A Unifying Method for Sizing Throttling Valves Under Laminar or Transitional Flow Conditions

1993 ◽  
Vol 115 (1) ◽  
pp. 166-169
Author(s):  
H. D. Baumann
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Prediction Method ◽  
Head Loss ◽  
Transitional Flow ◽  
Velocity Head ◽  
Reasonable Accuracy ◽  
Flow Conditions ◽  
Head Loss Coefficient

The mass flow passing through a given valve will decrease in Reynolds number ranges below approximately 10,000 due to the transition from fully developed turbulent to laminar flow. The objective of this study is to provide a uniform prediction method to establish, with reasonable accuracy, the ratio between the turbulent and transitional or laminar flow rate passing through a given valve, taking into account the valve’s hydraulic diameter and the initial turbulent velocity head loss coefficient. Experimental data from prior research tends to support a proposed “unified sizing method” that is applicable for all single-stage valves regardless of size or type.

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

Laminar and transitional flow of drilling muds and various suspensions in circular tubes

1967 ◽  
Vol 30 (3) ◽  
pp. 449-464 ◽  
Author(s):  
Bernard Le Fur ◽  
Madeleine Martin
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Rheological Behaviour ◽  
Simple Expression ◽  
Transitional Flow ◽  
Transition Flow ◽  
Flow Rates ◽  
Circular Tubes ◽  
Head Losses ◽  
Drilling Muds

Most suspensions exhibit a rheological behaviour which cannot be represented by either Bingham's or Ostwald–De Waele's law. In studying such cases a very simple expression with only three parameters may be used. Starting with an intermediate law of this sort, this paper gives velocity profiles and head losses in laminar flow, which have been computed and plotted on diagrams in non-dimensional co-ordinates.It has been found that transition flow rates in circular tubes for data taken from the literature and from experiments conducted on drilling muds at the Institut Français du Pétrole, are efficiently predicted by an empirical criterion (Ryan & Johnson 1959) which establishes a relation between a generalized Reynolds number and a generalized Hedström number.

A Study of Flow of Plastics Through Pipes

1946 ◽  
Vol 13 (2) ◽  
pp. A101-A105
Author(s):  
R. C. Binder ◽  
J. E. Busher
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Friction Coefficient ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Dynamic Viscosity ◽  
Apparent Viscosity ◽  
Turbulent Viscosity ◽  
Yield Value

Abstract The pipe friction coefficient for true fluids is usually expressed as a function of Reynolds number. This method of organizing data has been extended to tests on the flow of different suspensions which behaved as ideal plastics in the laminar-flow range and as true fluids in the turbulent-flow range. In the laminar-flow range, Reynolds number below about 2100, the denominator in Reynolds number is taken as the apparent viscosity. The apparent viscosity can be determined from the yield value and the coefficient of rigidity. In the turbulent-flow range, the denominator in Reynolds number is an equivalent or turbulent viscosity equal to the dynamic viscosity of a true fluid having the same friction coefficient, velocity, diameter, and density as that of the plastic. The various experimental data on plastics correlate well with this extension of the method for true fluids.

scholarly journals Local head loss caused in connections used in micro-irrigation systems

2019 ◽  
Vol 23 (7) ◽  
pp. 492-498 ◽  
Author(s):  
Wagner W. Á. Bombardelli ◽  
Antonio P. de Camargo ◽  
José A. Frizzone ◽  
Rogério Lavanholi ◽  
Hermes S. da Rocha
Keyword(s):  
Flow Rate ◽  
Head Loss ◽  
International Standards ◽  
Flow Conditions ◽  
Irrigation Systems ◽  
Head Losses ◽  
Satisfactory Performance ◽  
Head Loss Coefficient ◽  
Micro Irrigation ◽  
The One

ABSTRACT Information about local head loss caused by connections employed in micro-irrigation systems is hard to be found in literature. The objective of this research was to experimentally determine the local head losses in connections commonly used in micro-irrigation and propose mathematical models using the theorem of Buckingham. The methodology of tests was based on international standards. The tests were carried out under controlled inlet pressure, at 150 kPa, and five to ten units of each connection model were tested. The curves relating flow and head losses were drawn based on 15 flow conditions, obtained under increase and decrease of flow rate. For each condition, 30 points were collected resulting in a sample size of 900 points in each test. For each connection model evaluated, the following information was obtained: curves of local head loss as a function of flow rate and of local head loss coefficient (KL). The obtained values of KL ranged from 2.72 to 24.16, which become constant for Reynolds number higher than 10,000. The sensitivity of the coefficient related to a ratio of the internal sections in the connections was also verified. The flow exponents presented values close to the one applied by the Darcy-Weisbach equation (m = 2). The models developed for the connections presented a satisfactory performance.

scholarly journals Challenging low Reynolds - SWT blade aerodynamics

2018 ◽  
Vol 234 ◽  
pp. 01004 ◽  
Author(s):  
Damian Kądrowski ◽  
Michał Kulak ◽  
Michał Lipian ◽  
Małgorzata Stępień ◽  
Piotr Baszczyński ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Model Performance ◽  
Transitional Flow ◽  
Flow Conditions ◽  
Scaled Model ◽  
Low Wind Speed ◽  
Speed Flow ◽  
Low Reynolds ◽  
Manufacturing Techniques

One of the main issues related to the design and development of small wind turbines (SWTs) is the low Reynolds number. Operation in the transitory regime makes the rotor aerodynamic analysis a challenging task. Project GUST (Generative Urban Small Turbine) realized currently at the Institute of Turbomachinery (Lodz University of Technology, Poland) is devoted to the development of SWT (D = 1.6 m) for low-Reynolds number (low wind speed) flow conditions. The emphasis is on the blade design, aiming at improving the rotor aerodynamic efficiency. The paper will highlight the rotor design process, based on contemporary methods of experiment-simulation integration approach and use of rapid manufacturing techniques. In-house wind tunnel measurements of a scaled model performance were executed. A numerical analysis using dedicated software (QBlade) was conducted in parallel. A comparison between the obtained results indicated that the chosen numerical tools are capable of providing a reliable output, even in complex, transitional flow conditions. Bearing in mind the above observations, QBlade was incorporated into the development process of a completely new blade geometry which would increase rotor performance. The selected design has indeed prove to show better power outcome in an additional experimental campaign.

scholarly journals An improved algebraic model for by-pass transition for calculation of transitional flow in pipe and parallel-plate channels

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1123-1131
Author(s):  
Konrad Nering ◽  
Kazimierz Rup
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Turbulence Intensity ◽  
Parallel Plate ◽  
Algebraic Model ◽  
Transitional Flow ◽  
Internal Flows ◽  
Fully Developed Flow ◽  
Turbulent Transition ◽  
Plate Channel

Modified algebraic intermittency model developed by E. Dick and S. Kubacki was used to describe laminar-turbulent transition. In this work a modification of this model was made for simulating internal flows in pipes and parallel-plate channel. In particular, constants present in this model were modified. These modified constants are the same for different flows in pipes and parallel-plate channels. In this work, a dependence of friction factor on Reynolds number and turbulence intensity were determined as well as the localization of laminar breakdown and fully developed flow. Obtained results were compared with theoretical and experimental data presented in the literature.

Water Single-Phase Fluid Flow and Heat Transfer in Capillary Tubes

2003 ◽  
Author(s):  
A. Bucci ◽  
G. P. Celata ◽  
M. Cumo ◽  
E. Serra ◽  
G. Zummo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Heat Transfer Correlations ◽  
Good Agreement

This paper reports the results of an experimental investigation of fluid flow and single-phase heat transfer of water in stainless steel capillary tubes. Three tube diameters are tested: 172 μm, 290 μm and 520 μm, while the Reynolds number varying from 200 up to 6000. Fluid flow experimental results indicate that in laminar flow regime the friction factor is in good agreement with the Hagen-Poiseuille theory for Reynolds number below 800–1000. For higher values of Reynolds number, experimental data depart from the Hagen-Poiseuille law to the side of higher f values. The transition from laminar to turbulent regime occurs for Reynolds number in the range 1800–3000. This transition is found in good agreement with the well known flow transition for rough commercial tubes. Heat transfer experiments show that heat transfer correlations in laminar and turbulent regimes, developed for conventional size tubes, are not adequate for calculation of heat transfer coefficient in microtubes. In laminar flow the experimental values of heat transfer coefficient are generally higher than those calculated with the classical correlation, while in turbulent flow regime experimental data do not deviate significantly from classical heat transfer correlations. Deviation from classical heat transfer correlations increase as the channel diameter decrease.

Experimental Study on the Leakage and Rotordynamic Coefficients of a Long Smooth Seal at Laminar Flow Conditions

2018 ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Laminar Flow ◽  
Transitional Flow ◽  
Radial Clearance ◽  
Inlet Temperature ◽  
Test Results ◽  
Flow Conditions ◽  
Transitional Regime ◽  
Pump Design ◽  
Flow Friction ◽  
Laminar Flow Conditions

This paper experimentally investigates the performance of a long smooth seal (length-diameter ratio L/D = 0.65 and radial clearance Cr = 0.140 mm) under laminar flow conditions. Tests are carried out at shaft speeds ω up to 10 krpm, pressure drops PD up to 48.3 bars, exit pressure Pe = 6.9 bars, and inlet temperature Ti = 39.4 °C. The seal is centered. Since there is no validated friction formula published for a liquid seal in the transitional regime, this paper uses San Andrés’s bulk-flow model with laminar-flow friction formula to produce predictions. Test results show that under laminar flow conditions, increasing ω decreases measured direct stiffness K, increases measured cross-coupled stiffness k, barely changes measured direct damping C, and generally increases measured cross-coupled damping c. The model correctly predicts these trends, and the predictions of K, k, C, and c are reasonably close to test results. Measured direct virtual-mass M values are normally larger than predictions. This paper also judges two cases with high PD or high ω to be in the transitional regime. For these cases, the predictions of K, k, C, and c based on the laminar-flow friction formula are significantly different from test results. This discrepancy further strengthens the judgment that the flow in these cases is transitional. For all test cases, measured leakage mass flow rate ṁ and measured effective damping Ceff are not sensitive to changes in ω, but increase as PD increases. The model with the laminar-flow friction formula adequately predicts ṁ and Ceff even when the flow within the seal annulus is at the start of the transitional flow regime. Also, Ceff predictions are lower than test results, allowing a safe margin for the pump design.

Experimental and Computational Study of Heat/Mass Transfer and Flow Structure for Four Dimple Shapes in a Square Internal Passage

2009 ◽  
Author(s):  
Fuguo Zhou ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Heat Mass Transfer ◽  
Computational Study ◽  
Computational Results ◽  
Flow Conditions ◽  
Naphthalene Sublimation ◽  
Sublimation Method

Mass/heat transfer measurements are made using the naphthalene sublimation method in a square internal passage where one wall has a single dimple. Four types of dimple shapes are studied: square, triangular, circular and teardrop. Sherwood numbers are obtained both inside and around the dimples. Measurements are made at a Reynolds number of 21,000. In addition, computations are performed for the same dimple geometries, and with the same flow conditions as in the experiments. Flow patterns for the four dimples are identified, and heat transfer distributions for each dimple are obtained. Computational results are compared with the experimental data and show satisfactory agreement. Both experimental and numerical results suggest that the teardrop dimple has the highest heat /mass transfer among the four dimple shapes studied.

Airfoil Heat Transfer Calculation Using a Low Reynolds Number Version of a Two-Equation Turbulence Model

1985 ◽  
Vol 107 (1) ◽  
pp. 60-67 ◽  
Author(s):  
J. H. Wang ◽  
H. F. Jen ◽  
E. O. Hartel
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Low Reynolds Number ◽  
Transitional Flow ◽  
Zone Model ◽  
Suction Surface ◽  
Free Stream Turbulence ◽  
Low Reynolds

A two-dimensional, boundary-layer program, STAN5, was modified to incorporate a low-Reynolds number version of the K-ε, two-equation turbulence model for the predictions of flow and heat transfer around turbine airfoils. The K-ε, two-equation model with optimized empirical correlations was used to account for the effects of free-stream turbulence and transitional flow. The model was compared with experimental flat plate data and then applied to turbine airfoil heat transfer prediction. A two-zone model was proposed for handling the turbulent kinetic energy and dissipation rate empirically at the airfoil leading edge region. The result showed that the predicted heat transfer coefficient on the airfoil agreed favorably with experimental data, especially for the pressure side. The discrepancy between predictions and experimental data of the suction surface normally occurred at transitional and fully turbulent flow regions.

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