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.

Mass and Heat Transfer From an Enclosed Rotating Disk With and Without Source Flow

1963 ◽  
Vol 85 (2) ◽  
pp. 153-162 ◽  
Author(s):  
Frank Kreith ◽  
E. Doughman ◽  
H. Kozlowski
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Correlation Equation ◽  
Rotating Disks ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Smoke Visualization ◽  
Source Flow

The heat-transfer characteristics of a partially enclosed rotating disk have been investigated experimentally by means of a mass-transfer analog. Mass-transfer rates to air from naphthalene coated disks of 4 and 8 in. diameter were measured at speeds between zero and 10,000 rpm and the influence of the spacing between the rotating disk and its housing was investigated with and without source flow. From the experimental results a dimensionless correlation equation suitable for predicting average heat and mass-transfer coefficients for rotating disks with source flow in turbulent flow at rotational Reynolds numbers up to 4 × 105 was deduced. The flow pattern was investigated by means of a hot wire, a smoke visualization technique, and the china clay method.

Experiments on In-line Pin Fin Arrays and Performance Comparisons with Staggered Arrays

1980 ◽  
Vol 102 (1) ◽  
pp. 44-50 ◽  
Author(s):  
E. M. Sparrow ◽  
J. W. Ramsey ◽  
C. A. C. Altemani
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Pressure Drop ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Naphthalene Sublimation Technique ◽  
Line Array ◽  
Naphthalene Sublimation ◽  
And Performance ◽  
Pin Fin Arrays

Heat transfer and pressure drop experiments were performed for in-line pin fin arrays to obtain basic data to complement available information for staggered arrays. The experimental data were utilized as input to analyses aimed at establishing performance relationships between in-line and staggered arrays. In the experiments, mass transfer measurements via the naphthalene sublimation technique were employed to determine the row-by-row distribution of the heat (mass) transfer coefficient. Fully developed conditions prevailed for the fourth row and beyond. In general, the fully developed heat transfer coefficients for the in-line array are lower than those for the staggered array, but the pressure drop is also lower. The deviations between the two arrays increase with increasing fin height. With regard to performance, the in-line array transfers more heat than the staggered array under conditions of equal pumping power and equal heat transfer area. On the other hand, at a fixed heat load and fixed mass flow rate, the staggered array requires less heat transfer surface than the in-line array.

Heat Transfer Characteristics of an Obliquely Impinging Circular Jet

1980 ◽  
Vol 102 (2) ◽  
pp. 202-209 ◽  
Author(s):  
E. M. Sparrow ◽  
B. J. Lovell
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Local Heat ◽  
Maximum Point ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Local Coefficients ◽  
Naphthalene Sublimation

Measurements of local heat (mass) transfer coefficients were made on a surface on which a circular jet impinges at an oblique angle. The angle of inclination of the jet relative to the surface was varied from 90 deg (normal impingement) to 30 deg. The Reynolds number and the distance between the jet orifice and the impingement plate were also varied parametrically. To facilitate the experiments, the naphthalene sublimation technique was employed, and the resulting mass transfer coefficients were converted to heat transfer coefficients by the well-established analogy between the two processes. It was found that the point of maximum mass transfer is displaced from the geometrical impingement point, with the extent of the displacement increasing with greater jet inclination. The local coefficients on the uphill side of the maximum point drop off more rapidly than do those on the downhill side, thus creating an imbalance in the cooling/heating capabilities on the two sides. Neither the maximum transfer coefficient nor the surface-averaged transfer coefficient are highly sensitive to the inclination of the jet; during the course of the experiments, the largest inclination-induced decreases in these quantities were in the 15 to 20 percent range.

Convective Heat Transfer From a Free Rotating Disk Subjected to a Forced Crossflow

2014 ◽  
Author(s):  
Christian Helcig ◽  
Stefan aus der Wiesche
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Forced Flow ◽  
High Angular Resolution ◽  
Angle Of Incidence ◽  
Transfer Coefficients

The understanding of the heat transfer and flow field behavior of rotating systems is essential from a fundamental point of view and for turbo machinery design. The majority of the publications considers enclosed rotating disk systems and only little is known about the convective heat transfer of free rotating disk systems in a forced flow. In this paper, a free rotating disk system, with particular look on the angle of incidence was investigated. The convective heat transfer from a rotating disk depends at least on three characteristic variables, namely the crossflow, rotational Reynolds numbers and the angle of incidence which are determining the mean Nusselt number. A clear study of the symmetry behavior of the flow field was conducted based on the measurement of the convective heat transfer coefficients. The angle of incidence was scanned with high angular resolution over the entire range between the both extreme cases of a perpendicular disk and a disk in a parallel forced flow. A large number of crossflow and rotational Reynolds numbers were covered by the experiments, too. Based on the experimental and theoretical results, a discussion of the different phenomena and heat transfer regimes is given in this paper.

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 on Rotating Channel With Various Heights of Pin-Fin

2008 ◽  
Author(s):  
Jun Su Park ◽  
Kyung Min Kim ◽  
Dong Hyun Lee ◽  
Hyung Hee Cho ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Pin Fins ◽  
Naphthalene Sublimation ◽  
Pin Fin Array

Pin-fins have been used to enhance the heat transfer near the trailing edge of a turbine airfoil. Previous pin-fin heat transfer studies focused mainly on the array geometry of pin height-to-diameter equal to unity in a stationary frame. This study experimentally examines the effects of pin height-to-diameter ratio (Hp/Dp) from 2 to 4 and rotation number (Ro) from 0 to 0.2. The tested model used a staggered pin-fin array with an inter-pin spacing of 2.5 times the pin-diameter (S/D = 2.5) in both longitudinal and transverse directions. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation technique with a heat-mass transfer analogy. The data measured suggest that an increase in Hp/Dp increases the level of array heat/mass transfer. Array averaged Sherwood numbers for Hp/Dp = 3 and Hp/Dp = 4 are approximately 10% and 35% higher than that of Hp/Dp = 2. The effect of rotation induces notable difference in heat/mass transfer between the leading surface and the trailing surface. The heat transfer coefficients change a little although the rotating number increases in the tested range because the pin-fins break the rotation-induced vortices.

Heat Transfer Coefficients on the Downstream Face of an Abrupt Enlargement or Inlet Constriction in a Pipe

1980 ◽  
Vol 102 (3) ◽  
pp. 408-414 ◽  
Author(s):  
E. M. Sparrow ◽  
J. E. O’Brien
Keyword(s):  
Heat Transfer ◽  
Transfer Coefficient ◽  
Working Fluid ◽  
Downstream Face ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Diameter Pipe ◽  
Naphthalene Sublimation ◽  
Flow Configurations

Measurements were made of the local and average heat transfer coefficients on the downstream face of an enlargement step in a pipe. Two flow configurations were investigated: (a) an abrupt enlargement from a smaller diameter pipe to a larger diameter pipe and (b) partial constriction of a pipe inlet by a large baffle plate. Air was the working fluid. The transfer coefficients were determined by means of the naphthalene sublimation technique; axial pressure distributions were also measured. The highest values of the local transfer coefficient were found to occur on the portion of the enlargement face adjacent to the aperture through which the flow enters the enlarged space. On the other hand, the lowest coefficients occur in the corner where the enlargement face meets the wall of the enlarged pipe. The radial distributions of the transfer coefficient on the enlargement face vary with the Reynolds number. With regard to average transfer coefficients, higher values (by at least 50 percent) are attained for the constricted inlet than for the abrupt enlargement. The average coefficients for the enlargement face are much higher (by a factor of two or three) than those on the wall of the enlarged pipe for fully developed flow conditions.

Turbulent Flow and Heat Transfer in Bends of Circular Cross Section: I—Heat Transfer Experiments

1986 ◽  
Vol 108 (1) ◽  
pp. 40-47 ◽  
Author(s):  
E. M. Sparrow ◽  
G. M. Chrysler
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Section ◽  
Circular Cross Section ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Local Maxima ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation

Experiments were performed to determine the local heat transfer characteristics of bends of circular cross section to which fluid was delivered either via a sharp-edged inlet or via a hydrodynamic development tube. The naphthalene sublimation technique, a mass transfer method, was used to facilitate the experiments. Bends subtending turning angles of 30, 60, and 90 deg were investigated, and the Reynolds number was varied between 5000 and 100,000. It was found that the local heat transfer coefficients at the outside of the bend were, for the most part, larger than those at the inside of the bend, but the deviations decreased as the Reynolds number increased. The streamwise distributions of the local transfer coefficient were markedly affected by the inlet condition; those for the sharp-edged inlet exhibited a universal shape, while the shapes of those for the tube-fed inlet depended both on the Reynolds number and on whether the distribution corresponded to the inside or the outside of the bend. In addition, the distributions for the case of the sharp-edged inlet exhibited higher local maxima and approached the fully developed regime more rapidly than did those for the tube-fed inlet. The heat transfer results were supplemented by flow visualization.

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.

scholarly journals The Influence of Rotation on Impingement Cooling

1996 ◽  
Author(s):  
Ch. Mattern ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Naphthalene Sublimation Technique ◽  
Cooling Pattern ◽  
Circular Jets ◽  
Naphthalene Sublimation ◽  
Local Measurements ◽  
Effects Of Rotation

The objective of the present work is the experimental investigation of the effects of rotation on the heat transfer due to a single row of circular jets impinging on a curved surface, relevant to turbine blade cooling. The local transfer coefficients were determined by means of the naphthalene sublimation technique using the analogy between heat and mass transfer. Spanwise average transfer coefficients were deduced from the local measurements and are discussed relative to the transfer in a nonrotating system. Results are presented for different stagger angles, jet Reynolds numbers and geometry parameters. The geometry parameters that were varied included the spacing between adjacent jet holes and the distance between the jet hole plate and the impingement surface. It is found that rotation does not improve heat transfer but can reduce it significantly, up to 40% below the transfer coefficient in a nonrotating system. Therefore, the effects of rotation have to be accounted for accurate predictions of the cooling pattern generated by impinging jets.

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