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Proceedings ArticleDOI

Effect of surface radiation on the transient cooling of heat sources under forced convection - A numerical study

20 May 2020-Vol. 2236, Iss: 1, pp 030001

Abstract: The cooling of electronic gadgets is the biggest challenge in recent years. The selection of innovative cooling techniques leads to the improvement in reliability and performance of electronic systems. Hence, the present study deals with the 3-D numerical modeling and simulation of seven high power protruding heat sources mounted on an SMPS (Switch Mode Power Supply) board using ANSYS FLUENT (R-16) under transient heat transfer mode. The heat sources are cooled under air medium using a velocity of 15 m/s and the heat dissipation rate is 10 W/cm2. The objective is to study the surface radiation effect on the cooling of these heat sources under forced convection and to analyze the heating and cooling cycle of the heat sources. Four different surface conditions (ɛ = 0.90, Non-metallic paint), (ɛ = 0.86, Gray surface, ɛ = 0.8, Steel oxidised paint) and (ɛ = 0.65, Fe-Cast surface) are considered to analyze the radiation effect and the values are compared with respect to the polished surface (ɛ = 0.1). It has been concluded that the surface radiation reduces the temperature of the heat sources by 18 to 25% and helps in better cooling. The time taken for both charging (heating) and discharging (cooling) of the heat sources are also reported for the above emissivity values, and it has been found that charging (heating) takes more time as compare to discharging (cooling) of the heat sources. To generalize the problem, a correlation is put forward for the non-dimensional temperature excess (θ) of the heat sources in terms of their surface emissivity (ɛ) and cooling rate (time).
Topics: Forced convection (58%), Emissivity (54%)
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References
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Journal ArticleDOI
Abstract: Continued miniaturization and demand for high-end performance of electronic devices and appliances have led to dramatic increase in their heat flux generation. Consequently, conventional coolants and cooling approaches are increasingly falling short in meeting the ever-increasing cooling needs and challenges of those high heat generating electronic devices. This study provides a critical review of traditional and emerging cooling methods as well as coolants for electronics. In addition to summarizing traditional coolants, heat transfer properties and performances of potential new coolants such as nanofluids are also reviewed and analyzed. With superior thermal properties and numerous benefits nanofluids show great promises in fulfilling the cooling demands of high heat generating electronic devices. It is believed that applications of such novel coolants in emerging techniques like micro-channels and micro-heat pipes can revolutionize cooling technologies for electronics in the future.

238 citations


Journal ArticleDOI
Sheng Chen1, Yang Liu1, S. F. Chan1, Chi Wah Leung1  +1 moreInstitutions (1)
Abstract: An experimental investigation has been performed to determine the effects of different arrangements of obstacles on the cooling of simulated electronic package. The considered simulated electronic package consisted of a channel formed by two parallel plates. The bottom plate is attached with five identical electrically heated square obstacles, which are perpendicular to the mean airflow and arranged with different side-to-side distances. The experimental results show that the conventional equi-spaced arrangement might not be the optimum option and should be avoided. A better thermal performance could be obtained when the side-to-side distances between the obstacles followed a geometric series. For example, at Re=800, the highest temperature of the optimum arrangement could be reduced by 12% compare to the equi-spaced arrangement and the maximum temperature difference among the five obstacles is lower than that of equi-spaced arrangement by 32.1%.

57 citations


Journal ArticleDOI
Abstract: This paper reports the results of experimental and numerical investigations of optimal heat distribution among the protruding heat sources under laminar conjugate mixed convection heat transfer in a vertical duct. A printed circuit board with 15 heat sources forms a wall of a,duct. Three-dimensional governing equations of flow and heat transfer were solved in the flow domain along with the energy equation in the solid domain using FLUENT 6 . 3 . A database of temperatures of each of the heat sources for different heat distributions is generated numerically. Artificial neural networks (ANNs) were used as a forward model to replace the time consuming complex computational fluid dynamics (CFD) simulations. The functional relationship between heat input distribution and the corresponding temperatures of the heat sources obtained by training the network is used to drive a genetic algorithm based optimization procedure to determine the optimal heat distribution. The optimal distribution here refers to the apportioning of a fixed quantity of heat among 15 heat sources, keeping the maximum of the temperatures of the heat sources to a minimum. Furthermore, the heat distribution corresponding to a set of specified target temperatures of the heat sources is obtained using a network that is trained and tested with a database of temperatures of the heat sources generated using FLUENT 6.3 in the range of total heat dissipation of 5-25 W. Using this network, it was possible to maximize the total heat dissipation from the heat sources for a given target temperature directly. In order to validate the optimization method, a low speed vertical wind tunnel has been used to carry out the mixed convection experiments for different combinations of heat distribution and also for the optimal heat distribution, and the temperatures of the heat sources were measured. The results of the numerical simulations, ANN, and the corresponding experimental results are in good agreement.

18 citations


Journal ArticleDOI
Abstract: 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.

17 citations


Journal ArticleDOI
S. Venkatachalapathy1, M. Udayakumar1Institutions (1)
Abstract: Heat transfer from a 5-by-4 array of protruding heat sources in the bottom wall of an adiabatic enclosure is investigated experimentally and numerically. The enclosure has a fixed inlet and different outlets. Flow velocity and applied heat fluxes are varied. Steady-state temperatures of the heat sources, air inlet and outlet temperatures, and enclosure wall temperature are measured. Results indicate that the first row is the coolest, and the Nusselt numbers of the heat sources, which are near the enclosure wall, are higher than those in the inner side. There is a good agreement between the experimental and numerical results.

10 citations


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