Slip-Flow Enhanced Heat Transfer in Microchannel Heat Sink via Carbon Nanotube-Based Nanofluid

Microchannel heat sinks (MCHS) belong to one of the most prominent methods of passive cooling of microelectronics. In this work, a circular microchannel-based MCHS was installed over a microelectronic mimicking heated surface, which was subjected to 50 to 125 kW/m², and the convective cooling of MCHS was studied using nanofluids of copper (Cu) and carbon nanotube (CNT) [both at 0.05 wt % concentration in de-ionized (DI) water] as coolant, along with DI water. The experimental results suggest that the nanofluid-cooled MCHS, especially the CNT one, outperformed the pure water-cooled system, with significantly higher heat transfer coefficient (HTC), and lower pumping power, rendering the former system more energetically favorable. At a flow rate of 60 ml/min and heat flux of 100 kW/m², the HTC enhancements in water + CNT and water + Cu were 15.7 and 6.2% more than water, respectively. Due to addition of surfactant in DI water for suspending CNT, an apparent slip flow became prevalent in the microchannel, leading to a significant pressure drop reduction while pumping water + CNT. This observation helped in gauging the total power saving that can be accessed using water + CNT, if one follows periodic heating/cooling between an upper critical temperature and safe temperature range rather than continuous cooling of the electronic surface.