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/Mass Transfer in 1:4 Rectangular Passages With Rotation

2003 ◽  
Author(s):  
Peeyush Agarwal ◽  
Sumanta Acharya ◽  
D. E. Nikitopoulos
Keyword(s):  
Mass Transfer ◽  
Cross Section ◽  
Heat Mass Transfer ◽  
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 to 40000 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 span-wise mass transfer distributions in the smooth and the ribbed cases are also examined.

Heat/Mass Transfer in a 4:1 AR Smooth and Ribbed Coolant Passage With Rotation in 90-Degree and 45-Degree Orientations

2004 ◽  
Author(s):  
S. Acharya ◽  
P. Agarwal ◽  
D. E. Nikitopoulos
Keyword(s):  
Mass Transfer ◽  
Test Section ◽  
Heat Mass Transfer ◽  
Rectangular Channel ◽  
Spanwise Direction ◽  
Degree Relative ◽  
Naphthalene Sublimation Technique ◽  
Rotation Numbers ◽  
Smooth Channel ◽  
Naphthalene Sublimation

The paper presents an experimental study of heat/mass transfer coefficient in 4:1 aspect ratio rectangular channel with smooth or ribbed walls for Reynolds number in the range of 5,000 to 30,000, rotation numbers in the range of 0–0.12 and for two different orientations of the test-section (90-degree and 45-degree relative to the plane of rotation). Such passages are encountered close to the trailing sections of the turbine blade. Inline normal tips (e/Dh = 0.15625 and p/e = 11.2) are used and placed on the leading and the trailing sides. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. It is observed that for the 45-degree orientation of the test-section, all the walls show an increase in the heat transfer with rotation as opposed to the 90-degree orientation where the stabilized wall shows reduction and the destabilized wall shows enhancement. The spanwise mass transfer distributions in the smooth and the ribbed cases are also presented, and show significant variations in the spanwise direction for the smooth channel.

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.

Mass∕Heat Transfer in Rotating, Smooth, High-Aspect Ratio (4:1) Coolant Channels With Curved Walls

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Eashwar Sethuraman ◽  
Sumanta Acharya ◽  
Dimitris E. Nikitopoulos
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Aspect Ratio ◽  
Cross Sections ◽  
Positive Curvature ◽  
Transfer Data ◽  
Naphthalene Sublimation Technique ◽  
Smooth Channel ◽  
Naphthalene Sublimation ◽  
Curved Walls

The paper presents an experimental study of heat∕mass transfer coefficient in 4:1 aspect ratio smooth channels with nonuniform cross sections. Curved leading and trailing edges are studied for two curvatures of 9.06 m−1 (0.23 in.−1) and 15.11 m−1 (0.384 in.−1) and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls) and the other configuration has leading and trailing walls that curve inward into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). A detailed study at Re=10,000 with rotation numbers in the range of 0–0.07 is undertaken for the two different curvature configurations. All experiments are done for a 90 deg passage orientation with respect to the plane of rotation. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. Only the radially outward flow is considered for the present study. The spanwise mass transfer distributions of fully developed regions of the channel walls are also presented. The mass transfer data from the curved wall channels are compared to those from a smooth 4:1 rectangular duct with similar flow parameters. The local mass transfer data are analyzed mainly for the fully developed region, and area-averaged results are presented to delineate the effect of the rotation number. Heat transfer enhancement especially in the leading wall is seen for the lower curvature channels, and there is a subsequent reduction in the higher curvature channel when compared to the 4:1 rectangular smooth channel. This indicates that an optimal channel wall curvature exists for which heat transfer is the highest.

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.

Mass/Heat Transfer in Rotating, Smooth, High-Aspect Ratio (4:1) Coolant Channels With Curved Walls

2006 ◽  
Author(s):  
Eashwar Sethuraman ◽  
Dimitris E. Nikitopoulos ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Aspect Ratio ◽  
Cross Sections ◽  
Positive Curvature ◽  
Transfer Data ◽  
Naphthalene Sublimation Technique ◽  
Smooth Channel ◽  
Naphthalene Sublimation ◽  
Curved Walls

The paper presents an experimental study of heat/mass transfer coefficient in 4:1 aspect ratio smooth channels with non-uniform cross-sections. Curved leading and trailing edges are studied, for two curvatures of 9.06 m−1 (0.23 in−1) and 15.11 m−1 (0.384 in−1) and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls), and the other configuration has leading and trailing walls that curve inwards into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). A detailed study at Re = 10,000 with rotation numbers in the range of 0–0.07 is undertaken for the two different curvature configurations. All experiments are done for a 90° passage-orientation with respect to the plane of rotation. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. Only the radially outward flow is considered for the present study. The span-wise mass transfer distributions of fully developed regions of the channel walls are also presented. The mass transfer data from the curved wall channels is compared to those from a smooth 4:1 rectangular duct with similar flow parameters. The local mass transfer data is analyzed mainly for the fully developed region, and area-averaged results are presented to delineate the effect of the rotation number. Heat transfer enhancement especially in the leading wall is seen for the lower curvature channels, and there is a subsequent reduction in the higher curvature channel, when compared to the 4:1 rectangular smooth channel. This indicates that an optimal channel wall curvature exists for which heat transfer is the highest.

Influence of Radial Rotation on Heat Transfer in a Rectangular Channel With Two Opposite Walls Roughened by Hemispherical Protrusions at High Rotation Numbers

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Miin. Liou ◽  
Wei-Chun Chen
Keyword(s):  
Heat Transfer ◽  
Infrared Thermography ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Flow Region ◽  
Transfer Data ◽  
Nusselt Numbers ◽  
Rotation Numbers ◽  
Heat Transfer Correlations ◽  
Rotating Channel

Detailed heat transfer distributions over two opposite leading and trailing walls roughened by hemispherical protrusions were measured from a rotating rectangular channel at rotation number up to 0.6 to examine the effects of Reynolds (Re), rotation (Ro), and buoyancy (Bu) numbers on local and area-averaged Nusselt numbers (Nu and Nu¯) using the infrared thermography. A set of selected heat transfer data illustrates the Coriolis and rotating buoyancy effects on the detailed Nu distributions and the area-averaged heat transfer performances of the rotating channel. The Nu¯ for the developed flow region on the leading and trailing walls are parametrically analyzed to devise the empirical heat transfer correlations that permit the evaluation of the interdependent and individual Re, Ro, and Bu effect on Nu¯.

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.

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