The Relation between the Coefficient of Friction and Pressure Drop by Using the Different Reynolds Number in a Circular Tube

In a system of rigid tubes under steady flow conditions, the coefficient of friction [CF = 2 delta P/(rho V2/A2)] (where delta P is pressure drop, rho is density, V is flow, and A is cross-sectional area) should be a unique function of Reynolds' number (Re). Recently it has been shown that at any given Re, the value of CF using transpulmonary pressure (PL) was lower when breathing He-O2 compared with air (Lisboa et al., J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 48: 878–885, 1980). One explanation for this discontinuity is that PL includes the pressure drop due to tissue viscance, which is independent of V, and thus would lead to an overestimate of CF on air compared with He-O2 at any Re. We tested this hypothesis by measuring V related to alveolar pressure, rather than PL, in normal subjects breathing air, He-O2, and SF6-O2. In each subject, for a given Re, CF was greatest breathing SF6-O2 and lowest breathing He-O2, similar to results using PL. Thus tissue viscance is not the sole cause of the discontinuous plot of CF vs. Re, and this phenomenon must be due to other factors, such as changing geometry or nonsteady behavior.

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CFD Study of Liquid Sodium inside a Wavy Tube for Laminar Convectors: Effect of Reynolds Number, Wave Pitch, and Wave Amplitude

Mathematical Problems in Engineering ◽

10.1155/2016/6146195 ◽

2016 ◽

Vol 2016 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Syed Murtuza Mehdi ◽

Maaz Akhtar ◽

Ahmad Hussain ◽

Dheya Shuja Alothmany ◽

Shahid Aziz

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Pressure Drop ◽

Liquid Metal ◽

Wave Amplitude ◽

Circular Tube ◽

Liquid Sodium ◽

Heat Output

Metallic tubes have been widely used as primary heat transfer elements in laminar convectors for domestic and aerospace heating purpose. This paper uses CFD tool to investigate the heat output and pressure drop of liquid sodium flowing inside a circular tube having a wavy profile throughout its length. The wavy tube can be utilized in laminar liquid metal convectors as basic heat transfer element. The effect of Reynolds number (500≤Re≤2000) wave pitch (25 mm≤λ≤100 mm) and wave amplitude (2 mm≤a≤6 mm) on the heat output and pressure drop has been numerically studied. Based on the CFD results important controlling parameters have been identified and it is concluded that the heat output from the wavy tube is affected by the wave pitch and the wave amplitude while the pressure drop is mostly affected by the Reynolds number and wave amplitude.

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Thermal Performance in Circular Tube with Co/Counter-Twisted Tapes

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.931-932.1198 ◽

2014 ◽

Vol 931-932 ◽

pp. 1198-1202 ◽

Cited By ~ 3

Author(s):

Suriya Chokphoemphun ◽

Chayodom Hinthao ◽

Smith Eiamsa-ard ◽

Pongjet Promvonge ◽

Chinaruk Thianpong

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Reynolds Number ◽

Nusselt Number ◽

Pressure Drop ◽

Circular Tube ◽

Experimental Results ◽

Enhanced Heat Transfer ◽

Twisted Tapes ◽

Twist Ratio

Thiswork presents an experimental study on enhanced heat transfer and pressure loss characteristics in a tube having a uniform heat-fluxed wall by using small double and triple co-and counter-twisted tapes at two twist ratios, y/w=4 and 4.5. The investigation has been conducted for Reynolds number from 5300-20,000. The experimental results of the heat transfer and pressure drop are proposed in terms of Nusselt number and friction factor, respectively.The experimental results reveal thatthe maximum TEF for the triple counter-twisted tapesat smaller twist ratio isabout 1.26.

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Laminar Pressure Drop Associated With the Continuum Entrance Region and for Slip Flow in a Circular Tube

Journal of Applied Mechanics ◽

10.1115/1.3627314 ◽

1965 ◽

Vol 32 (4) ◽

pp. 765-770 ◽

Cited By ~ 10

Author(s):

S. T. McComas ◽

E. R. G. Eckert

Keyword(s):

Reynolds Number ◽

Pressure Drop ◽

Circular Tube ◽

Slip Flow ◽

Mean Free Path ◽

Entrance Region ◽

Absolute Pressure ◽

Fully Developed Flow ◽

Number Range ◽

A Value

The pressure drop in the entrance region of an abrupt inlet circular tube was determined experimentally. Local values of K, the dimensionless factor for laminar flow which expresses the excess of pressure drop over that of fully developed flow, were determined for the Reynolds range from 200 to 600. Variations in absolute pressure were used at each Reynolds number in order to produce different bulk velocities. The results for this Reynolds number range agreed with the analyses for smooth entrance tubes, and no dependency on bulk velocity was observed. The absolute pressure of the test section was also reduced sufficiently to obtain a large mean free path for air, thus producing a slip effect at the tube wall. Pressure-drop measurements were made for a Knudsen number range of 0.001 to 0.07, and the slip-flow correction was determined in this range. The data agreed well with Kennard’s prediction for slip flow in a tube if a value of 0.9 was used for the diffuse factor.

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Measurements of Friction in a Pipe for Subsonic and Supersonic Flow of Air

Journal of Applied Mechanics ◽

10.1115/1.4009532 ◽

1946 ◽

Vol 13 (2) ◽

pp. A91-A100 ◽

Cited By ~ 1

Author(s):

J. H. Keenan ◽

E. P. Neumann

Keyword(s):

Boundary Layer ◽

Reynolds Number ◽

Mach Number ◽

Supersonic Flow ◽

Coefficient Of Friction ◽

Reynolds Numbers ◽

The Coefficient Of Friction ◽

Mach Numbers ◽

Pipe Inlet ◽

Oblique Shocks

Abstract The apparent friction coefficient was determined experimentally for the flow of air through smooth pipes at subsonic and supersonic velocities. Values of the Mach number ranged from 0.27 to 3.87, and of Reynolds number from 1 × 105 to 8.7 × 105. In supersonic flow the results were found to be strongly influenced by the presence of oblique shocks formed at the junction of nozzle and pipe. The effect of these shocks on the coefficient of friction was determined. Nozzle forms were devised which eliminated the shocks and their effects. It was found that at distances from the pipe inlet greater than 50 diam the apparent coefficient of friction for compressible flow at Mach numbers greater or less than 1 is approximately equal, for equal Reynolds numbers, to the coefficient of friction for incompressible flow with completely developed boundary layer. Mach numbers greater than 1 are rarely maintained for lengths greater than 50 diam. For attainable lengths, the coefficient of friction is a function of the ratio of length to diameter and the Reynolds number, with the Mach number at entrance determining the maximum attainable length.

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Effect of Liquid Reynolds Number on Pressure Drop of Evaporative R-290 in 500µm Circular Tube

International Journal of Technology ◽

10.14716/ijtech.v8i5.867 ◽

2017 ◽

Vol 8 (5) ◽

pp. 851

Author(s):

Sentot Novianto ◽

Agus S. Pamitran ◽

Raldi Koestoer ◽

Jong-Taek Oh ◽

Kiyoshi Saito

Keyword(s):

Reynolds Number ◽

Pressure Drop ◽

Circular Tube

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Light conveyor belts. Determination of the coefficient of friction

10.3403/30106633u ◽

2015 ◽

Keyword(s):

Coefficient Of Friction ◽

The Coefficient Of Friction ◽

Conveyor Belts

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Experimental Investigation of aluminum doping crumb rubber/epoxy composite in reciprocating motion

Journal of Communications Technology Electronics and Computer Science ◽

10.22385/jctecs.v3i0.12 ◽

2015 ◽

Vol 3 ◽

pp. 1

Author(s):

Goutam Chandra Karar ◽

Nipu Modak

Keyword(s):

Experimental Investigation ◽

Coefficient Of Friction ◽

Epoxy Composite ◽

Normal Load ◽

Crumb Rubber ◽

The Other ◽

Reciprocating Motion ◽

Molding Process ◽

Friction Tester ◽

The Coefficient Of Friction

The experimental investigation of reciprocating motion between the aluminum doped crumb rubber /epoxy composite and the steel ball has been carried out under Reciprocating Friction Tester, TR-282 to study the wear and coefficient of frictions using different normal loads (0.4Kg, 0.7Kgand1Kg), differentfrequencies (10Hz, 25Hz and 40Hz).The wear is a function of normal load, reciprocating frequency, reciprocating duration and the composition of the material. The percentage of aluminum presents in the composite changesbut the other components remain the same.The four types of composites are fabricated by compression molding process having 0%, 10%, 20% and 30% Al. The effect of different parameters such as normal load, reciprocating frequency and percentage of aluminum has been studied. It is observed that the wear and coefficient of friction is influenced by the parameters. The tendency of wear goes on decreasing with the increase of normal load and it is minimum for a composite having 10%aluminum at a normal load of 0.7Kg and then goes on increasing at higher loads for all types of composite due to the adhesive nature of the composite. The coefficient of friction goes on decreasing with increasing normal loads due to the formation of thin film as an effect of heat generation with normal load.

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Tribological Aspects, Optimization and Analysis of Cu-B-CrC Composites Fabricated by Powder Metallurgy

Materials ◽

10.3390/ma14154217 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4217

Author(s):

Üsame Ali Usca ◽

Mahir Uzun ◽

Mustafa Kuntoğlu ◽

Serhat Şap ◽

Khaled Giasin ◽

...

Keyword(s):

Weight Loss ◽

Wear Rate ◽

Coefficient Of Friction ◽

Applied Load ◽

Practical Significance ◽

Tribological Characteristics ◽

M 10 ◽

Wide Range ◽

The Coefficient Of Friction ◽

Four Levels

Tribological properties of engineering components are a key issue due to their effect on the operational performance factors such as wear, surface characteristics, service life and in situ behavior. Thus, for better component quality, process parameters have major importance, especially for metal matrix composites (MMCs), which are a special class of materials used in a wide range of engineering applications including but not limited to structural, automotive and aeronautics. This paper deals with the tribological behavior of Cu-B-CrC composites (Cu-main matrix, B-CrC-reinforcement by 0, 2.5, 5 and 7.5 wt.%). The tribological characteristics investigated in this study are the coefficient of friction, wear rate and weight loss. For this purpose, four levels of sliding distance (1000, 1500, 2000 and 2500 m) and four levels of applied load (10, 15, 20 and 25 N) were used. In addition, two levels of sliding velocity (1 and 1.5 m/s), two levels of sintering time (1 and 2 h) and two sintering temperatures (1000 and 1050 °C) were used. Taguchi’s L16 orthogonal array was used to statistically analyze the aforementioned input parameters and to determine their best levels which give the desired values for the analyzed tribological characteristics. The results were analyzed by statistical analysis, optimization and 3D surface plots. Accordingly, it was determined that the most effective factor for wear rate, weight loss and friction coefficients is the contribution rate. According to signal-to-noise ratios, optimum solutions can be sorted as: the highest levels of parameters except for applied load and reinforcement ratio (2500 m, 10 N, 1.5 m/s, 2 h, 1050 °C and 0 wt.%) for wear rate, certain levels of all parameters (1000 m, 10 N, 1.5 m/s, 2 h, 1050 °C and 2.5 wt.%) for weight loss and 1000 m, 15 N, 1 m/s, 1 h, 1000 °C and 0 wt.% for the coefficient of friction. The comprehensive analysis of findings has practical significance and provides valuable information for a composite material from the production phase to the actual working conditions.

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