Distribution Of Discrete Heat Sources Research Articles

Numerical investigation of natural and mixed convection heat transfer on optimal distribution of discrete heat sources mounted on a substrate

The paper deals with the numerical investigation of natural and mixed convection heat transfer on optimal distribution of five non-identical protruding discrete heat sources (Aluminium) mounted on a substrate (Bakelite) board. The heat sources are subjected to a uniform heat flux of 2000 W/m2. The temperature of heat sources along with the effect of thermal interaction between them is predicted by carrying out numerical simulations using ANSYS Icepak, and the results are validated with the existing experimental findings. The results suggest that mixed convection is a better method for cooling of discrete heat source modules. Also, the temperature of heat sources is a strong function of their shape, size, and positioning on the substrate. Effect of radiation is studied by painting the surface of heat sources by black paint. The results conclude that, under natural convection heat transfer, the temperature of heat sources drops by 6-13% from polished to black painted surface, while mixed convection results in the drop by 3-15%. The numerical predictions are in strong agreement with experimental results.

Optimal Distribution of Discrete Heat Sources Under Natural Convection Using ANN–GA Based Technique

Experiments have been conducted from five protruding rectangular discrete heat sources (aluminum) of non-identical sizes arranged at different positions on a substrate board (Bakelite), under natural convection, to determine their optimal configuration. A substrate board is designed for conducting experiments on multiple configurations of heat sources using the same board. A heuristic non-dimensional geometric parameter, λ, is defined for the purpose of identifying the optimal configuration for which the maximum temperature excess among the five heat sources of a configuration is the minimum, among all possible configurations. The maximum temperature excess is found to decrease with λ, so the configuration with highest λ is deemed to be the optimal one. The effect of surface radiation on the heat transfer rate from the heat sources is studied by painting their surfaces with black paint of high emissivity, which reduces their temperature by as much as 15%. An empirical correlation is developed for the non-dimensional maximum temperature excess (θ) in terms of λ, taking into account the effect of radiation. To minimize the error between the temperatures obtained by prediction (correlation) and experiment, and to determine the global optimal configuration of heat sources more rigorously, an artificial neural network (ANN) is trained using the experimental data, which then powers the genetic algorithm (GA) code.

Experiment Driven Ann-GA Based Technique for Optimal Distribution of Discrete Heat Sources Under Mixed Convection

This article reports the results of mixed convection heat transfer studies from five heat sources (aluminum) mounted at different positions on a substrate board (Bakelite). The goal is to determine the optimal arrangement, such that, the maximum temperature excess is minimum among all the possible configurations. For accomplishing this, a completely experimental driven hybrid optimization strategy, that combines Artificial neural network (ANN) with Genetic algorithm (GA) is used. Initial optimization studies are carried out by employing a heuristic non-dimensional geometric parameter λ, which is identified to be the key parameter to decide the maximum temperature in the system.

Optimal Distribution of Discrete Heat Sources Under Mixed Convection—A Heuristic Approach

Steady state experiments are conducted in a low speed horizontal wind tunnel under mixed convection for five discrete heat sources (aluminum) of nonidentical sizes arranged at different positions on a substrate board (bakelite) to determine the optimal configuration. The optimal configuration is one for which the maximum temperature excess (difference between the maximum temperature among the heat sources of that configuration, and the ambient temperature) is the lowest among all the other possible configurations and is determined by a heuristic nondimensional geometric parameter λ. The maximum temperature excess is found to decrease with λ, signifying an increase in heat transfer coefficient. In view of this, the configuration with highest λ is deemed to be the optimal one. The effect of surface radiation on the heat transfer characteristic of heat sources is also studied by painting their surface with black, which reduces their temperature by as much as 12%. An empirical correlation is developed for the nondimensional maximum temperature excess (θ) in terms of λ, by taking into account the effect of surface radiation. The correlation when applied for highest λ of the configuration returns the minimum value of θ at the optimal condition, which is a key engineering quantity that is sought in problems of this class.

Effect of surface radiation heat transfer on the optimal distribution of discrete heat sources under natural convection

Experiments have been conducted for natural convection heat transfer from protruding discrete heat sources, mounted at different positions on a substrate, to determine the optimal configuration, and to study the effect of surface radiation on them, which reduces their temperature upto 12 %. The optimal configuration has been determined by a non-dimensional geometric distance parameter (λ). An empirical correlation has been proposed between the non-dimensional steady state temperature (θ) and λ, by taking into account the effect of surface radiation heat transfer.

Heat Transfer in a Microtube or Microchannel with Protrusions

This paper presents the effects of protrusions on heat transfer in a microtube and in a two-dimensional microchannel of finite wall thickness. The effects of protrusion shape, size, and number were investigated. Calculations were done for incompressible flow of a Newtonian fluid with developing momentum and thermal boundary layers under uniform and discrete heating conditions. It was found that the local Nusselt number near a protrusion changes significantly with the variations of Reynolds number, height, width, and distance between protrusions, and the distribution of discrete heat sources. The results presented in the paper demonstrate that protrusions can be used advantageously for the enhancement of local heat transfer whereas the global performance may be enhanced or diminished based on the channel geometry.

Constructal multi-scale structures for maximal heat transfer density

This paper reviews recent constructal-theory advances: the optimal distribution of discrete heat sources cooled by laminar natural convection. Three scenarios are investigated: (i) many small heat sources mounted on a vertical wall, (i) a few small finite-size heat sources mounted on the side wall of a two-dimensional enclosure, and (iii) one heated area on the wall of a vertical diverging or converging channel with chimney flow. In (i) and (ii), the optimally distributed heat sources are not equidistant. In (iii), the geometry changes by varying the space between the walls, the distribution of heating along the walls, and the angle between the two walls. Numerical simulations in the Rayleigh number range 10 5≤Ra H≤10 7 show that for maximal heat transfer rate density it is better to install heated sections at the channel entrance. The optimal angle between the two walls is approximately zero when Ra H is large. The robustness of flow architectures with optimized distribution of heat sources is discussed.

Optimal distribution of discrete heat sources on a plate with laminar forced convection

In this paper constructal theory is applied to the fundamental problem of how to arrange discrete heat sources on a wall cooled by forced convection. The global objective is to maximize the conductance between the discrete heated wall and the fluid. This is equivalent to minimizing the temperature of the hot spot on the wall, when the heat generation rate is specified. The mechanism by which the global objective is achieved is the generation of flow configuration, in this case the distribution of discrete heat sources. Two different analytical approaches are used: (i) large number of small heat sources, and (ii) small number of heat sources with finite length, which are mounted on a flat wall. Both analyses show that the heat sources should be placed nonuniformly on the wall, with the smallest distance between them near the tip of the boundary layer. If the Reynolds number is high enough, then the heat sources should be mounted flush against each near the entrance to the channel. The analytical results are validated by a numerical study of discrete heat sources that are distributed nonuniformly inside a channel formed by parallel plates.

Optimal distribution of discrete heat sources on a wall with natural convection

This paper is an application of the constructal method to the discovery of the optimal distribution of discrete heat sources cooled by laminar natural convection. The global objective is to maximize the global conductance between the wall and the fluid, or to minimize the hot-spot temperatures when the total heat generation rate and global system dimensions are specified. Two scenarios are investigated: (i) a large number of small heat sources mounted on a vertical wall facing a fluid reservoir, and (ii) a small number of finite-size heat sources mounted on the inside of the side wall of a two-dimensional enclosure. It is shown that the optimal distribution is not uniform (the sources are not equidistant), and that as the Rayleigh number increases the heat sources placed near the tip of a boundary layer should have zero spacings. In both (i) and (ii), the optimal configuration of the wall with discrete sources is generated by the pursuit of maximal global performance subject to global constraints.

AN OPTIMUM SPACING PROBLEM FOR FIVE CHIPS ON A HORIZONTAL SUBSTRATE IN AN ENCLOSURE – NATURAL CONVECTION

International Journal of Computational Engineering ScienceVol. 01, No. 01, pp. 167-186 (2000) No AccessAN OPTIMUM SPACING PROBLEM FOR FIVE CHIPS ON A HORIZONTAL SUBSTRATE IN AN ENCLOSURE – NATURAL CONVECTIONYANG LIU, CHUN WAH LEUNG, TAL LEUNG CHANG, and PHAN-THUEN NHANYANG LIUDepartment of Mechanical Engineering, The Hong Kong Polytechnic University, Hum Hom, Kowloon, Hong Kong, P. R. China Search for more papers by this author , CHUN WAH LEUNGDepartment of Mechanical Engineering, The Hong Kong Polytechnic University, Hum Hom, Kowloon, Hong Kong, P. R. China Search for more papers by this author , TAL LEUNG CHANGDepartment of Mechanical Engineering, The Hong Kong Polytechnic University, Hum Hom, Kowloon, Hong Kong, P. R. China Search for more papers by this author , and PHAN-THUEN NHANInstitute of High Performance Computing, National University of Singapore, Singapore 119260, SingaporePermanent address: Department of Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia. Search for more papers by this author https://doi.org/10.1142/S1465876300000094Cited by:3 Previous AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractThe optimum spacing problem for five heated chips rested on a conductive substrate in a two dimensional enclosure filled with air is solved by an operator-splitting pseudo-time-stepping finite element method, which automatically satisfies the continuity of the interfacial temperature and heat flux. It is found that the conventional equi-spaced arrangement is not an optimum option. An optimum thermal performance can be obtained when the center-to-center distances between the chips follow a geometric series. The maximum relative temperature drop in the optimum configuration can be as much as 17% of the equi-spaced arrangement. FiguresReferencesRelatedDetailsCited By 3Optimal Distribution of Discrete Heat Sources Under Natural Convection Using ANN–GA Based TechniqueTapano Kumar Hotta and Shakkottai P. Venkateshan25 August 2014 | Heat Transfer Engineering, Vol. 36, No. 2Optimal Distribution of Discrete Heat Sources Under Mixed Convection—A Heuristic ApproachTapano Kumar Hotta, C. Balaji and S. P. Venkateshan29 July 2014 | Journal of Heat Transfer, Vol. 136, No. 10Effect of surface radiation heat transfer on the optimal distribution of discrete heat sources under natural convectionTapano Kumar Hotta, Pullarao Muvvala and S. P. Venkateshan18 October 2012 | Heat and Mass Transfer, Vol. 49, No. 2 Recommended Vol. 01, No. 01 Metrics History Received 2 August 1999 Accepted 4 November 1999 PDF download