Showing papers by "Avram Bar-Cohen published in 2002"

Thermal challenges in next generation electronic systems - summary of panel presentations and discussions

Abstract: The presentations made, as well as the discussions, in the panels at the workshop, Thermal Challenges in Next Generation Electronic Systems (THERMES), are summarized in this paper. The panels dealt with diverse topics including thermal management roadmaps, microscale cooling systems, numerical modeling from the component to system levels, hardware for future high performance and Internet computing architectures, and transport issues in the manufacturing of electronic packages. The focus of the panels was to identify barriers to further progress in each area that require the attention of the research community.

Intravascular temperature sensor

Abstract: Devices and methods for detecting vulnerable plaque within a blood vessel are disclosed. A catheter in accordance with the present invention includes an elongate shaft having a proximal end, a distal end, and an outer surface. At least one temperature sensor is disposed proximate to the distal end of the elongate shaft. In one preferred embodiment, the at least one temperature sensor is adpated to contact inner surface of the blood vessel. In another preferred embodiment, at least one temperatre sensor is disposed within a channel defined by a body member that is disposed about the elongate shaft.

Design and optimization of air-cooled heat sinks for sustainable development

Abstract: The development of heat sinks for microelectronic applications, which are compatible with sustainable development, involves the achievement of a subtle balance between a superior thermal design, minimum material consumption, and minimum pumping power. Due to the rapid proliferation of electronic systems, substantial material streams and energy consumption rates are associated with the cooling of computers, as well as other categories of electronic equipment. This presentation explores the potential for the least-energy optimization of natural- and forced-convection cooled rectangular plate heat sinks. The results are evaluated in terms of a heat sink coefficient of performance, relating the cooling capability to the energy invested. Guidelines for "sustainable" heat sink designs are suggested.

Experimental modeling of the passive cooling limit of notebook computers

Abstract: Rapid expansion of the portable computing market segment coupled with ever increasing power dissipation and severe battery power limitations are combining to bring new importance to the development of minimum-energy thermal solutions for notebook-type computers. Passive cooling provides a very attractive thermal management option for such systems. Determination of the amount of heat that can be passively dissipated from the outer surfaces of a notebook computer provides thermal designers with a well-defined performance target and a quantitative demarcation between actively and passively cooled equipment categories. Previous work has analytically and numerically estimated the passive cooling limit from the external surfaces of a 305/spl times/248 mm notebook and found that as much as 38.8 Watts could be dissipated. The current paper describes the experimental validation of the natural convection models, underpinning those results, and the apparatus used to obtain the necessary data. The measurement error and repeatability in this apparatus are also described. In addition to validating the isolated, isothermal natural convection models, experiments were conducted to explore "real world" behavior, such as 3-D flow effects and interactions between heat dissipating surfaces. The experimental results are used to refine the theoretical limits on passive cooling.

Energy efficient cooling of notebook computers

Abstract: The majority of today's leading-edge notebook computers relies on heat pipes for internal spreading and use forced convection, with micro-fans, to reject heat to the ambient. Such techniques have worked efficiently in the relatively flat form factor of these computers, but may not be capable of providing high heat flux cooling in ever shrinking volumes. Moreover, the power limitations of portable computers, as well as growing concern for the environment, make it desirable that the requisite thermal management be accomplished with a minimum expenditure of energy. It is, thus, essential that the developers of such notebook computers follow a rigorous design methodology and achieve an optimal design for energy and space savings. This paper illustrates a "top down" thermal design methodology aimed at achieving energy efficient thermal management in a compact notebook computer, while satisfying the requirements for highly integrated design. The paper begins with a review of the passive cooling limits, and uses analytic models to determine the thermal performance that can be attained in a standard notebook form factor. Numerical modeling, along with additional analysis, is used to design the optimum compact active cooling system for both for space and energy efficiency.

Design and Optimization of Forced Convection Heat Sinks for Sustainable Development

Abstract: The development of forced convection heat sinks for microelectronic applications, which are compatible with sustainable development, involves the achievement of a subtle balance between a superior thermal design, minimum material consumption, and minimum pumping power. Due to the rapid proliferation of electronic systems, substantial material streams and energy consumption rates are associated with the cooling of computers, as well as other categories of electronic equipment. The study reported herein explores the potential for the least-energy optimization of forced convection cooled rectangular plate heat sinks. Analytical models are used to determine the thermal performance of such heat sinks, for pressure drops in the range of 20 to 80Pa and flow rates between 0.01 and 0.04 m3/s. The results are evaluated in terms of a heat sink Coefficient of Performance, relating the cooling capability to the energy invested. Guidelines for "sustainable" heat sink designs are suggested.

Least-energy optimization of forced convection plate-fin heat sinks

Abstract: A coefficient of performance (COP/sub T/) analysis for plate fin heat sinks in forced convection is presented and shown to provide a viable technique for combining least-material optimization with the entropy minimization methodology. The COP/sub T/ metric relates the heat sink cooling capability to the invested fan pumping work and the thermodynamic work required to manufacture and assemble the heat sink. The proposed optimization methodology maximizes the forced convection cooling that can be achieved by a heat sink occupying a specified volume, with a fixed energy investment and entropy generation rate. In addition, the study identifies the presence of an optimal resource allocation ratio, providing the most favorable distribution of existing energy resources, between heat sink manufacturing and operation, over a fixed product life cycle.