Tube Bank Fin Research Articles

Experimental and 3-D Numerical Analysis of the Thermal-Hydraulic Characteristics of Elliptic Finned-Tube Heat Exchangers

Fluid flow and heat transfer over a 4-row. elliptic, finned-tube heat exchanger having an axis ratio of 2.83:1 are studied experimentally and numerically. Three types of finned-tube configurations have been investigated under dry and wet conditions for different values of inlet frontal velocity ranging from 2 to 7 m/s: two elliptic finned tubes with staggered and in-line arrangements and one circular finned tube with staggered arrangement. The experimental results indicate that the average heat transfer coefficient of an elliptic finned lube is 35–50% of the corresponding circular finned tube having the same tube perimeter, while the pressure drop for an elliptic finned-tube bank is only 25–30% of the circular finned-tube bank configuration. Three-dimensional numerical results of a laminar model for dry coils are also presented and are compared with the experimental data.

無音気流風洞を用いた空力騒音の実験

Clarifying the generation mechanism of aerodynamic noise is essential in attempting to reduce noise deriving from turbomachinery and high velocity vehicles. For studying aerodynamic noise, an air flow with quiet noise is very useful. Under these bases, a “Quiet Flow Wind Tunnel”, with the measuring section eauipped in an anechoic chamber, was developed and installed in 1982. The maximum velocity of air flow from the nozzle, with a section of 400mm × 400mm, is 50m/s and the turbulent level is below 0.5%. The noise levels around the measuring section are below 48dB (A) at a velocity of 35m/s. Studyies utilizing this facility include among others : vortex sound from crossing two cylinders, flow-noise from finned-tube bank, noise from vanes for a flow leaning. These studies concluded that simultaneous measurment on both the fluid-dynamic and acoustic phenomena is enabled by this facility. Conventional type wind tunnels are incapable for such measurment. The Quiet Flow Wind Tunnel is proven capable of making quantitative estimations on the generation of flow-sounds. The results of studies obtained through it are being effectively used in developing low-noise machines and systems.

Heat Transfer and Pressure Drop of Finned Tube Banks with a Staggered Arrangement in Forced Convection. (2nd Report. Pressure Drop Characteristics and Correlation of Spirally Finned Tube Banks).

Pressure drop characteristics of a spirally finned tube bank with a staggered tube arrangement for waste heat recovary form the hot gas have been experimentally investigated. The finned tube banks used in this study have a tube arrangement, tube dimension, and fin material different to that of air-cooled heat exchangers. It is shown that the pressure dorp characteristics of these finned tube banks differs greatly from these of the finned tube with the equilateral triangular tube geometry for the air-cooled heat exchangers. A new correlation for the prediction of the pressure drop in the finned tube banks for waste heat recovery is induced concerning the effect of the tube geometry, which differs from that of an air-cooled heat exchanger.

Heat Transfer and Pressure Drop of Finned Tube Banks with a Staggered Arrangement in Forced Convection. (1st Report. Heat Transfer Characteristics and Correlation of Spirally Finned Tube Banks).

Heat transfer characteristics of a spirally finned tube bank with a staggered tube arrangement for waste heat recovery from the hot gas have been experimentally investigated. The finned tube banks used in this study have a tube arrangement, tube dimension, and fin material different to that of air-cooled heat exchangers. It is shown that the heat transfer characteristics of these finned tube banks differs greatly from those of the finned tube with the equilateral triangular tube geometry for the air-cooled heat exchangers. The new heat transfer correlation for the prediction of the heat transfer coefficient of the finned tube banks for waste heat recovery is induced concerning the effect of the nonequilateral tube geometry, which differs from that of anair-cooled heat exchanger.

Heat Transfer and Friction Factor Correlations for Crossflow over Staggered Finned Tube Banks

Abstract The analysis of visual patterns of flow distribution in finned tube banks with individual fins permits the Reparation of major factors affecting heat transfer and pressure drop. A flow model and governing dimensionless variables are established on the basis of this analysis and similarity with heat transfer phenomena in channels. Heat transfer and friction factor correlations are recommended for crossflow over staggered tube banks with plain and segmented fins in the range of Reynolds numbers Reh = 300−10,000. Correlation coefficients are evaluated using original and published experimental data. The correlations correspond with most of the available test data within 10%.

Row Number Effects on the Heat Transfer Performance of In-Line Finned Tube Banks

Abstract In-line finned tube banks are preferred for waste heat recovery applications because they can be cleaned with commercially available on-line soot-blowing methods. However, there is some uncertainty about the heat transfer effectiveness of in-line finned tube banks. It is first demonstrated that the outside heat transfer coefficients of in-line finned tube banks are about 0.7 to 0.8 of those of similar staggered banks if the banks are deep and the Reynolds number is large. It is then shown that the thermal performance of a particular in-line finned tube bank decreases with row number and reaches about 0.25 to 0.35 of the staggered value with seven tube rows. Herein lies the uncertainty. New data are also presented, which show that stagnation regions develop in the wakes behind the tubes in the front rows but do not develop deeper in the bundle. The number of tube rows with the stagnation region decreases with increasing Reynolds number. It is apparent, then, that the heat transfer performance of a...

The development of the quiet flow wind tunnel for aeroacoustics.

For decreasing the noise of turbo-machineries, making clear the generation mechanism of fluid-dynamic noise is important and an air flow having quiet noise is very useful for the study of aerodynamic noise. A "Quiet Flow Wind Tunnel", whose measuring section is in the annechoic chamber, has been developed and established. The maximum velocity of air flow from the nozzle with a section size of 400 mm×400 mm is 42 m/s and its turbulence is less than 0.5 %. The noise levels around the measuring section are less than 48 dB(A) at a velocity of 35 m/s. By using this facility, further studies have been made, "vortex sound from crossing two cylinders", "flow-noise from finned-tube bank", "noise from ventilating-gallery", "noise of inner flow in straight ducts" etc.. It has been recognised, through these experiments, that this facility can measure both phenomena of fluid-dynamics and acoustics at the same time although these are still impossible by usual wind tunnels.

Flow characteristics of condensate on a vertical column of horizontal low finned tubes.

Experiments were performed to study the flow characteristics of condensate on a simulated bank of horizontal low finned tubes. Two or three tubes arranged in a vertical column were set in a stationary vapor. The top tube had a longitudinal slit at the upper end through which the test liquid was fed uniformly on the tube surface. Cooling water was passed through the lower tubes. The test fluids used were R-113, methanol and normal propanol. Four major flow modes: droplet, column, column-sheet and sheet, were observed as the liquid flow rate was increased. Experimental data on the number of instantaneous falling sites, the proportion of surface area covered with the falling liquid and the flooding angle below which the inter-fin sp. ace was flooded with condensate were obtained for a range of liquid flow rates. Theoretical considerations were given to the effect of liquid flow rate on the flow mode transition and on the measured quantities.

Noise prevention in tube-type heat exchangers employed in gas turbines.

Unusual noise is sometimes caused by tube-type heat exchangers employed to recover waste heat from a gas turbine. There are a few studies on Karman vortex-induced nosie from bare tubes or bare-tube banks placed in the air flow, but there is no study concerning Karman vortex-induced noise from finned tube banks. For the purpose of this investigation leading to reduce Karman vortex-induced nosie from heat exchangers, various finned tube models were made, and Karman vortex-induced noise was compared between this model and finned tubes used in a heat exchanger. As it was confirmed that there was an acceptable parallelism between the model and the finned tubes, the effect of interference plates on Karman vortex-induced noise was determined by varing the position and eccetricity of interference plates placed at the trailing end of the finned tube banks. As a result, unusual noise due to Karman vortex-induced nosie was successfully prevented.

Row Depth Effects on Vortex Shedding and Turbulent Buffeting Formation

P vortex shedding or buffeting excitations caused by flow passing through finned tube banks have caused acoustic resonance problems in some boilers. The resonance is caused by the coincidence of the natural acoustic frequency with the oscillations in the flow through the tube bundle. When published data failed to adequately correlate the tones, an extensive laboratory test program was undertaken to extend the range of available data.

Design and Optimization of Air-Cooled Heat Exchangers

A computer code has been developed for analysis of air-cooled heat exchangers and was coupled with a numerical optimization program to produce an automated air-cooled, heat-exchanger design and optimization procedure. A general iteration free approximation method was used for the analysis which calculates the mean overall heat-transfer coefficient and the overall pressure drop for many flow arrangements. The analysis takes into account the variation of the heat-transfer coefficients and the pressure drop with temperature and/or length of flow path. The code is not limited to surfaces found in the literature, but will accommodate any triangular pitch bank of finned tubes in multiple-pass configurations. The numerical optimization code is a general purpose program based on the Method of Feasible Directions and the Augmented Lagrange Multiplier Method. The capability is demonstrated by the design of an air-to-water finned-tube heat exchanger and is shown to be a useful tool for heat exchanger design.

Investigation of the aerodynamic resistance of a staggered bank of finned tubes

Investigation of the aerodynamic resistance of a staggered bank of finned tubes

Tube Spacing in Finned-Tube Banks

Abstract One of the methods used to fulfill application requirements in the design of finned-tube gas coolers for industrial use more adequately is to vary the spacing of the tubes. In the past there has been very little information available on the effect of tube spacing on cooler performance. This paper covers the results of a series of tests made to determine the effect of tube spacing on the pressure drop and the heat-transfer coefficient of air flowing across a bank of helically finned tubes. The tests covered a wide range of tube spacings, both at right angles to air flow and between rows in the direction of air flow. All tests were made on staggered tube rows. The tests showed that tube spacing has a marked effect on air pressure drop, but a negligible effect on the air-side heat-transfer coefficient. The number of fins per linear inch of tube had a similar effect. Baffles in the spaces at the ends of short tube rows were found to be beneficial in minimizing edge effects, the improvement in heat transfer gained by their use more than compensating for the increase in air pressure drop.