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.

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

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.

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.

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.

scholarly journals Effect of Upstream Wake on Shower-Head Film Cooling

1996 ◽  
Vol 2 (4) ◽  
pp. 269-280
Author(s):  
Ping-Hei Chen ◽  
Jr-Ming Miao
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Mass Transfer Rate ◽  
Leading Edge ◽  
Suction Side ◽  
Convective Transport ◽  
Wake Flow ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation ◽  
The Difference

The present study aims to investigate the effect of an upstream wake on the convective transport phenomena over a turbine blade with shower-head film cooling. A naphthalene sublimation technique was implemented to obtain the detailed mass transfer distributions on both suction and pressure surfaces of the test blade. All mass transfer runs were conducted on a blowing-type wind tunnel with a six-blade linear cascade. The leading edge of the test blade was drilled with three rows of equally spaced injection holes. The upstream wake was simulated by a circular bar with the same diameter as that of the trailing edge of the test blade.The test condition was fixed at Re = 397,000, M = 0.8, and Tu = 0.4% and upstream wakes were generated at four different locations ahead of the blade cascade. Measured results show that there is a difference in mass transfer rate from the case without upstream wake. This difference is greater on the suction side than on the pressure side. The difference results from the interaction between the wake flow that is induced by the upstream wake and the injection flows that are ejected from the multi-rows of injection holes on the test blade. It was also found that the location of upstream wake generation significantly affects the mass transfer distributions on both surfaces of test blade.

scholarly journals Mass Transfer over a Film-Cooled Turbine Blade

1996 ◽  
Vol 2 (4) ◽  
pp. 221-236
Author(s):  
Ping-Hei Chen ◽  
Jr-Ming Miao
Keyword(s):  
Mass Transfer ◽  
Turbine Blade ◽  
Leading Edge ◽  
Secondary Flows ◽  
Spanwise Direction ◽  
Edge Region ◽  
Blade Surface ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

A naphthalene sublimation technique was employed to study the mass transfer distributions over a turbine blade surface with secondary flows ejected in the spanwise direction through three rows of equally-spaced injection holes located in the leading edge region. The mass transfer measurements were conducted in a range of blowing ratios from 0.6 to 1.2 at two different mainstream turbulence levels (0.4% and 6.0%) while keeping the exit Reynolds number,Re⁡2, at a constant value of 397,000.

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.

scholarly journals Film Cooling Effectiveness and Mass/Heat Transfer Coefficient Downstream of One Row of Discrete Holes

1998 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin ◽  
R. L. Olson
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35° inclination angle with 3d hole spacing and relatively small hole length to diameter ratio (L/d = 6.3). Both film cooling effectiveness and mass/heat transfer coefficient are determined for blowing rates from 0.5 to 2.0 with density ratio of 1.0. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficient obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. The laterally-averaged and local film cooling effectiveness agree with previous experiments. The difference between mass/heat transfer coefficients and previous heat transfer results indicates that conduction error may play an important role in the earlier heat transfer measurements.

Mass Transfer from a Rotating Inclined Plate

1981 ◽  
Vol 103 (2) ◽  
pp. 204-211 ◽  
Author(s):  
Hitoshi Koyama ◽  
Sei-ichi Ohsawa ◽  
Akira Nakayama
Keyword(s):  
Mass Transfer ◽  
Incidence Angle ◽  
Leading Edge ◽  
Wake Flow ◽  
Flat Plates ◽  
Inclined Plate ◽  
Transfer Processes ◽  
Naphthalene Sublimation Technique ◽  
Mass Transfer Processes ◽  
Naphthalene Sublimation

An extensive experimental investigation using the Naphthalene Sublimation Technique, has been carried out to explore the mass transfer processes on inclined flat plates at rotation. It has been found that the flows responsible for the transfer processes can be classified into three types, namely, flow without a separated region, flow with a separated region located near the leading edge, and flow with a separated region all over the surface. A wind tunnel experiment on stationary flat plates has been also performed so as to isolate the effects of incidence angle from the rotational effects. A tremendous increase in transfer rate has been observed for the surface of the rotational system exposed to a wake flow.

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