Repozitorij Univerze v Novi Gorici

Iskanje po repozitoriju
A+ | A- | Pomoč | SLO | ENG

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju

Opcije:
  Ponastavi


21 - 30 / 68
Na začetekNa prejšnjo stran1234567Na naslednjo stranNa konec
21.
Concentration-dependent thermal duality of hafnium carbide nanofluid for heat transfer applications : a mode mismatched thermal lens study
Vijayakumar Gokul, Mohanachandran Nair Sindhu Swapna, Vimal Raj, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek

Opis: he mode mismatch dual-beam thermal lens technique is a sensitive tool for studying the nanofuids’ thermal difusivity in thermal engineering. The work reports the low-temperature green synthesis of hafnium carbide (HfC) using rice four as a natural carbon precursor and its potential in heat transfer nanofuids by studying the concentration-dependent thermal difusivity. The structure characterisations confirm the formation of HfC, whose refractory nature is revealed through the high thermal stability observed in the thermogravimetric analysis. The Tauc plot analysis shows direct bandgap energy of 2.92 eV. The fuorescence study suggests bluish-pink emission with CIE coordinates (0.271, 0.263). The existence of the critical concentration of HfC in the nanofuid decides its suitability for heat transfer or heat trap applications indicating a concentration-dependent thermal duality. Thus, the study is signifcant as it overcomes the major drawbacks of the existing methods of the synthesis of refractory HfC, using toxic chemical and costly equipment for heat transfer applications.
Ključne besede: hafnium carbide, hydrothermal synthesis, rice flour, thermal lens spectroscopy
Objavljeno v RUNG: 04.07.2022; Ogledov: 1089; Prenosov: 0
Gradivo ima več datotek! Več...

22.
Laser-induced thermal lens study of the role of morphology and hydroxyl group in the evolution of thermal diffusivity of copper oxide
Riya Sebastian, Mohanachandran Nair Sindhu Swapna, Vimal Raj, Sankaranarayana Iyer Sankararaman, 2022, izvirni znanstveni članek

Opis: The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens (TL) technique. For this purpose, the decomposition of Cu(OH)2 into CuO is studied in a time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications, from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement of base fluid’s thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of CuO.
Ključne besede: thermal diffusivity, CuO, thermal lens, morphology, hydroxyl group
Objavljeno v RUNG: 04.07.2022; Ogledov: 974; Prenosov: 0
Gradivo ima več datotek! Več...

23.
Acclimatisation through thermal diffusivity tuning of coconut oil – A mode mismatched dual-beam thermal lens study
Mohanachandran Nair Sindhu Swapna, 2022, izvirni znanstveni članek

Opis: Background: Ayurvedic medicinal oils traditionally prepared by blending herbal extracts in different compositions are commonly used for treatment and improving health. The estimation of the thermal properties of medicinal oils is essential for practical applications. Objective: The present work aims to expound the ability of medicinal oils for the acclimatization of body temperature by determining its thermal diffusivity and thereby providing a validation to the traditional knowledge. Materials and methods: The medicinal oils are prepared by incorporating black pepper (Piper nigrum), aloe vera (Aloe barbadensis), hibiscus bud (Hibiscus rosa-sinensis) and Ocimum sanctum in coconut oil base. The samples are subjected to thermal diffusivity study using the mode-mismatched dual-beam thermal lens technique. Results: The study reveals that the incorporation of black pepper (Piper nigrum), having hot potency (Ushna veerya), to the base fluid lowers the thermal diffusivity value, suggesting its potential in heat-trapping. The addition of aloe vera (Aloe barbadensis), hibiscus bud (Hibiscus rosa-sinensis), and O. sanctum dissipates heat energy quickly, thus increases the thermal diffusivity of coconut oil revealing a cold potency (Sheeta veerya). The study provides a validation for traditional knowledge and delineates the possiblity of thermal diffusivity tuning of the base fluids. Conclusion: The thermal diffusivity tuning through incorporation of herbal extracts can effectively be used to acclimatize the human body temperature with the surroundings. A higher thermal diffusivity value induces a cooling effect and the lower value causes heating effect. This, opens up the possibility of using thermally tuned oils depending on climate and geographical location.
Ključne besede: Ayurveda, Acclimatization, Medicinal oils, Thermal lens spectroscopy Thermal diffusivity
Objavljeno v RUNG: 04.07.2022; Ogledov: 971; Prenosov: 0
Gradivo ima več datotek! Več...

24.
Allotropic transformation instigated thermal diffusivity of soot nanofluid: Thermal lens study
Mohanachandran Nair Sindhu Swapna, RAJ VIMAL, Sankararaman S, 2019, izvirni znanstveni članek

Opis: 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.
Ključne besede: petrol soot, thermal lens, thermal diffusivity
Objavljeno v RUNG: 04.07.2022; Ogledov: 1093; Prenosov: 0
Gradivo ima več datotek! Več...

25.
Tuning the thermal diffusivity of the seed matter for enhanced biosynthesis: A thermal lens study
Mohanachandran Nair Sindhu Swapna, Sankararaman S, 2020, izvirni znanstveni članek

Opis: 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.
Ključne besede: seed matter, thermal diffusivity, thermal lens, carbon nanoparticle, soot
Objavljeno v RUNG: 04.07.2022; Ogledov: 1124; Prenosov: 0
Gradivo ima več datotek! Več...

26.
Absolute Porosity Analysis in Carbon Allotropic Nanofluids: A Sankar–Swapna Model Approach
Mohanachandran Nair Sindhu Swapna, SREEJYOTHI S, Sankararaman S, 2020, izvirni znanstveni članek

Opis: Porous materials have gained significant attention in recent years as a class of material exhibiting interesting chemical and physical properties. The existing methods of porosity analysis have limitations that prevent absolute porosity measurement. Hence, a technique independent of surface physical properties alone can give the absolute porosity of the material. The porosity greatly influences the thermal diffusivity of a material. The manuscript is the first report of employing the Sankar–Swapna model for analyzing the porosity variations in carbon allotropic nanofluids. The model helps not only in getting information about the absolute porosity variations among samples, but also suggests morphological modifications through the thermal diffusivity study using the sensitive single-beam thermal lens technique. The variations in thermal diffusivity and absolute porosity values are also correlated to morphological modifications based on the theoretical model and thereby proposing this as a surrogate method for absolute porosity analysis.
Ključne besede: absolute porosity, Sankar–Swapna model, thermal diffusivity, thermal lens, thermal conductivity
Objavljeno v RUNG: 04.07.2022; Ogledov: 1140; Prenosov: 0
Gradivo ima več datotek! Več...

27.
Organometallic sodium carbide for heat transfer applications: A thermal lens study
Mohanachandran Nair Sindhu Swapna, Sankararaman S, 2020, izvirni znanstveni članek

Opis: 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.
Ključne besede: Aloe vera, Heat transfer, Organometallic, Sodium carbide, Thermal lens
Objavljeno v RUNG: 04.07.2022; Ogledov: 1020; Prenosov: 0
Gradivo ima več datotek! Več...

28.
29.
Development of Zinc Oxide-Multi-Walled Carbon Nanotube hybrid nanofluid for energy-efficient heat transfer application: A thermal lens study
Mohanachandran Nair Sindhu Swapna, 2021, izvirni znanstveni članek

Opis: This paper addresses the need for developing an energy-efficient hybrid nanofluid with zinc oxide–multi-walled carbon nanotube (ZnO-MWCNT) for overcoming the bottleneck of efficient heat transfer in thermal systems. The concentration-dependent thermal diffusivity modifications are analyzed using the highly sensitive mode mismatched thermal lens technique. The hybrid composite is prepared by the solid-state mixing and annealing of a pure multi-walled carbon nanotube (MWCNT) and zinc oxide (ZnO), synthesized by the solution combustion method. The composite formation is studied by structural, morphological, and optical characterization techniques. Among the three nanofluids ZnO, MWCNT, and ZnO-MWCNT, the composite exhibits a drastic enhancement in thermal diffusivity at a lower solid volume fraction of 0.047 mg/ml containing 0.009 mg/ml of MWCNT. All the nanofluids show an optimum concentration beyond which the thermal diffusivity decreases with the nanoparticle concentration. Thus, this study suggests the potential application of ZnO-MWCNT hybrid nanofluids in thermal system design to enhance internal combustion engines' efficiency during cold-start.
Ključne besede: Zinc Oxide, MWCNT, hybrid nanofluid, thermal lens, diffusivity, engine efficiency
Objavljeno v RUNG: 30.06.2022; Ogledov: 1207; Prenosov: 0
Gradivo ima več datotek! Več...

30.
Pharmacological application of thermal Lens technique - A thermal diffusivity study
Mohanachandran Nair Sindhu Swapna, 2018, izvirni znanstveni članek

Opis: The photothermal phenomenon has emerged as a potential tool for the nondestructive evaluation of thermal and optical properties of materials. Thermal analysis of drugs is an unavoidable part of preformulation study, as temperature variations can induce structural changes of the constituents of drugs. Techniques based on photothermal phenomena are highly sensitive, as only the absorbed radiation contributes to the signal. Periodic illumination and subsequent nonradiative de-excitation generate thermal lens signals of various types within and around the sample. Variation of thermal diffusivity with a concentration of the commonly used drug terbutaline is studied through the single-beam thermal lens technique. The ultraviolet–visible spectrum of the drug shows strong absorption around 500 nm, which suggests the possible wavelengths that can be used for the study. It is found that concentration of the drug in liquid form decides its thermal stability, as its thermal diffusivity varies with concentration. The study gives information about the optimum value for the concentration of the drug noted above for which the chance of thermal stability is high.
Ključne besede: thermal lens, thermal diffusivity, pharmacology, drug
Objavljeno v RUNG: 30.06.2022; Ogledov: 1030; Prenosov: 0
Gradivo ima več datotek! Več...

Iskanje izvedeno v 0.06 sek.
Na vrh