Experimental study of the effects of nanofluids on wicking ability and thermal performance of a vertical open microgrooves heat sink

摘要

Open microgrooves heat sinks (OMHSs) are one kind of capillary-driven heat transfer systems and achieve highly efficient heat transfer by evaporation and boiling. Thermal performance of an OMHS depends on its wicking ability, which is evaluated by the axial wetting length (AWL). This work investigated the effects of Fe3O4-water nanofluids on wicking ability and thermal performance of a vertical OMHS at relatively low particle concentrations. The AWL was characterized by infrared thermal imaging. At each concentration, the wall superheat is reduced significantly due to the enhanced wicking. There exists an optimum concentration, 0.00375 vol% which leads to a 41% decrease in the wall superheat and a 22% increase in the AWL compared with those for the base liquid. Either increasing or decreasing the concentration reduces the enhancements. It is demonstrated that the suspended particles in the liquid and the particle deposition are all important for enhancing the wicking ability and thermal performance and their contributions to the enhancements are simultaneously maximized at 0.00375 vol%. The suspended particles are supposed to promote liquid wetting and the pinning of three-phase contact line by inducing an additional structural disjoining pressure. At 0.00375 vol%, the pinning in the corner-flow region was confirmed and found to be responsible for the rise of AWL when boiling occurred. (C) 2019 Elsevier Ltd. All rights reserved.