Energy 2030

Organizing Committee

Final Program

Poster Exhibition Venue 2006 Proceedings


Proceedings of the Second International Energy 2030 Conference,
November 4-5, 2008, Abu Dhabi, U.A.E.

Thermal Design for Sustainability of Air Cooled Heat Sinks

Avram Bar-Cohen

University of Maryland, USA

Madhusudan Iyengar

International Business Machines, USA

Extended surfaces of fins, or so-called heat sinks, are in common use in the electronic industry and serve to extend the thermal capability of convective cooling with air. The use of passive, natural convection cooled heat sinks offers substantial advantages in cost and reliability, but is often accompanied by relatively low heat transfer rates, and significant added mass. The use of fan driven forced air cooling facilitates high performance, compact, and lighter heat sink designs, but at the increased burden of pumping power. Thus, the substantial material stream and energy consumption rate associated with the cooling of electronic equipment using air cooled heat sinks, lends urgency and importance to the "perfection" of these fin arrays. The financial constraints at work in the electronic industry make it essential that specific cooling requirements be achieved with the lowest cost solution. It is anticipated that in large volume production, as worldwide energy costs escalate, the “least-energy” solution will nearly always provide the lowest cost solution.

The least-energy optimization of natural and forced-convection plate-fin heat sinks is described. Emphasis is placed on the use of a Coefficient of Performance, COPT, relating cooling capability to the energy invested in the formation, fabrication, and operation of the heat sink. It is shown possible to determine the heat sink geometry, which maximizes the value of COPT, for each operating condition and cooling mode. For forced convection cooling, the most favorable distribution of invested energy - between heat sink formation/fabrication and operation - can also be found. Although optimum natural convection heat sinks can deliver highly reliable, noise-free, operation, the COPT values for forced convection cooled heat sinks are found to far exceed the values associated with passive cooling. The thermal analysis of the natural convection rectangular plate-fin array has been carried out using a previously developed model by Iyengar and Bar-Cohen [1], which utilizes the composite Nusselt number correlation developed by Bar- Cohen and Rohsenow [2] to calculate the fin average heat transfer coefficient. The forced convection results are obtained using a well-validated, semi-analytical model developed by Holahan et al. [3]. In order to concretize the benefits of such "least-energy" heat sink designs, the proposed modeling and optimization techniques will be applied to an advanced heat sink configuration, considered suitable for the cooling of a high-end microprocessor. Thus, many of the results are derived for an aluminum plate-fin heat sink on a 10cm × 10cm base, and 5cm fin height, operating at an excess temperature of 25 K.


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