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Analysis of Some Standard Types of Heat Exchangers on an Elementary Basis
Published in Holger Martin, Heat Exchangers, 2018
The drag coefficient so defined depends on a Reynolds number () Re = ωdSv = ndS2v
Optical Tweezers
Published in Yuri L. Lyubchenko, An Introduction to Single Molecule Biophysics, 2017
where γ is the hydrodynamic drag coefficient. The drag coefficient depends on the shape of the object and on the fluid viscosity (η). For a sphere of radius R far from any surface, we get γ = 6πηR (Batchelor 1967).
External Flows
Published in Ron Darby, Raj P. Chhabra, Chemical Engineering Fluid Mechanics, 2016
As seen in Figure 12.2, the drag coefficient for the sphere exhibits a sudden drop from 0.45 to about 0.15 (almost 70%) at a Reynolds number of 2–5 × 105. For the cylinder, the drop is from about 1.1 to about 0.35. This drop is due to the transition of the flow inside the boundary layer from laminar to turbulent flow and can be explained as follows.
Significance of SWCNTs and MWCNTs on the dynamics of hybrid nanofluid flow over a stretching surface
Published in Waves in Random and Complex Media, 2022
Asia Ali Akbar, Aziz Ullah Awan, Nadeem Abbas
Figures 11 and 12 represent the impact of drag coefficient on the dimensionless temperature and velocity curves. The velocity profile accelerates due to the augmentation of the drag coefficient. The drag coefficient measures the resistance to the flowing fluid. So, the increment of drag coefficient resists the fluid causing the decline in velocity profile and hence the momentum boundary layer thickness decreases. As seen in Figure 12 that the velocity distribution has a parabolic behavior at the starting and ending point of the domain. The velocity distribution has a very minor change for different values of the drag coefficient. The reverse effect is seen for the temperature profile as it increases by increasing the drag coefficient. The physical parameters of interest such as skin friction coefficient increases due to the augmentation of drag coefficient, while the Nusselt number shows converse behavior. Among the three models of hybrid nanofluid, the Xue model has higher values for the Nusselt number and ultimately gives the higher thermal conductivity.
Aerodynamic investigation of the inrun position in Ski jumping
Published in Sports Biomechanics, 2021
where is the density of air, V is the relative velocity, CD is the drag coefficient and A is the frontal area of the object. The drag coefficient is dependent on the Reynolds number, the shape of the object and the surface roughness and is often combined with the frontal area of the object in a variable called the drag area (CDA). The drag area is proportional to the drag force and is often used as a parameter measuring in a wind tunnel (Virmavirta, 2016). As the influence of the drag force relative to ski friction will increase with speed. The drag force is a dominating resistive force, as the ski jumper will accelerate fast up to high speeds due to the inclination at the start of the inrun.
Development of new finned tube heat exchanger: Innovative tube-bank design and thermohydraulic performance
Published in Heat Transfer Engineering, 2020
The results of this investigation are shown in a non-dimensional form in Figures 14–16, for pressure losses and heat transfer performance, respectively. The non-slotted elliptical tube (Case A) configuration has also been plotted in these figures for comparison. The Reynolds number is based on the hydraulic diameter, for the particular elliptical tube-bank types. Figure 14 provides a relation between the friction factor f and the Reynolds number . The friction factor f indicates the capability to determine a pressure drop characteristics for a given airflow rate and geometry conditions. It is observed that the f decreases with an increase in for all tube-bank configurations investigated. Moreover, we can clearly observe that when the Reynolds number increases, the variation in the drag coefficient is reduced, i.e., based on cross-sectional area and over a large range in Reynolds number it is nearly constant.