-excitation spectrum which can be used as a design guideline over a void fraction range from 25 percent to 99 percent and over a practical range of flow rates. The data are further analyzed to determine the dependence of the vibration response on Reynolds number, void fraction and frequency. Measurements taken on a single tube, a row of tubes and on tubes having varying end conditions were used to assist in interpreting the bundle data.
13
Zhang, Xu, Bin Jiang, Luhong Zhang, and Xiaoming Xiao. "Fluid-Elastic Instability Tests on Parallel Triangular Tube Bundles with Different Mass Ratio Values under Increasing and Decreasing Flow Velocities." Shock and Vibration 2016 (2016): 1–20. http://dx.doi.org/10.1155/2016/1680218.
Abstract:
To study the effects of increasing and decreasing flow velocities on the fluid-elastic instability of tube bundles, the responses of an elastically mounted tube in a rigid parallel triangular tube bundle with a pitch-to-diameter ratio of 1.67 were tested in a water tunnel subjected to crossflow. Aluminum and stainless steel tubes were tested, respectively. In the in-line and transverse directions, the amplitudes, power spectrum density functions, response frequencies, added mass coefficients, and other results were obtained and compared. Results show that the nonlinear hysteresis phenomenon occurred in both tube bundle vibrations. When the flow velocity is decreasing, the tubes which have been in the state of fluid-elastic instability can keep on this state for a certain flow velocity range. During this process, the response frequencies of the tubes will decrease. Furthermore, the response frequencies of the aluminum tube can decrease much more than those of the stainless steel tube. The fluid-elastic instability constants fitted for these experiments were obtained from experimental data. A deeper insight into the fluid-elastic instability of tube bundles was also obtained by synthesizing the results. This study is beneficial for designing and operating equipment with tube bundles inside, as well as for further research on the fluid-elastic instability of tube bundles.
14
Gylys, J., M. Jakubcionis, S. Sinkunas, and T. Zdankus. "AVERAGE HEAT TRANSFER OF TUBES IN DOWNWARD FOAM FLOW." Revista de Engenharia Térmica 2, no. 1 (June 30, 2003): 38. http://dx.doi.org/10.5380/reterm.v2i1.3518.
Abstract:
The model of heat exchanger was investigated experimentally. This model consists of three vertical lines of horizontal tubes with five tubes in each. Tubes were arranged in a staggered order. Heat transfer of staggered bundle of tubes to downward static stable foam flow was investigated experimentally. Heat transfer dependence on specific gas and liquid velocity was determined. Dependence of volumetric void fraction of foam on heat transfer was investigated also. Heat transfer rate dependence on tube position in the line of tube bundle was investigated experimentally. It was established that heat transfer rate highly depends on tube position in the line. Influence of tube position on heat transfer from tube bundle in upward foam flow was compared. Heat transfer dependence on tube position in the bundle was investigated experimentally also. Influence of wall of foam generator on heat transfer to sideline of tubes was established. Experimental results of heat transfer of bundle of tubes to downward static stable foam flow were generalized using dependence between Nusselt and Reynolds numbers.
15
Zhang, Shujuan, Chunbo Wang, Min Xie, Jinyu Liu, Zhe Kong, and Hui Su. "Actin Bundles in The Pollen Tube." International Journal of Molecular Sciences 19, no. 12 (November 22, 2018): 3710. http://dx.doi.org/10.3390/ijms19123710.
Abstract:
The angiosperm pollen tube delivers two sperm cells into the embryo sac through a unique growth strategy, named tip growth, to accomplish fertilization. A great deal of experiments have demonstrated that actin bundles play a pivotal role in pollen tube tip growth. There are two distinct actin bundle populations in pollen tubes: the long, rather thick actin bundles in the shank and the short, highly dynamic bundles near the apex. With the development of imaging techniques over the last decade, great breakthroughs have been made in understanding the function of actin bundles in pollen tubes, especially short subapical actin bundles. Here, we tried to draw an overall picture of the architecture, functions and underlying regulation mechanism of actin bundles in plant pollen tubes.
16
Marto, P. J., and C. L. Anderson. "Nucleate Boiling Characteristics of R-113 in a Small Tube Bundle." Journal of Heat Transfer 114, no. 2 (May 1, 1992): 425–33. http://dx.doi.org/10.1115/1.2911291.
Abstract:
Heat transfer measurements were made during nucleate boiling of R-113 from a bundle of 15 electrically heated, smooth copper tubes arranged in an equilateral triangular pitch. The bundle was designed to simulate a portion of a refrigeration system flooded-tube evaporator. The outside diameter of the tubes was 15.9 mm, and the tube pitch was 19.1 mm. Five of the tubes that were oriented in a vertical array on the centerline of the bundle were each instrumented with six wall thermocouples to obtain an average wall temperature and a resultant average heat transfer coefficient. All tests were performed at atmospheric pressure. The majority of the data were obtained with increasing heat flux to study the onset of nucleate boiling and the influence of surface “history” upon boiling heat transfer. Data taken during increasing heat flux showed that incipient boiling was dependent upon the number of tubes in operation. The operation of lower tubes in the bundle decreased the incipient boiling heat flux and wall superheat of the upper tubes, and generally increased the boiling heat transfer coefficients of the upper tubes at low heat fluxes where natural convection effects are important. The boiling data confirmed that the average heat transfer coefficient for a smooth-tube bundle is larger than obtained for a single tube.
17
Gorobets, Valery, Yurii Bohdan, Viktor Trokhaniak, Ievgen Antypov, and Mykola Masiuk. "Summarizing of Nusselt numbers and Euler numbers in depending of Reynoldsnumber for the compact tube bundle of small diameter tubes by experimental and numerical methods of researches." E3S Web of Conferences 128 (2019): 04002. http://dx.doi.org/10.1051/e3sconf/201912804002.
Abstract:
The work reports on the experimental research on the determination of the number of Nusselt concerning the compact bundle of small diameter smooth tubes. Having an inline arrangement, it lacks the gapsbetween adjacent tubes of longitudinal rows. In comparison to the traditional inline arrangement, this type of bundle is noticed to have significant advantages such as an increased coefficient of heat transfer and reduced aerodynamic resistance of the tube bundle. At the same time, the use of the compact bundle of small diameter smooth tubes leads to the beneficial reduction of the size and mass of heat exchangers of the shell–and–tubes type. Several series of experimental investigations uponthe aforementioned kind of bundle in open circuit section type wind tunnel of subsonic speeds applyingvarious hydrodynamic flow conditions are ran. As a result of these investigations, the correlations and definite dependences of the Nusselt numbers Nu and Euler numbers Eu on the Reynolds number Re of tube bundle were revealed.
18
Akhtar, Muhammad Moin, and Javaria Qadeer. "Experimental Analysis of Flow Induced Vibrations in Heat Exchanger Tube Bundles with P/D of 1.54 Subjected to Crossflow." International Conference on Applied Engineering and Natural Sciences 1, no. 1 (July 19, 2023): 108–13. http://dx.doi.org/10.59287/icaens.975.
Abstract:
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.
19
Gao, Weikai, Xiaoyang Xie, Xiaowei Li, and Xinxin Wu. "Influence of Coiling Direction of Helical Tube Bundles on the Thermal-Hydraulics of the HTGR Steam Generator." Journal of Physics: Conference Series 2048, no. 1 (October 1, 2021): 012032. http://dx.doi.org/10.1088/1742-6596/2048/1/012032.
Abstract:
Abstract Helical tube bundles were usually adopted in the steam generators (SGs) or intermediate heat exchangers (IHXs) of high temperature gas-cooled reactors (HTGRs). Heat transfer tubes in neighboring tube layers can be coiled in the same direction or in the opposite direction. The coiling direction has influences on the thermal-hydraulic performances of the SGs or IHXs. The cross flow convection over helical tube bundles with neighboring tube layers having the same coiled direction and opposite coiled direction were numerically investigated. Reynolds stress model with standard wall functions was used for the turbulence modeling. For a helical tube bundle with neighboring layers coiled in the same direction (parallel tube layers), the tangential velocity along the coiled circumferential direction could be observed obviously. For a helical tube bundle with neighboring layers coiled in the opposite direction (crossed tube layers), there is no average tangential velocity of the whole flow filed. And the streamlines of the fluid are very complex. The flow resistances and heat transfer coefficients over helical tube bundle with parallel tube layers and crossed tube layers were compared. Although the heat transfer over helical tube bundles with crossed tube layers was 9.39% smaller than that with parallel tube layers, the pressure drop over tube bundle with crossed tube layers was much smaller compared with those with parallel tube layers.
20
Liu, W., J. H. Davidson, and F. A. Kulacki. "Thermal Characterization of Prototypical Integral Collector Storage Systems With Immersed Heat Exchangers." Journal of Solar Energy Engineering 127, no. 1 (February 1, 2005): 21–28. http://dx.doi.org/10.1115/1.1824106.
Abstract:
Natural convection is measured in an enclosure that represents an integral collector storage system (ICS) with an immersed tube-bundle heat exchanger. Heat transfer coefficients for bundles of 240 tubes contained in a thin enclosure of aspect ratio of 9.3:1 and inclined at 30 deg to the horizontal are obtained for a range of transient operating modes and pitch-to-diameter ratios of 1.5, 2.4, and 3.3. Results for isothermal and stratified enclosures yield a correlation for the overall Nusselt number NuD=2.45±0.03RaD0.188,230⩽RaD⩽9800. The characteristic temperature difference in the Rayleigh number is that between the average water temperature within the bundle and the tube wall temperature. Nusselt numbers are three times larger than those for a similarly configured single-tube and an eight-tube bundle. This increase is attributed to stronger fluid motion within the bundle and higher overall large scale circulation rates in the enclosure.
21
Petinrin, M. O., O. A. Towoju, S. A. Ajiboye, and O. E. Zebulun. "Numerical Study of the Effect of Changing Tube Pitches on Heat and Flow Characteristics from Tube Bundles in Cross Flow." Journal of Engineering Sciences 6, no. 2 (2019): e1-e10. http://dx.doi.org/10.21272/jes.2019.6(2).e1/.
Abstract:
Tube bundles are found in various heat transfer equipment for thermal energy transfer between fluids. However, the inter-spatial arrangement of the tubes of any tube bundle is a determining factor for its thermal and hydraulic performance. In this paper, the effect of varying the transverse and longitudinal pitches downstream staggered circular tube bundle on the heat transfer and flow characteristic was numerically analyzed. Seven variations of tube arrangements were studied by changing the tube pitches within a Reynolds number range of 7 381 to 22 214. The analyses were carried out using the k-ε equation model imposed with the realizability constraint and were solved with finite volume CFD code, COMSOL Multiphysics. The results obtained were found to be in good agreement with existing correlations. The tube bundles with decreasing pitches demonstrated better heat transfer performance while those with increasing pitches exhibited a lower friction factor. Thus, the best thermal-hydraulic performance was obtained from increasing pitch arrangements. Keywords: cross flow, varying pitch, tube bundle, heat transfer, thermal-hydraulic performance.
22
Sukhotski, A. B., and Е. S. Danil’chik. "Convective Heat Exchange of Single-Row Bundles from Tubes with Rolled Aluminum Fins of Various Height at a Low Values of the Reynolds Number." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 64, no. 4 (July 21, 2021): 336–48. http://dx.doi.org/10.21122/1029-7448-2021-64-4-336-348.
Abstract:
The experimental study of the heat flow intensity of a single-row horizontal air-cooled tubular bundle of heat exchanger with spiral aluminum rolling fins at low Reynolds numbers (Re < 2000) is performed. The geometrical dimensions of the bimetallic finned tubes of the bundle, the following: the outer diameter of the fins d = 56.0 mm; the diameter of the tube at the base d0 = 26.8 mm; fin height h = 14.6 mm; pitch of fins s = 2.5 mm; the average fin thickness Δ = 0.5 mm; the coefficient of finned tubes φ = 19.3; heat transfer length l = 300 mm. The outer diameter of the load-bearing steel tube dн = 25 mm; wall thickness d = 2 mm. The research was carried out by the method of full thermal modeling at a specially designed experimental stand with electric heating of tubes and an exhaust shaft installed above the bundle. The air flow rate through the bundle was regulated by changing the height and cross-sectional area of the exhaust shaft. Calibration experiments were carried out and confirmed the reliability of the data obtained. Then the fins were sanded so to form new types of tubes, which were arranged in a single-row six-tube bundle with a constant relative cross-step σ1 = S1/d = 1.14 = const, and the thermal studies were repeated. As a result, a generalized criterion equation for heat transfer of a finned horizontal single-row bundle at small Reynolds numbers for various heights of the tube finning h = 0-14.6 mm was obtained. The effective height of the tube finning (h = 8 mm) for a single-row horizontal bundle was determined by dimensional and metal-intensive criteria.
23
Belghazi, M., A. Bontemps, and C. Marvillet. "Condensation Heat Transfer on Enhanced Surface Tubes: Experimental Results and Predictive Theory." Journal of Heat Transfer 124, no. 4 (July 16, 2002): 754–61. http://dx.doi.org/10.1115/1.1459728.
Abstract:
Condensation heat transfer in a bundle of horizontal enhanced surface copper tubes (Gewa C+ tubes) has been experimentally investigated, and a comparison with trapezoidal shaped fin tubes with several fin spacing has been made. These tubes have a specific surface three-dimensional geometry (notched fins) and the fluids used are either pure refrigerant (HFC134a) or binary mixtures of refrigerants (HFC23/HFC134a). For the pure fluid and a Gewa C+ single tube, the results were analyzed with a specifically developed model, taking into account both gravity and surface tension effects. For the bundle and for a pure fluid, the inundation of the lowest tubes has a strong effect on the Gewa C+ tube performances contrary to the finned tubes. For the mixture, the heat transfer coefficient decreases dramatically for the Gewa C+ tube.
24
Kawamura, K., and A. Yasuo. "Turbulence-Induced Vibration of Tube Bundle in Cross and Parallel Jet Mixed Flow." Journal of Pressure Vessel Technology 111, no. 4 (November 1, 1989): 352–60. http://dx.doi.org/10.1115/1.3265691.
Abstract:
In the multi-tube type of heat exchanger, baffle plates are located at appropriate intervals to support the heat transfer tubes. Depending on the baffle plate type employed, the flow field in the tube bundle will consist of a mixture of the cross flow (the fluid flows at right angles to the tube bundle along the baffle plate surfaces) and the parallel jet flow (the fluid streams through channels such as the flow holes of the baffle plates in the form of jets and flows in parallel with the tube bundle). Vibrations induced by the flow can cause fretting wear and fatigue of the heat transfer tubes. Therefore, it it essential to establish a method of evaluating heat transfer tube vibrations induced by the mixed flow for the purpose of evaluating the integrity of heat exchanger tubes. In this paper, three different flows, that is, cross, parallel jet and mixed flows, were simulated in order to clarify the relationships between the flow conditions and vibration of the tube bundle, and to study a method for evaluating tube bundle vibrations induced by turbulence in the mixed flow field by using the vibration characteristics in the cross flow field and the parallel jet flow field.
25
Qadeer, Javaria, Muhammad Moin Akhtar, and Riffat Asim Pasha. "Fluid-elastic Instability Effect of Groove Cylinder in Heat Exchanger." International Conference on Applied Engineering and Natural Sciences 1, no. 1 (July 21, 2023): 791–96. http://dx.doi.org/10.59287/icaens.1095.
Abstract:
The fluidelastic instability impact of groove cylinders in heat exchangers are investigated in this study, and explores associated phenomena of flow-induced vibration and fluidelastic instability. The primary focus is on investigating the performance of various rows of tubes in the tube bundle, with a particular emphasis on the largest instability identified in the third row. The analysis also considers the impact of a triangular arrangement of tubes within the tube bundle. The addition of groove tubes in the heat exchanger proved to greatly delay the onset of fluidelastic instability, lowering the possibility of flow induced vibration. Despite the improved impact of groove cylinders, the study found that the third row of tubes in the tube bundle had a higher degree of instability than the other rows. This result emphasizes the significance of tube location and arrangement throughout the design phase in reducing fluidelastic behavior. Overall, this study shows that groove tubes may delay fluidelastic instability and reduce the frequency of flow-induced vibration in heat exchangers. The design may significantly improve the operating efficiency and reliability of the heat exchanger by using groove cylinders and carefully studying tube designs and optimize heat exchanger performance.
26
Kracík, Petr, and Jiří Pospíšil. "Influence of Underpressure on Heat Transfer and Temperature Field at Sprinkled Tube Bundle." Applied Mechanics and Materials 832 (April 2016): 200–206. http://dx.doi.org/10.4028/www.scientific.net/amm.832.200.
Abstract:
Sprinkled tube bundles with a thin liquid film flowing over them are used in various technology processes where it is necessary to separate the vapour and liquid phases quickly and efficiently at low temperatures with a corresponding decrease of pressure around the tube bundle. In ideal conditions water boils at the whole surface of an exchanger, but in practice it must be considered that in original spots of contact between water and the exchanger wall the water will not boil at the tubes' surface but the cooling liquid will merely be heated-up. The article focuses on these processes. Experiments have been carried out at a tube bundle consisting of copper tubes of 12 mm diameter placed horizontally one above another that have been heated by water of an average input temperature approx. 40 °C. This bundle has been sprinkled by cool water at temperature of 15 °C and pressure has been gradually decreased using an exhauster at constant flow rates of heating and falling film liquid inside an experimental device's chamber. Was tested flow of sprinkled liquid in the range of 4-9 liters per minute, which corresponds to the range of Reynolds numbers of about 300 to 600 [-]. The result of these experiments is a studied heat transfer coefficient at the surface of a sprinkled tube bundle during heating of the cooling liquid with a transition into boiling of the liquid at the bundle. At a flow of 8 liters per minute were acquired sequence thermal camera FLIR SC 660. After evaluation of the sequences were generated maps of the temperature field according to decreasing the pressure and its standard deviation. From the contour graphs can evaluate the thermal stability of the liquid film on the spray tube bundle.
27
Adom, Ebenezer, Peter Kew, and Keith Cornwell. "Boiling Heat Transfer on Small Diameter Tube Bundle." International Journal of Engineering Research in Africa 2 (June 2010): 41–52. http://dx.doi.org/10.4028/www.scientific.net/jera.2.41.
Abstract:
An experimental study has been carried out using a tube bank representing a section of a tube bundle. The bank comprised 3 columns each of 10 stainless steel electrically heated tubes of 3mm outside diameter with pitch to diameter ratio of 1.5 in an in-line arrangement. Flow rate through the test section was controlled. Each tube in the central column was instrumented to permit determination of the tube temperature and heat flux, hence permitting calculation of the heat transfer coefficient. These tests were carried out using distilled water at nominal atmospheric pressure over a range of heat fluxes between 6 - 21 kW/m2. Results of the heat transfer tests are presented and compared with correlations used for conventionally sized bundles. Correlations developed for large tube bundle overestimate the experimental results.
28
Pettigrew, M. J., J. H. Tromp, C. E. Taylor, and B. S. Kim. "Vibration of Tube Bundles in Two-Phase Cross-Flow: Part 2—Fluid-Elastic Instability." Journal of Pressure Vessel Technology 111, no. 4 (November 1, 1989): 478–87. http://dx.doi.org/10.1115/1.3265706.
Abstract:
An extensive experimental program was carried out to study the vibration behavior of tube bundles subjected to two-phase cross-flow. Fluid-elastic instability is discussed in Part 2 of this series of three papers. Four tube bundle configurations were subjected to increasing flow up to the onset of fluid-elastic instability. The tests were done on bundles with all-flexible tubes and on bundles with one flexible tube surrounded by rigid tubes. Fluid-elastic instabilities have been observed for all tube bundles and all flow conditions. The critical flow velocity for fluid-elastic instability is significantly lower for the all-flexible tube bundles. The fluid-elastic instability behavior is different for intermittent flows than for continuous flow regimes such as bubbly or froth flows. For continuous flows, the observed instabilities satisfy the relationship V/fd = K(2πζm/ρd2)0.5 in which the minimum instability factor K was found to be around 4 for bundles of p/d = 1.47 and significantly less for p/d = 1.32. Design guidelines are recommended to avoid fluid-elastic instabilities in two-phase cross-flows.
29
SAHRANE, Sara, and Slimane NIOU. "CFD Investigation of Shell and Tube Heat Exchanger: Impact of Various Tube Bundle Combinations on Heat Transfer Coefficient and Pressure Drop." Eurasia Proceedings of Science Technology Engineering and Mathematics 26 (December 30, 2023): 225–33. http://dx.doi.org/10.55549/epstem.1409489.
Abstract:
Shell and tube heat exchangers play a crucial role in various industries, including chemical processing, oil and gas, power generation, and HVAC systems. These exchangers are widely used for transferring heat between two fluids while maintaining their separation. The design of a shell and tube heat exchanger consists of a bundle of tubes enclosed within a larger shell. The hot fluid flows through the tubes, while the cold fluid circulates around them in the shell, facilitating efficient heat transfer and pressure drop of the system. The performance of a shell and tube heat exchanger is influenced by various factors, including the configuration of the tube bundle. The choice of different tube bundle combinations can significantly impact the overall performance of the heat exchanger. In this paper, a numerical study is conducted to examine the effects of two combination of circular and square tube bundle with the simple arrangement: i) circular, ii) square, on a shell and tube heat exchanger. COMSOL Multiphysics is employed to model and simulate this heat exchanger under various mass flow rates. The result shown that the combined geometry heat exchanger exhibits the highest overall heat transfer coefficient compared to heat exchangers with single arrangements. The pressure drop on the tube and shell side was also studied for all cases of heat exchangers. The placement of circular tubes in the center and near the shell has a significant effect on heat transfer and pressure losses. It has been demonstrated that the tubes located at the ends of the shell have a much greater impact on heat transfer compared to the tubes positioned in the center.
30
Choe, Yong Chol, Un Chol Han, and Jong Min Kim. "Influence of Initiation Modes in the Bundle-Series Initiation of a Large Number of Shock Tubes by Detonators." Shock and Vibration 2023 (June 20, 2023): 1–11. http://dx.doi.org/10.1155/2023/9915373.
Abstract:
The bundle-series initiation is currently used as the method for simultaneously transmitting blast signals from a detonator to a large number of shock tubes for blasting using shock tubes and its initiation modes affect the ability and probability of signal transmission. A numerical study of the influence of initiation modes on the pressure impulse generated by detonators and transmitted to a large number of shock tubes has been undertaken with ANSYS AUTODYN code and validated through experimental results of signal transmission probability of shock tubes. Numerical simulations and experiments used lateral and frontal bundle-series initiation modes for a large number of shock tubes. For a bundle of many shock tubes, peak pressures of pressure impulses affected within all shock tubes beside the first layer around a detonator, and signal transmission probabilities were higher for frontal bundle-series initiation mode than for lateral bundle-series initiation mode. The magnitude of a numerically obtained pressure impulse to a bundle of shock tubes shows a good correlation with the experimentally obtained signal transmission probability of shock tubes. Finally, the results are employed in the application of a frontal bundle-series initiation mode with the simultaneous bundle-series initiating a large number of shock tubes for blastings in mining and construction.
31
Khalatov, А. А., І. І. Borisov, G. Kovalenko, and M. Muliarchuk. "APPLICATION OF DIMPLES AND HELICAL GROOVES ON THE OUTTER SURFACE OF TUBES TO INCREASE THERMAL-HYDRAULIC EFFICIENCY OF TUBE BUNDLES AT CROSS FLOW." Thermophysics and Thermal Power Engineering 46, no. 3 (July 25, 2022): 16–22. http://dx.doi.org/10.31472/ttpe.3.2022.11.
Abstract:
The flow structure and thermo-hydraulic efficiency of cross flow of tube bundles with dimples and helical grooves have been analyzed. The Reynolds number range (103-104) was typical for industrial heat exсhangers. It was found that dimples and grooves decrease scientifically the cylinder wake area and reduces the hydraulic losses. The heat transfer augmentation in five-row tube bundle by dimples is 35-40% while pressure drop increase by 10-15%. The hydraulic resistance of two-row bundle of tube with helical grooves is 20% lower than that of a smooth tube bundle, while heat transfer augmentation is absent. The value of Reynolds analogy factor for tube bundles with dimples and helical grooves exceeds unity. The high thermo-hydraulic efficiency of tube bundles with dimples and helical grooves, allows us to recommend it for practical use in the development of modern heat exchange equipment of the tubular type.
32
Medeiros, M. S., and A. J. K. Leiroz. "A PROCEDURE FOR TUBE COUNT DETERMINATION IN SINGLE AND MULTIPLE PASS TUBULAR HEAT EXCHANGERS." Revista de Engenharia Térmica 4, no. 2 (December 31, 2005): 97. http://dx.doi.org/10.5380/reterm.v4i2.5408.
Abstract:
The development of a simple computational procedure that allows the precise determination of important parameters for the thermal and mechanical design of tubular heat exchangers is discussed in the present work. The design of tubular heat exchangers for a wide variety of applications can involve the use of empirical expressions and data tables for the determination of the tube bundle parameters, such as the tube count and the tube bundle outside diameter. The motivation for developing the discussed procedure resides in addressing cases for which empirical expressions are inapplicable or data table are unavailable. Initially, the shell positions in which tubes can be placed are determined based on specified tube pitch, angle of arrangement, inlet and outlet nozzle diameters and tube bundle-to-shell clearance. The maximum number of tubes for the given configuration is obtained from the tube position searching procedure. A sorting algorithm, based on the tube distance to the shell center, is used to appropriately place a specified number of tubes within the heat exchanger cross section. Results for a single- and multiple-pass fixed-tubesheet heat exchangers are presented and compared with available tube count tables.
33
Lin, Tsun-Kuo, and Ming-Huei Yu. "Simulation of Flow Induced Vibrations of Tube Bundle in Cross Flow." Journal of Mechanics 17, no. 3 (September 2001): 139–47. http://dx.doi.org/10.1017/s1727719100004500.
Abstract:
ABSTRACTThe flow-induced vibration of tubes in a rotated triangular array subject to cross flow is simulated numerically. In the study, the flow field around the tube bundle is computed by solving the continuity and Navier-Stokes equations with assumption of constant fluid properties, and the kε-model for turbulent Reynolds stress. With the flow field known, the fluid forces on the tube surfaces can be calculated, and then the displacement of each tube due to the fluid force can be evaluated. Iteration is needed to obtain the dynamic response of the tube structure in the fluid flow. The parameters in the study are inlet velocity of the cross flow and properties of the tube bundle including natural frequency, damping factor, and mass. Based on the tube response, the critical flow conditions of tube vibration are determined for varying mass damping. Once tube vibrations occur, it is shown that the vibrations of the tubes in the second and fourth tube rows are significant as compared to other tubes. The orbits of the tube vibration look like an ellipse with major axis in the cross-stream direction, implying large lift force on the tubes. The dominant frequency in the spectrum of lift coefficients of the tubes is the same as the natural frequency, and the corresponding amplitude is increased with increasing the inlet velocity. The calculated data predicted for the critical reduced velocity agrees well with the data by Kassera and Strohmeier [17].
34
Kracik, Petr, Marek Balas, Martin Lisy, and Jiri Pospisil. "Experimental Verification of Impact of Sprinkled Area Length on Heat Exchange Coefficient." Advances in Materials Science and Engineering 2019 (April 1, 2019): 1–7. http://dx.doi.org/10.1155/2019/9262438.
Abstract:
On a sprinkled tube bundle, liquid forms a thin liquid film, and, in the case of boiling liquid, the liquid phase can be quickly and efficiently separated from the gas phase. There are several effects on the ideal flow mode and the heat transfer from the heating to the sprinkling liquid. The basic quantity is the flow rate of the sprinkling liquid, but also diameter of the tubes, pipe spacing of the tube bundle, and physical state of the sprinkling and heating fluid. Sprinkled heat exchangers are not a new technology and studies have been carried out all over the world. However, experiments (tests) have always been performed under strict laboratory conditions on one to three relatively short tubes and behaviour of the flowing fluid on a real tube bundle has not been taken into account, which is the primary aim of our research. In deriving and comparing the results among the studies, the mass flow rate based on the length of the sprinkled area is used, thus trying to adjust the different length of the heat exchanger. This paper presents results of atmospheric pressure experiments measured on two devices with different lengths of the sprinkled area but with the same number of tubes in the bundle with same pitch and surface at a temperature gradient of 15/40°C, where 15°C is the sprinkling water temperature at the outlet of the distribution pipe and 40°C is the temperature of heating water entering the bundle.
35
Dubot, Claire, Cyrille Allery, Vincent Melot, Claudine Béghein, Mourad Oulghelou, and Clément Bonneau. "Numerical Prediction of Two-Phase Flow through a Tube Bundle Based on Reduced-Order Model and a Void Fraction Correlation." Entropy 23, no. 10 (October 16, 2021): 1355. http://dx.doi.org/10.3390/e23101355.
Abstract:
Predicting the void fraction of a two-phase flow outside of tubes is essential to evaluate the thermohydraulic behaviour in steam generators. Indeed, it determines two-phase mixture properties and affects two-phase mixture velocity, which enable evaluating the pressure drop of the system. The two-fluid model for the numerical simulation of two-phase flows requires interaction laws between phases which are not known and/or reliable for a flow within a tube bundle. Therefore, the mixture model, for which it is easier to implement suitable correlations for tube bundles, is used. Indeed, by expressing the relative velocity as a function of slip, the void fraction model of Feenstra et al. and Hibiki et al. developed for upward cross-flow through horizontal tube bundles is introduced and compared. With the method suggested in this paper, the physical phenomena that occur in tube bundles are taken into consideration. Moreover, the tube bundle is modelled using a porous media approach where the Darcy–Forchheimer term is usually defined by correlations found in the literature. However, for some tube bundle geometries, these correlations are not available. The second goal of the paper is to quickly compute, in quasi-real-time, this term by a non-intrusive parametric reduced model based on Proper Orthogonal Decomposition. This method, named Bi-CITSGM (Bi-Calibrated Interpolation on the Tangent Subspace of the Grassmann Manifold), consists in interpolating the spatial and temporal bases by ITSGM (Interpolation on the Tangent Subspace of the Grassmann Manifold) in order to define the solution for a new parameter. The two developed methods are validated based on the experimental results obtained by Dowlati et al. for a two-phase cross-flow through a horizontal tube bundle.
36
Janzen, V. P., E. G. Hagberg, M. J. Pettigrew, and C. E. Taylor. "Fluidelastic Instability and Work-Rate Measurements of Steam-Generator U-Tubes in Air–Water Cross-Flow." Journal of Pressure Vessel Technology 127, no. 1 (February 1, 2005): 84–91. http://dx.doi.org/10.1115/1.1849229.
Abstract:
The dynamic response of U-tubes to two-phase cross-flow has been studied in tests involving a simplified U-tube bundle with a set of flat-bar supports at the apex, subjected to air–water cross-flow over the mid-span region. Tube vibration and the interaction between tubes and supports were measured over a wide range of void fractions and flow rates, for three different tube-to-support clearances. The vibration properties and tube-to-support work-rates could be characterized in terms of the relative influence of fluidelastic instability and random-turbulence excitation. For the first time, in a U-bend tube bundle with liquid or two-phase flow, fluidelastic instability was observed both in the out-of-plane and in the in-plane direction. This raises the possibility of higher-than-expected tube-to-support work-rates for U-tubes restrained by flat bars, particularly if fluidelastic instability, random turbulence and loose supports combine adversely.
37
Kracík, Petr, and Jiří Pospíšil. "EFFECT OF TUBE PITCH ON HEAR TRANSFER IN SPRINKLED TUBE BUNDLE." Acta Polytechnica 55, no. 5 (October 31, 2015): 329. http://dx.doi.org/10.14311/ap.2015.55.0329.
Abstract:
Water flowing on a sprinkled tube bundle forms three basic modes: the Droplet mode (the liquid drips from one tube to another), the Jet mode (with an increasing flow rate, the droplets merge into a column) and the Membrane (Sheet) mode (with a further increase in the flow rate of the falling film liquid, the columns merge and create sheets between the tubes. With a sufficient flow rate, the sheets merge at this stage, and the tube bundle is completely covered by a thin liquid film). There are several factors influencing both the individual modes and the heat transfer. Beside the above-mentioned falling film liquid flow rate, these are for instance the tube diameters, the tube pitches in the tube bundle, or the physical conditions of the falling film liquid. This paper presents a summary of data measured at atmospheric pressure, with a tube bundle consisting of copper tubes of 12 millimetres in diameter, and with a studied tube length of one meter. The tubes are situated horizontally one above another at a pitch of 15 to 30 mm, and there is a distribution tube placed above them with water flowing through apertures of 1.0mm in diameter at a 9.2mm span. Two thermal conditions have been tested with all pitches: 15 °C to 40 °C and 15 °C to 45 °C. The temperature of the falling film liquid, which was heated during the flow through the exchanger, was 15 °C at the distribution tube input. The temperature of the heating liquid at the exchanger input, which had a constant flow rate of approx. 7.2. litres per minute, was 40 °C, or alternatively 45 °C.
38
Wang, Xiao Lu, and Da Yu Huang. "Thermal Analysis and Design Applications of the Spiral Groove Tubes in Condensers." Advanced Materials Research 1070-1072 (December 2014): 1705–8. http://dx.doi.org/10.4028/www.scientific.net/amr.1070-1072.1705.
Abstract:
In this paper, condensation mechanism of the Freon refrigerants outside spiral grooved tube is discussed. The heat transfer coefficient of Freon refrigerants condensation outside spiral grooved tube is obtained. A calculation example of heat transfer coefficient on the tube bundle of condenser with baffle bars is presented. It shows the excellent thermal performance of the spiral groove tubes compared to smooth tubes.
39
Lian, H. Y., G. Noghrehkar, A. M. C. Chan, and M. Kawaji. "Effect of Void Fraction on Vibrational Behavior of Tubes in Tube Bundle Under Two-Phase Cross Flow." Journal of Vibration and Acoustics 119, no. 3 (July 1, 1997): 457–63. http://dx.doi.org/10.1115/1.2889745.
Abstract:
The effects of local two-phase flow parameters on the vibrational behavior of tubes have been studied in an in-line 5 × 20 tube bundle subjected to air-water cross-flow. One of the tubes was flexibly mounted and instrumented for vibration measurement and the others were rigid. Parameters obtained include local void fraction fluctuations, RMS amplitude of void fraction fluctuations, void fraction distributions across the tube bundle, flow regimes based on probability density function of void fraction signals, damping ratio, and tube vibration response as a function of mass flux, void fraction and dynamic pressure. Damping and tube vibration amplitude in two-phase flow have been found to be closely related to the RMS amplitudes of the local void fraction fluctuations and dynamic pressure fluctuations, respectively.
40
Gogonin, Ivan, and Oleg Volodin. "Influence of the developing region of the thermal boundary layer on heat transfer during vapor condensation on horizontal tube bundles." E3S Web of Conferences 459 (2023): 05004. http://dx.doi.org/10.1051/e3sconf/202345905004.
Abstract:
The purpose of this publication is to describe a phenomenon that is fundamentally important and, at the same time, hardly elucidated in the literature. In the process of film condensation of vapor on the bundles of horizontal tubes, a developing region of the thermal boundary layer is formed on each tube of the bundle; the role of this region in heat transfer is important, and in some cases decisive. The paper presents experimental results on the influence of various contributions of the developing region on heat transfer during film vapor condensation on tube bundles. Based on the data obtained, an algorithm for calculating a condenser during condensation of a stationary vapor without non-condensable impurities is proposed.
41
Li, Hui Fang, Cai Fu Qian, and Xiao Dong Yu. "Effects of Tube Stiffness and Tubesheet Thickness on the Thermal Stress of the Tubes and Tubesheet." Advanced Materials Research 314-316 (August 2011): 1552–55. http://dx.doi.org/10.4028/www.scientific.net/amr.314-316.1552.
Abstract:
In this paper, numerical simulation was carried out for the tube bundle of a float-head heat exchanger with concentration on the effects of tube stiffness and tubesheet thickness on the thermal stress of the tubes and tubesheet. It is found that decreasing the tube stiffness by using corrugated tubes can reduce the axial thermal stress at the tubes and, thus, decrease the possibility of strength failure of the connection between the tubes and tubesheet. Decreasing the tubesheet thickness can reduce the thermal stress at the tubesheet, which is meaningful for the heat exchangers with large temperature difference between the shell-side fluid and tube-side fluid and under small pressures.
42
Gylys, J., S. Sinkunas, and T. Zdankus. "ANALYSIS OF TUBE BUNDLE HEAT TRANSFER TO VERTICAL FOAM FLOW." Revista de Engenharia Térmica 4, no. 2 (December 31, 2005): 91. http://dx.doi.org/10.5380/reterm.v4i2.5038.
Abstract:
Phenomena of foam flow and associated heat transfer are rather complex. Foam is a twophase flow, which structure changes while it passes an obstacle: bubbles divide into smaller bubbles and liquid drains down from flow. Due to these peculiarities, an application of analytical methods for their study is a complex subject. Thus experimental method of investigation was selected in our work. The investigation apparatus consisted of foam generator, vertical channel and staggered bank of horizontal tubes. The cross section of the channel had square profile with side dimension 140 mm. Tubes in the bank were located in three vertical rows with five tubes in each of them. Experiments were performed within Reynolds number diapason for gas from 190 to 450 and foam void volumetric fraction from 0.996 to 0.998. Direction of foam motion in vertical channels also influences heat transfer intensity. Investigations of heat transfer process of upward and downward moving statically stable foam flow from horizontal tube bank were performed. Experimental heat transfer results of tube bundle in vertical cross foam flow were summarized by criterion equations, which enable determination of heat transfer intensity of the entire bundle or of a separate tube of the bundle for different values of void volumetric fractions and regime parameters of statically stable foam flow.
43
Adom, Ebenezer, Peter Kew, and Keith Cornwell. "Comparison of the Three–Zone Evaporation Model with Boiling Heat Transfer in a Compact Tube Bundle." International Journal of Engineering Research in Africa 5 (July 2011): 53–63. http://dx.doi.org/10.4028/www.scientific.net/jera.5.53.
Abstract:
The recent interest in boiling heat transfer in small diameter tubes has led to the study of boiling heat transfer outside a compact tube bundle of diameter 3mm. The bank comprised 3 columns each of 10 stainless steel electrically heated tubes of 3mm outside diameter, with pitch to diameter ratio of 1.5 in an in-line arrangement. These tests were carried out using distilled water and R113 at nominal atmospheric pressure over a range of heat fluxes between 4-21 kW/m2 for mass fluxes from G=5.6 - 32.8 kg/m2s. The recent three-zone evaporation model developed by Thome, Dupont and Jacobi for boiling inside micro channels was used to compare with experimental results as photographic study showed that bubbles confined within the bundle were responsible for the heat transfer enhancement observed. It was observed that the three state model was promising in its application to the bundle arrangement as the confinement number Co for bundle has been shown to be in the order of 0.63
44
Kumar Rai, Mayank, Rajesh Khanna, and Sankar Sarkar. "Control of tube parameters on SWCNT bundle interconnect delay and power dissipation." Microelectronics International 31, no. 1 (December 20, 2013): 24–31. http://dx.doi.org/10.1108/mi-03-2013-0016.
Abstract:
Purpose – This paper aims to propose to study the control of tube parameters in terms of diameter, separation between adjacent tubes and length, on delay and power dissipation in single-walled carbon nanotube (SWCNT) bundle interconnect for VLSI circuits. Design/methodology/approach – The paper considers a distributed-RLC model of interconnect. A CMOS-inverter driving a distributed-RLC model of interconnect with load of 1 pF. A 0.1 GHz pulse of 2 ns rise time provides input to the CMOS-inverter. For SPICE simulation, predictive technology model (PTM) is used for the CMOS-driver. The performance of this setup is studied by SPICE simulation in 22 nm technology node. The results are compared with those of currently used copper interconnect. Findings – SPICE simulation results reveal that delay increases with increase in separation between tubes and diameter whereas the reverse is true for power dissipation. The authors also find that SWCNT bundle interconnects are of lower delay than copper interconnect at various lengths and higher power dissipation due to dominance of larger capacitance of tube bundle. Originality/value – The investigations show that tube parameters can control delay and this can also be utilized to decrease power dissipation in SWCNT bundle interconnects for VLSI applications.
45
Weaver, D. S., S. Ziada, Z. Sun, and P. Feenstra. "The Effect of Platen Fins on the Flow-Induced Vibrations of an In-Line Tube Array." Journal of Pressure Vessel Technology 123, no. 4 (July 10, 2001): 437–41. http://dx.doi.org/10.1115/1.1408303.
Abstract:
This paper presents the results of an experimental study of the effect of streamwise “platen” fins on the fluidelastic instability of an in-line tube array. The fins are fixed parallel to the axis of the tubes in the streamwise direction and effectively prevent any transverse flow between streamwise tube rows. A geometrically identical, dynamically scaled bundle of finless tubes were used as a datum case for comparison. The results showed that, while the fins eliminate vortex shedding, they enhance the fluidelastic coupling between adjacent tubes and substantially reduce the stability threshold.
46
Marshalova, G. S., and S. A. Sverchkov. "Comparative analysis of experimental investigations and numericalsimulation of single-row finned tube bundle at mixed convection." Proceedings of the National Academy of Sciences of Belarus. Physics and Mathematics Series 54, no. 4 (January 11, 2019): 499–506. http://dx.doi.org/10.29235/1561-2430-2018-54-4-499-506.
Abstract:
Mixed convective heat transfer is very important for a wide class of engineering tasks. However, the experimental study of mixed convection requires significant implementation costs, high-power equipment, as well as large time costs, so it is proposed to expand the scope of experimental studies using numerical simulation. Numerical simulation of the single-row bundle consisting of bimetallic finned tubes at mixed air convection conditions was performed and experimental data were compared. The formulation of the third-dimensional problem for numerical simulation was realized. The conjugated problem for heat exchange modeling from the tube fins to air was solved. In numerical simulation of air momentum it was taken into account that the Reynolds number based on tube diameter and velocity in the space between fins was varied from 100 to 720. Menter’s k–ω shear stress transport model in standard formulation was used to close the Reynolds equations. Flow visualization on the tube surface revealed the transient nature of the air flow. The temperature distribution visualization in the bundle and the exhaust mine made it possible to see the nature of cooling the finned bundle at mixed convection. Results of numerical simulation and experimental investigations are in good agreement and can be used for expansion of the scope of experiments. The experimental data and the numerical simulation results for the single-row bundle consisting of bimetallic finned tubes at mixed air convection are compared in this paper. Flow near tube surfaces was visualized, and the temperature and velocity distributions in a bundle and in the exhaust mine were obtained.
47
Konstantinidis, E., D. Castiglia, and S. Balabani. "An experimental study of steady and pulsating cross-flow over a semi-staggered tube bundle." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 219, no. 3 (March 1, 2005): 283–98. http://dx.doi.org/10.1243/095440605x16848.
Abstract:
This paper describes an experimental study of the cross-flow characteristics in a semi-staggered tube bundle for Reynolds numbers in the range 1100-12 900. It is shown that by displacing transversely the tubes in the even rows of an in-line bundle by one diameter the vortex-shedding mechanism is suppressed. Vortex shedding is re-established and reinforced by pulsations superimposed on to the approaching flow and a considerable increase in the power of the associated velocity fluctuations is observed in the bundle. Two cases of pulsating flow are examined with different effects on the flow structure of the bundle. Detailed measurements of the mean and fluctuating velocity fields in the semi-staggered tube bundle together with flow visualization images are also reported in the paper in order to examine in depth the effects of tube displacement and flow pulsations. Comparisons with in-line and staggered configurations having the same spacing-to-diameter ratios are made.
48
Rajput, Kishore Shankarsinh, and Vidya Shivram Patil. "Structure and development of cortical bundles in Couroupita guianensis Aubl. (Lecythidaceae)." Anales de Biología, no. 38 (June 27, 2016): 95–102. http://dx.doi.org/10.6018/analesbio.38.10.
Abstract:
El desarrollo de haces corticales, en ramas y pedúnculos de Couroupita guianensis (Lecythidaceae), comienza cerca del meristemo apical concomitante con los haces vasculares normales. Cada haz cortical llega a estar rodeado por una vaina de fibras que, a menudo, mostraba la presencia de una capa gelatinosa (fibras G). A medida que avanza el crecimiento, cada haz se puede dividir en dos o tres haces. Algunos de los haces son mayores y muestran elementos vasculares bien diferenciados debido a su asociación con frutos en desarrollo, mientras que los más pequeños, con pocos vasos, pueden ser trazas foliares o de yemas de flores que caen antes de la fecundación. El xilema secundario del haz cortical está compuesto de vasos, fibras y células del parénquima axial, mientras que el floema consiste en tubos cribosos, células de acompañamiento y células del parénquima axial.The development of cortical bundles, in the branches and peduncles of Couroupita guianensis (Lecythidaceae), initiates close to the apical meristem concomitant with the normal vascular bundles. Each cortical bundle becomes surrounded by a sheath of fibres, which most often showed presence of gelatinous layer (G-fibres). As growth progresses, theses bundle may divide into two-three bundles. Some of the bundles are larger and show well differentiated vascular elements due to their association with developing fruits while narrower bundles, with few vessels, may be leaf traces or flower bud traces that fell down before fertilization. The secondary xylem of cortical bundle is composed of vessels, fibres and axial parenchyma cells while phloem consists of sieve tubes, companion cells and axial parenchyma cells.
49
Alzamily, Abdulrazaq Nadhim, Abbas J. Sultan, Amer A. Abdulrahman, and Hasan Sh Majdi. "Study of the Impact of Tube Configurations on the Local Heat Transfer Coefficient in Mimicked Fischer-Tropsch Bubble Column Reactor." Processes 10, no. 5 (May 13, 2022): 976. http://dx.doi.org/10.3390/pr10050976.
Abstract:
An experimental investigation was conducted to examine, for the first time, the influences of using different designs of tube arrangements on the local heat transfer coefficient (LHTC) in a bubble column (with a diameter of 0.13 m) equipped densely with a bundle of tubes. The effect of using two different designs of tube arrangements has been examined for a broad range of gas flow rates using a sophisticated heat transfer technique. The obtained results indicate that the LHTC increases significantly with increasing the gas velocity, regardless of the design and installation of the tubes in the column. Additionally, the shape of the LHTC’s profiles alters considerably by the presence of a bundle of tubes and their arrangements. Moreover, the results indicate that the square tube pitch arrangement provides uniform heat transfer profiles, which enhance the performance of the bubble column reactor by 30%. Furthermore, the heat transfer profiles were found to be varied with the axial height of the column. The new experimental results obtained in this investigation will provide experimental reference data for creating and validating a mathematical model for predicting LHTCs. In addition, this will facilitate this kind of reactor’s design, scale-up, and operation.
50
Jensen, M. K., and J. T. Hsu. "A Parametric Study of Boiling Heat Transfer in a Horizontal Tube Bundle." Journal of Heat Transfer 110, no. 4a (November 1, 1988): 976–81. http://dx.doi.org/10.1115/1.3250601.
Abstract:
Boiling heat transfer outside of a section of a uniformly heated horizontal tube bundle in an upward crossflow was investigated using R-113 as the working fluid. The inline tube bundle had five columns and 27 rows with a pitch-to-diameter ratio of 1.3. Heat transfer coefficients obtained from the 14 instrumented tubes are reported for a range of fluid and flow conditions; slightly subcooled liquid inlet conditions were used. At most heat fluxes there was no significant variation in the local heat transfer coefficients throughout the tube bundle. However, at low heat fluxes and mass velocities, the heat transfer coefficient increased at positions higher in the tube bundle. As pressure and mass velocity increased so did the heat transfer coefficients. For the local heat transfer coefficient, a Chen-type correlation is compared to the data; the data tend to be overpredicted by about 20 percent. Reasons for the overprediction are suggested.