scholarly journals Leakage Characteristic of Helical Groove Seal Designed in Reactor Coolant Pump

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Meng Zhang ◽  
Xiao-fang Wang ◽  
Sheng-li Xu ◽  
Shuo Yin
Keyword(s):  
Reynolds Number ◽  
High Pressure ◽  
Friction Factor ◽  
Helix Angle ◽  
Operation Condition ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Friction Factors ◽  
Helical Groove ◽  
Groove Seal

Helical groove seal is designed in reactor coolant pump to control the leakage along the front surface of the impeller face due to its higher resistance than the circumferentially grooved seal. The flow and the friction factors in helical groove seals are predicted by employing a commercial CFD code, FLUENT. The friction factors of the helical groove seals with helix angles varying from 20 deg to 50 deg, at a range of rotational speed and axial Reynolds number, were, respectively, calculated. For the helically grooved stator with the helix angle greater than 20 deg, the leakage shows an upward trend with the helix angle. The circumferentially grooved stator has a lower resistance to leakage than the 20 deg and 30 deg stators. It can be predicated that, for a bigger helix angle, the friction factor increases slightly with an increase in high axial Reynolds number, which arises from the high-pressure operation condition, and the friction factor is generally sensitive to changes in the helix angle in this operation condition. The study lays the theoretical foundation for liquid seal design of reactor coolant pump and future experimental study to account for the high-pressure condition affecting the leakage characteristic.

Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Henrique Stel ◽  
Rigoberto E. M. Morales ◽  
Admilson T. Franco ◽  
Silvio L. M. Junqueira ◽  
Raul H. Erthal ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Geometric Configurations ◽  
Corrugated Surfaces ◽  
Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

Frictional Pressure Drop in Micro-Channel

2004 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Hiroki Takahashi ◽  
Yoshiaki Ohno
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Frictional Pressure Drop ◽  
Turbulent Transition ◽  
Friction Factors ◽  
Turbulent Flow Regime ◽  
Form Pressure ◽  
Laminar And Turbulent Flow ◽  
Flow Through

The friction characteristics of water in a sub-millimeter scale channel were investigated experimentally. The friction factors and the critical Reynolds number were measured using water flow through circular tubes with diameters of 0.5, 0.25 and 0.17 mm. The experimental results show that the measured friction factor for water agreed well with the conventional Poiseuille (λ = 64/Re) and Blasius (λ = 0.316 Re−0.25) equations in laminar and turbulent flow regime; the laminar-turbulent transition Reynolds number was approximately 2300 for diameter 0.5 mm. For diameter 0.25 mm, the friction factor evaluated by the form pressure drop also agreed well with the Poiseuille equation. For diameter 0.17 mm, the measured total friction factor was close to the Poiseuille prediction.

Developing an Optimal Helix Angle As a Function of Pressure for Helical Groove Seals

2017 ◽  
Author(s):  
Cori Watson ◽  
Houston G. Wood
Keyword(s):  
High Pressure ◽  
Mass Flow ◽  
Helix Angle ◽  
Pressure Differential ◽  
Lower Pressure ◽  
Inlet Pressure ◽  
Circumferential Velocity ◽  
Labyrinth Seals ◽  
Screw Pump ◽  
Helical Groove

Helical groove seals are non-contacting annular seals used in pumps between impeller stages and at the balance drum. These seals have helically machined grooves on the surface of the rotor and/or stator. They work to sustain a pressure difference given a mass flow rate of the impeller through two flow phenomena which can be characterized by their flow direction. Fluid flowing axially dissipates kinetic energy through turbulent mixing as fluid is pushed through the jet stream region and mixes in the larger groove region, thus producing a pressure differential. Fluid flowing in the groove direction rotates with the rotor wall and is positively displaced toward the high pressure region, essentially acting as a screw pump. Previous work with optimization of helical groove seals has shown that the ideal helix angle of the seal is steeper for lower pressure applications and shallower for higher pressure applications. This is due to lower pressure applications having higher circumferential velocity in the grooves. In high pressure applications, the groove circumferential velocity has even been shown to be negative, and therefore the fluid leaks out the end of the grooves. The objective of this study is to use computational fluid dynamics simulations to find the optimal helix angle of the seal given the pressure differential. To accomplish this goal, simulations were run in ANSYS CFX for various inlet pressures, given zero gauge outlet pressure, and the helix angle of the grooves are varied. The helical grooves seals in this study have grooves on only the stator surface. The number of grooves is varied with the angle to keep the axial cross section of the seal consistent. By doing this, the study is able to focus in on the pumping mechanism of the helical groove seal without substantially changing the energy dissipation. The mass flow rates from each simulation for a given inlet pressure are plotted and quadratic regression was used to calculate an optimal helix angle as a function of inlet pressure. This study also answers the question of whether is there a limit where circumferentially grooved, i.e. labyrinth, seals outperform helical groove seals for very high pressures. Results comparing the powerloss of helical groove seals versus labyrinth seals and the effect of helix angle on powerloss are also given.

Laminar, Transitional and Turbulent Friction Factors for Gas Flows in Smooth and Rough Microtubes

2008 ◽  
Author(s):  
Marco Lorenzini ◽  
Gian Luca Morini ◽  
Sandro Salvigni
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Turbulent Regime ◽  
Turbulent Friction ◽  
Compressibility Effect ◽  
Flow Acceleration ◽  
Friction Factors ◽  
Macro Scale ◽  
Fully Developed Turbulent Flow ◽  
Microscale Transport

Theoretical and experimental works on microscale transport phenomena have been carried out in the past decade in the attempt to analyse possible new effects and to assess the influence of scaling on the classical correlations which are used in macro-scale heat and fluid flow, following the need to supply engineers with reliable correlations to be used in the design of micro-scale devices. These results were sometimes in mutual contrast, as is the case for the determination of the friction factor, which has been found to be lower, higher or comparable to that for macroscopic channels, depending on the researchers. In this work the compressible flow of nitrogen inside circular microchannels from 26 μm to 508 μm in diameter and with different surface roughness (<1%) is investigated for the whole range of flow conditions: laminar, transitional and turbulence. Over 5000 experimental data have been collected and analysed. The data confirmed that in the laminar regime the agreement with the conventional theory is very good in terms of friction factors both for rough and smooth microtubes. For the smaller microchannels (<100 μm) when Re is greater than 1300 the friction factor tends to deviate from the Poiseuille law because the flow acceleration due to compressibility effect gains in importance. The transitional regime was found to start no earlier than at values of the Reynolds number around 1800–2000. Both smooth and sudden changes in the flow regime have been found, as reported for conventional tubes. Fully developed turbulent flow was attained with both smooth and rough tubes, and the results for smooth tubes seem to confirm Blasius’s relation, while for rough tubes the Colebrook’s correlation is found to be only partially in agreement with the experimental friction factors. In the turbulent regime the dependence of the friction factor on the Reynolds number is less pronounced for microtubes with respect to the prediction of the Colebrook’s correlation and the friction factor tends only to depend on the microtube relative roughness.

An Experimental and Analytical Investigation of Friction Factors for Fully Developed Flow in Internally Finned Triangular Ducts

1986 ◽  
Vol 108 (3) ◽  
pp. 507-512 ◽  
Author(s):  
H. Chegini ◽  
S. K. Chaturvedi
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Analytical Investigation ◽  
Momentum Equation ◽  
Fully Developed Flow ◽  
Finite Difference Technique ◽  
Friction Factors ◽  
Experimental Values ◽  
Good Agreement

Friction factors for fully developed flow in triangular ducts with fins of various height and width are investigated for Reynolds numbers ranging from 150 to 90,000. Two triangular ducts having apex angles of 60 and 38.8 deg are studied. Results are presented in the form of standard plots of friction factor as a function of Reynolds number. Friction factor values for the smooth triangular duct cases are in good agreement with the existing results. For the finned-duct cases, the fully developed axial velocity profiles in laminar flow are determined by solving the x-momentum equation iteratively by the Gauss–Seidel finite-difference technique. The theoretically determined friction factors for these cases are in good agreement with the experimental values of friction factors based on pressure drop measurements.

An Experimental Investigation of Pressure Distributions in a Journal Bearing Operating in the Transition Regime

1986 ◽  
Vol 200 (4) ◽  
pp. 251-264 ◽  
Author(s):  
J B Roberts ◽  
P J Mason
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Journal Bearing ◽  
Transition Regime ◽  
Pressure Measurements ◽  
Eccentricity Ratio ◽  
Clearance Ratio ◽  
Viscosity Parameter ◽  
Pressure Distributions ◽  
Friction Factors

Experimental results are presented, relating to friction factors and circumferential pressure distributions, for a plain cylindrical journal bearing with a central circumferential inlet groove. The length-diameter ratio of each journal bearing land was 0.25 and the clearance ratio was 0.0031. The friction factor results showed the existence of a distinct ‘transition regime’, characterized by a pronounced ‘hump’ in the friction factor-Reynolds number relationship. Pressure measurements recorded when operating in this transition regime revealed the inadequacy of many existing ‘turbulent’ theories for superlaminar lubrication. By using a short-bearing theory a good correlation of the pressure distribution results was obtained, in terms of a non-dimensional viscosity parameter, kz, which is dependent on both the eccentricity ratio and Reynolds number. The magnitude of kz in this regime was considerably higher than the corresponding value for laminar flow, and was similar to the magnitude predicted from a simple theory based on relating kz to the variation of measured friction factor with Reynolds number.

scholarly journals Improvement of Reliability and Ecological Safety of NPP Reactor Coolant Pump Seals

2020 ◽  
pp. 47-55
Author(s):  
S. Shevchenko ◽  
O. Shevchenko
Keyword(s):  
High Pressure ◽  
Flow Characteristics ◽  
Environmental Safety ◽  
Mechanical Seal ◽  
Ecological Safety ◽  
Mechanical Seals ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Optimal Value ◽  
Contact Surfaces

The paper presents the analysis of existing designs of NPP reactor coolant pumps (RCP) rotor sealing systems. The most common design solutions of sealing units that provide the necessary tightness, reliability and service life under high pressure, temperature and sliding speeds typical for RCP, as well as trends for their improvement to increase tightness and environmental safety of activities were identified. Designs of impulse seals with a self-adjusting clearance are presented as the most promising assemblies for sealing pump shafts with high parameters. A computer model of impulse mechanical seal as an automatic control system is proposed. A framework for calculating impulse mechanical seals has been developed, allowing the choice of their main geometric parameters to ensure the optimal value of the mechanical clearance and the friction moment on the sealing contact surfaces. Expressions are obtained for constructing the static and flow characteristics of a impulse mechanical seal, the condition for its dynamic stability is determined. The paper presents the shaft sealing system of RCP, main nodes of which are several stages of impulse mechanical seals with a self-regulating clearance.

Pressure Drop and Heat Transfer of Nanofluid in Turbulent Pipe Flow Considering Particle Coagulation and Breakage

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Jian-Zhong Lin ◽  
Yi Xia ◽  
Xiao-Ke Ku
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Pipe Flow ◽  
Volume Concentration ◽  
Particle Diameter ◽  
Turbulent Pipe Flow ◽  
Particle Volume ◽  
Friction Factors

Numerical simulations of Al2O3/water nanofluid in turbulent pipe flow are performed with considering the particle convection, diffusion, coagulation, and breakage. The distributions of particle volume concentration, the friction factor, and heat transfer characteristics are obtained. The results show that the initial uniform distributions of particle volume concentration become nonuniform, and increase from the pipe wall to the center. The nonuniformity becomes significant along the flow direction from the entrance and attains a steady state gradually. Friction factors increase with the increase of particle volume concentrations and particle diameter, and with the decrease of Reynolds number. The friction factors increase remarkably at lower volume concentration, while slightly at higher volume concentration. The presence of nanoparticles provides higher heat transfer than pure water. The Nusselt number of nanofluids increases with increasing Reynolds number, particle volume concentration, and particle diameter. The rate increase in Nusselt number at lower particle volume concentration is more than that at higher concentration. For a fixed particle volume concentration, the friction factor is smaller while the Nusselt number is larger for the case with uniform distribution of particle volume concentration than that with nonuniform distribution. In order to effectively enhance the heat transfer using nanofluid and simultaneously save energy, it is necessary to make the particle distribution more uniform. Finally, the expressions of friction factor and Nusselt number as a function of particle volume concentration, particle diameter and Reynolds number are derived based on the numerical data.

Effect of Wetting on Friction Factors for Turbulent Flow of Mercury in Annuli

1976 ◽  
Vol 98 (1) ◽  
pp. 113-116 ◽  
Author(s):  
O. E. Dwyer ◽  
P. J. Hlavac ◽  
B. G. Nimmo
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Maximum Velocity ◽  
Outer Wall ◽  
Limited Range ◽  
Friction Factors ◽  
Fully Developed Turbulent Flow

Friction factors were determined for fully developed turbulent flow of mercury in smooth concentric annuli under conditions where either both walls were unwetted, or both were wetted, or the inner wall was wetted and the outer one unwetted. Three radius ratios (r2/r1) were used, i.e., 2.09, 2.78, and 4.00. Unwetted walls gave the lowest friction factors, which were practically independent of the r2/r1 ratio over the limited range tested. The factors were 10 ± 1 percent higher than the commonly accepted values for smooth pipes (at the same Reynolds number). The highest friction factors were obtained with the inner wall wetted and the outer wall unwetted, and the greater the r2/r1 ratio the greater was the effect. For example, at r2/r1 = 4.00, the friction factors were 9.9% greater than for the situation when both walls were unwetted. The wetting conditions affected the location of the radius of maximum velocity (rm); and it was found that the nearer rm approached r2, the higher was the friction factor.

Viscosity and Friction Factor of Aluminum Oxide–Water Nanofluid Flow in Circular Tubes

2013 ◽  
Vol 4 (2) ◽  
Author(s):  
Clement C. Tang ◽  
Sanjib Tiwari ◽  
Matthew W. Cox
Keyword(s):  
Reynolds Number ◽  
Aluminum Oxide ◽  
Friction Factor ◽  
Rheological Characterization ◽  
Nanofluid Flow ◽  
Circular Tubes ◽  
Fluid Behavior ◽  
Nanoparticle Dispersions ◽  
Friction Factors ◽  
Al2o3 Nanofluid

Experiments have been conducted to characterize the viscosity and friction factor of aluminum oxide (Al2O3) nanoparticle dispersions at 6 vol. % in water. Rheological characterization of the Al2O3 nanofluid has shown that it exhibits a Newtonian fluid behavior for the shear rate range of 6 to 122 s−1 at temperatures between 6 and 75 °C. Friction factor results of the nanofluid flowing through circular tubes of 1 m in length with different inner tube diameters (2.97 and 4.45 mm) were experimentally measured in the laminar and the onset of transition regions. The experimental results from this study indicate that, when the nanofluid properties are properly characterized, the friction factors of the Al2O3 nanofluid are largely in agreement with classical friction factor theory for single-phase flow. An early transition to turbulent flow is observed for the nanofluid flow at a Reynolds number of approximately 1500, when compared with water flow where transition occurs at the textbook Reynolds number of roughly 2300.

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