In-line Tube Bank Research Articles

216 気柱共鳴現象発生前後における格子配列管群からの渦放出に関する研究(流体工学(騒音・音響・渦2))

216 気柱共鳴現象発生前後における格子配列管群からの渦放出に関する研究(流体工学(騒音・音響・渦2))

Experimental study on titanium heat exchanger used in a gas fired water heater for latent heat recovery

Abstract In general, latent heat recovery is usually accompanied by the corrosion of the heat exchanger, which is caused by the strongly acidic condensate when the temperature of the flue gas is lowered below the acid dew point. The present study has been conducted to investigate the heat and mass transfer characteristics in a titanium heat exchanger with excellent corrosion resistance used for waste heat recovery with the condensation arranged in a gas fired water heater. In addition, the thermal efficiency of the gas fired water heater was evaluated based on the net calorific value at the maximum rated output during latent heat recovery from the exhaust flue gas. Parametric studies were conducted for the flue gas flow rate, inlet temperature and mass flow rate of the supplied water, respectively. Different arrangements of the tubes of the heat exchanger including in-line and staggered configurations were investigated. The experimental results indicate that the thermal efficiency of the gas fired water heater with a latent heat recovery (LHR) heat exchanger was enhanced by about 10% compared with conventional instantaneous water heaters, i.e., water heaters without heat recovery. In addition, in terms of the Nusselt number and the Sherwood number, the heat and mass transfer performance of the staggered tube bank type were approximately 50% and 10% higher than that on the in-line tube bank type when the Reynolds number of the flue gas was 103.

Effect of cavities inside tube banks on acoustic resonance

In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We measured the sound pressure level, the amplitude and the phase delay of acoustic pressures and the gap velocity. As a result, we found many peak frequencies of sound pressure level with different Strouhal numbers, mainly about S t =0.15, 0.26 and 0.52. The variation of SPL for S t =0.26, 0.52 components in the tube banks with cavities was the same as the result of no cavities. The existence of cavities inside in-line tube banks caused the resonance of S t =0.15. And the acoustic resonance of the first mode in the transverse direction was generated if the small cavities existed inside the tube banks. This resonance was not generated from the tube banks of no cavities. The resonance onset velocity in the transverse mode was fairly slower than that of no cavities. It was easy to generate acoustic resonance when there were small cavities inside in-line tube banks.

1019 流れ方向に密な格子配列管群からの渦放出と音響共鳴現象に関する研究(OS10-4 流体関連振動・騒音,オーガナイズドセッション)

In the present paper the attention is focused on relationship between acoustic resonance and vortex shedding from closely arranged In-line tube banks which occurred in the two-dimensional model of boiler. We have examined the characteristics of vortex shedding, acoustic damping and acoustic resonance generated from in-line tube banks with tube pitch ratio of 1.33, 1.44, 1.56, 1.67, 1.76 and 2.0 in the flow direction. As the tube pitch ratio in the flow direction decreased, the acoustic damping increased and the vortex shedding frequency became broad-band. The resonance mode of low acoustic damping was generated in the broad-band vortex shedding frequency. It was easy to generate acoustic resonance of low order transverse mode as the tube pitch ratio in the flow direction increased.

704 気柱共鳴現象発生時の密な格子配列管群からの渦放出に関する研究(GS 流体工学VII)

704 気柱共鳴現象発生時の密な格子配列管群からの渦放出に関する研究(GS 流体工学VII)

267 気柱共鳴現象と渦放出に及ぼす格子配列管群の管ピッチ比の影響(空力音響現象のメカニズムと計測制御,OS-22 流体関連振動・音響メカニズムと計測制御,総合テーマ「伝統を,未来へ!」)

267 気柱共鳴現象と渦放出に及ぼす格子配列管群の管ピッチ比の影響(空力音響現象のメカニズムと計測制御,OS-22 流体関連振動・音響メカニズムと計測制御,総合テーマ「伝統を,未来へ!」)

109 渦放出に及ぼす格子配列円管群内のキャビティの影響(空力騒音(1))

In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on vortex shedding. We measured the SPL of acoustic resonance, the spectrum of velocity fluctuation, the amplitude and phase delay of acoustic pressures and the gap velocity. As a result, we found broad-band frequencies of velocity fluctuation with Strouhal number about S_t=0.09-0.22 in the cavities without acoustic resonance. The center frequency of velocity fluctuation was about S_t=0.15. The vortex shedding frequency in the cavities was the same as the result of no cavities. And the periodicity and intensity of velocity fluctuation due to vortex shedding increased rather than that of tube banks. Therefore, it was easy to generate acoustic resonance of S_t=0.15 when there were small cavities inside in-line tube banks.

気柱共鳴現象に及ぼす格子配列円管群内のキャビティの影響(流体工学,流体機械)

In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We measured sound pressure level (SPL), amplitude and phase delay of acoustic pressures and gap velocity. As a result, we found many peak frequencies of sound pressure level with different Strouhal numbers, mainly about S_t=0.15, 0.26 and 0.52. The variation of SPL for S_t=0.26, 0.52 components in tube banks with cavities were the same as the result of no cavities. The existence of cavities inside in-line tube banks caused the resonance of S_t=0.15. And the acoustic resonance of first mode in the transverse direction was generated if the small cavities existed inside tube banks. This resonance was not generated from tube banks of no cavities. The resonance onset velocity in the transverse mode was fairly slower than that of no cavities. It was easy to generate acoustic resonance when there were small cavities inside in-line tube banks. And we have examined the effect of baffle plates for controlling acoustic resonance generated from tube banks with cavities.

562 気柱共鳴現象に及ぼす格子配列管群の抗力方向管ピッチ比の影響

In the present paper the attention is focused on effect of arrangement of in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We have examined the characteristics of acoustic resonance generated from in-line tube banks with tube pitch ratio of 1.33, 1.44, 1.56 and 2.0 in the flow direction. As the tube pitch ratio in the flow direction increased, the acoustic resonance of low order mode in the transverse direction was generated, and the resonance onset velocity in the transverse mode was fairly slower than that of small tube pitch ratio. It was easy to generate acoustic resonance of transverse mode as the tube pitch ratio in the flow direction increased.

Effect of tube spacing on the vortex shedding characteristics of laminar flow past an inline tube array: A numerical study

The effect of tube spacing on the vortex shedding characteristics and fluctuating forces in an inline cylinder array is studied numerically. The examined Reynolds number is 100 and the flow is laminar. The numerical methodology and the code employed to solve the Navier–Stokes and continuity equations in an unstructured finite volume grid are validated for the case of flow past two tandem cylinders at four spacings. Computations are then performed for a six-row inline tube bank for eight pitch-to-diameter ratios, s, ranging from 2.1 to 4. At the smallest spacing examined ( s = 2.1) there are five stagnant and symmetric recirculation zones and weak vortex shedding activity occurs only behind the last cylinder. As s increases, the symmetry of the recirculation zones breaks leading to vortex shedding and this process progressively moves upstream, so that for s = 4 there is clear shedding from every row. For any given spacing, the shedding frequency behind each cylinder is the same. A critical spacing range between 3.0 and 3.6 is identified at which the mean drag as well as the rms lift and drag coefficients for the last three cylinders attain maximum values. Further increase to s = 4 leads to significant decrease in the force statistics and increase in the Strouhal number. It was found that at the critical spacing there is 180° phase difference in the shedding cycle between successive cylinders and the vortices travel a distance twice the tube spacing within one period of shedding.

Acoustic Vibration Behavior of Full Size Steam Generator and Tubular Heat Exchanger In-Line Tube Banks: A Brief Note

Based on recent laboratory experimental data by Feenstra et al. (2004, “The Effects of Duct Width and Baffles on Acoustic Resonance in a Staggered Tube Array,” in Proceedings of the Eighth International Conference on Flow-Induced Vibration FIV 2004, E. de Langre and F. Axisa, eds., Paris France, Jul. 6–9, pp. 459–464; 2006, “A Study of Acoustic Resonance in a Staggered Tube Array,” ASME J. Pressure Vessel Technol., 128, pp. 533–540), it has been determined that for larger test section widths, the maximum acoustic pressures generated during acoustic resonance were greater by more than a factor of 4 than those predicted by Blevins and Bressler (1993, “Experiments on Acoustic Resonance in Heat Exchanger Tube Bundles,” J. Sound Vib., 164, 503–533). We have evaluated a great number of resonant and nonresonant cases from in-service experience of full size steam generator and tubular heat exchanger tube banks in order to see the general vibratory behavior of the full size units. Fifteen vibrating and twenty-seven nonvibrating cases were evaluated and compared to the Feenstra et al. relationship. It is shown that on average the results from the full size units correlate well with the relationship of Feenstra et al. A gap exists between the vibratory and the nonvibratory cases. The nonvibratory cases produce acoustic pressures, which are at or below the Blevins and Bressler relationship. From the results, it can be concluded that the full size units, regardless of their size and also acoustic mode, produce high acoustic pressures at resonance, with the maximum acoustic pressure on average more than 50–75 times higher than the input energy parameter defined by the product of Mach number and pressure drop through the tube bank. The results are tabulated and plotted for comparison.

242 気柱共鳴現象発生時の管群からの双子渦放出に関する研究

242 気柱共鳴現象発生時の管群からの双子渦放出に関する研究

Acoustic Resonance and Vortex Shedding from Tube Banks of Boiler Plant

This paper focuses on the relationship between acoustic resonance and vortex shedding from the tube banks of a boiler plant. We have built a model similar to the actual boiler plant to clarify the characteristics of acoustic resonance phenomena and vortex shedding. The model used in-line tube banks with a small tube pitch ratio. We examined the relationship between the acoustic resonance of the actual plant and that of the model, and measured the sound pressure level, acoustic pressure mode shape, spectrum of velocity fluctuation, and gap velocity. Gap velocity was defined as the mean velocity in the smallest gaps between two neighboring tubes in the transverse direction. As a result, the resonant frequencies and mode shapes of the acoustic resonances in the actual boiler plant agreed well with those in the similar model. We found many peak frequencies in the sound pressure level spectrum when acoustic resonances occurred. The typical Strouhal numbers at the onset velocity of acoustic resonances were about 0.19, 0.26 and 0.52. Periodic velocity fluctuation caused by vortex shedding was observed inside the tube banks without acoustic resonance. The Strouhal number measured for vortex shedding was 0.15. Acoustic resonances of higher-order modes were generated in this plant.

Numerical simulation of gas-particle flows over an in-line tube bank

We present a numerical investigation of particle-wall collision phenomenon and its contribution to particle phase flows in an in-line tube bank. Particles with diameters of 30$\mu$m and 93$\mu$m were simulated using a Lagrangian particle tracking model, which included a particle-wall collision model and a stochastic wall roughness model. The predicted mean velocity and fluctuation profiles for both gas and 93$\mu$m particles were validated against experimental data. The numerical predictions reveal that the wall roughness has a considerable effect by altering the rebounding behaviours of large particles, and consequently affecting particle trajectories downstream.

Numerical modelling and validation of gas-particle flow in an in-line tube bank

This paper presents a numerical study of dilute gas-particle flows in an in-line tube bank. The physical characteristics of the particle–wall collisions and their contributions to particle phase flow field were investigated employing a Lagrangian particle-tracking model, which includes an algebraic particle–wall collision model and a stochastic wall roughness model. Particles with corresponding diameters of 1 μm, 15 μm and 93 μm were simulated under the gas flow condition of 11.2 m/s. The predicted mean velocities and fluctuations for both gas and 93 μm particles were validated against experimental data. The numerical predictions revealed that the wall roughness has a considerable effect by altering the rebounding behaviours of the large particles, and consequently affecting the particles motion downstream and shifting particle collision frequency distribution on the tubes. Also, the results demonstrated that the velocity fluctuations for large particles are predominantly determined by the particle–wall collisions.

Flow induced acoustic resonance in in-line tube banks

In the present paper the attention is focused on the relation between vortex shedding phenomena and acoustic resonance which occurred in the two-dimensional model of boiler. There were tube banks with in-line arrangement for small tube pitch ratio. We measured the sound pressure level, the phase delay of acoustic pressures, the spectrum of velocity fluctuation and the gap velocity. As a result, we found two peak frequencies of sound pressure level with different Strouhal numbers St, mainly about 0.26 and 0.52. The noise of St=0.26 was the resonance of transverse mode and St=0.52 was longitudinal mode. The vortex shedding of St=0.15 was generated inside the tube banks without acoustic resonance. As gap velocity increased, we observed that the peak level of spectrum was weak and broad-banded. The onset velocity of the acoustic resonance of longitudinal mode was lower than that of transverse mode.

305 流れ方向に密な格子配列管群における気柱共鳴現象と渦放出

In the present paper the attention is focused on similarity between the phenomena of acoustic resonance which occurred in actual boiler plant and that of the two-dimensional model of boiler. We measured a gap velocity, sound pressure level, acoustic mode shape, spectrum and phase delay of velocity fluctuations in the tube banks. As a result it was made clear that the phenomenon of acoustic resonance in the model is similar with that of the actual plant. The relation between vortex shedding phenomena inside of in-line tube banks and acoustic resonance in the model was experimentally examined.

113 気柱共鳴騒音に及ぼす格子配列管群内のキャビティサイズの影響(音・振動の実験解析,騒音・振動評価・改善技術)

113 気柱共鳴騒音に及ぼす格子配列管群内のキャビティサイズの影響(音・振動の実験解析,騒音・振動評価・改善技術)

Analysis of Laminar Forced Convection of Air Crossflow in In-Line Tube Banks with NonSquare Arrangements

ABSTRACT Numerical analysis is made of forced-convection heat transfer in laminar two-dimensional steady crossflow in banks of plain tubes in square and nonsquare in-line arrangements. A finite-volume method with a nonorthogonal, boundary-fitted grid and co-located variable storage is used to solve the Navier–Stokes equations and energy conservation equation for a tube bundle with five longitudinal rows, including inlet and outlet sections. Local and overall heat transfer and fluid flow results are presented at combinations of transverse and longitudinal pitch-to-diameter ratios of 1.25, 1.5, and 2.0 at Reynolds numbers of 100 and 300 for a Prandtl number of 0.71. A comparison of the present study results with well-established experiments and empirical correlations showed good overall agreement. New equations are proposed for a correction factor for the effects of nonsquare arrangements on average friction factor.

117 抗力方向の気柱共鳴現象発生時の格子配列管群からの渦放出

117 抗力方向の気柱共鳴現象発生時の格子配列管群からの渦放出