SUMMARYNumerical simulations were performed to investigate convective±conductive heat transfer due to a laminar boundary layer¯ow of air over a two dimensional array of rectangular chip blocks which represent the ®nite heat sources. The main focus of this study is on the simulation of the¯ow ®elds and temperature variations of the air and the chip blocks. The purpose of this study is to verify the eects of the openings of the board in the areas between the chip blocks on the enhancement of cooling the heating blocks. Due to a pressure dierential occurring across the opening, the induced vertical¯ow serves as a suction or blowing force and consequently enhances heat dissipation to the ambient¯uid. The optimal con®guration of the chip board regarding cooling the heat source would yield lower chip temperatures with limited chip-to-chip temperature variations.A time-accurate numerical scheme algorithm, PISO (pressure-implicit with splitting of operators), is used to simulate the conjugate heat transfer between the¯uid and solid phases. In this work, a set of false solid properties was employed to force the solid side to have a time scale comparable to that of the¯uid side in order to avoid numerical instabilities due to dierent time scales used in the calculations. The results of the simulations show that the existence of the array of blocks results in stagnant¯ow regions between blocks in which heat convected to the ambient¯ow ®eld is limited. It was found that heat transfer can be enhanced passively, especially in the areas between blocks, by opening the chip board between blocks. The enhancement of heat transfer thus occurring is presumably due to a pseudo-suction force which induces a vertical¯ow between blocks. The enhancement of heat transfer for the chips on-board is re¯ected by a global increase of the Nusselt number on the chip blocks, especially on the west sides of the chips located further downstream of the¯ow direction. Further investigation shows that the chip-to-chip temperature variations diminish if the openings located upstream of the front end block and downstream of the rear end block are sealed. The optimal cooling con®guration for the array of chip blocks can be utilized by the electronics industry.

An innovative concept of an electronic learning system has been established in an attempt to achieve a technology that provides engineering students with an instructive and affordable framework for learning engineering-related courses. This system utilizes an existing Computational Fluid Dynamics (CFD) package, Active Server Pages (ASP) programming, Hyper Text Markup Language (HTML) web page, and a database in the development of a user-friendly interface for the e-learning system. The structure of this learning system includes three components: a pre-processor which creates and defines the problems, a control program which links CFD package; searches for the identical problem with previously executed results or creates a new CFD execution and then saves the results in the database, and a postprocessor which yields a graphic presentation of the computational results. This system would provide engineering students with a solid comprehension of the physical phenomena by changing the input parameters of a specific problem.ß2005 Wiley Periodicals, Inc. Comput Appl Eng

No abstract

This study examined the deposition of CoFeB thin films on a glass substrate at room temperature (RT), as well as the effects of conducting postannealing at heat annealingTA=150°C for 1 h. The thickness (tf) of the CoFeB thin films ranged from 100 Å to 500 Å. The microstructure, average contact angle, and surface energy properties were also investigated. X-ray diffraction (XRD) revealed that CoFeB films are nanocrystalline at RT and that post-annealing treatment increases in conjunction with the crystallinity. The surface energy of the CoFeB thin films is related to adhesive strength. The CoFeB films form a contact angle of larger than90∘with water as a test liquid. This finding demonstrates that the CoFeB film is hydrophobic. Astfincreases from 100 Å to 500 Å, the surface energy at RT decreases from 40 mJ/mm2to 32 mJ/mm2. During post-annealing treatment, the surface energy increases from 32 mJ/mm2to 35 mJ/mm2, astfincreases from 100 Å to 300 Å; then it decreases to 31 mJ/mm2, astfincreases from 300 Å to 500 Å. The surface energy of the as-deposited CoFeB thin films exceeds that during post-annealing treatment at thicknesses of 100 Å and 200 Å, suggesting that as-deposited CoFeB thin film increases the adhesion.