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.
Display omitted
•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.
Display omitted
•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.
A comprehensive study was performed to explore the thermal characteristics of NS-dielectric-barrier discharge (DBD) plasma actuation over an airfoil/wing surface and evaluate the anti-/de-icing ...performance of NS-DBD plasma actuators for aircraft in-flight icing mitigation. While the fundamentals of thermal energy generation and heat transfer in NS-DBD plasma actuation over the airfoil/wing model were described in great details, a series of experiments were conducted to evaluate the effects of different environmental parameters on the heating efficiency of NS-DBD plasma actuators over the airfoil/wing surface. With the temporally-synchronized-and-spatially-resolved high-speed visualization and infrared imaging system, not only the transient thermal characteristics of NS-DBD plasma actuation over the airfoil/wing surface were revealed, but also the anti-icing performances of the NS-DBD plasma actuators were evaluated under different icing conditions, i.e. rime, mixed, and glaze. The impacts of incoming airflow velocity, air temperature, and angle of attack of the airfoil/wing model on the thermal characteristics of NS-DBD plasma actuation over the airfoil/wing surface were systematically investigated based on the measurement results. It was found that the thermal characteristics of NS-DBD plasma actuation over the airfoil/wing surface are closely coupled with the boundary layer airflow and the unsteady heat transfer process over the airfoil/wing model exposed in the frozen-cold airflows. The anti-icing performances of the NS-DBD plasma actuators under the different icing conditions were found to be varying significantly due to the variations of surface heating efficiency of the NS-DBD plasma actuators. The anti-/de-icing performance of the NS-DBD plasma actuators was found to be improved dramatically by increasing the operating frequency of the plasma actuators. The findings derived from the present study are very helpful to explore/optimize design paradigms for the development of novel plasma-based anti-/de-icing strategies tailored specifically for aircraft inflight icing mitigation to ensure safer and more efficient aircraft operation in atmospheric icing conditions.
Display omitted
•Numerical simulation of the nitrogen molecular emission spectra in plasma.•Plasma temperature measurement based on a synthetic spectral modeling of N2.•Thermal characteristics of ...low-pressure nitrogen plasma.•Change of the electron energy loss channel in low-pressure nitrogen plasma.
Nitrogen plasma is highly sought after in industries due to its unique properties, including high chemical reactivity and internal energy, which enhance process efficiency. However, a detailed understanding of thermal characteristics of nitrogen plasma is required to control nitrogen plasma properties and produce desirable reactants. Therefore, in this work, we proposed an advanced numerical simulation by clustering synthetic spectra of three molecular band systems (i.e., N2 B-A, N2 C-B, and N2+ B-X). Through this method, rotational, vibrational, and excitation temperatures of excited species in inductively coupled nitrogen plasmas (5 mTorr, 50 W − 900 W) were determined. Results revealed that rotational and vibrational temperatures increased at various input power with an inflection point at around 250 W. However, the excitation temperature decreased with input power below 250 W but increased with input power above 250 W. We also found that energy states were not in thermal equilibrium and that vibrational temperature and excitation temperature were reciprocally related. Finally, correlations between dissociation, ionization, and excitation temperature were discussed by examining N I and N2+ intensities as a function of input power.
The present study investigated the effect of adding hydrogen to methane on the thermal characteristics and ignition delay in methane-air, oxygen-enriched and oxy-fuel MILD combustion. For this ...purpose, numerical simulation of MILD furnace is performed by k-ε turbulence, modified EDC combustion, and DO radiation models. Additionally, a well stirred reactor (WSR) analysis alongside with CFD simulations is used for getting the better insight of combustion process and numerical results. The results show that H2 addition to CH4 provides a more uniform temperature field with higher peak and average temperatures under a similar oxidizer atmosphere. Also, more ignition delay time (IDT) obtained by the replacement of CO2 with N2, can be compensated by consideration of H2 in the fuel composition. This study implies that the use of H2 as an additive to methane is an effective strategy for conversion of methane-air to oxy-fuel combustion system with almost identical thermal and ignition characteristics.
•H2/CH4 MILD combustion is studied on the heat transfer and ignition delay time.•Enrichment of CH4 by H2 increases the temperature uniformity in the MILD regime.•High values of H2 cause to the migration of MILD to other combustion regimes.•H2 improves the ignition delay characteristics under the oxy-fuel MILD combustion.•H2 addition to CH4 is an efficient way to move toward the oxy-fuel MILD combustion.
