Executive Summary : | The server computers, which are used to process big data, are prone to generate higher heat density, which in turn leads to the increase in temperature of the microprocessor/central processing unit (CPU) and thereby demands for appropriate heat dissipation mechanism. Moreover, the present era of miniaturization of server computers brings in additional challenge of imbalance in the microprocessor power distribution, which then leads to the generation of hot spots. This adversely impacts the microprocessor performance, consistency as well as drops its cooling efficiency. Among the options available to cool the CPU electric circuitry, air cooling technique with heat sink is one of the most effective techniques, in terms of the cost, reliability and weight etc. The design criteria needed to be considered for CPU heat sink manufacturing are enhanced heat transfer rate, higher thermal conductivity of the material being used for heat sink development, simpler structure, and low pressure drop. Although liquid cooling techniques of CPU heat sinks are more effective than that of air cooling, however, liquid cooling techniques demands for regular maintenance, design complexities, and thereby expensive. In the above context, staggered micro-pin-fin heat sinks offers promise to dissipate higher heat flux for a particular flow rate of working fluid and heat transfer surface of the heat sink. However, there are challenges to use micro-pin-fin heat sinks for CPU cooling, such as achieving cost effectiveness by adopting appropriate micro fabrication technique of heat sink development as well as choosing low cost, high thermal conductivity heat sink material. In view of the above, the present proposal has been planned to develop novel Micro-stirr cast (μStirr) heat sink out of novel Al-Si-MWCNT alloy composite for Thermal management of CPU main board chips of High-Performance Servers, which is expected to be of thermal conductivity of 300-500 W/mK. Here, the micro metal casting i.e., semi solid casting via micro-stirr casting route offers promise to manufacture micro-pin-fin heat sinks in near-net shape, with utmost design freedom and cost efficiency. Whereas the targeted thermal conductivity values of the proposed heat sink material are significantly higher than the thermal conductivity of presently available Al alloy based micro CPU heat sinks (96.2-161 W/mK), which offers promise towards significant improvement of the performance/life expectancy of the heat-generating component/CPU chip. It is to be noted here that the proposed μStirr technique facilitates orientation of MWCNTs within the inter-globular spacings of primary Al grains of the said composite and thereby improves its thermal conductivity significantly. Further, it is worthwhile to mention here that, M/S Qualitek Engineers, Bengaluru, a leading Indian manufacturer of heat sinks for various applications, has given their consent to participate in the project as an "Industry partner". |