Experimental study on influences of cylindrical grooves on thermal efficiency, exergy efficiency and entropy generation of CPU cooled by nanofluids

An experiment set for researching the flow and heat transfer characteristics of nanofluids flowing through CPU is established and validated. The influences of groove depths (1 mm, 2 mm, 3 mm) and arrangement modes (aligned and staggered arrangements) on thermo-hydraulic performances of CPU cooled by TiO2 -water nanofluids are explored. In addition, the influences of nanoparticle mass fractions (0.0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%) and Reynolds numbers (472-1198) are studied. It is found that there is a most appropriate nanoparticle mass fraction (0.3%) and groove depth (2 mm) for the lowest CPU temperature. Heat transfer augmentation of CPU heat sink is more sensitive to staggered arrangement grooves and high Reynolds number. Nanofluids (0.3%) in CPU heat sink with staggered arrangement grooves (2 mm) show the best heat transfer performances. Lastly, thermal efficiency, exergy efficiency and entropy generation are applied to analyze the cooling performance of enhanced structure. Results show that the thermal efficiency decreases with mass fraction when Reynolds number is less than 791, but increases with the depth of groove. Exergy efficiency of the groove structure can be obviously strengthened under the same pumping power and mass flow rate. From entropy generation analysis, it is found that the aligned arrangement shows lower entropy generation performance than aligned arrangement. (C) 2019 Elsevier Ltd. All rights reserved.