Heat Generation Surface Research Articles

Heat sink evolutionary optimization by natural construction method

In the present study, a new optimization method called natural construction (NC) method was presented. This method was inspired by constructal law and it is an effort to extend this theorem by eliminating its predefined constraints. The proposed NC method was implemented on evolutionary optimization of embedded high conductive continuous strips in a cold plate to cool a uniformly heat-generating surface. These strips guide the generated heat to a localized constant temperature heat sink. The proposed method is a straightforward approach with a low computational cost which works based on gradual growth of the constructal cells and unlike the majority of optimization methods, does not need any special assumption about the initial shape of strips configuration or constructal cell size. Moreover, since in this method constructal cells are added gradually, the effect of each element on maximum or mean temperature can be assessed at each step while the proper amount of required area fraction of high conductive material will be evaluated accordingly. The NC method is a general constraint-free optimization method that can apply to a wide variety of engineering problems and will be very useful in different disciplines.

Design and Analysis of a Rectangular Fin with Comparing by Varying Its Geometry and Material, With Perforation and Extension

Extending fins improve the rate of heat transfer or decrease convection. A fin is only for the reason of increasing the surface area in order to maximize heat transmission like a motor, heat exchanger, CPU, or to a heat-generating surface area. The benefit of performing thermal analysis on a flat fin is that it will tell how far heat is dissipated. This paper's primary purpose is to design and evaluate the thermal properties of rectanglular fin with varying geometry and content, and to expand the rectangular fin plate with Catia5R tools. Catia and Ansys are used to construct the geometries, and analyses of thermal properties are applied to them The tip is 5mm wide at present, decreased to 4mm. The aluminum alloy used in the manufacture of the rectangular fin body has thermal conductivity of 110-160 mK. The conducting coating on this paper is replaced with Aluminum Alloy 1100, which has a thermal conductivity of 210 to the mW/mk for the substrate and many unusual and prolonged margins. Case studies are used and graphed as well as total conclusions are drawn.

METHOD FOR CALCULATING HEAT PIPES THAT DIVERT HEAT FROM THE HEAT-EMITTING SURFACE

The results of complex studies of the parameters of the heat-conducting collectors, development of the methods for their calculation are presented. The main diffi culty in this case is the calculation of the design and parameters in the region of the contact zone between the heat pipe and the heat-generating surface. It is shown that the calculation methods used for convective collectors can not be applied to collectors with heat pipes in which the elements do not depend on each other. It is established that semiempirical models provide an opportunity to study the specifi cs of the processes taking place in the reservoir, the degree of their infl uence on its effi ciency. The simplifi ed calculation technique proposed in this article allows us to make the required estimates and calculations at the engineering level.

Effect of non-local equilibrium on minimal thermal resistance porous layered systems

In this paper, the cooling of a heat-generating surface by a stacking of porous media (e.g., metallic foam) through which fluid flows parallel to the surface is considered. A two-temperature model is proposed to account for non-local thermal equilibrium (non-LTE). A scale analysis is performed to determine temperatures profiles in the boundary layer regime. The hot spot temperature is minimized with respect to the three design variables of each layer: porosity, pore diameter, and material. Global cost and mass are constrained. The optimization is performed with a hybrid genetic algorithm (GA) including local search to enhance convergence and repeatability. Results demonstrate that the optimized stacks do not operate in LTE. Therefore, we show that assuming LTE might result in underestimation of the hot spot temperature, and into different final designs as well.

Experimental Investigation of the Heat Transfer Characteristics of Aluminum-Foam Heat Sinks With Restricted Flow Outlet

This study investigates the heat transfer characteristics of aluminum-foam heat sinks with restricted flow outlets under impinging-jet flow conditions. An annular flow-restricting mask is used to control the height of the flow outlet of the aluminum foam sink, forcing the cooling air to reach the heat-generation surface. The enhanced heat transfer characteristics of aluminum-foam heat sinks using these flow-restricting masks are measured experimentally in this work. The effects of porosity, pore density and length of sample, air velocity, and flow outlet height on the heat transfer characteristics of aluminum-foam heat sinks are investigated. Results show that the effect of the flow outlet height is stronger than that of the pore density, porosity, or height of the aluminum heat sinks studied in this work. A general correlation between the Nusselt number and the Reynolds number based on the equivalent spherical diameter of the aluminum foam is obtained for 32 samples of aluminum-foam heat sinks with different sample heights (20–40mm), pore densities (5–40ppi(pore∕inch)), porosities (0.87–0.96), and flow outlet heights (5–40mm). It should be noted that, based on the measured velocity profile, the increase of the Nusselt number of the aluminum-foam heat sink with the decrease in the flow outlet height is caused by the reduced convective resistance at the solid-gas interface through the increased velocity near the heat-generation surface. The reduction in flow outlet height increases the local thermal nonequilibrium condition near the heat-generation surface.

The cooling of a heat-generating board inside a parallel-plate channel

This paper addresses the fundamental question of how to position a heat-generating board inside a parallel-plate channel, where it is cooled by forced convection. It is shown that when the board substrate is a relatively good thermal conductor, the best board position is near one of the channel walls, and the worst position is in the middle of the channel. The best and worst positions switch places when the board substrate is a relatively poor conductor. The optimal spacing between a heat-generating surface (uniform temperature, or uniform heat flux) and the insulated wall that completes a parallel-plate channel is reported. Finally, it is shown under what conditions it is advantageous to divide a heat-generating board into two or more equidistant boards inside the same channel, when the total rate of heat generation of all the boards and the channel spacing are fixed.

Measurement of profiles of temperature and local vapor content near a heat-generating surface in water boiling in a large volume

Results are presented of simultaneous measurement of temperature profiles and local vapor content in a boundary layer in the boiling of water.

Heat transfer with boiling of a thin water film on a Teflon surface

An experimental investigation has been made of heat transfer with boiling of a thin water film on a horizontal heat-generating surface, made of Teflon-4.