A Comparative Study of Natural Convective Transfer in Rectangular and Square Geometry Micro Fins

The increase in usage of high performance micro-electronic components leads to increase in high heat generation. In order to increase the life time of the electron devices proper ventilation of heat needs to be planned with the available space. In the electronic system the space occupied by the heat sink is small, as well as the heat has to be dissipated without disturbance. There are two types of cooling arrangement namely active cooling and passive cooling. Active cooling requires additional system such as blower and fan over passive cooling. In this study rectangular and square fin micro-fins are fabricated on copper and aluminium for a height of 0.25mm, with spacing and thickness of 5mm to study the natural convective heat transfer. The study reveals that the rectangular geometry enhances the heat transfer rate by 3% compared to the square fin.

Effect of precipitation mineralization reactions on convective dissolution of CO2 : an experimental study

<p>To analyze the influence of a precipitation mineralization reaction between dissolved CO<sub>2</sub> and calcium ions on the convective transfer of CO<sub>2</sub> towards an aqueous phase, the convective dissolution of CO<sub>2</sub> into aqueous solutions of calcium hydroxyde (Ca(OH)<sub>2</sub>) and calcium chloride (CaCl<sub>2</sub>) of various concentrations is studied experimentally. We show that different precipitation patterns develop in the aqueous solution depending on the nature and concentration of the reactant in the host phase. In the case of Ca(OH)<sub>2</sub>, precipitation coupled to convection leads to vigorous convective mixing in the host phase and sedimentation of solid particles of calcium carbonate (CaCO<sub>3</sub>) down to the bulk of the reservoir. Conversely, dissolution of CO<sub>2</sub> in buffered CaCl<sub>2</sub> solutions leads to a stabilisation of the buoyancy-driven convection due to a decrease in density and the adherence of the precipitate to the cell walls.</p>

THEORY AND PRACTICE OF THE APPLICATION OF ULTRASONIC INFLUENCES IN THE PROCESSES OF CONCENTRATION OF ORE AND NON-METALLIC RAW MATERIALS

The features of the application of ultrasonic influences in the processes of concentration of ore and nonmetallic raw materials are considered. It is shown that microflows of the liquid arising during the passage of an ultrasonic wave through a liquid act on the boundary layer near the grains. At the same time, the resistance to diffusion and convective transfer of reactants decreases and the rate of chemical processes increases.

Maximum Density Effects on Natural Convection over an Isothermal Vertical Plate Embedded in an Anisotropic Porous Medium

Keywords: Natural convection, anisotropic porous medium, inversion of density.Abstract. The natural convection in the porous medium has attracted considerable attention with its applications in various industrial sectors, such as the agro-alimentary, the pharmaceutical and oil processing industries. The present work is about the study of the phenomenon of natural convection at 4°C on the vertical plate lining in an anisotropic porous medium in permeability. The wall of the vertical surface is subjected to a constant temperature with defined hydrodynamic conditions and thermal limits. Generalized Darcy’s law was used to establish the governing equations of the system. The control parameters governing the system are respectively the permeability ratio K*, the angle ϴ of the major axis and the inversion parameter R. The general basic equations were solved numerically using Runge-Kutta and shooting method. There was validated against previous work. The effect of these parameters on the heat transfer was highlighted. From the analysis result, it comes out the following conclusions: The convective flow is significantly affected by the anisotropic parameter; heat transfer along the vertical surface is maximum (minimum) when the main shaft having the high permeability is oriented parallel (perpendicular) to the gravitational field; the rate of heat transfer is depending on the inversion parameter R. The convective transfer rate illustrated by the local Nusselt number is symmetric with respect to R=0.45, where it reaches its smallest value. It is inversely proportional to the distribution of the thickness of boundary layer. A high convective transfer rate corresponds to a low boundary layer thickness and this inversely.

Coupling a sunspace to a hyper insulated building: Field tests of different configurations to optimize the energy and comfort performance

An experimental study was conducted on a hyper insulated building coupled with a sunspace, to investigate the role of the major design parameters (depth, glass percentage and typology, etc.) and mechanically controlled convective transfer (VMC) on the energy performance. Based on 132 dynamic simulations, a modifiable sunspace was built on the sun-exposed side of a nZEB mock-up in Central Italy and monitored via an extensive sensor network. The conditioning system tracked the seasonal set point via a bang-bang controller, while the VMC was governed by a bespoke temperature-driven logic. In a previous run, irradiative and combined irradiative-convective modes were tested on a 30% glazed sunspace: VMC was found to dump the daily energy consumption to -27%. Then; a second monitoring campaign compared the 30% and 50% configurations. The former guaranteed very stable indoor conditions (20.1±0.3°C), yet the latter still preserved global comfort at a remarkably lower (-40%) energy expenditure.