Hydrodynamic and hydromagnetic stability

Application to natural convection enclosed flows of a lattice Boltzmann BGK model coupled with a general purpose thermal boundary condition

Heat transfer—A review of 2003 literature

The study of two-dimensional mixed convection from a heated square solid cylinder located at the center of a vented cavity filled with air (Pr = 0.71) is performed. The horizontal walls and the right vertical wall are kept adiabatic, while the left vertical wall is maintained at a constant temperature T c . The flow is assumed to be laminar, steady and of constant physical properties except for the density in the buoyancy term, which follows the Boussinesq approximation. The developed mathematical model is governed by the coupled equations of continuity, momentum, and energy and is solved by the finite-difference method. This study investigates the effects of the outlet positions, Richardson numbers, Reynolds numbers, locations, and aspect ratios of inner square cylinder on the flow and the thermal fields. The parameters studied and their ranges are as follows: the Richardson number and Reynolds number are varied in the ranges from 0–10 and 50–200, respectively, location of the inner cylinder (0.25 ≤ L X ...

Mixed Convection Heat Transfer of Air inside a Square Vented Cavity with a Heated Horizontal Square Cylinder

The flow structure and heat transfer characteristics of a square cylinder in cross flow are investigated numerically for both unconfined and channel-confined (blockage ratios, 10–50% in steps of 10%) flow situations at Reynolds numbers of 50, 100, and 150, and a Prandtl number of 0.7. As the blockage ratio is increased, the Reynolds number for the onset of vortex shedding increases and then decreases. Increases in Strouhal number, drag coefficient, pumping power, and cylinder Nusselt number are also observed with increasing blockage ratio. The enhancement of cylinder Nusselt number due to channel confinement is investigated for uniform heat flux and constant cylinder temperature boundary conditions.

Effect of channel confinement on the two-dimensional laminar flow and heat transfer across a square cylinder

Three-dimensional mixed-convection flow in a horizontal rectangular duct at low Reynolds numbers has been investigated numerically. Multiple strip heat sources are flush-mounted on the bottom surface, modeling integrated circuit chips on printed circuit boards, and the fluid considered is air. According to the stability diagram presented, four different flow patterns might exist. The discontinuous thermal boundary condition on the bottom makes the longitudinal rolls expand and shrink periodically, and also helps in the generation of transverse rolls. The steady transverse rolls were found even at subcritical Rayleigh numbers for relatively low Reynolds numbers. The implications of these observations to the cooling of electronic equipment are discussed.

Instability and heat transfer in mixed-convection flow in a horizontal duct with discrete heat sources

Convection in a horizontal rectangular duct under constant and variable property formulations

Three-dimensional conjugate heat transfer in a rectangular duct with two discrete flush-mounted heat sources has been studied numerically in the context of cooling of electronic equipments. The Grashof number is fixed as 10 6 and the working fluid is taken as air The effects of the spatial arrangement of heat sources, the thermal conductivity ratio of the bottom plate material to air, and the Reynolds numbers on the overall and local heat transfer in the duct are evaluated. The magnitudes of the conduction and the convection transport are compared for different parametric combinations. Of particular interest are the transverse variation in the flow, temperature and heat transfer, the interaction between the heat sources, and the effects of conjugate transport

Three-Dimensional Conjugate Heat Transfer in a Horizontal Channel With Discrete Heating

Ted-aj03-252 three dimensional conjugate heat transfer in a horizontal channel with discrete heating

The objective of this research is to study the resonance oscillatory flow in a channel and the resulting effect on thermal transport, leading to cooling enhancement in electronic systems. The unsteady mixed convection through a horizontal channel with two isolated protruding blocks on the bottom wall has been studied numerically. For this geometry, at moderate Reynolds numbers, the flow is found to separate at the leading edge of the first block, and then reattach at the top surface of the second block. At a given Grashof number, when Re exceeds a critical value, vortex is shed only from the second block, and rolls over the bottom wall with its size decaying, while one or two recirculating cells are trapped in the groove. The base vortex shedding frequency is dependent on the buoyancy level Gr/Re2. The critical value of Re is much lower when perturbation is introduced by a rectangular or square promoter in the channel. The frequency and amplitude of perturbation are changed by adjusting the geometry of th...

Qinghua Wang

Papers

Instability and heat transfer in mixed-convection flow in a horizontal duct with discrete heat sources

Convection in a horizontal rectangular duct under constant and variable property formulations

Three-Dimensional Conjugate Heat Transfer in a Horizontal Channel With Discrete Heating

Ted-aj03-252 three dimensional conjugate heat transfer in a horizontal channel with discrete heating

Unsteady mixed convection in a horizontal channel with protruding heated blocks and a rectangular vortex promoter