Local Convective Behavior and Fin Efficiency in Shallow Banks of In-Line and Staggered, Annularly Finned Tubes

1996 ◽  
Vol 118 (2) ◽  
pp. 317-326 ◽  
Author(s):  
S. P. Kearney ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Flow Area ◽  
Average Heat ◽  
Fin Efficiency ◽  
Finned Tubes ◽  
High Profile ◽  
Naphthalene Sublimation Technique ◽  
Local Mass Transfer ◽  
Naphthalene Sublimation

Local mass transfer data for high-profile fins in the second row of in-line and staggered, circular-finned tubes are presented for Reynolds numbers from 5000 to 28,000 based on hydraulic diameter and velocity at the minimum flow area. The data, obtained using an optical adaptation of the naphthalene sublimation technique, show that local variations in heat transfer do not cause significant fin efficiency deviations from the analytical solution of Gardner (contrary to earlier reports). Average heat transfer and pressure drop data indicate that the thermal performance of the in-line arrangement is comparable to the staggered configuration.

Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 1 — Average Results

2000 ◽  
Author(s):  
S. Acharya ◽  
V. Eliades ◽  
D. E. Nikitopoulos
Keyword(s):  
Heat Transfer ◽  
Rectangular Cross Section ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Square Duct ◽  
Surface Mass ◽  
Turbine Engine ◽  
Naphthalene Sublimation Technique ◽  
Detailed Surface ◽  
Naphthalene Sublimation

The effect of ribs with different cross-stream profiles are investigated through detailed, surface mass (heat) transfer distributions along four active walls of a square duct containing a sharp 180° bend. The duct simulates two passes of an internal coolant channel in a gas turbine engine with ribs mounted on two opposite walls. Mass (heat) transfer measurements, taken using the naphthalene sublimation technique, are presented for Reynolds numbers of 30,000, and rotation number of 0.3. Comparisons are made with conventional ribs having a rectangular cross-section. It is shown that the use of certain profiled ribs provides considerable heat transfer enhancements over conventional ribs with the same blockage ratio in the duct. These enhancements are attributed to the generation of longitudinal vorticity (or secondary flows) by the profiled ribs in the channel.

Heat Transfer From an Asymmetrically Heated Channel Partially Enclosing a Rotating Disk

1995 ◽  
Vol 117 (1) ◽  
pp. 79-84 ◽  
Author(s):  
R. R. Schmidt ◽  
P. Patel
Keyword(s):  
Heat Transfer ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Correlation Equation ◽  
Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Heated Channel ◽  
Naphthalene Sublimation ◽  
Parallel Surfaces ◽  
Insight Into

Experiments have been performed to determine the heat transfer from an asymmetrically heated channel partially enclosing a vertically oriented rotating disk. Parallel rectangular surfaces enclose the rear portion of a disk (slightly less than 1/2 of the disk is enclosed) allowing air to enter and exit the perimeter of the channel, except the rear vertical portion bridging the two parallel surfaces. The experiments encompassed data runs where one of the parallel walls was isothermal and the other was adiabatic. The experiments encompassed a range of spacings between the rotating disk and the adjacent parallel surfaces and a range of rotational speeds varying by a factor of 30. The experiments were performed using the naphthalene sublimation technique. From the experimental results a dimensionless correlation equation suitable for predicting average heat and mass transfer coefficients of the enclosing surfaces for various rotational Reynolds numbers and disk-to-wall spacings was deduced. Finally, to gain some insight into the air flow pattern along the enclosing walls, a visual flow technique was employed, the results of which will be described herein.

Heat Transfer in 1:4 Rectangular Passages With Rotation

2003 ◽  
Vol 125 (4) ◽  
pp. 726-733 ◽  
Author(s):  
Peeyush Agarwal ◽  
Sumanta Acharya ◽  
D. E. Nikitopoulos
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Cross Section ◽  
Rectangular Channel ◽  
Transfer Data ◽  
Naphthalene Sublimation Technique ◽  
Rotation Numbers ◽  
Local Mass Transfer ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The paper presents an experimental study of heat/mass transfer coefficient in 1:4 rectangular channel with smooth or ribbed walls for Reynolds number in the range of 5000–40,000 and rotation numbers in the range of 0–0.12. Such passages are encountered close to the mid-chord sections of the turbine blade. Normal ribs (e/Dh=0.3125 and P/e=8) are placed on the leading and the trailing sides only. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. For purposes of comparison, selected measurements are also performed in a 1:1 cross section. The local mass-transfer data in the fully developed region is averaged to study the effect of the Reynolds and the rotation numbers. The spanwise mass transfer distributions in the smooth and the ribbed cases are also examined.

Heat Transfer and Friction in Channels With Very High Blockage 45° Staggered Turbulators

2003 ◽  
Author(s):  
Jeremy C. Bailey ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Flow Area ◽  
Test Technique ◽  
Heat Transfer Coefficients ◽  
Smooth Channel ◽  
Constant Pitch ◽  
Transfer Behavior ◽  
Very High

Heat transfer and friction coefficients have been measured within a rectangular passage of aspect ratio 0.4 containing 45-degree staggered turbulators of very high blockage. Using a constant pitch-to-height ratio of 10 for all geometries, turbulator height-to-channel hydraulic diameter ratios from 0.193 to 0.333 were investigated. This range of e/D creates actual channel blockage ratios e/H from 0.275 to 0.475, presenting significant flow area restrictions. A liquid crystal test technique is used to obtain both detailed heat transfer behavior on the surfaces between turbulators, as well as averaged fully developed heat transfer coefficients. Reynolds numbers from 20000 to 100000 were tested. Nusselt number enhancements of up to 3.6 were obtained over that of a smooth channel, with friction coefficient enhancements of as much as 65. In contrast to low-blockage turbulated channels, the 45-degree turbulated Nu is found to be lower than that at 90-degree orientation, given very similar e/D and e/H values.

Heat transfer and drag for transverse flow past bundles of finned tubes at low reynolds numbers

1978 ◽  
Vol 14 (10) ◽  
pp. 905-907
Author(s):  
A. S. Lyshevskii ◽  
V. G. Sokolov ◽  
V. M. Sychev ◽  
L. Ya. Shkret
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Transverse Flow ◽  
Low Reynolds Numbers ◽  
Finned Tubes ◽  
Flow Past ◽  
Low Reynolds

Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 2—Detailed Measurements

2000 ◽  
Vol 123 (1) ◽  
pp. 107-114 ◽  
Author(s):  
D. E. Nikitopoulos ◽  
V. Eliades ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Heat Mass Transfer ◽  
Blockage Ratio ◽  
Average Heat ◽  
Rotation Numbers ◽  
Naphthalene Sublimation ◽  
Side Walls ◽  
Made In

Detailed heat/mass transfer distributions are presented inside a two-pass rotating ribbed coolant channel for two profiled-rib configurations. Several profiled-rib configurations have been studied (Acharya et al., 2000), and it was found that the best performance was achieved by saw-tooth ribs, and a pyramid–valley rib combination. The profiled ribs were placed directly opposite to each other on the leading and trailing surfaces. Smooth side walls were used in all the experiments. Heat transfer measurements were compared with straight ribs of equal blockage ratio. The measurements were made in a two-pass rotating facility using the naphthalene sublimation mass transfer technique, which provides highly resolved surface distributions. The results presented are for a Reynolds number of 30,000, two rotation numbers (0 and 0.3), and include average heat/mass transfer over the entire inter-rib module as well as detailed heat/mass transfer contours for two profiled-rib cases. Significant enhancement of up to 25 percent in heat/mass transfer was obtained with the pyramid–valley and saw-tooth shaped ribs under rotating conditions.

Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 2 — Detailed Measurements

2000 ◽  
Author(s):  
D. E. Nikitopoulos ◽  
V. Eliades ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Heat Mass Transfer ◽  
Blockage Ratio ◽  
Average Heat ◽  
Rotation Numbers ◽  
Naphthalene Sublimation ◽  
Side Walls ◽  
Made In

Detailed heat/mass transfer distributions are presented inside a two-pass rotating ribbed coolant channel for two profiled-rib configurations. Several profiled-rib configurations have been studied (Acharya et al.; 2000), and it was found that the best performance was achieved by saw-tooth ribs, and a pyramid–valley rib combination. The profiled ribs were placed directly opposite to each other on the leading and trailing surfaces. Smooth side walls were used in all the experiments. Heat transfer measurements were compared with straight ribs of equal blockage ratio. The measurements were made in a two-pass rotating facility using the naphthalene sublimation mass transfer technique which provides highly resolved surface distributions. The results presented are for a Reynolds number of 30,000 two Rotation numbers (0 and 0.3) and include average heat/mass transfer over the entire inter-rib-module as well as detailed heat/mass transfer contours for two profiled-rib cases. Significant enhancements of up to 25% in heat/mass transfer was obtained with the pyramid-valley, and saw-tooth shaped ribs under rotating conditions.

Heat Transfer From Rectangular Plates Inclined at Different Angles of Attack and Yaw to an Air Stream

1985 ◽  
Vol 107 (2) ◽  
pp. 307-312 ◽  
Author(s):  
D. G. Motwani ◽  
U. N. Gaitonde ◽  
S. P. Sukhatme
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Rectangular Plates ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Aspect Ratios ◽  
Air Stream ◽  
Angle Of Yaw

Average heat transfer coefficients during forced convection air flow over inclined and yawed rectangular plates have been experimentally determined. Tripping wires at the edges ensured that a turbulent boundary layer prevailed over the plates. The experiments were carried out for a constant surface temperature and covered two plates of different aspect ratios, angles of attack from 0 to 45 deg, angles of yaw from 0 to 30 deg, and Reynolds numbers from 2 times; 104 to 3.5 times; 105. The results show that the average heat transfer coefficient is essentially insensitive to the aspect ratio and angle of yaw. However, it is a function of Reynolds number and the angle of attack. Correlation equations for various angles of attack are suggested.

Study on Free Convection Heat Transfer in a Finned Tube Array

2015 ◽  
Vol 23 (01) ◽  
pp. 1550007 ◽  
Author(s):  
Ryoji Katsuki ◽  
Tsutomu Shioyama ◽  
Chikako Iwaki ◽  
Tadamichi Yanazawa
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Finned Tube ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
Finned Tubes ◽  
Air Cooled Heat Exchanger ◽  
The Heat Transfer Coefficient

We have been developing a free convection air cooled heat exchanger without power supply to improve economic efficiency and mechanical reliability. However, this heat exchanger requires a larger installation area than the forced draft type air cooled heat exchanger since a large heating surface is needed to compensate for the small heat transfer by natural convection. Therefore, we have been investigating a heat exchanger consisting of an array of finned tubes and chimney to increase the heat transfer coefficient. Since the heat transfer characteristics of finned tube arrays have not been clarified, we conducted experiments with a finned tube array to determine the relation between the configuration of finned tubes and the heat transfer coefficient of a tube array. The results showed that the average heat transfer coefficient increased with pitch in the vertical direction, and became constant when the pitch was over five times the fin diameter. The average heat transfer coefficient was about 1.4 times higher than that of a single finned tube in free space. The ratio of the average heat transfer coefficient of the finned tube array with chimney to that of a single finned tube was found to be independent of the difference in temperature between the tube surface and air.

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