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Natural Convection
Published in Je-Chin Han, Lesley M. Wright, Analytical Heat Transfer, 2022
From the above momentum equation, one can see that natural convection is due to temperature difference between the surface and fluid and the gravity force. This implies that there is no natural convection if there exists no temperature gradient or no gravity force. The larger delta T and gravity (means larger Grashof number) will cause larger natural circulation and results in thinner boundary-layer thickness and higher friction (shear) and higher heat transfer coefficient. The Grashof number in natural convection plays a similar role as Reynolds number does in forced convection; the larger Grashof number causes higher heat transfer in natural convection as the greater Reynolds number has higher heat transfer in forced convection. Prandtl number plays the same role in both natural and forced convection, basically the fluid property.
R
Published in Carl W. Hall, Laws and Models, 2018
The Rayleigh number equals the Prandtl number times the Grashof number. There are nine different Rayleigh numbers. Keywords: convection, diffusivity, gravity, thermal RAYLEIGH, John William Strutt, Third Baron, 1842-1919, English physicist; Nobel prize, 1904, physics Sources: Bolz, R. E. and Tuve, G. L. 1970; Kakac, S. et al. 1987; Land, N. S. 1972; Perry, R. H. 1967; Potter, J. H. 1967; Rohsenow, W. M. and Hartnett, J. P. 1973; Tapley, B. D. 1990. See also GRASHOF; PRANDTL RAYLEIGH RATIO--SEE RAYLEIGH LAW OF LIGHT SCATTERING REACTION, FIRST ORDER LAW OF; OR MASS ACTION, LAW OF The rate of any unimolecular reaction should at any time be proportional to the concentration in the system at that instance: dCA/dt = –k1 CA where CA = concentration at that time t = time k1 = a constant (first order)
G
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[biomedical, fluid dynamics, geophysics, thermodynamics] Dimensionless number showing the proportional factor between buoyant force and the net viscous force, where β is the linear expansion coefficient, g the gravitational acceleration, ρ density, Ts the surface temperature, T∞ the main body of liquid temperature, L the characteristic length of the object, and ηkin is the kinematic viscosity. The Grashof number is particularly important in fluid flow containing natural convection. The Grashof number describes the conditions for turbulent versus laminar flow, where at low Grashof number the flow is laminar, the transition from laminar to turbulent flow occurs from 108 < Gr < 109 beyond which the flow is fully turbulent, specifically for natural convection involving vertical flat plates. The multiplication of the Grashof number by the Prandtl number yields the Rayleigh number. For mass transfer there is an equivalent Grashof number describing the natural convection, the mass transfer Grashof number (Grm), seeGrashof number, mass transfer.
A generalized electro-osmotic MHD flow of hybrid ferrofluid through Fourier and Fick’s law in inclined microchannel
Published in Numerical Heat Transfer, Part A: Applications, 2023
Dolat Khan, Gohar Ali, Poom Kumam, Panawan Suttiarporn
Figure 8 shows the effect of on the fluid of the hybrid Ferro. This displays an increase in the as the values increase. Physically the Grashof number physically represents the relative strength of buoyancy forces compared to viscous forces in a fluid system. A large Grashof number indicates that buoyancy forces are dominant and can drive natural convection, whereas a small Grashof number indicates that viscous forces are dominant and convection is suppressed. This happened as a result of the concentration gradient, which also helped to increase the buoyancy forces in the hybrid ferrofluid, which in turn caused an increase in the
Blood-based ternary hybrid nanofluid flow-through perforated capillary for the applications of drug delivery
Published in Waves in Random and Complex Media, 2022
Abeer S. Alnahdi, Saleem Nasir, Taza Gul
The effects of thermal buoyancy forces were represented in Figure 8. The velocity of all CuO/blood, CuO + TiO2/blood and CuO + TiO2 + Al2O3/blood nanofluids appears to be increasing in concert with an increase in the thermal (Grashof number). Generally, the thermal Grashof number is the ratio of the buoyant force induced by wide variation in the density of the fluid (due to thermal variations) to the restricting force caused by the fluid viscosity. The Grashof number is a dimensionless quantity that is used to correlate heat and mass transfer caused by thermally induced natural convection at a solid surface submerged in a fluid. As a result, an intensification in the thermal improves the corresponding velocity and thicknesses of the velocity boundary layer in case of nano, hybrid and tri-hybrid nanofluid. Figure 9 indicates that as the (Casson fluid parameter) is enhanced, the velocity of the CuO/blood, CuO + TiO2/blood and CuO + TiO2 + Al2O3/blood nanofluids improves and as a result the thickness of the boundary layer intensifies. When comparing CuO + TiO2 + Al2O3/blood, CuO + TiO2/blood and CuO/blood nanofluids, it is clear that incorporating three nanoparticles reduces the velocity profile.
Thermal aspects of radiation in Casson fluid with nonlinear stretching surface: non-similar solutions
Published in Waves in Random and Complex Media, 2022
Muavia Mansoor, M. Shoaib Kamran, Qazi Mahmood Ul-Hassan, Muhammad Irfan
This part mainly explains about velocity profile behavior, temperature and concentration and sketches have been drawn for these profiles against different parameters. Figures 2–5 endorse the reverberation of distinct parameters for velocity profile. Figures 6–9 evaluate changing trends in the temperature profile. Figure 10 elucidates changing development in concentration sketches. Figure 2 describes the effect of magnetic parameter on the velocity profile. By increasing values for magnetic parameters, velocity profile de-escalates. Figure 3 explains the velocity distribution for the Casson parameter . By increasing values of , the velocity profile depletes. Figures 4 and 5 are plotted to observe the effects of Grashof numbers and on the velocity of the fluid. By enhancing the values of both Grashof numbers for heat and mass transfer results in an accelerating velocity profile. As Grashof number is the ratio of buoyancy force to restraining (viscous) force, and its increasing values is responsible for lowering the viscosity which in turn enhances the velocity of the fluid. Figure 6 demonstrates the effects of the Joule heating parameter for temperature profile. By enhancing values for the Joule heating parameter, the temperature profile shows increasing behavior.