scholarly journals Discussion: “Friction-Factor Data for Flat-Plate Tests of Smooth and Honeycomb Surfaces” (Ha, T. W., and Childs, Dara W., 1992, ASME J. Tribol., 114, pp. 722–729)

1992 ◽  
Vol 114 (4) ◽  
pp. 729-730
Author(s):  
J. K. Scharrer
Keyword(s):  
Flat Plate ◽  
Friction Factor ◽  
Factor Data

scholarly journals Friction-Factor Data for Flat-Plate Tests of Smooth and Honeycomb Surfaces

1992 ◽  
Vol 114 (4) ◽  
pp. 722-729 ◽  
Author(s):  
T. W. Ha ◽  
Dara W. Childs
Keyword(s):  
Flat Plate ◽  
Friction Factor ◽  
Smooth Surface ◽  
Factor Model ◽  
Test Apparatus ◽  
Cell Width ◽  
Plate Test ◽  
Friction Factors ◽  
Line Flow ◽  
Factor Data

Friction-factors for honeycomb surfaces are measured with a flat plate tester. The flat plate test apparatus is described and a method is discussed for determining the friction-factor experimentally. The friction-factor model is developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction-factor are plotted for smooth surface and twelve-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressure, and 5,000 to 130,000 range of the Reynolds number. The optimum geometries for the maximum friction-factor are found as a function of cell width to cell depth and clearance to cell width ratios.

Correlating Isothermal Friction Factor Data for Micro-Fin Tubes Using Logistic Dose-Response Curve Fitting Method

2014 ◽  
Vol 35 (11-12) ◽  
pp. 996-1006
Author(s):  
Hou Kuan Tam ◽  
Lap Mou Tam ◽  
Afshin J. Ghajar ◽  
Pak Hang Fu ◽  
Cheong Sun
Keyword(s):  
Friction Factor ◽  
Dose Response ◽  
Curve Fitting ◽  
Response Curve ◽  
Dose Response Curve ◽  
Fitting Method ◽  
Factor Data ◽  
Curve Fitting Method ◽  
Fin Tubes

Friction Factor Behavior From Flat-Plate Tests of 12.15 mm Diameter Hole-Pattern Roughened Surfaces

2011 ◽  
Author(s):  
Thanesh Deva Asirvatham ◽  
Dara W. Childs ◽  
Stephen Phillips
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Friction Factor ◽  
Dynamic Pressure ◽  
Reynolds Numbers ◽  
Stagnation Temperature ◽  
Flat Plates ◽  
Number Range ◽  
Current Test ◽  
Rough Plate

A flat-plate tester is used to measure the friction-factor behavior for a hole-pattern-roughened surface facing a smooth surface with compressed air as the medium. Measurements of mass flow rate, static pressure drop and stagnation temperature are carried out and used to find a combined (stator + rotor) Fanning friction factor value. In addition, dynamic pressure measurements are made at four axial locations at the bottom of individual holes of the rough plate and at facing locations in the smooth plate. The description of the test rig and instrumentation, and the procedure of testing and calculation are explained in detail in Kheireddin in 2009 and Childs et al. in 2010. Three hole-pattern flat-plates with a hole-pattern diameter of 12.15 mm were tested having depths of 0.9, 1.9, and 2.9 mm. Tests were done with clearances at 0.254, 0.381, and 0.653 mm, and inlet pressures of 56, 70 and 84 bar for a range of pressure ratios, yielding a Reynolds-number range of 100,000 to 800,000. The effects of Reynolds number, clearance, inlet pressure, and hole depth on friction factor are studied. The data are compared to friction factor values of three hole-pattern flat-plates with 3.175 mm diameter holes with hole depths of 1.9, 2.6, and 3.302 mm tested in the same rig described by Kheireddin in 2009. The test program was initiated mainly to investigate a “friction-factor jump” phenomenon cited by Ha et al. in 1992 in test results from a flat-plate tester using facing hole-pattern plates where, at elevated values of Reynolds numbers, the friction factor began to increase steadily with increasing Reynolds numbers. Friction-factor jump was not observed in any of the current test cases.

Test Results for Liquid “Damper” Seals Using a Round-Hole Roughness Pattern for the Stators

1999 ◽  
Vol 121 (1) ◽  
pp. 42-49 ◽  
Author(s):  
Dara W. Childs ◽  
Patrice Fayolle
Keyword(s):  
Friction Factor ◽  
Round Hole ◽  
Test Results ◽  
Partial Explanation ◽  
Rotordynamic Coefficients ◽  
Stiffness Coefficients ◽  
Friction Factors ◽  
Direct Stiffness ◽  
Factor Data ◽  
Pressure Driven Flow

Test results are reviewed for two annular liquid seals (L = 34.9 mm; D = 76.5 mm) at two clearances (.1 and .12 mm). The seal stators use hole-pattern-roughened stators that are identical except for hole depths of .28 and 2.0 mm. Tests are conducted at three speeds out to 24,600 rpm and three pressures out to 68 bars. Test data consist of leakage rates and rotordynamic coefficients at centered and eccentric positions with static eccentricity ratios out to 0.5. Test results are consistent with expectations in regard to the reduction of cross-coupled stiffness coefficients due to stator roughness. However, the measured direct stiffness coefficients were unexpectedly low. A partial explanation for these results is provided by measured friction factor data which show an increase in the friction factors for pressure-driven flow with an increase in clearance. A prediction model for rotordynamic coefficients, incorporating the friction-factor data, predicted a substantial loss in direct stiffness but could not explain the very low (or negative) values that were measured. The model did explain the measured drop in cross coupled stiffness (k) and provides an alternative explanation to observed reductions in k values; specifically, an increase in the friction factor with increasing clearance causes a reduction in k irrespective of any parallel reduction in the average circumferential velocity.

Thermal and Friction Factor Data for Three Packed Block Construction Wavy Fin Surfaces

1994 ◽  
Vol 208 (3) ◽  
pp. 225-229 ◽  
Author(s):  
R J Gough BEng ◽  
T T Al-Shemmeri
Keyword(s):  
Reynolds Number ◽  
Heat Exchanger ◽  
Wind Tunnel ◽  
Friction Factor ◽  
Experimental Work ◽  
Performance Data ◽  
Wavy Surfaces ◽  
Block Construction ◽  
Factor Data

This paper describes an experimental work undertaken to determine performance data for packed block wavy fins. A purpose-built heat exchanger testing wind tunnel was used to investigate three wavy surfaces. The data were then presented in the form of Colburn (j) factors and friction (f) factors versus Reynolds number. Results showed a favourable comparison with published works pertaining to similar surface geometries; in addition, geometries were also tested which varied considerably from those in the literature to date.

Heat Transfer Enhancement in Air-Heating Flat-Plate Solar Collectors

1984 ◽  
Vol 106 (3) ◽  
pp. 358-363 ◽  
Author(s):  
Ye-Di Liu ◽  
L. A. Diaz ◽  
N. V. Suryanarayana
Keyword(s):  
Flat Plate ◽  
Friction Factor ◽  
Heated Plate ◽  
Plate Temperature ◽  
Air Heating ◽  
Pin Fins ◽  
Mass Flow Rates ◽  
Significant Temperature ◽  
Extended Surfaces ◽  
Flat Plate Solar Collector

The efficiency of an air-heating flat-plate solar collector can be increased by reducing the absorber plate temperature by providing it with extended surfaces. An experimental study was conducted to determine the temperature depression and the increase in friction factor, by providing a uniformly heated plate with pin fins. Data were obtained with three spacings of the fins for five mass flow rates of air and two values of heat flux. Significant temperature depressions can be obtained leading to increase in efficiency but these are acompanied by increases in friction factor. Employing different length scales and the concept of pumping power factor, it is shown that the data can be correlated by j = 1.018 Re−0.49 and Nu = 1.03 F0.19.

Friction Factor Behavior From Flat-Plate Tests of Smooth and Hole-Pattern Roughened Surfaces With Supply Pressures up to 84 bars

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Dara W. Childs ◽  
Bassem Kheireddin ◽  
Stephen Phillips ◽  
Thanesh Deva Asirvatham
Keyword(s):  
Flat Plate ◽  
Friction Factor ◽  
Dynamic Pressure ◽  
Pressure Oscillation ◽  
Reynolds Numbers ◽  
Test Facility ◽  
Pressure Measurements ◽  
Narrow Channels ◽  
Roughened Surface ◽  
Dynamic Pressure Measurements

A flat-plate tester was used to measure the friction factor behavior for a hole-pattern roughened surface apposed to a smooth surface. The tests were executed to characterize the friction factor behavior of annular seals that use a roughened-surface stator and a smooth rotor. Friction factors were obtained from measurements of the mass flow rate and static pressure measurements along the smooth and roughened surfaces. In addition, dynamic pressure measurements were made at four axial locations at the bottom of individual holes and at facing locations in the smooth plate. The test facility is described, and a procedure for determining the friction factor is reviewed. Three clearances were investigated: 0.635 mm, 0.381 mm, and 0.254 mm. Tests were conducted with air at three different inlet pressures (84 bars, 70 bars, and 55 bars), producing a Reynolds numbers range from 50,000 to 700,000. Three surface configurations were tested, including smooth-on-smooth, smooth-on-hole, and hole-on-hole. The hole-pattern plates are identical with the exception of the hole depth. For the smooth-on-smooth and smooth-on-hole configurations, the friction factor remains largely constant or increases slightly with increasing Reynolds numbers. The friction factor increases as the clearance between the plates increases. The test program was initiated to investigate a friction-factor jump phenomenon cited by Ha et al. (1992, “Friction-Factor Characteristics for Narrow-Channels With Honeycomb Surfaces,” Trans. ASME, J. Tribol., 114, pp. 714–721) in test results from a flat-plate tester where, at elevated values of Reynolds numbers, the friction factor began to increase steadily with increasing Reynolds numbers. They tested apposed honeycomb surfaces. For the present tests, the phenomenon was also observed for tests of apposed roughened surfaces but was not observed for smooth-on-smooth or smooth-on-rough configurations. When the phenomenon was observed, dynamic pressure measurements showed a peak-pressure oscillation at the calculated Helmholtz frequency of the holes.

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