Thermal Lensing of Multi-walled Carbon Nanotube Solutions as Heat Transfer Nanofluids

Abstract

This paper unwraps nanofluids' particle dynamics with multi-walled carbon nanotubes (MWCNTs) in base fluids such as acetone, water, and ethylene glycol. Having confirmed the morphology and structure of the MWCNTs by field emission scanning electron microscopy, X-ray diffraction, and Raman spectroscopic analyses, the nanofluids are prepared in three different concentrations. The nonzero absorbance at the laser wavelength, revealed through the UV−visible spectrum, makes the thermal diffusivity study of the sample by the sensitive nondestructive single beam thermal lens (TL) technique possible. The TL signal analysis by time series and fractal techniques divulges the complex particle dynamics, through phase portrait, sample entropy, fractal dimension, and Hurst exponent. The study unveils the effect of the amount of nanoparticles and the viscosity of the medium on thermal diffusivity and particle dynamics. The observed inverse relation between thermal diffusivity and viscosity is in good agreement with the Sankar−Swapna model. The complexity of particle dynamics in MWCNT nanofluids reflected through sample entropy, and fractal dimension shows an inverse relation to the base fluid's viscosity. This paper investigates the role of viscosity of the base fluid on particle dynamics and thermal diffusivity of the nanofluid to explore its applicability in various thermal systems, thereby suggesting a method to tune the sample entropy through proper selection of base fluid.

Solid‐Volume‐Fraction Retained Tailoring of Thermal Diffusivity of Multiwalled Carbon Nanotube Nanofluid: A Photothermal Investigation

“…The (002) plane is attributed to the ordered CNTs and the sp 2 ‐bonded carbon atoms of the graphitic E 2g mode, and (100) plane is due to the honeycomb‐like hexagonal lattice present in MWCNTs. [ 6 ] The effect of annealing on MWCNT's structure becomes evident from the variation of the peak intensities at 25.8° and 42.5°, shown in Figure 4b,c, respectively. The intensity of both the peaks shows a decreasing trend due to the decrease in the number of planes responsible for the diffraction.…”

“…The setup is standardized by estimating the α of base fluid, and it is obtained as (0.98 ± 0.01) × 10 −7 m 2 s −1 , which agrees well with the literature reports. [ 6 ] From the variation of the value of α of nanofluids with MWCNTs annealed at a different temperature, shown in Figure , it is evident that the annealing of MWCNTs has a profound effect on the thermal diffusivity of nanofluids. Figure 12 suggests a second‐order nonlinear variation with R 2 = 0.95.…”

“…The literature shows that a substantial amount of work has been done on CNT nanofluids. [ 6,10,16,18,20 ]…”

Time-Resolved cw Thermal Z-scan for Nanoparticles Scattering Evaluation in Liquid Suspension

“…Consequently, different physical phenomena can be explored using the thermal lens (TL) principle to study: for example, properties of solid-state laser glasses [ 7 ]. In [ 8 ], the authors investigated the molecular/particle dynamics and, in [ 9 ], by measuring photothermal parameters of opaque solids. Moreover, Z-scan [ 10 ] based methods were performed at different regimes of excitation to understand the origin of the third-order nonlinear optical response [ 11 ] and the influence of the accumulated thermal effect, which can be an artifact in femtosecond closed-aperture Z-scan measurements [ 12 ].…”

Numerical Simulation of the Whole Thermal Lensing Process with Z-Scan-Based Methods Using Gaussian Beams

“…Many applications use the thermal lens (TL) principle as an ultrasensitive spectrophotometric readout [1] to characterize different physical phenomena, for example (recently found in the literature) to investigate molecular/particle dynamics [2], to measure the photothermal parameters of opaque solids [3], to understand thermal lensing effects using Z-scan-based methods at multiple laser repetition rates and multiple average powers [4,5], to study the effect of highly localized thermal gradients on the catastrophic optical damage process of high-power laser diodes [6], to evaluate optically induced temperature changes in colloidal samples for photothermal therapy [7], to quantify very low concentrations in solutions [8], and to image single light-absorbing nanoparticles by photothermal microscopy [9]. Recently, we have demonstrated experimentally the feasibility of extracting an image of the phase shift induced by TL and applying this method to map an inhomogeneous thin film doped with different concentrations of silver nanoparticles transversally [10].…”