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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.
Found in: osebi
Keywords: MWCNT, thermal lens, fractals, nonlinear time series, phase portrait, sample entropy
Published: 28.06.2022; Views: 449; Downloads: 0
Fulltext (3,59 MB)

Abstract: The manuscript elucidates the potential of phase portrait, fast Fourier transform, wavelet, and time-series analyses of the heart murmur (HM) of normal (healthy) and mitral regurgitation (MR) in the diagnosis of valve-related cardiovascular diseases. The temporal evolution study of phase portrait and the entropy analyses of HM unveil the valve dysfunctioninduced haemodynamics. A tenfold increase in sample entropy in MR from that of normal indicates the valve dysfunction. The occurrence of a large number of frequency components between lub and dub in MR, compared to the normal, is substantiated through the spectral analyses. The machine learning techniques, K-nearest neighbour, support vector machine, and principal component analyses give 100% predictive accuracy. Thus, the study suggests a surrogate method of auscultation of HM that can be employed cost-effectively in rural health centres.
Found in: osebi
Keywords: phase portrait, auscultation, mitral valve dysfunction, heart murmur, nonlinear time series analysis
Published: 28.06.2022; Views: 388; Downloads: 0
Fulltext (2,02 MB)

Abstract: The search for excellent heat transfer fuids necessitates the development of novel nanofuids. The paper is the frst report revealing the potential of sodium carbide (Na2C2) nanoparticle for heat transfer and thermal shielding applications. For this, Na2C2 is prepared from the porous carbon matrix of Aloe vera leaves by hydrothermal method. The morphological changes on hydrothermal treatment and the thermal stability are analyzed by Field Emission Scanning Electron Microscopy and Thermogravimetry. The X-ray difraction analysis reveals the formation of sodium carbide, which is confrmed by Fourier transform infrared, Ultraviolet–Visible–Near Infrared, and Raman spectroscopic analyses. The spectroscopic study of the sample synthesized shows indirect bandgap energy of 1.58 eV. The thermal difusivity of Na2C2 nanofuid, determined by the single-beam thermal lens technique, exhibited 87 % enhancement for the base fuid, suggesting its potential in heat transfer applications.
Found in: osebi
Keywords: Aloe vera, Heat transfer, Organometallic, Sodium carbide, Thermal lens
Published: 04.07.2022; Views: 320; Downloads: 0
Fulltext (1,75 MB)

Abstract: The thermodynamics of the seed matter after imbibition is highly significant as the growth and germination involve complex biochemical exergonic process. The germination of seed and compositional variation of the seed matter has always been a fascinating field of research. The present work unveils the thermodynamics associated with the changing thermal diffusivity of the seed matter through the green technology-based single-beam thermal lens technique. Investigations are carried out in Vigna radiata seeds, germinating in media with and without carbon allotropes, through various spectroscopic techniques. The morphology of the soot and carbon allotropes is understood from the field emission scanning electron microscope images. The thermal lens study throws light into the energy trapping nature of the seed matter of the seed growing in carbon allotropic media which facilitates biosynthesis. The observed increased rate of growth of the seed is substantiated through the ultraviolet–visible–near-infrared (NIR), Fourier transform infrared, and photoluminescence (PL) spectroscopic analyses. The NIR and PL studies also reveal the formation of chlorophyll molecule during germination. Thus, the study suggests a mechanism for tuning the thermal diffusivity of the seed matter as to trap the biochemical energy to facilitate the further biosynthesis and thereby to enhance the growth rate.
Found in: osebi
Keywords: seed matter, thermal diffusivity, thermal lens, carbon nanoparticle, soot
Published: 04.07.2022; Views: 337; Downloads: 0
Fulltext (2,68 MB)

Abstract: This paper employs the sensitive single-beam thermal lens technique for analyzing the thermal behavior of gasoline soot containing allotropes of carbon by preparing its nanofluid (NF). The soot, annealed at different temperatures up to 400 ○C (the samples), used for preparing the NF, is found to enhance the thermal diffusivity (α) up to 95% without changing the solid volume fraction, suggesting its possible use in coolants. The thermal induced modifications are understood from the field emission scanning electron microscopic, X-ray diffraction (XRD),thermogravimetric, and Raman spectroscopic analyses. The variation of α of the sample is found to exhibit similar variations observed in XRD and Raman spectroscopic analyses. The study stresses the significance of the optimum temperature (300 ○C) for the soot NF above which morphological and structural modifications may lead to thermal energy trapping rather than dissipation or cooling.
Found in: osebi
Keywords: petrol soot, thermal lens, thermal diffusivity
Published: 04.07.2022; Views: 403; Downloads: 0
Fulltext (3,08 MB)