Fully Developed Laminar Free Convection With Variable Thermophysical Properties Between Two Open-Ended Vertical Parallel Plates Heated Asymmetrically With Large Temperature Differences

2005 ◽  
Vol 128 (4) ◽  
pp. 405-408 ◽  
Author(s):  
Asterios Pantokratoras
Keyword(s):  
Volume Flow Rate ◽  
Engine Oil ◽  
Large Temperature ◽  
Parallel Plates ◽  
Governing Equations ◽  
Fully Developed Flow ◽  
Vertical Heat ◽  
Direct Numerical Solution ◽  
Vertical Heat Flux ◽  
Steady Laminar

The steady laminar fully developed flow between two isothermal parallel plates is studied in this paper. The investigation concerns air, engine oil, and water taking into account the variation of all physical properties (μ, k, and ρ) with temperature. The results are obtained with the direct numerical solution of the governing equations and cover large temperature differences not treated until now. The largest differences of volume flow rate and vertical heat flux from the corresponding constant properties values reach 1568% and 2120% in air, 139% and 247% in oil, and 62% and 55% in water.

Fully Developed Couette Flow of Three Fluids With Variable Thermophysical Properties Flowing Through a Porous Medium Channel Heated Asymmetrically With Large Temperature Differences

2006 ◽  
Vol 129 (12) ◽  
pp. 1742-1747 ◽  
Author(s):  
Asterios Pantokratoras
Keyword(s):  
Porous Medium ◽  
Saturated Porous Medium ◽  
Engine Oil ◽  
Large Temperature ◽  
Parallel Plates ◽  
Moving Plate ◽  
Direct Numerical Solution ◽  
Oil Water ◽  
Fluid Saturated Porous Medium ◽  
Steady Laminar

In this paper, we study the steady laminar flow in a fluid-saturated porous medium channel bounded by two parallel plates with constant but unequal temperatures. One plate is moving with constant velocity while the other is stationary. For the porous medium, the Brinkman–Darcy–Forchheimer model is used. The investigation concerns engine oil, water, and air, taking into account the variation of their physical properties with temperature. The results are obtained with the direct numerical solution of the governing equations and cover large temperature differences. It is found that dynamic viscosity plays an important role on the results, which depart significantly from those of a fluid with constant properties when the temperature difference between the plates is large. Except that there are cases where the flow is restricted near the moving plate while at the lower part of the channel, the fluid is motionless.

Symmetric Sink Flow Between Parallel Plates

1978 ◽  
Vol 100 (4) ◽  
pp. 477-484 ◽  
Author(s):  
H. D. Murphy ◽  
M. Coxon ◽  
D. M. McEligot
Keyword(s):  
Boundary Layer ◽  
Volumetric Flow Rate ◽  
Internal Boundary Layer ◽  
Internal Boundary ◽  
External Boundary ◽  
Parallel Plates ◽  
Fully Developed Flow ◽  
Developing Flow ◽  
Steady Laminar ◽  
Disk Spacing

Steady, laminar, incompressible flow converging radially between two stationary disks is investigated numerically as a continuously developing flow problem under the internal boundary layer approximations. At dimensionless radii much greater than one the velocity profile becomes parabolic and invariant, but at radii less than one a typical external boundary layer evolves close to the wall with an approximately uniform core region; and the boundary layer thickness decreases from one-half the disk spacing to values proportional to the local radii as the flow accelerates. At large radii the friction factor approaches the classic value obtained for fully developed flow between infinite plates, 6ν/Vt, but at small radii it approaches the constant 2.17/R0, where R0 is an overall Reynolds number based on the volumetric flow rate and the disk spacing and is independent of radius. Tabular and graphical results are provided for the intermediate range of radii, where both viscous and inertial effects are important and exact analyses are not available.

Natural Convective Coutte Flow in a Vertical Parallel Plate Microchannel

2014 ◽  
Vol 705 ◽  
pp. 182-187 ◽  
Author(s):  
Marneni Narahari ◽  
Rajashekhar Pendyala
Keyword(s):  
Nusselt Number ◽  
Flow Rate ◽  
Parallel Plate ◽  
Volume Flow Rate ◽  
Fluid Velocity ◽  
Volume Flow ◽  
Grashof Number ◽  
Dimensionless Velocity ◽  
Vertical Heat ◽  
Vertical Heat Flux

In the present paper, the exact analysis of steady state fully developed natural convective Couette flow in a vertical parallel plate microchannel is performed. Exact solutions are derived for the dimensionless velocity, temperature, volume flow rate, vertical heat flux and Nusselt number. The effects of Grashof number, wall-ambient temperature difference ratio and Knudsen number on the velocity, volume flow rate and Nusselt number have been discussed through graphs. The study revealed that the fluid velocity and volume flow rate increases with increasing Grashof number whereas the Nusselt number decreases with increasing Grashof number.

The Classical Plane Couette-Poiseuille Flow With Variable Fluid Properties

2006 ◽  
Vol 128 (5) ◽  
pp. 1115-1121 ◽  
Author(s):  
Asterios Pantokratoras
Keyword(s):  
Thermal Conductivity ◽  
Poiseuille Flow ◽  
Variable Viscosity ◽  
Volume Flow Rate ◽  
Variable Thermal Conductivity ◽  
Engine Oil ◽  
Large Temperature ◽  
Temperature Profiles ◽  
Straight Line ◽  
Classical Plane

A theoretical study of the effect of variable viscosity and variable thermal conductivity on the classical plane Couette-Poiseuille flow is presented in this brief communication. The investigation concerns engine oil, air, and water taking into account the variation of these quantities with temperature. The results are obtained with the numerical simulation of the governing equations and cover large temperature differences. Velocity and temperature profiles are presented as well as the volume flow rate and the heat flux between the plates. It is found that temperature profiles are close to the straight line for oil and water and depart significantly from the straight line for air due to nonlinear thermal conductivity. Dynamic viscosity plays an important role on the results which depart significantly from those of a fluid with constant properties.

The Influence of Lubricant Supply Conditions and Bearing Configuration on the Performance of (Semi) Floating Ring Bearing Systems for Turbochargers

2017 ◽  
Author(s):  
Luis San Andrés ◽  
Feng Yu ◽  
Kostandin Gjika
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Engine Oil ◽  
Large Temperature ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
The Impact ◽  
Bearing System

Engine oil lubricated (semi) floating ring bearing (S)FRB systems in passenger vehicle turbochargers (TC) operate at temperatures well above ambient and must withstand large temperature gradients that can lead to severe thermo-mechanical induced stresses. Physical modeling of the thermal energy flow paths and an effective thermal management strategy are paramount to determine safe operating conditions ensuring the TC component mechanical integrity and the robustness of its bearing system. On occasion, the selection of one particular bearing parameter to improve a certain performance characteristic could be detrimental to other performance characteristics of a TC system. The paper details a thermohydrodynamic model to predict the hydrodynamic pressure and temperature fields and the distribution of thermal energy flows in the bearing system. The impact of the lubricant supply conditions (pressure and temperature), bearing film clearances, oil supply grooves on the ring ID surface are quantified. Lubricating a (S)FRB with either a low oil temperature or a high supply pressure increases (shear induced) heat flow. A lube high supply pressure or a large clearance allow for more flow through the inner film working towards drawing more heat flow from the hot journal, yet raises the shear drag power as the oil viscosity remains high. Nonetheless, the peak temperature of the inner film is not influenced much by the changes on the way the oil is supplied into the film as the thermal energy displaced from the hot shaft into the film is overwhelming. Adding axial grooves on the inner side of the (S)FRB improves its dynamic stability, albeit increasing the drawn oil flow as well as the drag power and heat flow from the shaft. The predictive model allows to identify a compromise between different parameters of groove designs thus enabling a bearing system with a low power consumption.

Micropolar Fluid Flow Between Two Inclined Parallel Plates

2017 ◽  
Author(s):  
Abbas Hazbavi ◽  
Sajad Sharhani
Keyword(s):  
Fluid Flow ◽  
Pressure Gradient ◽  
Micropolar Fluid ◽  
Constant Heat Flux ◽  
Hydrodynamic Characteristics ◽  
Parallel Plates ◽  
Governing Equations ◽  
Micropolar Fluid Flow ◽  
Flow Through ◽  
The Magnetic Field

In this study, the hydrodynamic characteristics are investigated for magneto-micropolar fluid flow through an inclined channel of parallel plates with constant pressure gradient. The lower plate is maintained at constant temperature and upper plate at a constant heat flux. The governing equations which are continuity, momentum and energy are are solved numerically by Explicit Runge-Kutta. The effect of characteristic parameters is discussed on velocity and microrotation in different diagrams. The nonlinear parameter affected the velocity microrotation diagrams. An increase in the value of Hartmann number slows down the movement of the fluid in the channel. The application of the magnetic field induces resistive force acting in the opposite direction of the flow, thus causing its deceleration. Also the effect of pressure gradient is investigated on velocity and microrotation in different diagrams.

scholarly journals Statistical Analysis of Sodium Doppler Wind–Temperature Lidar Measurements of Vertical Heat Flux

2008 ◽  
Vol 25 (3) ◽  
pp. 401-415 ◽  
Author(s):  
Liguo Su ◽  
Richard L. Collins ◽  
David A. Krueger ◽  
Chiao-Yao She
Keyword(s):  
Heat Flux ◽  
Photon Counting ◽  
Doppler Lidar ◽  
State University ◽  
Colorado State University ◽  
Lidar Measurements ◽  
Vertical Heat ◽  
Different Seasons ◽  
Flux Measurements ◽  
Vertical Heat Flux

Abstract A statistical study is presented of the errors in sodium Doppler lidar measurements of wind and temperature in the mesosphere that arise from the statistics of the photon-counting process that is inherent in the technique. The authors use data from the Colorado State University (CSU) sodium Doppler wind-temperature lidar, acquired at a midlatitude site, to define the statistics of the lidar measurements in different seasons under both daytime and nighttime conditions. The CSU lidar measurements are scaled, based on a 35-cm-diameter receiver telescope, to the use of large-aperture telescopes (i.e., 1-, 1.8-, and 3.5-m diameters). The expected biases in vertical heat flux measurements at a resolution of 480 m and 150 s are determined and compared to Gardner and Yang’s reported geophysical values of 2.3 K m s−1. A cross-correlation coefficient of 2%–7% between the lidar wind and temperature estimates is found. It is also found that the biases vary from −4 × 10−3 K m s−1 for wintertime measurements at night with a 3.5-m telescope to −61 K m s−1 for summertime measurements at midday with a 1-m telescope. During winter, at night, the three telescope systems yield biases in their heat flux measurements that are less than 10% of the reported value of the heat flux; and during summer, at night, the 1.8- and 3.5-m systems yield biases in their heat flux measurements that are less than 10% of the geophysical value. While during winter at midday the 3.5-m system yields biases in their heat flux measurements that are less than 10% of the geophysical value, during summer at midday all of the systems yield flux biases that are greater than the geophysical value of the heat flux. The results are discussed in terms of current lidar measurements and proposed measurements at high-latitude sites.

scholarly journals The development of biofilm architecture

2016 ◽  
Vol 472 (2188) ◽  
pp. 20150798 ◽  
Author(s):  
A. C. Fowler ◽  
T. M. Kyrke-Smith ◽  
H. F. Winstanley
Keyword(s):  
Bacterial Biofilm ◽  
Governing Equations ◽  
Biofilm Growth ◽  
One Dimensional ◽  
Direct Numerical Solution ◽  
The Common ◽  
Common Observation ◽  
The Stability ◽  
The One ◽  
A Free Boundary Problem

We extend the one-dimensional polymer solution theory of bacterial biofilm growth described by Winstanley et al . (2011 Proc. R. Soc. A 467 , 1449–1467 ( doi:10.1098/rspa.2010.0327 )) to deal with the problem of the growth of a patch of biofilm in more than one lateral dimension. The extension is non-trivial, as it requires consideration of the rheology of the polymer phase. We use a novel asymptotic technique to reduce the model to a free-boundary problem governed by the equations of Stokes flow with non-standard boundary conditions. We then consider the stability of laterally uniform biofilm growth, and show that the model predicts spatial instability; this is confirmed by a direct numerical solution of the governing equations. The instability results in cusp formation at the biofilm surface and provides an explanation for the common observation of patterned biofilm architectures.

Heat Transfer Enhancement in Corrugated Pipes

2010 ◽  
Author(s):  
Dennis A. Siginer ◽  
F. Talay Akyildiz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Heat Transfer Enhancement ◽  
Temperature Fields ◽  
Governing Equations ◽  
Transfer Enhancement ◽  
Exact Analytical Solutions ◽  
Velocity And Temperature Fields ◽  
Steady Laminar

The temperature distribution and heat transfer coefficient are investigated in forced convection with Newtonian fluids in pressure gradient driven hydrodynamically and thermally fully developed steady laminar flow in transversally corrugated pipes. The governing equations are solved by means of the epitrochoid conformal mapping and exact analytical solutions are derived for the velocity and temperature fields without viscous dissipation. The effect of the corrugations and the number of waves on the friction factor, the temperature distribution and the heat transfer enhancement is discussed.

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