Journal of Thermal Analysis and Calorimetry

Sharma, Jeet Prakash; Sharma, Aashish; Jilte, Ravindra D.; Kumar, Ravinder; Ahmadi, Mohammad Hossein

doi: 10.1007/s10973-019-08741-4pmid: N/A

At present, miniaturization of the devices in order to make them for effective performance, reliability and ease at cost is the primary need of any nation. In this direction, the role of microchannels can play an important role in the further development of industrial growth. The increased demand of the microchips in the industrial areas has increased the number of transistors for the improved functionality which leads to the emission of the higher heat flux, which is already a big challenge in the electronic sector. In the present paper, a comprehensive review on microchannels has been done regarding single-phase and multi-phase studies. In the present paper, an intensive review of the thermal and hydraulic characteristics of fluid flow in microchannels at different hydraulic diameters and their effects on performance has been done. The effects of the various parameters such as the Reynolds number (Re), Nusselt number (Nu), friction factor (f), pressure drop (P), working fluid and cross-sectional geometry of duct, as well as the hydrodynamic and thermal aspects, has been also studied. It was concluded through the literature study that transition from laminar to turbulent is very much affected by channel cross-sectional geometry, aspect ratio, channel wall roughness and compressibility effects. Also, researchers only explored the laminar region for its pressure drop and heat transfer characteristics, while the turbulent flow regime is yet to be explored. It was observed that most of the correlation over-estimated the value of pressure drop in multi-phase flow.

Rajendran, Duraisamy Ramalingam; Ganapathy Sundaram, Esakkimuthu; Jawahar, Paulraj; Sivakumar, Vaithilingam; Mahian, Omid; Bellos, Evangelos

doi: 10.1007/s10973-019-08759-8pmid: N/A

The solar collector (reflector and receiver) is the primary device being used in the concentrating solar power technologies for tapping the solar energy to meet various objectives. The performance of the solar collector is influenced by the type of reflector and receiver being selected, and its material also has significant impact. The choice of the heat transferring medium, storage material, receiver design and its performance parameter also influences the solar collector’s performance. In this regard, a review has been carried out for these parameters and presented in this paper to highlight the challenges encountered, new methodologies identified and proposed, and future research needs by various researchers to improvise the thermal efficiencies of the different types of collectors used in the concentrating solar power technologies.

Chebli, Abdelhak; Djekoun, Abdelmalik; Suñol, Joan Josep; Nižňanský, Daniel

doi: 10.1007/s10973-019-08772-xpmid: N/A

In this paper, Fe50Se50 alloy powders were synthesized from pure elemental powder by mechanical allowing. The structure, microstructure, morphology, chemical composition and thermal behavior at a function of milling times (0–39 h) were investigated by X-ray diffraction (XRD), scanning electron microscopy attached with energy-dispersive spectroscopy and differential scanning calorimetry (DSC). In addition, the interaction hyperfine and magnetic proprieties was examined by transmission Mössbauer spectroscopy (TMS) and thermomagnetic measurements (VSM) respectively. For milling times up to 6 h, the results of refinement of the X-ray diffraction pattern by MAUD software reveal the formation of the β-FeSe hexagonal, amorphous selenium and nanocrystalline α-Fe. The DSC curves show several exothermic and endothermic peaks associated with various phases’ transitions such as the exothermic peak at 103 °C related to crystallization amorphous selenium. However, after prolonging the milling time to 39 h, the XRD shows the formation of α-FeSe phase tetragonal which has plenty of technological interests especially the superconductivity. The Mössbauer spectroscopy confirmed the formation the two-phase paramagnetic hexagonal β-FeSe and α-FeSe tetragonal, according to the XRD and DSC. Measurement of magnetization (VSM) displays that saturation magnetization (MS) decreases as the milling time increases.

Solangi, K. H.; Sharif, S.; Nizamani, Bilal

doi: 10.1007/s10973-019-08835-zpmid: N/A

This work presents the convective heat transfer and friction loss characteristics of novel functionalized graphene-based and metal oxide nanofluids. The convective heat transfer in circular tubes of different materials (copper, aluminium and stainless steel 316) was used at constant wall heat flux of 23,870 W m−2. An innovative approach was used to prepare highly dispersed propylene glycol-treated graphene nanoplatelets–water (GNP1) and trimethylolpropane tris amine–water (GNP2) by functionalization method. The measured thermal conductivity of GNP1 and GNP2 nanofluids showed incredible performance which increased up to 32% and 31% higher than that of basefluid. By comparing material effect, copper tube showed the highest HTC up to 119% in GNP1 at 0.1 mass%, while in aluminium and stainless steel 316 tube the highest heat transfer coefficient (HTC) was 110.2% and 100.68%. Besides, alumina and silicon dioxide nanofluids also presented decent increment in HTC which was up to 29.1% and 31.6%, respectively. The highest rise in friction factor for GNP1 and GNP2 was obtained up to 10.2% and 10%, respectively. For alumina and silicon dioxide nanofluids, the friction factor was measured up to 5.92% and 7.14% at velocity range of 1–3 m s−1. The maximum enhancement in Nusselt number (Nu) for GNP, GNP2, alumina and silicon dioxide nanofluids was achieved up to 84%, 72%, 26% and 28%. The results suggest that the copper tube which is a good conductor of heat could be used in the heat exchangers and functionalized GNP nanofluids can be used as the heat exchanging fluids in heat transfer applications which could give a decent substitute to traditional working fluids in heat exchangers and in thermal fluid systems.

Hemmat Esfe, Mohammad; Kamyab, Mohammad Hassan

doi: 10.1007/s10973-019-08698-4pmid: N/A

In this study, effective parameters on viscosity of a suitable oil for lubrication of heavy-duty engines (vehicles that are in use in construction, farm, and logging equipment, semi-trucks, delivery trucks, etc.) are studied. SAE50 as a single-degree engine oil is examined in present experimental work. The mentioned engine oil is enriched by MgO and MWCNT nanoparticles (NPs). The nanofluid was prepared in six solid volume fractions (SVF) and in temperature range of 25–50 °C. The results showed the viscosity dependence on shear rate, so nanolubricant has a non-Newtonian behavior. 2–4% Viscosity reduction in concentrations of 0.0625% and 0.125% reported in comparison with viscosity of pure fluid. Also sensitivity analysis of viscosity measurement was lower than 1% for all investigated conditions. To lower experimental costs, a mathematical correlation was proposed to predict the viscosity. The R2 was considered as criterion for accuracy of proposed correlation. Having amount of 0.9995 for R2 shows accommodation of correlation predictions with experimental results. Also maximum deviation of < 3% indicates that the proposed correlation has a high accuracy.Graphic abstract[graphic not available: see fulltext]

Obradović, Nina; Fahrenholtz, William G.; Filipović, Suzana; Marković, Smilja; Blagojević, Vladimir; Lević, Steva; Savić, Slobodan; Đorđević, Antonije; Pavlović, Vladimir

doi: 10.1007/s10973-019-08846-wpmid: N/A

Cacua, Karen; Murshed, S. M. Sohel; Pabón, Elizabeth; Buitrago, Robison

doi: 10.1007/s10973-019-08817-1pmid: N/A

Stability of nanofluids is one of the major challenges for their real-world applications and benefits. Although ultrasonication and addition of surfactant are commonly used to obtain better stability of nanofluids, there is a lack of adequate knowledge on the effects of various parameters and duration of ultrasonication as well as some other influences of surfactant. The effect of ultrasonication on the dispersion of nanoparticles and agitation as well as temperature on the thermal conductivity measurements of aqueous TiO2 nanofluids was experimentally studied. An UV–Vis absorbance analysis was performed to identify the degree of dispersion of nanoparticles (stability) and also to determine the right amplitude as well as the duration of the ultrasonication. In addition, agitation of nanofluids during the measurement of thermal conductivity showed a serious adverse effect as significant fraction of nanoparticles adhered to both the probe and the wall of the sample container. Furthermore, present results showed that the enhanced thermal conductivity of this nanofluid further increases noticeably with increasing temperature.

Gao, Zehua; Lu, Lihong; Shi, Congling; Qian, Xiaodong; Wang, Xuebao; Zhang, Guoyun; Zhou, Mingtao; Pan, Yuhao

doi: 10.1007/s10973-019-08659-xpmid: N/A

The effect of OZnAl-LDH and OZnFe-LDH on the catalytic dechlorination, thermal decomposition and smoke suppression of polyvinyl chloride (PVC) during pyrolysis processes was investigated and compared. The thermal degradation and combustion behavior of the PVC composites were investigated by thermogravimetric analysis and cone calorimetry, respectively. The results indicate that the addition of LDHs brought about the improved thermal stability and reduced heat release of PVC composites at high temperature. The smoke suppression properties of the composites are investigated by steady-state tube furnace. The results revealed that the toxic gases such as CO, CH4, NOx and N2O were inhibited by both two LDHs, but the OZnAl-LDH has better effect on the smoke suppression. Subsequently, the char layer was investigated by scanning electron microscopy–energy-dispersive spectrometry and Raman analysis. The results indicated that the LDHs can promote the dechlorination of PVC and form graphitized structures. Generally, OZnAl-LDH and OZnFe-LDH can be potential catalysts for waste disposal and improve the fire safety of PVC.

Dahshan, A.; Alharbi, S. R.; Aly, K. A.; Saddeek, Y.

doi: 10.1007/s10973-019-08810-8pmid: N/A

The current study focuses on the impact of As addition on the thermal, mechanical, electrical and thermoelectric properties of ternary Bi0.02AsxSe0.98-x\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\text{Bi}}_{0.02} {\text{As}}_{\text{x}}\,{\text{Se}}_{{0.98 - {\text{x}}}}$$\end{document} (0.02≤x≤0.08\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$0.02 \le x \le 0.08$$\end{document}) glasses. Different elastic moduli such as the micro-hardness (H), Young’s modulus (Y), bulk modulus (K), Poisson’s ratio (Pr) and shear modulus (S) as well as Debye temperature (TD) for the studied glasses were estimated by using the measured values of the ultrasonic speeds (transfer, vl, and shear, vs) and density (ρ). Moreover, the measured values of the dc electrical conductivity (σdc) and thermoelectric power (Sthermo) were used to estimate the activation energies for the electrical (ΔEdc) and for thermoelectric (ΔEthermo) conductions, respectively. It was found that σdc increases, whereas Sthermo, ΔEdc and ΔEthermo decrease with increasing the As content for the Bi0.02AsxSe0.98-x\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\text{Bi}}_{0.02} {\text{As}}_{\text{x}}\,{\text{Se}}_{{0.98 - {\text{x}}}}$$\end{document} (0.02≤x≤0.08\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$0.02 \le x \le 0.08$$\end{document}) thin films. In addition, replacement of Se with As atoms results in an increase in the average coordination number (CN), cross-linking density (Cd), cohesive energy (CE), ρ, H, Y, K, S and TD, whereas the molar volume (Vm), Pr and the homopolar Se–Se bonds decreased. Both of Y and K as well as ΔEdc are correlated with the glass transition temperature (Tg).

Hussain, S. Imran; Kalaiselvam, S.

doi: 10.1007/s10973-019-08732-5pmid: N/A

Nanoencapsulated phase change material (NEPCM) was prepared with oleic acid as phase change material by its encapsulation into Ag2O nanoparticles (NPs)-based urea formaldehyde (UF) resin. NEPCMs were synthesized by in situ polymerization with different surfactants, to obtain a better shell material in terms of energy release, leak arrest and enhanced thermal properties. The morphology and particle size of the prepared NEPCM were analyzed by digital microscope and scanning electron microscope. Fourier transform infrared spectroscopy was used to determine the chemical structure. X-ray diffraction studies were carried out to ensure the presence of Ag2O NPs containing UF resin as shell material and its cubic crystal system. Thermo-physical properties were evaluated using differential scanning calorimetry (DSC), thermogravimetric analysis and thermal diffusivity analysis. DSC results revealed that the cationic surfactant-assisted synthesis of shell material has a comparatively good encapsulation ratio of 45.52%, and to further enhance the encapsulating capacity, Ag2O NPs was introduced. Addition of Ag2O NPs into the shell material shows improved encapsulation ratio of 54.82% with latent heat of 71.7 J g−1 for melting at 5.21 °C and hence better surface morphology, good thermal stability, better thermal conductivity and more suitability toward thermal energy storage in buildings.Graphic abstract[graphic not available: see fulltext]