著者

小西 祐一郎 堀内 敬介 西原 淳夫

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.845, pp.16-00243, 2017 (Released:2017-01-25)

参考文献数

10

被引用文献数

2 1

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In order to reduce thermal resistance of power module system, Thermal Interface Materials (TIMs) have been used at the interface between baseplate of power module and heat sink. TIMs have an important role to reduce thermal resistances due to solid surfaces with roughness or waviness. Thermal grease is a primary candidate to fill the gap between them. The grease can be pumped out of the gap during thermal cycling while the grease has the advantages of reduced cost compared to the other TIMs and TIM’s thickness. New reliability test of the grease is required for thermal management as the pump-out phenomena cause an increase of the thermal contact resistances. This study shows a visualization test method to evaluate pump-out phenomena of the grease during thermal cycling. A bimetal plate consisting of copper and invar is used to simulate thermal deformation of baseplate in power module. The grease is filled between the bimetal plate and Al thick plate, and then thermal cycling test is conducted. A 25 MHz ultrasonic imaging is used to visualize the grease layer. The ultrasonic images show a sequence of the grease behavior after the thermal cycling. The ultrasonic imaging results indicate that voids occur in non-curing grease under repeated pressure while cracks are detected in curing grease. It is also found that the curing grease layer applied in power devices can be designed by the evaluation of initial thermal contact resistances at the interface. Sensitivity analysis of correlated factors shows pump-out phenomena are strongly affected by curing of grease.

著者

西原 淳夫

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.73, no.728, pp.1052-1058, 2007-04-25 (Released:2011-03-03)

参考文献数

15

被引用文献数

1 1

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An optimization method for fin pitch in naturally cooled heat sinks is described. Because the heat sinks for the power units of electric trains are stacked vertically, lower heat sinks heat upper heat sinks. However the fin pitch of conventional heat sinks is optimized as single heat sink without accounting for the influence of the lower heat sinks. Equations to predict heat dissipation and a rise in exhaust air temperature in the heat sinks, along with an optimization method for the fin pitch are presented. These equations were carried out from a developed profile of velocity and temperature between two plates. A valid range of the Rayleigh number for the equations is shown, and the optimizing process for the fin pitch of stacked heat sinks is described. The experimental results of the rise in fin temperature of triple stacked heat sinks are compared with the calculated results. The heat sink with optimized arrangement of fins shows over 10% improvement in performance compared with the conventional heat sink.

著者

鈴木 健二郎 林 哲郎 SCHUERGER Matthew J. 西原 淳夫 林 政克

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.55, no.516, pp.2457-2464, 1989-08-25

被引用文献数

2

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The interruption of a fin surface causes renewed boundary layers starting from the leading edge of each interrupted fin. This results in boundary layer thinner in the average over entire length of fin surfaces compared to the uninterrupted case. Therefore, a higher degree of interruption is normally expected to lead to a higher degree of heat transfer. However, to realize this expectation actually, care must be taken of the geometrical allocation of each fin in an array so as to avoid other undesirable effects relating to the fin geometry. Numerical computation of flow and thermal fields have been made for two-dimensional models of two types of parallel louver fins and an offset fin. Heat transfer characteristics of parallel louver fins are discussed in comparison with those of an offset fin based upon the results obtained from the performed numerical computation. It is demonstrated that a cartain type of parallel louver fin has a higher heat transfer performance than that obtained with an offset fin.