Buoyancy and Thermocapillary Driven Flows in an Open Cavity with Bottom Heating and Symmetrical Cooling from Sides (original) (raw)
Related papers
International Journal of Heat and Mass Transfer, 1995
Abstraet--Steady natural convection in an enclosure heated from below and symmetrically cooled from the sides is studied numerically, using a streamfunction-vorticity formulation. The Allen discretization scheme is adopted and the discretized equations were solved in a line by line basis. The Rayleigh number based on the cavity height is varied from 103 to 10 7. Values of 0.7 and 7.0 for the Prandtl number are considered. The aspect ratio L/H (length to height of the enclosure) is varied from 1 to 9. Boundary conditions are uniform wall temperature and uniform heat flux. For the range of the parameters studied, a single cell is observed to represent the flow pattern. Numerical values of the Nusselt number as a function of the Rayleigh number are reported, and the Prandtl number is found to have little influence on the Nusselt number. A scale analysis is presented in order to better understand the phenomenon.
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
“Effects Of Heat Source Location On Natural Convection In A Square Cavity”
2012
Natural convection in a closed square cavity has occupied the centre stage in many fundamental heat transfer analysis which is of prime importance in certain technological applications. Infact buoyancy driven convection in a sealed cavity with differentially heated isothermal walls is a prototype of many industrial applications such as energy efficient buildings, operation and safety of nuclear reactor and convective heat transfer associated with electronic cooling equipment. The internal flow problems are considerably more complex than external ones. In electronic systems normally the heat generating bodies exist within the cavity. The effect of the presence of heat source on the mass flow rate and heat transfer is considered in present case for investigation. In order to verify the methodology of using fluent, the commercial software, the available problem in the literature is verified for parametric study on the location of heat source and its strength is considered for study. In present work, the given source is split into two parts and its effect on the flow rate and heat transfer is studied. An attempt is made for the best location of the heat source in the cavity so that it can be used in the electronic equipment generating heat.
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.
International Journal of Engineering Research and Technology (IJERT), 2021
https://www.ijert.org/numerical-analysis-on-natural-convection-in-a-square-enclosure-with-thin-baffles-on-vertical-walls-at-different-positions https://www.ijert.org/research/numerical-analysis-on-natural-convection-in-a-square-enclosure-with-thin-baffles-on-vertical-walls-at-different-positions-IJERTV10IS070076.pdf Natural convection is the mode of heat transfer which occurs due to the existence of temperature gradient. It didn't require any external agent such as fan, pump and blower; it not only saves energy but avoids unwanted noise. Enclosure is a square segment which is a regular geometry, found in a number of applications such as a fully filled duct pipes, electronic systems, computer technologies, air conditioning applications, lubrication system, solar collector, a sheet metal covered store, a solar air heater and a compact plate heat exchanger etc. The current study investigates laminar natural convection in a square enclosure with isothermal vertical walls along with two thin baffles at different positions on them and with adiabatic base and top of the enclosure. The domain is filled with air. This two-dimensional study focuses attention to understand changes in flow and temperature field development due to variation in position of baffles for each cases of Rayleigh number varies. The flow behaviour and thermal characteristics have been investigated in different cases through streamlines and isotherms respectively. Complete domain has been chosen for analysis. Asymmetric solutions are also observed for some of the cases. These results are confirmed by development of the corresponding convection loops and also by the variation of Average Nusselt number. Finally, the thesis report summarizes the effects of different parameters on rate of heat transfer.
A Study on Natural Convection of Air in a Square Cavity with Partially Thermally Active Side Walls
Open Journal of Fluid Dynamics, 2017
In this present work, we study heat transfer in a confined environment. We have to determine the thermal and dynamics fields of the cavity while observing the effect of the Rayleigh number which depends on the characteristics of the fluid and the temperatures imposed. The behavior of boundary layers in natural convection is analyzed along this square cavity. The central halves of its vertical walls are heated at different temperatures. The left active part is at a higher temperature than the one on the right wall. The remaining inactive parts and the horizontal walls (upper and lower) are adiabatic. The thermal and dynamic modeling of two-dimensional problem was done using a calculation code Fortran 90 and a visualization software ParaView based on the finite volume method. The equations governing this phenomenon of unsteady flow have thus been solved. This allows the modeling of both air flow and heat transfer with a numerical stabilization of the solution. So, we have presented our results of numerical simulations using a visualization tool. The results show the different velocity and temperature curves, velocity vectors and isotherms in laminar flow regime.
IJERT-Numerical Investigation of Natural Convection Heat Transfer in a Square Cavity
International Journal of Engineering Research and Technology (IJERT), 2015
https://www.ijert.org/numerical-investigation-of-natural-convection-heat-transfer-in-a-square-cavity https://www.ijert.org/research/numerical-investigation-of-natural-convection-heat-transfer-in-a-square-cavity-IJERTV4IS070206.pdf Natural convection heat transfer in enclosures find many applications such as heating and cooling of building spaces, solar energy utilization, thermal energy storage, cooling of electrical and electronic components etc. In the present study, Numerical Investigation is conducted in a square cavity with one vertical wall maintained at a high temperature and with the opposing vertical wall at a low temperature. The influence of Grashof numbers ranging from 20000 to 200000 for Prandtl number 0.7 (air) is studied. The governing vorticity and energy equations are solved by finite difference methods including Alternating Direction Implicit (ADI) and Successive Over Relaxation (SOR) techniques with C coding. Steady state isothermal lines and streamlines are obtained for all the Grashof numbers considered. In addition, the average Nusselt number, over the hot wall for the range of Grashof numbers is calculated. The contours of streamlines and isothermal lines are presented for all the parameters investigated. Changes in the streamline and isothermal line patterns are observed with the change in Grashof numbers. The results obtained in this study are useful for the design of devices with enclosures subjected to high temperature differences.
Natural convection in a rectangular enclosure with two heated sections on the lower surface
International Journal of Heat and Fluid Flow, 2005
The development of unsteady free convective flow in a rectangular enclosure has been numerically studied. The enclosure considered has rectangular horizontal lower and upper surfaces and vertical side surfaces. The horizontal width of enclosure is twice the vertical height and longitudinal length of the enclosure. There are two square isothermal heated sections on the lower surface, the rest of this surface being adiabatic. The vertical side-walls of the enclosure are kept at a uniform low temperature. The horizontal rectangular upper surface of the enclosure is either (a) adiabatic or (b) isothermal and at the same low temperature as the vertical side-walls. The governing unsteady, three-dimensional flow equations, written in dimensionless form, have been solved using an iterative, semi-implicit finite-difference method. The solution has the following parameters: the Rayleigh number, Ra, the Prandtl number, Pr, the dimensionless size, w H , of the square heated sections and the dimensionless distance between the heated sections on the lower surface, w S . Results have been obtained for a Prandtl number of 0.7. Most of the results presented here are for w H = w S = 1/3. The results indicate that for the flow situation considered the flow is steady at low Rayleigh numbers, becomes unsteady at intermediate Rayleigh numbers and then again becomes steady at higher Rayleigh numbers The conditions under which unsteady flow develops and the nature of the unsteady flow have been investigated and the variation of mean Nusselt number with Rayleigh number has been explored.