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.

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.

scholarly journals An Investigation of Heat Transfer by Leading Edge Film Cooling Applying the Naphthalene Sublimation Technique

1996 ◽  
Author(s):  
J. Richter ◽  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Film Cooling ◽  
Incidence Angle ◽  
Leading Edge ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The dependence of heat transfer on film cooling near the leading edge of a blade was investigated using the naphthalene sublimation technique and applying the analogy between heat and mass transfer. Therefore, the local sublimation rate with and without film cooling was measured. The symmetric leading edge was cooled by an air mass flow out of two staggered rows of holes. The measurements were carried out with a constant Reynolds number Re = 80000, different incidence angles φ = 0° to 10° and a blowing rate varying from M = 0.3 to 2.5. The flow without film cooling was visualized around the leading edge with smoke to indicate the existence of separation bubbles. To determine the dependence of incidence angle and blowing rate on jet trajectories, smoke was mixed to the cooling air. The mass transfer coefficient was determined with the naphthalene sublimation technique. Due to the high resolution of the sublimation technique the local mass transfer distribution around the cooling holes could also be measured. Furthermore, the location of stagnation points and separation bubbles were investigated. The results of the tests without film cooling were also compared with those obtained by observing stagnation point mass transfer on a cylinder and with those by laminar flow across a flat plate. The mass transfer coefficient of film cooling experiments was related to the mass transfer coefficient without film cooling to describe the local dependence of heat transfer coefficient on film cooling. An increase on relativ heat transfer near the film cooling holes is obtained by increasing the blowing rate. No further influence on heat transfer along the pressure side is detected for an incidence angle larger than 10° as the cooling films were shifted around the leading edge from the pressure to the suction side.

Effect of Rib Angle on Local Heat/Mass Transfer Distribution in a Two-Pass Rib-Roughened Channel

1988 ◽  
Vol 110 (2) ◽  
pp. 233-241 ◽  
Author(s):  
P. R. Chandra ◽  
J. C. Han ◽  
S. C. Lau
Keyword(s):  
Mass Transfer ◽  
Sherwood Number ◽  
Heat Mass Transfer ◽  
Local Heat ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Test Channel ◽  
Mass Transfer Coefficients ◽  
Square Duct ◽  
Naphthalene Sublimation Technique

The heat transfer characteristics of turbulent air flow in a two-pass channel were studied via the naphthalene sublimation technique. The test section, which consisted of two straight, square channels joined by a sharp 180 deg turn, resembled the internal cooling passages of gas turbine airfoils. The top and bottom surfaces of the test channel were roughened by rib turbulators. The rib height-to-hydraulic diameter ratio (e/D) was 0.063 and the rib pitch-to-height ratio (P/e) was 10. The local heat/mass transfer coefficients on the roughened top wall, and on the smooth divider and side walls of the test channel, were determined for three Reynolds numbers of 15,000, 30,000, and 60,000, and for three angles of attack (α) of 90, 60, and 45 deg. The results showed that the local Sherwood numbers on the ribbed walls were 1.5 to 6.5 times those for a fully developed flow in a smooth square duct. The average ribbed-wall Sherwood numbers were 2.5 to 3.5 times higher than the fully developed values, depending on the rib angle-of-attack and the Reynolds number. The results also indicated that, before the turn, the heat/mass transfer coefficients in the cases of α = 60 and 45 deg were higher than those in the case of α = 90 deg. However, after the turn, the heat/mass transfer coefficients in the oblique-rib cases were lower than those in the traverse-rib case. Correlations for the average Sherwood number ratios for individual channel surfaces and for the overall Sherwood number ratios are reported.

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.

Sublimation Rate of Vertically Oriented Naphthalene Cylinders in Natural Convection

2017 ◽  
Author(s):  
Lauren Carley ◽  
William S. Janna ◽  
Jeffrey Marchetta
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Sublimation Rate ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation ◽  
Sublimation Rates ◽  
Rayleigh Numbers ◽  
Sublimation Technique

The naphthalene sublimation technique was used to determine the rate of mass transfer from three solid naphthalene cylinders in a natural convection environment. The cylinder diameters measured 2.5 cm (1 in), 3.8 cm (1.5 in), and 5 cm (2 in) nominally. Sublimation rates were measured and the mass transfer coefficients were calculated. Correlations were developed for the Sherwood vs. Rayleigh numbers, Sherwood vs. Grashof numbers, and mass transfer coefficient vs. diameter.

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.

Measurements of Heat Transfer and Pressure Drop for an Array of Staggered Plates Aligned Parallel to an Air Flow

1980 ◽  
Vol 102 (3) ◽  
pp. 426-432 ◽  
Author(s):  
E. M. Sparrow ◽  
A. Hajiloo
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Air Flow ◽  
Plate Thickness ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation

The heat transfer and pressure drop characteristics of an array of staggered plates, aligned parallel to the direction of a forced convection air flow, have been studied experimentally. During the course of the experiments, the plate thickness and Reynolds number were varied parametrically. Mass transfer measurements employing the naphthalene sublimation technique were made to obtain the heat transfer results via the heat-mass transfer analogy. For a given operating condition, the per-plate heat transfer coefficients were found to be the same for the second and all subsequent rows. The fully developed heat transfer coefficients increase with Reynolds number for all the plate thicknesses investigated, but in a different manner for the different thicknesses. In general, thicker plates give rise to higher heat transfer coefficients, especially at the larger Reynolds numbers. The measured friction factors also increase with plate thickness. For the thickest plates, the friction factor was found to be independent of the Reynolds number, signalling the dominance of inertial losses.

A New Analogy Function for the Naphthalene Sublimation Technique to Measure Heat Transfer Coefficients on Turbine Airfoils

1995 ◽  
Author(s):  
M. Häring ◽  
B. Weigand
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Schmidt Number ◽  
Numerical Solutions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Transfer Equations ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The naphthalene sublimation technique is based on the analogy between mass and heat transfer. This analogy is only fully valid for incompressible flow and if the Prandtl and Schmidt number are equal. In the present investigation the energy- and mass transfer equations were solved simultaneously to establish an analogy function which allows the calculation of the Nusselt number from the Sherwood number in function of the Mach, the Prandtl and the Schmidt number. For a laminar flow this new analogy function is based on similarity solutions of the conservation equations for high Mach number flows. Also a numerical investigation was conducted to study the influence of the pressure gradient and the Soret effect as well as varying fluid properties. For a turbulent flow, a flat plate solution was established for Pr=1. Energy and mass transfer equations were additionally solved for a two dimensional duct flow to study the influence of the Prandtl number on the analogy function independently. The resulting analytical and numerical solutions are shown for various pressure gradients, Prandtl and Mach numbers. In addition, approximations for the analogy function are derived. The influence of the present theory on heat transfer measurements on a turbine airfoil is shown. The theory is validated against experimental results in Häring et. al. (1995) showing a good agreement between the heat transfer coefficients calculated with the new analogy function and measurements of actual heat transfer.

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