Practical laws for natural convection of viscous fluids heated from above in a shallow cavity (original) (raw)
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Numerical Study of Natural Convection Inside a Square Cavity with Non-uniform Heating from Top
Journal of The Institution of Engineers (India): Series C, 2020
The prime objective of the present numerical study is to analyse buoyancy-driven thermal flow behaviour inside an enclosure with the application of nonlinear heating from top surface which is commonly essential in glass industries. A fluid-filled square cavity with sinusoidal heating from top surface, adiabatic bottom wall and constant temperature side walls is considered here. The thermal flow behaviour has been numerically observed with the help of relevant parameters like stream functions, isotherms and Nusselt number. For the present investigation, Rayleigh number (Ra), Prandtl number (Pr) and heating frequency of the wall (x) are varied from 10 3 to 10 6 , 0.7 to 7 and 0.5 to 2, respectively. It has been noticed from the investigation that flow dynamics drastically alter with Ra, x and Pr. However, the effect of Ra on heat transfer rate has been found to be significantly higher while compared with the influences by x and Pr. Keywords Free convection Á Buoyancy Á Rayleigh number Á Pr number Á Sinusoidal heating Greek letters a Thermal diffusivity (m 2 s-1) b Volumetric expansion coefficient (K-1) q Kinetic viscosity (m 2 s-1) t Density of fluid (kg m-3) h Dimensionless temperature x Heating frequency of the top wall
International Journal of Thermal Sciences, 2008
A two-dimensional numerical study of combined heat transfer (laminar and turbulent natural convection, surface thermal radiation and conduction) in a square cavity with a glass wall is presented. The cavity is modeled as one vertical isothermal wall, two horizontal adiabatic walls and one vertical glass wall. Numerical results in the cavity are obtained by means of a control volume approach where the conditions are set as: 21 • C uniform temperature in the isothermal wall, 35 • C outside ambient temperature and 750 W/m 2 constant direct normal solar irradiation over the glass wall. The Rayleigh number was varied between the range 10 3 Ra 10 12 . Results show that the flow pattern is not symmetric due to the combined effect of non-isothermal glass wall and radiative exchange inside the cavity. A correlation for the total Nusselt number was obtained for both laminar and turbulent flow considering conjugate heat transfer.
Simulation of Natural Convection in a Square Cavity with Partially Heated and Cooled Vertical Walls
Proceeding of 5th Thermal and Fluids Engineering Conference (TFEC)
Natural convection driven by temperature differences between partially heated and cooled vertical walls in a square cavity is studied numerically. Steady or unsteady cellular flow structures and temperature patterns are illustrated along with the evolution of heat transfer rates in terms of Nusselt number. The cavity is filled with fluids of various Prandtl number, including .024 (liquid metal), .71 (air), 6 (water), and 450 (silicon oil). The effect of Prandtl and Rayleigh numbers on the flow regime and heat transfer is established along with two different thermal boundary conditions.
Simulation of Natural Convection in a Cavity: Cooling with Top versus Bottom Partition
Journal of Energy and Power Engineering, 2019
Natural convection in a square cavity is studied numerically with vertical hot walls and a cold partition located at the bottom or top walls. The effect of orientation of partition on isotherms, flow patterns, and heat transfer is analyzed for different fluids and Rayleigh numbers. The placement of partition is found to considerably influence the isotherms, flow patterns, and heat transfer. Heat transfer rate is observed always to increase when the partition is moved from bottom to top wall.
Numerical Modeling of the Thermal Convection of the Viscoud Fluid Flow in the Square Cavity
2014
The paper presents the results of a numerical simul ation of thermal convection in a liquid with a quad r tic dependence of viscosity on temperature in the cavit y at various angles of inclination to the horizonta l. The integral heat transfer coefficients for isothermal borders are in vestigated to plot the minimum critical Rayleigh nu mber on the angle of inclination of the cavity.
2013
A numerical study is performed to analyze the steady natural convection phenomena of air in a square cavity with different locations of the heating portion. The heat sources parts in the left, right and bottom walls of the cavity are maintained at a higher temperature Th, whereas the other parts of these sidewalls are kept at a lower temperature Tc. The enclosure’s top wall is kept insulated. The coupled equations of continuity, momentum and energy are solved by a finite volume method. The SIMPLE algorithm is used to solve iteratively the pressurevelocities coupling. The numerical investigations in this analysis is made over a wide range of parameters, Rayleigh number ( ) and dimensionless heater lengths. The effect of three different heating locations on the vertical walls (bottom, Centre, and top) and the local heat source on the bottom wall was evaluated. Results are presented graphically in the form of streamlines, isotherms and also with a velocity profiles and average Nusselt ...
IOP Conference Series: Materials Science and Engineering, 2019
Effects of cavity aspect ratios and cavity inclination angles to natural convection in a rectangular cavity are numerically investigated. Investigation is performed at the Rayleigh number (Ra) equal to 104, the cavity aspect ratios from 1 to 50 and the cavity inclination angles from 0 to 180°. Consequently, Heat transfer enhancement or decreasing due to the effects is exposed. In addition, streamline contours in the rectangular cavity are illustrated. Multi-cellular flow figuring on the appropriate conditions is exhibited. A new correlation of the average Nusselt number, the cavity aspect ratio and the cavity inclination angle is formulated at Ra equal to 104.