Local and Average Transfer Coefficients for Developing Laminar Flow Between Parallel Flat Plates

1983 ◽  
Vol 7 (1) ◽  
pp. 12-16
Author(s):  
E.C. Fernandes ◽  
F.E.M. Saboya
Keyword(s):  
Mass Transfer ◽  
Laminar Flow ◽  
Equivalent Diameter ◽  
Transfer Coefficients ◽  
Flat Plates ◽  
Experimental Conditions ◽  
Average Mass ◽  
Channel One ◽  
Plate Length ◽  
Naphthalene Sublimation Technique

Local and average mass transfer coefficients in the entrance region between parallel flat plates were experimentally determined. The mass transfer experiments were performed using the naphthalene sublimation technique. In accordance with the analogy between heat and mass transfer, the experimental conditions simulated the heat transfer situation characterized by laminar flow in a parallel plate channel, one wall being isothermal and the other insulated, The temperature and velocity fields were simultaneously developing. Results were obtained for Reynolds numbers from 100 to 1500 and plate length-to-equivalent diameter ratios from 5 to 20. By use of the reciprocal of the Graetz number as an independent variable, the data for the various test runs could be brought together. The experimental results were compared with analytical predictions and a very good agreement was observed. Overall mass transfer results were measured with a precision balance and compared with the integral local values; the two methods gave results that agree to within a few percent (typically 2%).

Effects of Tip Geometry and Tip Clearance on the Mass/Heat Transfer From a Large-Scale Gas Turbine Blade

2002 ◽  
Author(s):  
M. Papa ◽  
R. J. Goldstein ◽  
F. Gori
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Flow Visualization ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Tip Clearance ◽  
Gas Turbine Blade ◽  
Transfer Coefficients ◽  
Average Mass ◽  
Naphthalene Sublimation Technique

An experimental investigation has been performed to measure average and local mass transfer coefficients on the tip of a gas turbine blade using the naphthalene sublimation technique. The heat/mass transfer analogy can be applied to obtain heat transfer coefficients from the measured mass transfer data. Flow visualization on the tip surface is provided using an oil dot technique. Two different tip geometries are considered: a squealer tip and a winglet-squealer tip having a winglet on the pressure side and a squealer on the suction side of the blade. Measurements have been taken at tip clearance levels ranging from 0.6% to 3.6% of actual chord. The exit Reynolds number based on actual chord is approximately 7.2 × 105 for all measurements. Flow visualization shows impingement and recirculation regions on the blade tip surface, providing an interpretation of the mass transfer distributions and offering insight into the fluid dynamics within the gap. For both tip geometries the tip clearance level has a significant effect on the mass transfer distribution. The squealer tip has a higher average mass transfer that sensibly decreases with gap level, whereas a more limited variation with gap level is observed for the average mass transfer from the winglet-squealer tip.

Effects of Tip Geometry and Tip Clearance on the Mass/Heat Transfer From a Large-Scale Gas Turbine Blade

2003 ◽  
Vol 125 (1) ◽  
pp. 90-96 ◽  
Author(s):  
M. Papa ◽  
R. J. Goldstein ◽  
F. Gori
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Flow Visualization ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Tip Clearance ◽  
Gas Turbine Blade ◽  
Transfer Coefficients ◽  
Average Mass ◽  
Naphthalene Sublimation Technique

An experimental investigation has been performed to measure average and local mass transfer coefficients on the tip of a gas turbine blade using the naphthalene sublimation technique. The heat/mass transfer analogy can be applied to obtain heat transfer coefficients from the measured mass transfer data. Flow visualization on the tip surface is provided using an oil dot technique. Two different tip geometries are considered: a squealer tip and a winglet-squealer tip having a winglet on the pressure side and a squealer on the suction side of the blade. Measurements have been taken at tip clearance levels ranging from 0.6 to 3.6% of actual chord. The exit Reynolds number based on actual chord is approximately 7.2×105 for all measurements. Flow visualization shows impingement and recirculation regions on the blade tip surface, providing an interpretation of the mass transfer distributions and offering insight into the fluid dynamics within the gap. For both tip geometries the tip clearance level has a significant effect on the mass transfer distribution. The squealer tip has a higher average mass transfer that sensibly decreases with gap level, whereas a more limited variation with gap level is observed for the average mass transfer from the winglet-squealer tip.

Influence of Injection Type and Feed Arrangement on Flow and Heat Transfer in an Injection Slot

2001 ◽  
Vol 124 (1) ◽  
pp. 132-141 ◽  
Author(s):  
Hyung Hee Cho ◽  
Jin Ki Ham
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Cooling System ◽  
Transfer Coefficients ◽  
Counter Flow ◽  
Flow Paths ◽  
Mass Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Vertical Injection ◽  
Injection Type

An experimental investigation is conducted to improve a slot film cooling system used for the cooling of a gas turbine combustor liner. The tangential slots are constructed of discrete holes with different injection types which are the parallel, vertical, and combined to the slot lip. The investigation is focused on the coolant supply systems of normal, inline, and counter-flow paths to the mainstream flow direction. A naphthalene sublimation technique has been employed to measure the local heat/mass transfer coefficients in a slot wall with various injection types and coolant feeding directions. A numerical simulation is also conducted to help understand the flow patterns inside the slot for different injection types. The velocity distributions at the exit of slot lip for the parallel and vertical injection types are fairly uniform with mild periodical patterns with respect to the injection hole positions. However, the combined injection type increases the nonuniformity of flow distribution with the period equaling twice that of hole-to-hole pitch due to splitting and merging of the ejected flows. The dimensionless temperature distributions at the slot exits differ little with blowing rates, injection types, and secondary flow conditions. In the results of heat/mass transfer measurements, the best cooling performance inside the slot is obtained with the vertical injection type among the three different injection types due to the effects of jet impingement. The lateral distributions of heat/mass transfer coefficients with the inline and counter-flow paths are more uniform than the normal-flow path. The average heat/mass transfer coefficients with the injection holes are about two to five times higher than that of a smooth two-dimensional slot path.

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.

MASS TRANSFER FROM FLAT PLATES TO POWER-LAW FLUIDS IN LAMINAR FLOW

1986 ◽  
Vol 43 (4-6) ◽  
pp. 335-345 ◽  
Author(s):  
U.K. GHOSH ◽  
K.N. DEY ◽  
S.N. GUPTA ◽  
S. KUMAR ◽  
S.N. UPADHYAY
Keyword(s):  
Mass Transfer ◽  
Laminar Flow ◽  
Power Law ◽  
Flat Plates ◽  
Power Law Fluids

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.

An Experimental Study on Heat/Mass Transfer and Pressure Drop Characteristics for Arrays of Nonuniform Plate Length Positioned Obliquely to the Flow Direction

1993 ◽  
Vol 115 (3) ◽  
pp. 568-575 ◽  
Author(s):  
Huai-Zhang Huang ◽  
Wen-Quan Tao
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Heat Mass Transfer ◽  
Flow Direction ◽  
Plate Length ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation ◽  
Nonuniform Plate ◽  
Short Plate ◽  
Parameter Ranges

In this paper, heat/mass transfer and pressure drop characteristics for arrays of nonuniform plate length, aligned at an angle of 25 deg to the flow direction, are investigated experimentally via a naphthalene sublimation technique. The measurements of cyclic average Sherwood numbers and friction factors in the fully developed regime are conducted for nine geometric configurations. The following parameter ranges are studied: length ratio of successive plates 1.5–2.5; ratio of the transverse pitch to the longitudinal pitch 0.381–0.8, and Reynolds number based on short plate length 1.98×102 to 1.66×103. Comparisons with the results for arrays with uniform plate length are conducted. Two constraints are used, identical pumping power and identical pressure drop. It is found that for most cases studied, the thermal performance of the array with a nonuniform plate length is better than that of the array with a uniform plate length.

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.

scholarly journals Features of the kinetics of mass transfer processes in the process of firing ceramic materials

2018 ◽  
pp. 29-31
Author(s):  
O.M. Nedbailo ◽  
O.G. Chernyshyn
Keyword(s):  
Mass Transfer ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Ceramic Materials ◽  
The Body ◽  
Mass Content ◽  
Transfer Coefficients ◽  
Average Mass ◽  
Firing Ceramic

In article the technique of definition factors of carrying over weight of substance in the course of roasting ceramic materials which is based on exponent dependences of change mass bodies from time of its heating is offered. The process of firing ceramic materials is associated with the transfer of heat and mass of matter. Therefore, for a more complete calculation of the heat treatment mode, it is necessary to know the conditions for the mass transfer in the product being calcined. The aim of the work is to determine the mass transfer coefficients of the substance in the process of firing ceramic materials. The mass loss rate of the bound matter or the mass loss per unit time will be directly proportional to the average mass content of the body. On the other hand, the mass loss rate of the bound matter is numerically equal to the slope of the mass content kinetics curve. Proposed in the work formulas can be applied when studying the process of mass transfer during firing of samples from different clays, as when firing clay samples of different diameters under the same conditions, they will differ in the mass content (mass loss rate of the bound substance) during heating and their final relative amount (mass content) of the lost mass will be the same.

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.

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