Combined Effects of Axial- and Radial-Gap Spacing on the Mass Transfer Characteristics of a Shrouded Rotor-Stator System

1991 ◽  
Author(s):  
M. K. Chyu ◽  
D. J. Bizzak
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Sherwood Number ◽  
Radial Clearance ◽  
Average Mass ◽  
Local Mass ◽  
Local Mass Transfer ◽  
Radial Gap ◽  
Gap Spacing ◽  
Shrouded Rotor

Heat transfer characteristics of a shrouded rotor-stator system are examined using a mass transfer analog technique. Both local and average mass-transfer coefficients for a naphthalene-coated disk rotating in a quiescent environment are obtained for 4.0×104 ≤ Re ≤ 2.4×105. The measured results, which correlate well with theoretical predictions, are used to evaluate the influence of radial-gap clearance and axial-gap spacing on average and local mass-transfer rates in a shrouded rotor-stator with no superposed coolant flow. Similar to a rotor-stator system without a shroud, a reduction in the axial gap tends to decrease the average mass transfer, with the magnitude of the decrease being inversely proportional to the Reynolds number. Such a reduction in mass transfer is also found to be influenced by the radial clearance gap. A reduction of the radial clearance from a/D=0.042 to 0.020 is shown to decrease the average Sherwood number by approximately 20 percent of the corresponding free disk value. Local mass transfer distributions illustrate a more significant axial gap effect. For small axial-gap spacings, local Sherwood number profiles are no longer uniform across the rotor face, but exhibit a significant increase near the rotor edge. The magnitude of this increase near the disk edge is shown to be inversely proportional to the radial clearance gap and the rotational Reynolds number.

Local Mass Transfer From Rotating Wedge-Shaped Blades

1977 ◽  
Vol 99 (4) ◽  
pp. 634-640 ◽  
Author(s):  
H. Koyama ◽  
A. Nakayama ◽  
K. Sato ◽  
T. Shimizu
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Sherwood Number ◽  
Negative Pressure ◽  
Local Mass ◽  
Contour Lines ◽  
Local Mass Transfer ◽  
Theoretical Considerations ◽  
Local Sherwood Number

The purpose of this investigation is to determine the mass transfer from rotating wedge-shaped blades in an air environment. Through theoretical considerations, effect of negative pressure gradient has been emphasized wherever possible. The experimental results are correlated with local Sherwood number and Reynolds number. Furthermore, a new method has been proposed to judge the flow type by reading directly the slope of contour lines of equal sublimation drawn on the surface.

The Effect of Naturally Developing Roughness on the Mass Transfer in Pipes Under Different Reynolds Numbers

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
D. Wang ◽  
D. Ewing ◽  
C. Y. Ching
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Initial Period ◽  
Reynolds Numbers ◽  
Multiple Time ◽  
Transfer Enhancement ◽  
Flow Loop ◽  
Local Mass ◽  
Mass Transfer Enhancement ◽  
Local Mass Transfer

The local mass transfer over dissolving surfaces was measured at pipe Reynolds number of 50,000, 100,000, and 200,000. Tests were run at multiple time periods for each Reynolds number using 203 mm diameter test sections that had gypsum linings dissolving to water in a closed flow loop at a Schmidt number of 1200. The local mass transfer was calculated from the decrease in thickness of the gypsum lining that was measured using X-ray-computed tomography (CT) scans. The range of Sherwood numbers for the developing roughness in the pipe was in good agreement with the previous studies. The mass transfer enhancement (Sh/Shs) was dependent on both the height (ep−v) and spacing (λstr) of the roughness scallops. For the developing roughness, two periods of mass transfer were present: (i) an initial period of rapid increase in enhancement when the density of scallops increases till the surface is spatially saturated with the scallops and (ii) a slower period of increase in enhancement beyond this point, where the streamwise spacing is approximately constant, and the roughness height grows more rapidly. The mass transfer enhancement was found to correlate well with the parameter (ep−v/λstr)0.2, with a weak dependence on Reynolds number.

Effect of Flow Angle-of-Attack on the Local Heat/Mass Transfer From a Wall-Mounted Cube

1994 ◽  
Vol 116 (3) ◽  
pp. 552-560 ◽  
Author(s):  
V. Natarajan ◽  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Angle Of Attack ◽  
Convective Transport ◽  
Stream Velocity ◽  
Flow Angle ◽  
Local Study ◽  
Local Mass ◽  
Local Mass Transfer

An experimental study of the local mass transfer over the entire surface of a wall-mounted cube is performed with a particular emphasis on the effects of flow angles-of-attack (0 deg ≤ α ≤ 45 deg). Invoking an analogy between heat transfer and mass transfer, the presently obtained mass transfer results can be transformed into their heat transfer counterparts. Reynolds number based on the cube height and mean free-stream velocity varies between 3.1 × 104 and 1.1 × 105. To substantiate the mass transfer results, streakline patterns are visualized on the cube surfaces as well as the endwall using the oil-graphite technique. Significantly different flow regimes and local mass transfer characteristics are identified as the angle-of-attack varies. The overall convective transport is dominated by three-dimensional flow separation that includes multiple horseshoe vortex systems and an arch-shaped vortex wrapping around the rear portion of the cube. In addition to the local study, power correlations between the surface-resolved mass transfer Sherwood number and the Reynolds number are presented for all α values studied. Mass transfer averaged over the entire cube is compared with that of its two-dimensional counterpart with crossflow around a tall prism.

scholarly journals Heat Transfer in a Two-Pass Internally Ribbed Turbine Blade Coolant Channel With Cylindrical Vortex Generators

1996 ◽  
Author(s):  
Richard G. Hibbs ◽  
Sumanta Acharya ◽  
Yi Chen ◽  
Dimitris E. Nikitopoulos ◽  
Tod A. Myrum
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Sherwood Number ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Transfer Rates ◽  
Average Mass ◽  
Side Walls

The effect of vortex generators on the mass (heat) transfer from the ribbed passage of a two pass turbine blade coolant channel is investigated with the intent of optimizing the vortex generator geometry so that significant enhancements in mass/heat transfer can be achieved. In the experimental configuration considered, ribs are mounted on two opposite walls: all four walls along each pass are active and have mass transfer from their surfaces but the ribs are non-participating. Mass transfer measurements, in the form of Sherwood number ratios, are made along the centerline and in selected inter-rib modules. Results are presented for Reynolds number in the range of 5,000 to 40,000. pitch to rib height ratios of 10.5 and 21, and vortex generator-rib spacing to rib height ratios of 0.55 and 1.5. Centerline and spanwise averaged Sherwood number ratios are presented along with contours of the Sherwood number ratios. Results indicate that the vortex generators lead to substantial increases in the local mass transfer rates, particularly along the side walls, and modest increases in the average mass transfer rates. The vortex generators have the effect of making the inter-rib profiles along the ribbed walls more uniform. Along the side walls, horseshoe vortices that characterize the vortex generator wake are associated with significant mass transfer enhancements. The wake effects and the levels of enhancement decrease somewhat with increasing Reynolds number and decreasing pitch.

scholarly journals Heat Transfer in a Two-Pass Internally Ribbed Turbine Blade Coolant Channel With Cylindrical Vortex Generators

1998 ◽  
Vol 120 (3) ◽  
pp. 589-600 ◽  
Author(s):  
R. G. Hibbs ◽  
S. Acharya ◽  
Y. Chen ◽  
D. E. Nikitopoulos ◽  
T. A. Myrum
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Sherwood Number ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Transfer Rates ◽  
Average Mass ◽  
Side Walls

The effect of vortex generators on the mass (heat) transfer from the ribbed passage of a two-pass turbine blade coolant channel is investigated with the intent of optimizing the vortex generator geometry so that significant enhancements in mass/heat transfer can be achieved. In the experimental configuration considered, ribs are mounted on two opposite walls; all four walls along each pass are active and have mass transfer from their surfaces but the ribs are nonparticipating. Mass transfer measurements, in the form of Sherwood number ratios, are made along the centerline and in selected interrib modules. Results are presented for Reynolds number in the range of 5000 to 40,000, pitch to rib height ratios of 10.5 and 21, and vortex generator-rib spacing to rib height ratios of 0.55 and 1.5. Centerline and spanwise-averaged Sherwood number ratios are presented along with contours of the Sherwood number ratios. Results indicate that the vortex generators lead to substantial increases in the local mass transfer rates, particularly along the side walls, and modest increases in the average mass transfer rates. The vortex generators have the effect of making the interrib profiles along the ribbed walls more uniform. Along the side walls, vortices that characterize the vortex generator wake are associated with significant mass transfer enhancements. The wake effects and the levels of enhancement decrease somewhat with increasing Reynolds number and decreasing pitch.

scholarly journals Mass transfer control of a backward-facing step flow by local forcing-effect of Reynolds number

2011 ◽  
Vol 15 (2) ◽  
pp. 367-378 ◽  
Author(s):  
Zouhaier Mehrez ◽  
Mourad Bouterra ◽  
Cafsi El ◽  
Ali Belghith ◽  
Quere Le
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Reynolds Numbers ◽  
Backward Facing Step ◽  
Local Mass ◽  
Eddy Simulation ◽  
Local Forcing ◽  
Large Eddy ◽  
Local Mass Transfer ◽  
Oscillating Jet

The control of fluid mechanics and mass transfer in separated and reattaching flow over a backward-facing step by a local forcing, is studied using Large Eddy Simulation (LES). To control the flow, the local forcing is realized by a sinusoidal oscillating jet at the step edge. The Reynolds number is varied in the range 10000 ? Re ? 50000 and the Schmidt number is fixed at 1. The found results show that the flow structure is modified and the local mass transfer is enhanced by the applied forcing. The observed changes depend on the Reynolds number and vary with the frequency and amplitude of the local forcing. For the all Reynolds numbers, the largest recirculation zone size reduction is obtained at the optimum forcing frequency St = 0.25. At this frequency the local mass transfer enhancement attains the maximum.

Measurement of Local Mass Transfer and the Resulting Roughness in a Large Diameter S-Bend at High Reynolds Number

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
D. Wang ◽  
D. Ewing ◽  
T. Le ◽  
C. Y. Ching
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Mass Transfer Rate ◽  
Large Diameter ◽  
Reynolds Numbers ◽  
High Mass ◽  
Local Mass ◽  
Roughness Elements ◽  
Local Mass Transfer ◽  
High Reynolds

The local mass transfer and the resulting roughness in a 203 mm diameter back-to-back bend arranged in an S-configuration were measured at a Reynolds number of 300,000. A dissolving wall method using gypsum dissolution to water at 40 °C was used, with a Schmidt number of 660. The topography of the unworn and worn inner surface was quantified using nondestructive X-ray computed tomography (CT) scans. The local mass transfer rate was obtained from the local change in radius over the flow time. Two regions of high mass transfer were present: (i) along the intrados of the first bend near the inlet and (ii) at the exit of the extrados of the first bend that extends to the intrados of the second bend. The latter was the region of highest mass transfer, and the scaling of the maximum Sherwood number with Reynolds number followed that developed for lower Reynolds numbers. The relative roughness distribution in the bend corresponded to the mass transfer distribution, with higher roughness in the higher mass transfer regions. The spacing of the roughness elements in the upstream pipe and in the two regions of high mass transfer was approximately the same; however, the spacing-to-height ratio was very different with values of 20, 10, and 6, respectively.

Local Mass/Heat Transfer on Turbine Blade Near-Tip Surfaces

2002 ◽  
Author(s):  
P. Jin ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Turbulence Intensity ◽  
Tip Clearance ◽  
Suction Surface ◽  
Transfer Rates ◽  
Local Mass ◽  
Pressure Surface ◽  
Local Mass Transfer

Local mass transfer measurements on a simulated high pressure turbine blade are conducted in a linear cascade with tip clearance, using a naphthalene sublimation technique. The effects of tip clearance (0.86%–6.90% of chord), are investigated at an exit Reynolds number of 5.8 × 105 and a low turbulence intensity of 0.2%. The effects of the exit Reynolds number (4–7 × 105) and the turbulence intensity (0.2% and 12.0%) are also measured for the smallest tip clearance. The effect of tip clearance on the mass transfer on the pressure surface is limited to 10% of the blade height from the tip at smaller tip clearances. At the largest tip clearance high mass transfer rates are induced at 15% of curvilinear distance (Sp/C) by the strong acceleration of the fluid on the pressure side into the clearance. The effect of tip clearance on the mass transfer is not very evident on the suction surface for curvilinear distance of Ss/C < 0.21. However, much higher mass transfer rates are caused downstream of Ss/C ≈ 0.50 by the tip leakage vortex atthe smallest tip clearance, while at the largest tip clearance, the average mass transfer is lower than that with zero tip clearance, probably because the strong leakage vortex pushes the passage vortex away from the suction surface. A high mainstream turbulence level (12.0%) increases the local mass transfer rates on the pressure surface, while a higher mainstream Reynolds number generates higher local mass transfer rates on both near-tip surfaces.

Local Mass/Heat Transfer on Turbine Blade Near-Tip Surfaces

2003 ◽  
Vol 125 (3) ◽  
pp. 521-528 ◽  
Author(s):  
P. Jin ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Turbulence Intensity ◽  
Tip Clearance ◽  
Suction Surface ◽  
Transfer Rates ◽  
Local Mass ◽  
Pressure Surface ◽  
Local Mass Transfer

Local mass transfer measurements on a simulated high-pressure turbine blade are conducted in a linear cascade with tip clearance, using a naphthalene sublimation technique. The effects of tip clearance (0.86–6.90% of chord) are investigated at an exit Reynolds number of 5.8×105 and a low turbulence intensity of 0.2%. The effects of the exit Reynolds number 4−7×105 and the turbulence intensity (0.2 and 12.0%) are also measured for the smallest tip clearance. The effect of tip clearance on the mass transfer on the pressure surface is limited to 10% of the blade height from the tip at smaller tip clearances. At the largest tip clearance high mass transfer rates are induced at 15% of curvilinear distance Sp/C by the strong acceleration of the fluid on the pressure side into the clearance. The effect of tip clearance on the mass transfer is not very evident on the suction surface for curvilinear distance of Ss/C<0.21. However, much higher mass transfer rates are caused downstream of Ss/C≈0.50 by the tip leakage vortex at the smallest tip clearance, while at the largest tip clearance, the average mass transfer is lower than that with zero tip clearance, probably because the strong leakage vortex pushes the passage vortex away from the suction surface. High mainstream turbulence level (12.0%) increases the local mass transfer rates on the pressure surface, while a higher mainstream Reynolds number generates higher local mass transfer rates on both near-tip surfaces.

Measurement of Local Mass Transfer Distribution in a Large Diameter S-Bend at High Reynolds Number

2014 ◽  
Author(s):  
D. Wang ◽  
D. Ewing ◽  
T. Le ◽  
C. Y. Ching
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Mass Transfer Rate ◽  
Large Diameter ◽  
High Mass ◽  
Flow Loop ◽  
Local Mass ◽  
Common Coordinate System ◽  
Local Mass Transfer ◽  
High Reynolds

The local mass transfer in a 203mm diameter back to back bend arranged in a S-configuration was measured at a Reynolds number of 300,000. A dissolving wall method using gypsum dissolution to water at 40°C was used, with a Schmidt number of 660. The experiment was performed in a flow loop by flowing water through the test section. The topography of the unworn and the worn inner surface was quantified using nondestructive X-ray Computed Tomography (CT) scans. The two scanned surfaces were aligned to a common coordinate system using commercial software and in-house routines. The local mass transfer rate was obtained from the local change in radius over the flow time. Two regions of high mass transfer were present: (i) along the intrados of the first bend near the inlet and (ii) at the exit of the extrados of the first bend that extends to the intrados of the second bend. The latter was the region of highest mass transfer in the S-bend.

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