Minimum Energy Design for Manufacturability of Air Cooled Heat Sinks

The substantial material stream, and energy consumption, associated with the cooling of desktop computers, servers, routers, and power electronic modules contribute significantly to the depletion of key resources. To reduce this severe environmental impact, while meeting the thermal management requirements of these components and systems, it is essential that a minimum energy, design-for-manufacturability approach be followed in the design and commercialization of such air-cooled heat sinks. In this paper, a design-for-manufacturability methodology (DFM) is combined with a least-energy optimization methodology, using the total Coefficient of Performance (COP_T), to identify practical low energy designs and existing gaps in manufacturing capability that prevent the attainment of the ideal minimum energy solutions. The COP_T methodology relates the heat sink cooling capability to the invested fan pumping work and the thermodynamic work required to manufacture and assemble the heat sink and seeks to maximize the thermal energy that can be extracted from a specified space, while minimizing the material and energy consumed in the fabrication and operation of the specified heat sink. This combined methodology was applied to aluminum, copper, and magnesium as potential heat sink materials for a fixed input work of 20 kWh, and for three different duty cycles, namely, sporadic (1500 h), periodic (6000 h), and continuous (26208 h), respectively. The results presented herein, are derived for heat sinks on a 10 cm by 10 cm isothermal base, and 5 cm fin height, operating at an excess temperature of 25 K relative to the inlet air. The thermo-fluid analysis of the forced convection rectangular plate-fin array has been carried out using a well-validated semi-analytical model. The energy-optimal aluminum, copper and magnesium designs are compared to draw quantitative and qualitative conclusions.