scholarly journals Аerodynamic drag at small Reynolds numbers and the method of calculation of the air velocity in one- and many-row finned beams with an exhaust shaft

2021 ◽  
Vol 57 (1) ◽  
pp. 108-118
Author(s):  
G. S. Marshalova ◽  
А. В. Sukhotskii
Keyword(s):  
Mixed Convection ◽  
Heat Exchangers ◽  
Aerodynamic Drag ◽  
Reynolds Numbers ◽  
Thermal Design ◽  
Air Velocity ◽  
Small Reynolds Numbers ◽  
Gravitational Pull ◽  
Air Flows ◽  
One And Many

The periodic switching of fans at certain ambient air temperatures and a constant power is a promising method to enhance the energy operating efficiency of air-cooled heat exchangers. Equipping these heat exchangers with devices increasing the propulsion (for example, an exhaust shaft) facilitates the intensification of heat transfer due to strengthening the free movement of air by lifting forces. Meanwhile, the heat exchanger is used at the mixed convection regime. To make the thermal design of air-cooled heat exchangers with an exhaust shaft, we must have data on the aerodynamic drag of tube beams at small Reynolds numbers (Re < 1000) that permit to calculate the air flow velocity. However, at present, studies on the aerodynamic drag at mixed convection are virtually missing. Moreover, it is necessary to take into account the influence of external air flows on the gravitational pull created by the shaft since air-cooled heat exchangers are designed for outdoor use. Using the results of the experimental investigation, we obtained information about the mass-exchange processes in the finned beam and the exhaust shaft, developed a method for calculating the air velocity in one- and many-row finned beams with the exhaust shaft and determined their aerodynamic drag at small Reynolds numbers. We also established the influence of external air flows on the gravitational pull created by the shaft.

scholarly journals Aerodynamic drag of a staggered flat-oval finning tube banks at the small reynolds numbers

ScienceRise ◽  
2015 ◽  
Vol 6 (2(11)) ◽  
pp. 90
Author(s):  
Максим Михайлович Вознюк ◽  
Иванна Сергеевна Башкир ◽  
Олександр Михайлович Терех ◽  
Валерій Андрійович Рогачов ◽  
Олександр Ігоревич Руденко
Keyword(s):  
Aerodynamic Drag ◽  
Reynolds Numbers ◽  
Small Reynolds Numbers ◽  
Tube Banks

Drag coefficients of air rifle pellets with wide range of geometries

2021 ◽  
pp. 095440622199119
Author(s):  
Nicos Ladommatos
Keyword(s):  
Drag Coefficient ◽  
Aerodynamic Drag ◽  
Reynolds Numbers ◽  
Air Velocity ◽  
Drag Coefficients ◽  
Small Influence ◽  
Wide Range ◽  
Coefficient Increase ◽  
Air Rifle ◽  
Mach And Reynolds Numbers

Air rifle and air pistol target shooting are included in major intentional and national sports competitions and are also highly popular sport pastimes. Published scientific studies of pellet drag are very rare, in contrast to a large number of scientific studies published on aerodynamic drag of sports balls and other sports projectiles. Measurements are presented of the drag coefficients for 31 air rifle pellets of mainly 4.5 mm (0.177 in) calibre having a wide range of geometries. The drag coefficient measurements were made with a low-turbulence open wind tunnel at flow velocity of 200 m/s (Mach and Reynolds numbers 0.57 and 56,000 for 4.5 mm pellets). The detailed geometry of some pellets was altered systematically in order to improve understanding of how pellet geometry affects drag coefficient. The drag coefficient for the 31 pellets varied widely from 0.36 to 0.78, and it was influenced substantially by the curvature of the flow separating from the pellet head rim. Large curvatures delayed flow re-attachment onto the pellet tail, thereby lowering pellet base pressure and increasing the value of drag coefficient. Pellets with hemi-spherical or ogive-shaped noses generally had lower values of drag coefficient than pellets with other nose shapes. The presence of the pellet tail was beneficial by providing a surface onto which the flow detaching from the pellet rim could re-attach. However, for minimisation of drag coefficient, the pellet tail had to be of a certain optimum length which depended on the shape of the pellet nose. Small differences in pellet geometry had significant influence on the value of drag coefficient. Increase in air velocity from 120 to 200 m/s had small influence on the value of drag coefficient for three common sports pellets having flat, conical and dome-shaped noses.

Transient Models to Analyze the Influence of the Air Velocity and Ducts Diameter on the Performance of Earth-Air Heat Exchangers

2016 ◽  
Vol 43 (5-6) ◽  
pp. 503-520 ◽  
Author(s):  
R. S. Brum ◽  
J. V. A. Ramalho ◽  
Luiz Alberto O. Rocha ◽  
L. A. Isoldi ◽  
E. D. dos Santos
Keyword(s):  
Heat Exchangers ◽  
Air Velocity ◽  
Transient Models

Pulsatile pipe flow pseudoplastic materials; The flow enhancement for Re ≪ 1

1983 ◽  
Vol 48 (6) ◽  
pp. 1579-1587 ◽  
Author(s):  
Ondřej Wein
Keyword(s):  
Small Parameter ◽  
Pipe Flow ◽  
Quantitative Estimation ◽  
Reynolds Numbers ◽  
Power Law Model ◽  
Viscosity Function ◽  
Small Reynolds Numbers ◽  
Title Problem ◽  
Flow Enhancement ◽  
Method Of Small Parameter

Solution of the title problem for the power-law model of viscosity function is constructed by the method of small parameter in the region of small Reynolds numbers. The main result of the paper is a quantitative estimation of the values of Re, when the influence of inertia on flow enhancement may be quite neglected.

scholarly journals Force distribution on a slender body close to an interface

1981 ◽  
Vol 24 (1) ◽  
pp. 27-36 ◽  
Author(s):  
J.R. Blake ◽  
G.R. Fulford
Keyword(s):  
Reynolds Numbers ◽  
Plane Wall ◽  
Slender Body ◽  
Force Distribution ◽  
Immiscible Liquids ◽  
Flat Interface ◽  
Small Reynolds Numbers ◽  
Rigid Plane ◽  
Limiting Case ◽  
Analytical Expressions

The motion of a slender body parallel and very close to a flat interface which separates two immiscible liquids of differing density and viscosity is considered for very small Reynolds numbers. Approximate analytical expressions are obtained for the distribution of forces acting on the slender body. The limiting case of a rigid plane wall yields results obtained previously.

Extra Drag Force on a Circular Cylinder Due to the Presence of Solid Particles in Subsonic Compressible Flow

1991 ◽  
Author(s):  
Stanley B. Mellsen
Keyword(s):  
Compressible Flow ◽  
Incompressible Flow ◽  
Aerodynamic Drag ◽  
Collection Efficiency ◽  
Reynolds Numbers ◽  
Solid Particles ◽  
Circular Cylinders ◽  
Critical Mach Number ◽  
Wide Range ◽  
Inertia Parameters

Abstract The effect of particles, such as dust in air on aerodynamic drag of circular cylinders was calculated for compressible flow at critical Mach number and for incompressible flow. The effect of compressibility was found negligible for particles larger than about 10 μm, for which the air can be considered a continuum. Drag coefficient and collection efficiency are provided for a wide range of inertia parameters and Reynolds numbers for both compressible and incompressible flow.

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