Abstract
Nanofluids, which are liquids containing nanoparticles, are used to modify heat transfer performance in various systems. To explain the mechanism of heat transfer modification with nanofluids, many theories have been suggested based on numerical simulations without experimental validation because there is no suitable experimental method for measuring the velocity fields of nanofluid flows. In this study, the measurement accuracy of micro-particle image velocimetry (μ-PIV) is systemically quantified with Al2O3 and multi-walled carbon nanotube (MWCNT) nanofluids. Image quality, cross-correlation signal-to-noise ratio, displacement difference, and spurious vector ratio are investigated with static images obtained at various focal plane positions along the beam pathway. Applicable depth is enough to investigate micro-scale flows when the concentrations of Al2O3 and MWCNT nanofluids are lower than 0.01% and 0.005%, respectively. The velocity fields of Hagen–Poiseuille flow are measured and compared with theoretical velocity profiles. The measured velocity profiles present good agreement with the theoretical profiles throughout. This study provides the criteria for μ-PIV application and demonstrates that μ-PIV is a promising technique for measuring the velocity field information of nanofluids.
Highlights
Over the past century, energy consumption reduction has received much attention in various research fields
This study provides the criteria for μ-particle image velocimetry (PIV) application and demonstrates that μ-PIV is a promising technique for measuring the velocity field information of nanofluids
The measurement accuracy of the μ-PIV technique is systemically quantified for measuring nanofluid flows with static images captured at various depths
Summary
Energy consumption reduction has received much attention in various research fields. In heat transfer systems such as heat exchangers and electronic components, many researchers have focused on the reduction of energy consumption called heat transfer enhancement [1,2]. To improve heat transfer performance in miniaturized systems, nanofluids, which are liquids containing nanometer-sized particles called nanoparticles, were introduced in 1995 by. Various studies have been widely conducted in the research fields of heat transfer using nanofluids, and it is found that the addition of nanoparticles affects thermo-physical properties such as thermal conductivity, viscosity, and surface tension [4,5,6,7,8,9,10,11,12,13]
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