In this work, melting of a high-temperature inorganic phase change material (PCM) eutectic (with a melting point of 569 °C) within a vertical cylindrical tank has been experimentally investigated. To ...promote the heat transfer rate, a periodic structure that is constructed by a commercial SS-304 mesh screen has been considered and immersed into the PCM tank. Thermal characteristics of the PCM-periodic structure tank under different initial temperatures (450, 490 and 546 °C) and wall temperatures (620, 640, 660, 680 and 700 °C), are then investigated and reported. The presented experimental data can facilitate practical engineers to find the best operating condition of similar PCM tanks; meanwhile, it can also be employed for the investigation of thermal response of transient heat conduction before melting starts.
Attempting to solve the problem of inconsistent dynamic thermal characteristics caused by transient changes in internal resistance of lithium-ion batteries (LIBs) for electric vehicles (EVs) under ...service conditions, taking a 9.4Ah prismatic LIB as the study object, the internal resistance data under different state of health (SOH), state of charge (SOC), temperature (T), charge/discharge rates of LIB are obtained through the mixed-rate hybrid pulse power characterization (MR-HPPC) test. Based on this, a dynamic internal resistance model (DIRM) considering the SOH is proposed by the prediction of the least squares support vector machines (LS-SVM) model. In this study, a thermoelectric coupling model and a resistance-thermal co-simulation of the LIB are established based on DIRM, and the temperature rise characteristics under constant rates and dynamic operating conditions are investigated at different SOH states. The maximum DIRM error (DIRME) between DIRM-based simulated maximum transient temperature (Tmax-tra) and test Tmax-tra is 0.88 °C at constant charge/discharge rate operating conditions, while the maximum DIRME between DIRM-based simulated Tmax-tra and test Tmax-tra is 0.21 °C under dynamic operating conditions. The results can provide a theoretical support for improving the modeling precision of the heat generation of LIBs with different aging levels for accurate thermal management design.
•A dynamic internal resistance model (DIRM) for LIB by considering SOH is proposed.•A DIRM-based electrothermal coupling model for LIB is established.•A resistance-thermal co-simulation architecture is constructed.•The temperature of LIB between the DIRM-based simulation and the test is verified.
The physical properties of buckled ZnO monolayers are studied using DFT. It is demonstrated that when the buckling of ZnO monolayers increases, the band gap decreases confirming by both PBEsol and ...HSE06 approximations. A buckled ZnO monolayer is dynamically and thermally stable as is confirmed by its phonon spectrum and AIMD calculation. If the buckling increases, the frequency ranges for the phonon dispersion decrease resulting in smaller lattice thermal conductivity. Furthermore, a planar ZnO monolayer has an active optical response in the Deep-UV region, however the tunable response reaches the near-UV.
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•Buckling reduces the band gap of ZnO monolayer using PBEsol and HSE06 approximations.•A buckled ZnO monolayer is dynamically and thermally stable.•Buckled ZnO monolayer has an active optical response in the Deep-UV region.•Lattice thermal conductivity is reduced by increasing the buckling parameter.
In the recent decade, growth of the natural fiber reinforced polymer (NFRP) composite has made a considerable impact on the polymer composite research and innovation. This rapid growth warranted ...their properties over low-cost synthetic fiber composites and reduced environmental impacts. As these materials have potential applications in the various engineering sectors, considerable efforts have been made to improve their performance. In recent year’s various modifications were introduced in the natural fiber composites which increased their capability. The aim of this review is to highlight the trends in the research and development on NFRP and its performance from the year 2000–2019. This review article covers current research efforts on the NFRP fabrication, its properties such as mechanical strength, tribological, water, and chemical resistance behaviour, thermal effects, biodegradability and machining characteristics along with their trends, challenges and prospects in the field of NFRP.
A novel curve tube design called Triple Tube Heat Exchanger was investigated to identify the thermofluidic characteristics in the current paper. This research analysis comprises of both computational ...fluid dynamics and experimental results. A three-dimensional computational fluid dynamics model was developed using Ansys R19.1 (fluent) research package, and the k-epsilon model is used to realize the thermofluidic characteristics. In this new design, an additional tube is introduced between a double concentric tube heat exchanger. The complete analysis is done under consideration of turbulent fluid to fluid heat transfer conditions. The influence of different thermal parameters such as overall heat transfer and effectiveness were the main points of research interest by using WO3/water nanofluid with different novel inserts like twisted tape, rib, and porous plate. The thermodynamic effect of nanofluid was considered under the concentration range of 0.5%–3.0%. The computational fluid dynamics method is used to simulate the process, and experimental data is used to validate it. The result shows that the maximum overall heat transfer rate and effectiveness were 1767.91 W/m2K, 1702.71 W/m2K, and 1.86, 1.79, respectively, at 1% optimized volume concentration with WO3/water nanofluid by using rib type insert during experimental and computational fluid dynamics methods, respectively. The maximum thermal performance factor by using nanofluid in the rib type insert was observed at 0.75. The study shows an enhancement of 11.84%, 12.38%, and 14.56%, 14.30% in overall heat transfer and effectiveness by using a rib-type insert for both experimental and computational fluid dynamics methods, respectively, in comparison to without using inserts. There was also a progressive decrement in friction factor during the increment in mass flow rates.
•Synthesis of multicomponent borosilicate glasses containing up to 40 wt% UO3.•U transforms IVSi-O-IVB to IVSi-O-IIIB and enhances glass transition temperature.•EXAFS fit shows that U is present as ...UVI/UV, with similar ratios within the series.•The dissolution rate of the 30 wt% sample is the lowest among the U-loaded samples.•Nanoindentation reveals 30 wt% U O3 sample is ∼ 11 % weaker than matrix glass.
The glass matrix of composition: 55SiO2–10B2O3–25Na2O-5BaO-5ZrO2 was incorporated with 10 to 40 wt% of UO3 by melt quenching technique. Neutron diffraction and Reverse Monte Carlo simulations revealed that the borosilicate network consists of SiO4, BO3 and BO4 units; upon adding 10 % UO3 the B-O coordination increases from 3.08 to 3.86 and subsequently decreases with a further in increase in UO3 content. X-ray absorption near edge and Extended X-ray absorption studies revealed that U exist in 5+ and 6+ oxidation states with U-O coordination numbers of 8 and 6 respectively. The thermal stability decreases and weight losses increases with the addition of UO3 in the glass matrix, the sample with 30 wt% UO3 has thermal stability comparable to that of matrix glass and exhibits lowest dissolution rate in water. Nanoindentation measurements showed that the microstructure of sample with 30 wt% UO3 is 11 % weaker than that of the matrix glass.
•A novel method of three-dimensional fluid–solid-heat coupled simulation proposed.•Different fluid–solid heat transfer coefficients calculated during oil injection.•The influent of oil injection on ...working chambers numerically analyzed.•Suction superheat increased by 29 K and compression temperature reduced by 17 K.
Investigating the heat transfer mechanisms in rolling piston type rotary compressors is crucial for improving their operational efficiency. A thermal test platform was established and steady-state temperature fields of key components were measured under various conditions, revealing a correlation between these temperatures and crank angles, except near the angle of 54° for the cylinder head-up. It provided important boundary conditions for simulation research. A novel three-dimensional fluid–solid-heat coupled simulation method was proposed, calculating heat transfer coefficients at fluid–solid interfaces. The two-phase heat transfer characteristics post oil–gas miscibility was studied, arising from the injection of lubricating oil into the working chamber. Two-phase oil-refrigerant mixtures, compared to single-phase refrigerant, increased heat transfer coefficients by 2.35 % in the suction channel and 2.99 % in the cylinder head-up, but decreased by 5.85 % in the cylinder head-down, 17.42 % in the piston, and 5.63 % in the cylinder. Oil injection was found to significantly enhance convective heat transfer in the suction chamber, increasing suction superheat in the cylinder by up to 29 K and reducing temperature of the compression chamber by up to 17 K. These results provide novel insights into the complex heat transfer in rotary compressors.
In this paper, a new type of micro combustor is designed to solve the problems of low output performance, insufficient heat source and low quality heat source of combustion-based micro thermoelectric ...systems. The combustor designed in this paper has the opposite intake arrangement, partial porous medium(PM) filling, central raised cavity and multistage sudden expansion structure. The effects of filling ratio of PM, thermal conductivity of PM and input power (Pin) on the thermal characteristics of combustor were investigated by numerical method. The results show that partially filled PM can stabilize the combustion position and shape, and increase the proportion of available energy of the combustor, so as to provide sufficient heat source for the thermoelectric system. The uniformity of combustor plane temperature increases with the increase of PM filling ratio and thermal conductivity. The combustible range of the combustor is 20–140 W. At the same time, at higher Pin, the filling ratio and thermal conductivity of the PM improve the thermal characteristics more obviously, so as to provide high quality heat source for the thermoelectric system. It is clear that strengthening heat transfer capacity, improving temperature uniformity and improving combustion stability are important ways to improve the thermal characteristics of combustor. In addition, the emission performance of the improvement effect is strong. Therefore, this research can be utilized as effective and feasible guidance for researching thermoelectric system and provide useful insights for the research of system heat source, i.e. combustor.
•A new type of micro combustor is designed to improve system performance.•A numerical model is developed to study the characteristics of combustor•Sufficient heat energy and wide combustion range are realized.•Several ways to improve the combustor thermal characteristics are obtained.•The emission performance of micro combustor is improved to some extent.
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•The decomposition of DR was divided into five main pseudo-reactions.•Gaseous N was mainly produced by decomposing protein-containing material in the DR.•DR-derived biochar has ...potential as an adsorbent due to the quality improvement.•High safety of heavy metals from biochar obtained by DR pyrolysis.
The current work has examined the pyrolytic properties, product formation mechanisms, biochar properties, and heavy metal (HMs) safety of biochar during food waste digestate residue (DR) pyrolysis. The results have shown that DR pyrolysis proceeded in five stages. The kinetic model for Stages 1, 3 and 4 was the simple reaction order model, the one-dimensional diffusion model for Stage 2, and the three-dimensional (Jander) diffusion model for Stage 5. Based on thermogravimetric-Fourier transform infrared spectrometry (TG-FTIR) and pyrolysis–gas chromatography-mass spectrometry (Py-GCMS) analysis, the volatile components of the DR pyrolysis were mainly produced by the Maillard, decarboxylation, and deamination reactions as H2O, CH4, CO2, CO, phenol, CO (anhydride/ketone/aldehyde), C-O and NH3. While there were six main components of the pyrolysis oil, that is, amines and amides, nitriles, N-hybrid compounds, oxides, and sulfides. Appropriate aromatic properties were observed in the prepared biochar, and the biochar obtained at a pyrolysis temperature of 700 °C had a relatively high specific surface area. The HMs results showed that the HMs in biochar obtained from DR pyrolysis at 400, 500, 600, 700, and 800 °C were predominantly in the oxidizable and residual fractions. The toxicity characteristic leaching procedure (TCLP) tests and the potential ecological risk indices for HMs have indicated a high safety profile for biochar. This work has elucidated the formation process of DR pyrolysis products and the physicochemical properties and safety of biochar. It has also provided an outlet for the application of biochar, which provides a strong contribution to promoting resource use of DR.
Solar greenhouses are agricultural facilities that use solar energy for growing vegetables. The thermal characteristics of a solar greenhouse wall have an important influence on the creation of the ...microclimate in the greenhouse and improving the heat storage capacity of the wall materials can prevent freezing damage of greenhouse crops. To increase the temperature of the internal temperature stabilisation layer and the heat storage and release characteristics of the wall, a novel greenhouse wall with micro-heat pipe arrays (MHPAs) and phase-change materials (PCMs) was proposed, and an experimental greenhouse with the proposed wall and an ordinary greenhouse were built in this study. The thermal performance of the greenhouse wall and the improvement effect on the greenhouse microclimate for typical weather conditions were analysed using dynamic evaluation indices, such as the air temperature, the inner surface temperature of the experimental wall, and the heat storage and release rate of the greenhouse wall. The combined use of MHPA and PCM solves the problem of the heat transport bottleneck caused by the low thermal conductivity of PCM and the traditional wall temperature stabilisation layer, and effectively increases the amount of heat stored in the wall, thereby ensuring the growth of crops at night. For typical days, the average total heat storage of the experimental wall was 18.89 MJ/m3, while that of the ordinary wall was 9.67 MJ/m3 (an increase of 95.35%). The average total heat release was 17.58 MJ/m3, while that of the ordinary wall was 8.95 MJ/m3 (an increase of 96.42%), which led to an increase in the air temperature during the night and provided an environment suitable for the crop growth.
•A novel greenhouse wall incorporating MHPAs and PCMs has been developed.•Two small-scale solar greenhouses for comparative experiment analysis were built.•The use of MHPA well solves the problem of a thick temperature stability layer in the traditional wall.•The effectiveness of the MHPA greenhouse in improving the thermal environment has been verified.
