Journal of Thermal Analysis and Calorimetry

Tye, R. P.

doi: 10.1007/s10973-019-08558-1pmid: N/A

Banjare, Ganesh Ram; Bisen, D. P.; Brahme, Nameeta; Belodhiya, Chitrkant; Dewangan, Pradeep; Chandrawansi, Ekta; Sahu, Ishwar Prasad

doi: 10.1007/s10973-019-08520-1pmid: N/A

Calcium barium orthosilicate (CaBaSiO4) phosphors having different concentrations of Dy3+ were prepared by solid-state reaction method, and phase structure of the sample was identified by X-ray diffraction (XRD) characterization. It is observed that the XRD pattern matched well with JCPDS file No. 48-0210. Thermoluminescence (TL) of the UV-irradiated (254 nm) samples was recorded using routine TL set-up Nucleonix TLD reader with constant heating rate 5 °C s−1. It is found that the sample containing 1 mol% of Dy3+ and exposed for 27 min gives optimum TL intensity at 130.14 °C and shows single TL glow peak. It order to examine the effect of charge compensator ion, Li+ ions are introduced and it is found the incorporation of charge compensator enhances the TL output. Samples having 1 mol% of Dy3+ and 6 mol% of Li+ exposed for 30 min to UV exposure show maximum intensity at 118 °C. It is also observed that temperature corresponding to TL peak varies with varying Li concentration (ranging from 105.76 to 123.88 °C). Samples having 1 mol% of Dy3+ and 6 mol% of Li+ exposed for 30 min to UV exposure were selected for further studies, such as activation energy, order of kinetics and frequency factor, and all these parameters were evaluated using peak shape method.

Omara, Adil A. M.; Abuelnuor, Abuelnuor A. A.; Mohammed, Hussein A.; Khiadani, Mehdi

doi: 10.1007/s10973-019-08645-3pmid: N/A

This paper comprehensively reviews the use of phase change materials (PCMs) as latent heat storage systems to improve the productivity of solar stills. Previous studies on enhancing the productivity of active and passive solar stills with PCM are also presented. These studies show that a passive solar still with PCM shows a productivity improvement of up to 120% compared with a solar still without PCM. Meanwhile, the productivity improvement of an active solar still with PCM could reach as high as 700%. These results indicate that productivity increases along with an increasing PCM mass and a decreasing saline water mass. The PCM is also observed to be less effective in daytime than in night-time. It is also shown that organic PCMs (such as paraffin) were mostly used in studies on productivity improvement, whilst very few studies have examined the effects of inorganic and eutectic types of PCM.

Seyednezhad, Mohadeseh; Sheikholeslami, M.; Ali, Jagar A.; Shafee, Ahmad; Nguyen, Truong Khang

doi: 10.1007/s10973-019-08634-6pmid: N/A

Producing potable water is a critical issue due to the lack of access to clean H2O and the increasing demands of environment. One of the main technologies for water purification is solar still using the sustainable and green source of energy. To augment the efficiency of solar unit, nanoparticles are combined with the saline water. Nanofluids are suspended materials that besides the different geometries (single slope, double slope, tubular…) of the solar stills have a significant impact on improvement of the thermal conductivity of the brackish H2O. Further, combining nanomaterial with solar energy system appears to be more cost-effective approach for potable water production since they boost the evaporation and condensation rate. This paper is a comprehensive literature on different types of nanofluid and various numerical, experimental and analytical methods that researchers have applied to augment the efficiency of system.

Abdelrazek, Ali H.; Kazi, S. N.; Alawi, Omer A.; Yusoff, Nukman; Oon, Cheen Sean; Ali, Hafiz Muhammad

doi: 10.1007/s10973-019-08562-5pmid: N/A

In the present study, the heat transfer and hydrodynamic analysis of flow through single-pipe heat exchangers of circular and square cross-sectional configurations were performed. The experimental and numerical investigations were conducted to evaluate the performance of two metallic oxides (Al2O3 and SiO2) and two carbon-based nanostructured nanofluids (KRG and GNP) in comparison with the distilled water (DW). The data obtained from the experimental runs with DW as a working fluid in both test sections were used to validate the 3-D numerical models for the square and circular pipe heat exchangers. The flow in both test sections is considered as a fully developed turbulent flow with the Reynolds number range of 6000–11,000, and both the test sections were subjected to a uniform heat flux at their outer surfaces. The concentrations of all nanofluids used in the present study were in the range of (0.025–0.1 mass%). The test rig was firstly validated during the water run by using different empirical correlations for the evaluation of pressure drop and Nusselt number and showing a very good agreement, and then, the numerical models were validated with the data obtained experimentally and the errors were less than 10% for both models. For the square tube flow, the average errors between the numerical and experimental findings of Nusselt number and pressure drop were 6.8% and 2.49%, respectively, and for the circular pipe flow, the evaluated errors were 9.34% and 5.92% for Nusselt number and pressure drop, respectively. The performance index for all the nanofluids was calculated to obtain the convective heat transfer coefficients and friction losses of the fluids in both the tubes. The results showed that the non-covalent graphene–DW is not suitable for heat transfer applications due to its higher viscosity. The results also showed a different enhancement of heat transfer for the same nanofluid in circular and square tube flows, whereas the performance index of the same nanofluid appears nearly the same for flow through both the cross sections.

Bhattacharyya, A.; Seth, G. S.; Kumar, R.; Chamkha, A. J.

doi: 10.1007/s10973-019-08644-4pmid: N/A

With an objective to unfold the flow and heat transfer characteristics of carbon nanotubes between two stretchable coaxial rotating disks, the present investigation has been carried out. The behavior of single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs) taking water as the base fluid is analyzed. To formulate the energy equation, we have incorporated Cattaneo–Christov heat flux model. Consideration of such kind of model accounts the contribution by thermal relaxation. von Karman transformation has been implemented in order to reconstruct the governing partial differential equations into a system of ordinary differential equations. Employing optimal homotopy analysis method series solutions are obtained. Error analysis has also been performed and presented in tabular form. The physical clarifications for the behavior of fluid velocity, temperature, skin friction coefficient and Nusselt number are well demonstrated with the help of graphs and contour plots. One of the major outcomes of the present study signifies that water-based SWCNTs have a tendency to cause less drag and higher rate of heat transfer as compared to water-based MWCNTs. This investigation finds numerous applications in different mechanisms of thermal conversion for nuclear propulsion and spacecraft.

Yuan, Shen; Li, Zhaoqian; Luo, Qingping; Duan, Xiaohui; Pei, Chonghua

doi: 10.1007/s10973-019-08613-xpmid: N/A

To improve the thermal decomposition property of cyclotrimethylenetrinitramine (RDX), a new nano-energetic combustion catalyst nitrated graphene oxide (NGO), which was synthesized by nitrifying graphene oxide with nitro-sulfuric acid, is introduced to RDX via a solvent–antisolvent method. A scanning electron microscope was used to investigate the morphology of RDX, NGO and the 2% NGO/RDX nano-energetic composite. The properties and the mechanisms of thermal decomposition of the NGO/RDX nano-energetic composites in different blend ratios were analyzed through thermogravimetry–differential scanning calorimetry and thermogravimetry–mass spectra, respectively. In comparison with RDX, the thermal decomposition temperature of 2%NGO/RDX decreased from 246 to 224 °C, and the apparent decomposition heat enhanced from 761 to 1651 J g−1. The tests of impact sensitivity and friction sensitivity were carried out by a standard method. The value of h50 of 2%NGO/RDX increased from 24 to 40 cm and the friction sensitivity of 2%NGO/RDX reduced from 86 to 12% compared with RDX. These results indicated that NGO had an excellent catalytic property upon the thermal decomposition of RDX and it can also improve its impact sensitivity and friction sensitivity.Graphic abstract[graphic not available: see fulltext]

Menya, E.; Olupot, P. W.; Storz, H.; Lubwama, M.; Kiros, Y.; John, M. J.

doi: 10.1007/s10973-019-08553-6pmid: N/A

Thermal behavior and chemical properties of selected raw and NaOH-pretreated rice husk varieties were investigated. NaOH-pretreatment process involved soaking 5 g rice husk samples in 40 mL of 2%w/v NaOH, shaking (400 rpm) and heating (50 °C) for 3 h. NaOH-pretreated samples were water-washed, oven-dried, and milled for use in the determination of their thermal behavior and surface functional groups. Alkaline wash-water was also analyzed for sugar components. Thermal decomposition temperatures, degradation rates, and the subsequent mass losses varied from one rice husk variety to another. These thermal properties increased after NaOH-pretreatment of the rice husk varieties, reducing their char yields (17.1–20.4% db). These changes mainly had to do with the lignin, hemicellulose, and ash removal from the rice husk varieties, as confirmed by their FTIR analysis, as well as by the sugar composition analysis of their alkaline wash-water. Consequently, the FTIR spectra differed between the raw and NaOH-pretreated rice husk varieties.

Litwinek, Ewa; Madej, Dominika

doi: 10.1007/s10973-019-08656-0pmid: N/A

In this paper, the influence of precursors (CA, C7A3Z, C12A7, C6SrA3Z, C7A2FZ and commercial calcium aluminate cement ‘Gorkal 70’) on the structure, microstructure and thermal stability characterizations of C3AH6 through hydration was investigated. The materials were characterized by X-ray diffraction, differential thermal analysis–thermogravimetric analysis–evolved gas analysis and scanning electron microscopy combined with energy-dispersive spectroscopy 24 h and 72 h after starting the hydration process. Results of investigation confirmed the influence of precursor on shape and grain size of C3AH6. The CaO/Al2O3 mass ratio of precursors before the hydration process affects the size of C3AH6 crystals: the higher the CaO/Al2O3 value, the larger the size of the crystals of C3AH6. Moreover, the presence of Sr and Fe affects the formation of stable C3AH6 crystals.

Gaglieri, Caroline; Alarcon, Rafael T.; de Moura, Aniele; Caires, Flávio J.

doi: 10.1007/s10973-019-08623-9pmid: N/A

This work aims to determine the nickel selenate hexahydrate thermal behavior by simultaneous thermogravimetry–differential thermal analysis and differential scanning calorimetry and characterize its thermal intermediates decomposition. Moreover, at 25 °C, this material is a green-colored compound; however, with the temperature increase (until 420 °C), a color change from yellowish green to yellowish orange and finally to yellow was observed. This characteristic is due to the water molecules release, changing the ultraviolet–visible/near-infrared spectroscopy analysis absorption spectra and consequently modifying the crystal structure, as confirmed by X-ray powder diffraction, and resulting in visual changes in photo-DSC. The new data are essential to determine the better conditions to use this material as a precursor in synthesis and also to use it in future applications.