A New Friction Factor Model and Entrance Loss Coefficient for Honeycomb Annular Gas Seals

1999 ◽  
Vol 122 (3) ◽  
pp. 622-627 ◽  
Author(s):  
Amro M. Al-Qutub ◽  
D. Elrod ◽  
Hugh W. Coleman
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Uncertainty Analysis ◽  
Friction Factor ◽  
Factor Model ◽  
Loss Coefficient ◽  
Curve Fit ◽  
Honeycomb Seals ◽  
Gas Seals ◽  
Number Curve

A new experimental friction factor model for a honeycomb surface was developed using a static seal tester. Three clearances and three lengths were tested for the seals, and Reynolds number ranged from 3000 to 49,000. It was found that the friction factor was a function of Reynolds number and seal clearance only. The clearance effect was dominant and the friction factor was found to increase with increased clearance. A new uncertainty analysis was developed for the experimental friction factor when calculating friction factor using Mach number curve fit. The entrance loss coefficient was found to be constant for both smooth and honeycomb seals. The entrance loss coefficient of Honeycomb seals was found to be 50 percent higher than that of smooth seals. [S0742-4787(00)02102-0]

A Study of the Fabrication and Analysis of Micro Diffuser/Nozzles

2003 ◽  
Author(s):  
Kai-Shing Yang ◽  
Ing-Young Chen ◽  
Bor-Yuan Shew ◽  
Chi-Chuan Wang
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Pressure Loss ◽  
Measured Data ◽  
Loss Coefficient ◽  
Opening Angle ◽  
Velocity Change ◽  
Pressure Loss Coefficient ◽  
Micro Nozzle ◽  
Volumetric Flowrate

In this study, an analysis of the performance of micro nozzle/diffusers is performed and fabrication of the micro nozzle/diffuser is conducted and tested. It is found that the pressure loss coefficient for the nozzle/diffuser decreases with the Reynolds number. At a given Reynolds number, the pressure loss coefficient for nozzle is higher than that of the diffuser due to considerable difference in the momentum change. For the effect of nozzle/diffuser length on the pressure loss coefficient, it is found that the influence is rather small. At a fixed volumetric flowrate, a “minimum” phenomenon of the pressure loss coefficient vs. nozzle/diffuser depth is encountered. This is related to the interactions of velocity change and friction factor. Good agreements of the measured data with the predicted results are found in this study except at a diffuser having an opening angle of 20° . It is likely that the departure of this case to the prediction is due to the separation phenomenon in a larger angle of the diffuser.

An Entrance Region Friction Factor Model Applied to Annular Seal Analysis: Theory Versus Experiment for Smooth and Honeycomb Seals

1989 ◽  
Vol 111 (2) ◽  
pp. 337-343 ◽  
Author(s):  
D. Elrod ◽  
C. Nelson ◽  
D. Childs
Keyword(s):  
Friction Factor ◽  
Factor Model ◽  
Experimental Results ◽  
Entrance Region ◽  
Analysis Theory ◽  
Annular Seal ◽  
Theory Versus ◽  
Direct Stiffness ◽  
Honeycomb Seals

A friction factor model is developed for the entrance-region of a duct. The model is used in an annular gas seal analysis similar to Nelson’s (1984). Predictions of the analysis are compared to experimental results for a smooth-stator/smooth-rotor seal and three honeycomb-stator/smooth-rotor seals. The model predicts leakage and direct damping well. The model overpredicts the dependence of cross-coupled stiffness on fluid prerotation. The model predicts direct stiffness poorly.

An Alternative (Preferable) Friction Factor

2006 ◽  
Author(s):  
Richard A. Gaggioli
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Pipe Flow ◽  
Incompressible Flows ◽  
Flow Regimes ◽  
Relative Roughness ◽  
Curve Fit ◽  
Moody Diagram ◽  
Approximate Formulas

An alternative to the traditional friction factor for pipe flow is presented (φ = [R]f). For incompressible flows, the correlation of this new friction factor with Reynolds Number [R] and Relative Roughness [ε] is presented graphically, and appears much simpler and more intuitive than the Moody Diagram (or other equivalents). Moreover, relatively simple curve-fit formulas for representing φ explicitly as a function of R and ε are presented for various flow regimes, along with measures of error associated with these approximate formulas.

Simulation of Compressible and Incompressible Flows Through Planar and Axisymmetric Abrupt Expansions

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Ali Nouri-Borujerdi ◽  
Ardalan Shafiei Ghazani
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Loss ◽  
Incompressible Flows ◽  
Splitting Method ◽  
Expansion Ratio ◽  
Loss Coefficient ◽  
Turbulent Regime ◽  
Reattachment Length ◽  
Pressure Loss Coefficient

In this paper, compressible and incompressible flows through planar and axisymmetric sudden expansion channels are investigated numerically. Both laminar and turbulent flows are taken into consideration. Proper preconditioning in conjunction with a second-order accurate advection upstream splitting method (AUSM+-up) is employed. General equations for the loss coefficient and pressure ratio as a function of expansion ratio, Reynolds number, and the inlet Mach number are obtained. It is found that the reattachment length increases by increasing the Reynolds number. Changing the flow regime to turbulent results in a decreased reattachment length. Reattachment length increases slightly with a further increase in Reynolds number. At a given inlet Mach number, the maximum value of the ratio of the reattachment length to step height occurs at the expansion ratio of about two. Moreover, the pressure loss coefficient is a monotonic increasing function of expansion ratio and increases drastically by increasing Mach number. Increasing inlet Mach number from 0.1 to 0.2 results in an increase in pressure loss coefficient by less than 5%. However, increasing inlet Mach number from 0.4 to 0.6 results in an increase in loss coefficient by 70–100%, depending on the expansion ratio. It is revealed that increasing Reynolds number beyond a critical value results in the loss of symmetry for planar expansions. Critical Reynolds numbers change adversely to expansion ratio. The flow regains symmetry when the flow becomes turbulent. Similar bifurcating phenomena are observed beyond a certain Reynolds number in the turbulent regime.

Local Friction Factor of Compressible Laminar or Turbulent Flow in Micro-Tubes

2011 ◽  
Author(s):  
Shintaro Murakami ◽  
Yutaka Asako
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Numerical Procedure ◽  
Choked Flow ◽  
Curvilinear Grid ◽  
Wide Range ◽  
Darcy Friction Factor ◽  
Fanning Friction Factor

Laminar/turbulent flows of compressible fluid in microtubes were simulated numerically to obtain the effect of compressibility on the local pipe friction factors. For gaseous flows, the effect of compressibility had not been clarified except for laminar flow whose Mach number is less than 0.45, so the present work extended this to handle higher speed flows including choked ones and turbulent flows. The numerical procedure based on arbitrary-Lagrangian-Eulerian method solves two-dimensional compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was adopted to calculate eddy viscosity coefficient and turbulence energy. The physical domain of simulation with the back region downstream from the outlet of the micro-tube was used to be able to calculate the case of under-expansion flow in the tube. The orthogonal curvilinear grid was used for the computational mesh to obtain accurate results. The computations were performed for a wide range of Reynolds number and Mach number including laminar/turbulent choked flows. It was found that in laminar regimes the ratio of the Darcy friction factor to its conventional (incompressible flow’s) value is a function of Mach number and the same goes for the Fanning friction factor. On the other hand, in turbulent regimes, the ratio is still a function of Mach number for the Darcy friction factor but is equal to about unity for the Fanning friction factor. Namely, the Fanning friction factor of gaseous flow in micro-tubes coincides with Blasius formula, even when Mach number is not small and compressibility effect appears. This fact can be seen in choked flow.

Experimental investigation of fluid flow in long rectangular micro-channels

2005 ◽  
Vol 219 (3) ◽  
pp. 227-235 ◽  
Author(s):  
R Rathnasamy ◽  
J H Arakeri ◽  
K Srinivasan
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Factor Versus ◽  
Steel Substrate ◽  
Liquid Mixtures ◽  
Turbulent Regime ◽  
Micro Channels ◽  
Measured Flow ◽  
Number Curve ◽  
Geometry Parameter

The objective of this paper is to report new data for flow of gases, liquids, and liquid mixtures in 11 m long micro-channels. Three test sections of the following dimensions (a) 1.5 mm deep × 0.75 mm wide (MC1), (b) 0.5 mm deep × 0.95 mm wide (MC2), and (c) 0.3 mm deep × 1.0 mm wide (MC3) were cut in a serpentine form on a stainless steel substrate. The gases studied were air, nitrogen, and oxygen. The liquids used were ethanol, methanol, and their mixtures. The measured flow rate and pressure drop were used to evaluate friction factors in the micro-channels. Analysis of friction factor versus Reynolds number relation shows a perceptible dependence on channel dimensions. Transitions to turbulent regime were identified by a change in slope of friction factor versus Reynolds number curve. Transitions were mild and occurred at lower Reynolds numbers than in normal channels. The results are interpreted in terms of a channel geometry parameter.

Numerical Simulation of Gaseous Flow Characterstics in Microchannels

2007 ◽  
Author(s):  
Tiantian Zhang ◽  
Li Jia
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Mach Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Incompressible Flow ◽  
Flow Characteristics ◽  
Heating Effect ◽  
Gaseous Flow ◽  
Nitrogen Flows

Flow characteristics of nitrogen flows in the three different microchannels (hydraulic diameter Dh ranging 30–3000 μm) have been investigated numerically considering of the effect of compressibility and viscosity heating. It indicated that pressure drop at inlet and outlet is nonlinear with Reynolds number. Transition Re is as low as about 1200 for microchannels with Dh = 300 μm. To incompressible flow, Dh, has no effect on friction factor f. However, L/Dh has great effect on f, and f increases with the decrease of L/Dh. It was found from numerical results that fRe can be expressed as a function of Mach number. By compared with the experimental results, the function has been proved right. When pressure drop at inlet and outlet is over 10kPa, the effect of compressibility could not be neglected. This implies that the effect of compressibility in microchannels can be described better by pressure drop at inlet and outlet than Ma, which is in contrast to the practice in the conventional scale. At last, the viscosity heating effect was simply analyzed. It was found that the effect of viscosity heating increases with the increase of Re and decrease of size.

Gas flow in micro-channels

1995 ◽  
Vol 284 ◽  
pp. 257-274 ◽  
Author(s):  
John C. Harley ◽  
Yufeng Huang ◽  
Haim H. Bau ◽  
Jay N. Zemel
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Friction Factor ◽  
Theoretical Investigation ◽  
Gas Flow ◽  
Slip Flow ◽  
First Order ◽  
Micro Channels ◽  
Theoretical Predictions ◽  
Good Agreement

An experimental and theoretical investigation of low Reynolds number, high subsonic Mach number, compressible gas flow in channels is presented. Nitrogen, helium, and argon gases were used. The channels were microfabricated on silicon wafers and were typically 100 μm wide, 104 μm long, and ranged in depth from 0.5 to 20 μm. The Knudsen number ranged from 10-3 to 0.4. The measured friction factor was in good agreement with theoretical predictions assuming isothermal, locally fully developed, first-order, slip flow.

Frictional Flow Properties of Coal-Oil Slurries at Low Reynolds Number

1986 ◽  
Vol 108 (3) ◽  
pp. 211-213
Author(s):  
E. W. Beans ◽  
K. C. Masiulaniec
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Particle Distribution ◽  
Reynolds Numbers ◽  
Loss Coefficient ◽  
Flow Properties ◽  
Pressure Loss Coefficient ◽  
Mass Fractions ◽  
Established Relationship

The pipe friction factor (f) and the pressure loss coefficient for a 90-deg EL (K90) were measured for coal-oil slurries at Reynolds numbers less than 100. A range of mass fractions (0 to 0.4) was examined for a single particle distribution. The pipe friction factor correlated well with the established relationship for laminar flow (f = 64/ReD) where Reynolds number is based on slurry properties. The loss coefficient for the elbow has a similar correlation.

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