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This paper presents a novel green combined heat and power generation system for industrial applications. It composes of a hydrogen-fueled combined cycle power plant and a battery energy storage. Firstly, the hydrogen-air rich mixture enters the combustion chamber of the gas turbine cycle for generating electricity, while recovering the heating energy from the exhausted flue gases for driving a steam turbine cycle. The heating energy extracted from the condenser heat exchanger is also used to supply the heating demand of the end-user. Moreover, a comprehensive thermodynamic model and analysis of H 2 combustion process is provided to estimate the adiabatic flame temperature based on enthalpies of reactants and products. The optimum operating point of the cogeneration system is found by solving a mixed-integer nonlinear problem using MATLAB and GAMS over a 24-h study horizon aiming to minimize its daily operation cost considering all technical constraints of system components and load-generation balance criterion. It is found that the energy efficiency of the hydrogen-fueled combined cycle changes from 46 to 58 % while generating 11.331–12.982 MW electricity and 4.436–4.984 MW heat. Two cases are studied without and with participation of battery in energy procurement strategy. It is demonstrated that the objective function of the optimization problem improves from 18 $ cost in case 1 to 29 $ revenue in case 2. • Thermodynamic model and analysis of a H 2 -fueled CHP plant is presented. • Adiabatic flame temperature is obtained based on enthalpies of reactants and products. • A high-temperature heat exchanger is used to produce steam from waste heat of gas turbine flue gases. • Optimal charge and discharge of battery is scheduled for higher cost savings. [ABSTRACT FROM AUTHOR]

The research has examined the effects of CO 2 dilution on ignition characteristics in H 2 /air mixtures. An ignition kernel was initiated by a laser-induced plasma in H 2 /air/CO 2 mixtures with a bulk velocity of 6.5 m/s. An infrared camera was used to measure radiation intensity emitted from H 2 O and ignition probabilities. A high-speed schlieren image system was utilized to measure ignition kernel areas and ignition time. High-speed chemiluminescence was performed to examine OH* intensities. Numerical simulations were conducted using GRI 3.0 mechanisms to calculate reaction rates and laminar flame speeds. The ignition probability is highest for the undiluted mixtures and decreases with increasing the CO 2 dilution fraction at constant adiabatic temperatures. A prolonged ignition time is observed at elevated CO 2 dilution concentrations. Increasing the CO 2 mole fraction decreases the ignition kernel growth, the integrated OH* intensity, and the integrated radiation intensity for each adiabatic temperature. CO 2 reacts with H radicals and decreases the production of OH*, OH, and H 2 O. The CO 2 dilution in the H 2 /air flames significantly contributes to the reduced reaction rate and flame speed, resulting in the low ignition probability. The high ignition probability is found at the large integrated OH* intensity in all cases. The ignition probability is high at the large integrated radiation intensity under the constant adiabatic flame temperatures. The OH* intensity is a critical parameter to estimate the ignition probability in the diluted lean hydrogen flames. • The effects of CO 2 dilution on the ignition process have been studied in lean premixed H 2 /Air flames. • The ignition probability decreases with increasing the CO 2 dilution fraction. • An increase in the CO 2 dilution fraction in the mixtures reduces OH* intensity and radiation intensity emitted from H 2 O. • The presence of CO 2 in the mixtures decreases reaction rates and flame speed. [ABSTRACT FROM AUTHOR]

Thermoelastic stress analysis (TSA) can be used to determine the stress field of structures or materials under cyclic loadings through temperature under adiabatic conditions. So high-frequency cyclic loadings are considered as a fundamental condition. However, loading frequencies in many practical applications do not meet the adiabatic conditions. In order to improve the accuracy of TSA under low-frequency fatigue loadings, the non-adiabatic response in TSA was derived by combining the classical thermoelastic equation and heat conduction equation. This response was used to create a modified model that accounted for heat transfer and temperature distribution under low-frequency loading conditions. Otherwise, fatigue test and finite element method were used to evaluate the correctness of the modified model using epoxy resin material. The results showed that the temperature change obtained from the modified model were in good agreement with the experiment results. The modified model can effectively evaluate the structural stress under low-frequency fatigue loadings. [ABSTRACT FROM AUTHOR]

Electrocaloric refrigeration shows the merits of environmental safeguarding, large efficiency, easy combination, and miniaturization as a novel solid-state refrigeration technique. In this paper, Sn4+ is doped into the B site of BLNT ceramics. By adjusting the doping content, the T-C phase transition peak was successfully shifted to room temperature and promoted the formation of relaxor ferroelectrics, resulting in a wider operating temperature range (T span) and improved adiabatic temperature change (ΔT). A comprehensive study was conducted on the crystal structure, surface morphology, dielectric properties, ferroelectricity, and electrical properties of BLNTS ceramics with varying levels of Sn4+ doping. Wherein, when the doping amount is 5Sn, a maximum adiabatic temperature change value (ΔT max) of 1.14 K was obtained, and the temperature span (T span) reached 45 °C (T span is defined as ΔT ≥ 80 % ΔT max). This work proposes a high-performance environmentally friendly electrocaloric effect (ECE) material suitable for solid-state cooling applications. [ABSTRACT FROM AUTHOR]

We present the results of direct measurements of the adiabatic temperature change (ΔTad) for the Fe50Rh50 alloy in a cyclic magnetic field (CMF) of 1.2 T. It is shown that increasing the frequency of the CMF from 1 to 30 Hz is accompanied by a shift of the position of temperature dependence ΔTad(T) maximum, Tmax, toward low temperatures. With an increase in the CMF frequency from 1 to 5 Hz, the ΔTmax value decreases by ∼12%. A further increase in frequency leads to stabilization of the effect. In the vicinity of the antiferromagnetic-ferromagnetic phase transition point TC = 370 K, ΔTad exhibits unconventional frequency behavior: while at T well above TC, the value of ΔTad monotonously decreases as frequency increases, at T = 370.4 K; an interval of frequency-independent ΔTad up to 10 Hz is observed, and at 368 K < T < TC, the maximum of ΔTad(f) dependence is found in the interval 1 < f < 10 Hz. Such behavior in the future can be applied in magnetic cooling technology due to large values of ΔTad and the frequency stability of the effect in alternating fields. The specific cooling power reaches giant values of ∼22 W/g at 20 Hz, which is comparable to the values under the same conditions for Gd −21.6 W/g. The unconventional behavior of ΔTad in the CMF is discussed in the context of the role of secondary phase localization, which leads to an enhanced internal local magnetic field and dynamic effects of ΔTad. [ABSTRACT FROM AUTHOR]

The evolution of plasticizing mechanism and mechanical properties of the Fe-11Mn-4Al-0. 2C medium-Mn steel during deformation were compared in this paper. With the increase of strain rate (0. 002~200 s-1), the trends of changes in yield strength and tensile strength for the medium-Mn steel are completely opposite. The yield strength increases from 507 MPa to 649 MPa, while the tensile strength decreases from 1 089 MPa to 876 MPa. The plasticizing mechanism of quasi‑static loading is dominated by the strong TRIP (transformation‑induced plasticity) effect. The plasticizing mechanism is dominated by the weak TRIP effect in the initial stage of dynamic loading, and the TRIP effect disappears and the plasticizing mechanism changes into the temperature rise softening effect and the TWIP (twinning‑induced plasticity) effect in the later stage of dynamic loading. The dislocation motion rate in the initial stage of dynamic loading is much higher than that of quasi‑static loading, which results in the higher yield strength of dynamic loading than that of quasi‑static loading. With the increase of strain, the cumulative adiabatic temperature rise inhibits the martensitic transformation and reduces the work‑hardening capacity under dynamic loading, while the high hardness martensite is produced continuously under quasi‑static loading, which results in the tensile strength of quasi‑static loading higher than that of dynamic loading. [ABSTRACT FROM AUTHOR]

Three clean gases (shale gas, biomass gas, and coalbed gas) are simulated by using Chemkin-Pro software. The GRI 3.0 mechanism, which exhibits superior predictive performance overall, is chosen for numerical simulation based on comparative analysis. The comprehensive analysis of the effects of fuel components on flame speed and temperature in the three mixtures. Based on the laminar burning velocity, the numerical decoupling method is used to separate the chemical and physical effects of CH4, as well as the dilution, thermal, and chemical effects of CO2. At the same time, verification and analysis are carried out by sensitivity analysis and flame structure analysis. Sensitivity analysis is employed to evaluate the impact of key fundamental reactions on laminar burning velocity and temperature, while flame structure analysis is utilized to ascertain variations in crucial species and temperatures during flame combustion. [ABSTRACT FROM AUTHOR]

In order to reveal the deflagration mechanism of DME/H2-blended gasses, the micro-mechanism was studied based on the constructed UC San Diego 2016 pyrolysis oxidation mechanism model. The results show that adiabatic flame temperature and laminar flame speed increase with the increase in the equivalence ratio (Φ); they first increase and then decrease with the increase in the hydrogen (H2)-blended ratio (λ), and with the increase in λ, the Φ corresponding to the peak laminar flame speed of the blended gas increases. The addition of H2 increases the consumption of O2, and H2 reacts with CO to form H2O and CO2, promoting complete combustion. When Φ = 1.0–1.2, the equilibrium mole fraction of H and OH-activated radicals reach the maximum, and with the addition of H2, the concentration of activating radicals gradually increases, while the number of promoted elementary reactions increases by two, and the number of inhibited elementary reactions does not increase. Meanwhile, the addition of H2 increases the reaction rate of most reactions on the main chemical reaction path CH3OCH3→CH3OCH2→CH2O→HCO→CO→CO2 of DME and increases the risk of the deflagration of DME/H2-blended gas. [ABSTRACT FROM AUTHOR]

In order to improve the magnetocaloric properties of MnNiSi-based alloys, a new type of high-entropy magnetocaloric alloy was constructed. In this work, Mn0.6Ni1−xSi0.62Fe0.4CoxGe0.38 (x = 0.4, 0.45, and 0.5) are found to exhibit magnetostructural first-order phase transitions from high-temperature Ni2In-type phases to low-temperature TiNiSi-type phases so that the alloys can achieve giant magnetocaloric effects. We investigate why chexagonal/ahexagonal (chexa/ahexa) gradually increases upon Co substitution, while phase transition temperature (Ttr) and isothermal magnetic entropy change (ΔSM) tend to gradually decrease. In particular, the x = 0.4 alloy with remarkable magnetocaloric properties is obtained by tuning Co/Ni, which shows a giant entropy change of 48.5 J∙kg−1K−1 at 309 K for 5 T and an adiabatic temperature change (ΔTad) of 8.6 K at 306.5 K. Moreover, the x = 0.55 HEA shows great hardness and compressive strength with values of 552 HV2 and 267 MPa, respectively, indicating that the mechanical properties undergo an effective enhancement. The large ΔSM and ΔTad may enable the MnNiSi-based HEAs to become a potential commercialized magnetocaloric material. [ABSTRACT FROM AUTHOR]

Materials with electrocaloric effect (ECE) and/or thermal switching ratio λ are desirable for developing various heat management devices, but developing high-performance candidates, especially those that simultaneously possess large near room-temperature ECE and λ is actually absent. The Zr-rich PbZr1−xTixO3 (PZT) displays a composition-induced antiferroelectric-ferroelectric (AFE-FE) phase boundary, where an unusual negative ECE is expected. Meanwhile, the electric field-sensitive dipole orientation during the AFE-FE phase transition can be employed to modulate λ. In this work, the Zr-rich PZT with coexisting AFE and FE phases was developed and the AFE-FE phase transition temperature is tuned toward room temperature by changing the Ti content to achieve large negative ECE and λ. A large adiabatic temperature change ΔT of −3.3 K accompanied by a giant λ of 1.84 near 60 °C is captured in optimal PbZr0.95Ti0.05O3 ceramics, demonstrating a prominent application prospect in solid-state refrigeration. [ABSTRACT FROM AUTHOR]

This study presents a new single-step synthesis of Fe 2 AlB 2 at 1150°C for 4 hours using hot isostatic pressing (HIPing). X-ray diffraction confirmed the material as single-phase, while metallographic etching revealed predominant equiaxial Fe 2 AlB 2 grains (∼25 μm) and minor unreacted boron particles and Al-rich zones at grain boundaries. Magnetocaloric investigations demonstrated an impressive isothermal entropy change of 2.9 J/kg.K at 2 T and 6.8 J/kg.K at 5 T, with corresponding adiabatic temperature changes of 1.1 K and 2.8 K at 2 and 5 T, respectively. The HIPed Fe 2 AlB 2 performance matches that of studies without post-treatments or doping. Fe 2 AlB 2 , composed of light and earth-abundant elements, can be synthesized in a single step using HIPing, making it an attractive option for magnetic refrigeration with improved energy efficiency and simplified manufacturing. • Successful synthesis of Fe2AlB2 through a single-step reactive hot isostatic pressing (HIPing) process. • Utilization of a 0.005 M NaOH + 0.01 M NaOCl solution for metallographic etching to reveal grain boundaries. • Equiaxial Fe2AlB2 grains (∼ 25 μm) in with Al enrichment at grain boundaries and a modest presence of unreacted B particles. • Magnetocaloric Effect (MCE) measurements show a -ΔSM of 2.9 and 6.8 J/kg·K at 2 and 5 T, respectively. • Determination of the relative cooling power (RCP) values of 39 J/kg and 142 J/kg at 2 and 5 T, respectively. [ABSTRACT FROM AUTHOR]

The paper presents research results of the synthesis, phase composition, and structure of products obtained by highly exothermic reactions between Ti and C10H8O4 mixture components, depending on the plastic waste concentration and Ti powder dispersiveness, density of initial samples, and synthesis medium. The dependence of the phase composition and structure of the synthesis products on the concentration of the polymer (plastic) component in the initial Ti -PET (C10H8O4) system was found. When the plastic waste content is 20 wt% to 25 wt %, synthesis products contain TiC0.5O0.5-TiC0.6-0.75 particle agglomerates. Further growth in the polyethylene terephthalate content from 30 wt% to 45 wt% leads to the formation of synthesis products consisting of titanium carbide (TiC0.6-1.0). The gaseous byproduct composition of the exothermic reaction is investigated for the Ti--C10H8O4 mixture composition. It is found that the gaseous by-product mostly contains hydrogen and carbon monoxide as well as impurities of different hydrocarbons (methane, acetylene, ethane, ethene) and carbon dioxide. The maximum adiabatic temperature of the gas combustion temperature is 2080 °C, which demonstrates the possibility of using gas as a fuel for energy generation devices. Based on the data obtained, it is possible to create a basis for a new plastic waste technology to fabricate carbide-containing materials. [ABSTRACT FROM AUTHOR]

Transient conjugate heat transfer measurements under varying temperature and velocity inlet boundary conditions at incompressible flow conditions were performed for flat plate and ribbed channel geometries. Therefrom, local adiabatic wall temperatures and heat transfer coefficients were determined. The data were analyzed using typical heat transfer correlations, e.g., Nu = C Re m Pr n , determining the local distributions of C and m. It is shown that they are closely linked. A relationship ln C = A − m B is observed, with A and B as modeling parameters. They could be related to parameters in log-law or power-law representations for turbulent boundary layer flows. The parameter m is shown to have a close link to local pressure gradients and, therewith, near wall streamlines as well as friction factor distributions. A normalization of the C parameter allows one to derive a Reynolds analogy factor and, therefrom, local wall shear stresses. [ABSTRACT FROM AUTHOR]

Interrupted and incremental tensile tests have been carried out on 316 austenitic stainless steel at different strain rates, revealing the correlation between the strain, strain rate, and temperature rise of martensitic transformation. The FERITSCOPE FMP ferrite tester and Telops FAST M2K infrared imager measured the martensite content and surface temperature rise at different strain rates, respectively. The effect of adiabatic temperature rise and strain rate on martensitic transformation was isolated by incremental tests. Compared with the incremental tensile test at a low strain rate (0.001 s−1), it has been found that the increase in strain rate has a negative effect on martensitic transformation, and the effect of strain rate on martensitic transformation seems to be more significant than that of adiabatic temperature rise. The formation and evolution mechanism of strain-induced martensitic transformation of 316 austenitic stainless steel were studied by electron backscattered diffraction. During the process of tensile plastic deformation, the nucleation and growth of new martensite mainly occurred near the twin boundary. [ABSTRACT FROM AUTHOR]

Phase change materials can be converted between solid, liquid, and gaseous states, absorbing or releasing a large amount of heat. PCM is incorporated into concrete to adjust the temperature difference between inside and outside of concrete, which can reduce cracking. In this paper, the finite element analysis method is used to establish the model of an ordinary concrete structure, doped with phase change materials, on the basis of mechanical properties and a temperature regulation test performed by calculating the adiabatic temperature rise of concrete with different contents of composite phase change material, comparing the experimental and simulation results of the ordinary concrete structures with phase change materials, and analyzing the change in temperature field of the concrete structure with the content of self-prepared composite phase change materials. It is found that the addition of self-prepared composite phase change materials reduces the temperature peak of the concrete structure in the stage of hydration heat and delays the time taken to reach the temperature peak. Then, the temperature field of the phase change mass concrete structure is established, and the influence law of composite phase change material admixture on the temperature field of mass concrete is summarized through the time–temperature curves of different admixture amounts and positions so as to predict the possibility of cracks in mass concrete. [ABSTRACT FROM AUTHOR]

The determination of the characteristics and main combustion properties of fuels is necessary for post-implementation in different applications. Among the most important combustion properties of a fuel are the combustion products, flame temperature and laminar burning velocity. Therefore, this paper describes the step-by-step development and coding of a MATLAB application that can determine 12 combustion products, flame temperature and laminar burning velocity in order to understand the logic of calculus procedure, so any user would be able to make improvements of new functionalities (add more fuels, add more combustion products, etc.). The numerical procedure and methods (Gaussian elimination, Taylor Series and Newton–Raphson) parallel with their implementation as code lines for the development of the application are carried out using flow charts. In addition, simulations in Ansys Chemkin were performed and included in the application as part of the results comparison. It was found that: (1) The MATLAB Application codification and development were successfully explained in detail, (2) the functions and execution sequence are described by using flow charts and code extract, (3) the application is available to everyone for modifications, (4) the application can only be used for hydrocarbons fuels, (5) the application execution time registered was less than 8 s. [ABSTRACT FROM AUTHOR]

Hydrogen-enriched methane (HEM) combustion is an effective method for reducing the consumption of carbonaceous fuels. However, high adiabatic flame temperature of H 2 can cause large NO emissions. To reduce the NO and CO 2 emissions from HEM combustion, the Box-Behnken design (BBD) method combining response surface experimental design, analysis of variance, and multi-nonlinear regression models was adopted. The effects of the H 2 doping ratio (X H2), preheated air temperature (T air), excess air coefficient of burners arranged at the bottom (E x,b), and their interactions on the NO, N 2 O, and CO 2 emissions of a gas-fired boiler were investigated. According to the BBD method, the NO, N 2 O, and CO 2 emissions prediction models with R2 exceeding 0.98 were proposed, respectively. The results showed that the increase of T air had a positive effect on reducing NO emissions, as the NO exhausted from HEM combustion is mainly thermal NO. Compared with T air and E x,b , X H2 was the most significant factor affecting N 2 O and CO 2 emissions, indicating that an increase in X H2 can significantly reduce greenhouse gas emissions. Additionally, the formation and consumption of N 2 O emissions presented a competitive mechanism at X H2 increased from 0 to 0.8, and CO 2 emissions reduced with the increase of X H2 , T air , and E x,b. Furthermore, a comprehensive emission prediction model with NO, N 2 O, and CO 2 emissions was proposed. With the target of minimizing total NO, N 2 O and CO 2 emissions, three groups of combinations for X H2 , T air , and E x,b were obtained from the equal weight, entropy weight method, and criteria importance through the inter-criteria correlation method as 1:1:1, 24:9:17, and 21:11:18. The results showed that for minimize emissions, there is not much difference in the results calculated based on the optimal boundary conditions under different weights. For various reduction targets for nitrogen, carbon, and greenhouse gases, three groups of optimal combinations of X H2 , T air , and E x,b were obtained and their accuracies were verified based on numerical calculations with relative errors below 6%. The proposed comprehensive pollutant emission prediction models are conducive to calculating the pollutant emissions of HEM combustion and guiding the investigation of prediction models considering other operating conditions. • Box-Behnken design method was first adopted to study NO, N 2 O, and CO 2 emissions. • NO, N 2 O and CO 2 emission prediction models for quick calculation were proposed. • A comprehensive emission prediction model for H 2 /CH 4 combustion was proposed. • The optimal boundary combination for less pollutant emissions was obtained. [ABSTRACT FROM AUTHOR]

Continuous dynamic recrystallization (CDRX) is widely acknowledged to occur during hot forming and plays a significant role in microstructure development in alloys with moderate to high stacking fault energy. In this work, the flow stress and CDRX behaviors of the TC18 alloy subjected to hot deformation across a wide range of processing conditions are studied. It is observed that deformation leads to the formation of new low-angle grain boundaries (LAGBs). Subgrains rotate by absorbing dislocations, resulting in an increase in LAGB misorientation and the transition of some LAGBs into high-angle grain boundaries (HAGBs). The HAGBs migrate within the material, assimilating the (sub)grain boundaries. Subsequently, an internal state variable (ISV)-based CDRX model is developed, incorporating parameters such as the dislocation density, adiabatic temperature rise, subgrain rotation, LAGB area, HAGB area, and LAGB misorientation angle distribution. The values of the correlation coefficient (R), relative average absolute error (RAAE), and root-mean-square error (RMSE) between the anticipated true stress and measured stress are 0.989, 6.69%, and 4.78 MPa, respectively. The predicted outcomes demonstrate good agreement with experimental findings. The evolving trends of the subgrain boundary area under various conditions are quantitatively analyzed by assessing the changes in dynamic recovery (DRV)-eliminated dislocations and misorientation angles. Moreover, the ISV-based model accurately predicts the decreases in grain and crystallite sizes with higher strain rates and lower temperatures. The projected outcomes also indicate a transition from a stable and coarse-grained microstructure to a continuously recrystallized substructure. [ABSTRACT FROM AUTHOR]

Materials exhibiting caloric effects can serve as green alternatives in place of the gas refrigerants used in traditional vapor refrigeration systems, which are facing rising energy usage and environmental issues. This study investigates the barocaloric effect of fatty acids, which are typical phase-change materials. Fatty acids exhibit a reversible isothermal entropy change of about 600 J kg−1 K−1 and an adiabatic temperature change of about 10 K at a pressure less than 60 MPa, resulting from the pressure-driven liquid–solid phase transition. In the solid state, the adiabatic temperature change of fatty acids is larger than that of the n-alkanes with similar transition temperatures. Raman analysis indicates that the population of the distorted molecular chains in fatty acids is remarkably decreased when they are transformed from liquid to solid state, leading to the colossal entropy change. For solid fatty acids, the intermolecular interactions characterized by the hydrogen bonds are significantly strengthened under pressure, which explains their large adiabatic temperature change. This study suggests fatty acids are promising refrigerants for eco-friendly barocaloric cooling. [ABSTRACT FROM AUTHOR]

Lead‐free electrocaloric (EC) materials have attracted considerable attention due to their potential applications in environmentally friendly solid‐state cooling devices. Achieving a large adiabatic temperature change (ΔTEC$\Delta T_{\text{EC}}$) at low applied voltage and good temperature stability is crucial and closely related to the phase structure and ferroelectric properties. In this study, 0.2Ba(Ti0.9Sn0.1)O3–0.8Ba(Zr0.18Ti0.82)O3 (BZSnT20) multilayer electrocaloric ceramics (MLEC) are synthesized and characterized for their phase structure and dielectric properties using X‐ray diffraction and dielectric testing. The ferroelectric performance of BZSnT20 is assessed by analyzing their polarization–electric field loops, and the ΔTEC$\Delta T_{\text{EC}}$ is measured using a heat‐flow measurement system. By investigating the mechanisms, structure–activity relationship between the BaO–CaO–SiO2 (BCS) glass sintering aid and the ΔTEC$\Delta T_{\text{EC}}$, the optimal content of BCS glass sintering aid is obtained. In the case of BZSnT20 MLEC, a positive relationship between effective volume and ΔTEC$\Delta T_{\text{EC}}$ is observed, consistent with theoretical calculations. Additionally, the ceramic layer is found to have no significant influence on the EC properties of the sample. In this study, valuable insights into modifying the dielectric and adiabatic temperature change performance in lead‐free MLEC are provided and a potential pathway for the development of low‐voltage EC cooling devices is suggested. [ABSTRACT FROM AUTHOR]

Understanding the intermetallic reaction is critical for reactive metal systems, among which Ni/Al nanolaminates have attracted extensive interest. A long-standing open question is how nanostructure such as premixed interlayer affects the reaction process. Here, we employ molecular dynamics simulations to investigate the effects of premixing degree on the shock-induced reaction mechanisms and reactivity for premixed Ni/Al nanolaminates. The multiple exothermic processes are identified, namely, the Ni–Al mixing driven by diffusion, the B2-NiAl crystallization in premixed interlayer, and the grain coarsening driven by grain boundary migration. Intriguingly, it is found that the specific exothermic processes depend strongly on the premixing degree. As the premixing degree increases, the B2-NiAl crystallization and the grain coarsening appear sequentially. The maximum crystallinity and grain size increase linearly and exponentially with premixing degree, respectively. Furthermore, inspired by the differences in exothermic processes, the intrinsic mechanism for the weakening effects of premixed interlayer on reactivity is elucidated. The B2-NiAl crystallization in premixed interlayer decreases the reaction heat and further the final adiabatic temperature, while the appearance of grain coarsening produces additional heat and alleviates the weakening effect. These findings can provide valuable insights into the nanostructure–reactivity relationship for reactive intermetallic materials. [ABSTRACT FROM AUTHOR]

Lead‐free electrocaloric (EC) materials have attracted considerable attention due to their potential applications in environmentally friendly solid‐state cooling devices. Achieving a large adiabatic temperature change (ΔTEC$\Delta T_{\text{EC}}$) at low applied voltage and good temperature stability is crucial and closely related to the phase structure and ferroelectric properties. In this study, 0.2Ba(Ti0.9Sn0.1)O3–0.8Ba(Zr0.18Ti0.82)O3 (BZSnT20) multilayer electrocaloric ceramics (MLEC) are synthesized and characterized for their phase structure and dielectric properties using X‐ray diffraction and dielectric testing. The ferroelectric performance of BZSnT20 is assessed by analyzing their polarization–electric field loops, and the ΔTEC$\Delta T_{\text{EC}}$ is measured using a heat‐flow measurement system. By investigating the mechanisms, structure–activity relationship between the BaO–CaO–SiO2 (BCS) glass sintering aid and the ΔTEC$\Delta T_{\text{EC}}$, the optimal content of BCS glass sintering aid is obtained. In the case of BZSnT20 MLEC, a positive relationship between effective volume and ΔTEC$\Delta T_{\text{EC}}$ is observed, consistent with theoretical calculations. Additionally, the ceramic layer is found to have no significant influence on the EC properties of the sample. In this study, valuable insights into modifying the dielectric and adiabatic temperature change performance in lead‐free MLEC are provided and a potential pathway for the development of low‐voltage EC cooling devices is suggested. [ABSTRACT FROM AUTHOR]

In this study, three hydration heat controlling materials (HHCMs), respectively, containing pure hydroxyl (polyvinyl alcohol, PVA), carboxylic (polyacrylic acid, PAA) and ester groups (maleic acid-ethylene glycol ester, P(MA-EG)) were synthesized and mixed with cement-based materials, and the hydration heat and setting time of cement pastes and the SEMI adiabatic temperature rise and strength of mortars were tested. The results showed that PAA and P(MA-EG) reduced the peak value of hydration exothermic rate by 77.45% and 62.28%, respectively, and prolonged 54.14 h and 15.56 h, respectively. Mechanism studies showed that HHCMs containing carboxylic or hydroxyl groups adsorbed on cement particles by Ca2+ complexation, while HHCMs containing ester groups hydrolyzed to carboxylic groups in alkaline cement pastes, which hydrolysis rate changed with the hydration temperature of cement-based materials to regulate the hydration process. This study aims to provide technical feasibility and theoretical basis for exploring new avenues of synthesizing HHCMs with different functional groups. [ABSTRACT FROM AUTHOR]

Under the action of cement hydration heat, the construction environment, thermal insulation measures, and pipe cooling systems, a mass concrete pile cap is subject to a complex internal temperature field, which makes it difficult to control its internal surface temperature difference (TISTD), the internal adiabatic temperature rise (TIATR), and the surface temperature (TST). In this study, a mass concrete pile cap of a very large bridge (the length, width, and height were 26.40 m, 20.90 m, and 5.00 m, respectively, and the central-pier pile cap was constructed with C40 concrete) was taken as the research object. The control factors affecting the temperature field of the pile cap were determined by comparing the field temperature measurements with the values calculated with finite element software simulation analysis. By using Midas Civil (2022 v1.2) and Midas FEA (NX 2022) finite element software, these factors (the concrete mold temperature, the concrete surface convection coefficient, the ambient temperature, the pipe cooling system parameters, etc.) were numerically analyzed, and their influence laws and degrees were determined. [ABSTRACT FROM AUTHOR]

Room-temperature elastocaloric cooling is considered as a zero-global-warming-potential alternative to conventional vapor-compression refrigeration technology. However, the limited entropy and large-deformation features of elastocaloric polymers hinder the creation of the breakthrough in their caloric responses and device development. Herein, we report that the addition of a small amount of inorganic nanofillers into the polymer induces the aggregate of the effective elastic chains via shearing the interlaminar molecular chains, which provides an additional contribution to the entropy in elastocaloric polymers. Consequently, the adiabatic temperature change of −18.0 K and the isothermal entropy change of 187.4 J kg−1 K−1 achieved in the polymer nanocomposites outperform those of current elastocaloric polymers. Moreover, a large-deformation cooling system with a work recovery efficiency of 56.3% is demonstrated. This work opens a new avenue for the development of high-performance elastocaloric polymers and prototypes for solid-state cooling applications. In this work, inorganic nanofillers are added to SEBS polymers to induce shearo-caloric effects, enhancing the elastocaloric response. Authors design and demonstrate a double-unit cooling device with a work recovery efficiency of 56.3% and a system coefficient of performance of 8.3. [ABSTRACT FROM AUTHOR]

Elastocaloric cooling technology has the prospect of becoming a commercialized green alternative to current vapor-compression technology, and the systematic characterization of the elastocaloric effect and microstructure has become increasingly significant for the optimization of elastocaloric coolers and heat pumps. In this work, a comprehensive elastocaloric effect characterization for a dog-bone shaped NiTi sheet with a thickness of 0.5 mm was performed for the application in a compact continuous rotating bending elastocaloric cooler. The elastocaloric effect was found to be nearly identical under Brayton-like and sinusoidal force-controlled cyclic tensile loadings. The maximum adiabatic temperature change values of 31 and 23 K were recorded in Brayton-like cyclic loadings under maximum applied stress of 600 and 400 MPa, respectively, with an applied strain rate of 0.1 s−1. During fatigue tests, large applied stress (>600 MPa) and high applied strain rates (>0.1 s−1) tended to result in premature failure of the NiTi sheet samples. In the continuous rotating bending elastocaloric cooler, the sheets generated a temperature span of 6 K between the copper heat sink and heat source. The results of this work provide a set of thermophysical property data for the elastocaloric solid refrigerant and insights for the optimization of structural and operational parameters in elastocaloric coolers and heat pumps. [ABSTRACT FROM AUTHOR]

In prior research on shock-induced reaction, the interfacial crystallization of intermetallics, which plays an important role in solid-state reaction kinetics, has not been explored in detail. This work comprehensively investigates the reaction kinetics and reactivity of Ni/Al clad particle composites under shock loading with molecular dynamics simulations. It is found that the reaction acceleration in a small particle system or the reaction propagation in a large particle system breaks down the heterogeneous nucleation and continuous growth of B2 phase at the Ni/Al interface. This makes the generation and dissolution of B2-NiAl show a staged pattern consistent with chemical evolution. Importantly, the crystallization processes are appropriately described by the well-established Johnson–Mehl–Avrami kinetics model. With the increase in Al particle size, the maximum crystallinity and growth rate of B2 phase decrease and the value of the fitted Avrami exponent decreases from 0.55 to 0.39, showing a good agreement with the solid-state reaction experiment. In addition, the calculations of reactivity reveal that the reaction initiation and propagation will be retarded, but the adiabatic reaction temperature can be elevated when Al particle size increases. An exponential decay relationship is found between the propagation velocity of the chemical front and the particle size. As expected, the shock simulations at non-ambient conditions indicate that elevating the initial temperature significantly enhances the reactivity of large particle systems and results in a power-law decrease in the ignition delay time and a linear-law increase in the propagation velocity. [ABSTRACT FROM AUTHOR]

A multi-stimuli cooling cycle can be used to increase the cyclic caloric performance of multicaloric materials like Ni–Mn–In Heusler alloys. However, the use of uniaxial compressive stress as an additional external stimulus to a magnetic field requires good mechanical stability. Improvement in mechanical stability and strength by doping has been shown in several studies. However, doping is always accompanied by grain refinement and a change in transition temperature. This raises the question of the extent to which mechanical strength is related to grain refinement, transition temperature, or precipitates. This study shows a direct comparison between a single-phase Ni–Mn–In and a two-phase Gd-doped Ni–Mn–In alloy with the same transition temperature and grain size. It is shown that the excellent magnetocaloric properties of the Ni–Mn–In matrix are maintained with doping. The isothermal entropy change and adiabatic temperature change are reduced by only 15% in the two-phase Ni–Mn–In Heusler alloy compared to the single-phase alloy, which results from a slight increase in thermal hysteresis and the width of the transition. Due to the same grain size and transition temperature, this effect can be directly related to the precipitates. The introduction of Gd precipitates leads to a 100% improvement in mechanical strength, which is significantly lower than the improvement observed for Ni–Mn–In alloys with grain refinement and Gd precipitates. This reveals that a significant contribution to the improved mechanical stability in Gd-doped Heusler alloys is related to grain refinement. [ABSTRACT FROM AUTHOR]

Lead-free ferroelectric materials are essential for environment-friendly solid-state cooling technology. In this respect, the electrocaloric effect of lead-free Ba0.8−xSr0.2SmxTiO3 (x = 0.01–0.05) ceramics has been investigated. The Rietveld refinement reveals that all the ceramics exhibit tetragonal symmetry and the tetragonality decreases for x > 0.03, which is the major reason behind the decrease in both isothermal entropy change and adiabatic temperature change. The degree of diffuseness parameter is enhanced by doping of Sm3+, which confirms the formation of polar nanoregion and the enhancement of the electrocaloric effect parameter by adding extra entropy. The relaxor behavior of the prepared samples is also confirmed by estimating the degree of deviation parameter (Δ T m = 77 K ) from the 1 ε r vs. T curve. So, the temperature stability of the prepared ceramics is improved in a broad temperature window. The highest isothermal entropy change (Δ S) , adiabatic temperature change (Δ T) , and electrocaloric strength ( Δ T Δ E ) are found to be 1.230 Jkg−1 K−1, 0.862 K, and 0.028 73 K cm/kV at 316 K, respectively, for Ba0.77Sr0.2Sm0.03TiO3. [ABSTRACT FROM AUTHOR]

Barocaloric cooling, that is, lowering the temperature of a material under pressure action, is an attractive solid‐state effect that can potentially compete with volatile gas‐based cooling. To observe the barocaloric effect (BCE), it is necessary for materials to have high‐entropy, low‐hysteretic phase transitions with a large volume change between phases. Here details on a new FeII complex [Fe(L)(NCS)2], L = N1,N3‐bis((1‐propyl‐1H‐1,2,3‐triazol‐4‐yl)methylene)‐2,2‐dimethylpropane‐1,3‐diamine) possessing spin crossover (SCO) behavior near room temperature with large entropy and volume change are reported, which provides high sensitivity to external pressure. The observed BCE effect, characterized using variable pressure calorimetry, powder X‐ray diffraction, UV–vis, IR, and Raman spectroscopy, shows a colossal isothermal entropy change of >100 J kg−1 K−1 and a reversible adiabatic temperature change of ≈16 K at a pressure of 1 kbar, demonstrating a high refrigerant efficiency compared to other solid‐state materials. These results stimulate further investigations of SCO materials as barocaloric refrigerants, which depend on the proper design of their constituent organic ligands. [ABSTRACT FROM AUTHOR]

Magnetocaloric effect (MCE) exhibits highly efficient and ecological cooling abilities for solid-state refrigeration in contrast to traditional vapor-compression refrigeration. Successive emerging two-dimensional (2D) magnetic materials provide a fertile platform for exploring low-dimensional MCE systems. Here, we focus on a series of 2D transition metal dihalides MX2 (M = Fe, Ru, Os; X = Cl, Br) to explore the maximum isothermal magnetic entropy change (− Δ S mag max ) and adiabatic temperature change (Δ T ad max ) under external magnetic field. It is found that FeCl2, FeBr2, and RuCl2 have intrinsically sizable − Δ S mag max , Δ T ad max , and high thermal conductivity near room temperature, demonstrating superior comprehensive refrigeration performance in comparison with other 2D magnets. It is revealed that strong nearest-neighbor ferromagnetic exchange interaction plays a decisive role in − Δ S mag max , and the high lattice thermal conductivities of FeCl2 and RuCl2 are attributed to the longer phonon lifetime and larger group velocity of low-frequency acoustic branch. Moreover, moderate strain and carriers doping are able to effectively regulate Curie temperature and magnetocrystalline anisotropy energy and correspondingly enhance − Δ S mag max . The present work provides important insights for the exploration of 2D magnets for magnetocaloric refrigeration near room temperature. [ABSTRACT FROM AUTHOR]

Developing readily available and cost-effective electrocatalysts as an alternative to the noble metals is a critical issue for renewable hydrogen energy generation. Mesoporous high-entropy oxides (HEOs) are among the most noteworthy candidates in the kinetically challenged process of oxygen evolution reaction (OER); The current study notifies the successful fabrication, and characterization of a series of meso-structured HEOs (5 elements) and MEOs (4 elements) nanopowders with remarkable electrocatalytic performance. Obtained results reveal that the synthesized HEOs and MEOs nanocompounds are meso-structured (with pore size of ⁓43–67 Å) with particle size of ⁓20–30 nm. Combusted HEOs and MEOs powders have high crystallinity degree (derived from XRD analysis) and homogenous elemental distributions. The electrocatalytic activity of the prepared HEOs and MEOs nanopowders were studied using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analyses. It was specified that HEO nanoparticles (HEO 0.95 sample) exhibit superior electrocatalytic performance compared to MEOs particles with respect to their overpotential of 310 mV at 10 mA cm−2 and Tafel slope of 53 mV.dec−1. The drop of the charge transfer resistance (R CT) and increase of the conductivity in HEO 0.95 sample contributes to the improved electrocatalytic OER activity of the HEOs nanopowders. Taking ECSA into account, the improved electrocatalytic activity of meso-structured HEO 0.95 sample relates to the large number of active sites in this sample. The XRD, TEM, and FE-SEM results of HEO 0.95 sample after OER analysis indicated no alteration in phase composition and morphology revealing the reusability of the synthesized nanoparticles. This study also provides an insight into the behavior of Co, Ni, Cu elements as typical electrocatalysts as well as Zn and Mg elements as obscure electrocatalysts for efficient OER electrocatalysis. Furthermore, the impact of adiabatic temperature, crystallinity degree and physicochemical features of meso-structured particles on electrocatalytic performance are explored. [ABSTRACT FROM AUTHOR]

Biodiesel is one of the most important alternative fuels due to limited conventional resources. Methyl octanoate with long alkyl chain and mono-alkyl ester is one of the surrogate fuels of actual biodiesel. In order to clarify distinctive combustion characteristics of methyl octanoate, comparison with alkane in traditional diesel is necessary. Therefore, this work chose n-nonane with same carbon number as methyl octanoate. The laminar flame speeds of two fuels were measured at different conditions (T = 423 K, P = 1 and 3 atm, and φ = 0.7–1.5) in a constant volume combustion bomb. Results show that laminar flame speed of n-nonane is higher than that of methyl octanoate in most conditions, but lower in fuel-rich conditions. The combined chemical kinetic model of methyl octanoate and n-nonane was developed through eliminating unnecessary reactions, which can well predict the experimental results of laminar flame speed and ignition delay time. The adiabatic flame temperature results from the updated kinetic model show that the temperatures of n-nonane are higher than methyl octanoate in whole conditions, which is unexpectedly opposite to their laminar flame speeds order in fuel-rich conditions. In overall conditions, the intermediates of methyl octanoate tend to produce CH3, which consumes H radicals, thereby reducing the laminar flame speed, which can explain the higher laminar flame speed of n-nonane in most conditions. Meanwhile, the oxidation reactions with oxygen molecules of intermediates of n-nonane are suppressed due to low combustion temperature at φ = 1.5 unlike at φ = 0.7 and 1.0. On the contrary, those of methyl octanoate have similar reactions between φ = 0.7, 1.0, and φ = 1.5. It means that the laminar flame speed of n-nonane decreases more significantly than methyl octanoate as the equivalence ratio increases from φ = 1.0 to φ = 1.5. [ABSTRACT FROM AUTHOR]

Solid‐state methods for cooling and heating promise a sustainable alternative to current compression cycles of greenhouse gases and inefficient fuel‐burning heaters. Barocaloric effects (BCE) driven by hydrostatic pressure (p) are especially encouraging in terms of large adiabatic temperature changes (|ΔT| ≈ 10 K) and isothermal entropy changes (|ΔS| ≈ 100 J K−1 kg−1). However, BCE typically require large pressure shifts due to irreversibility issues, and sizeable |ΔT| and |ΔS| seldom are realized in a same material. Here, the existence of colossal and reversible BCE in LiCB11H12 is demonstrated near its order‐disorder phase transition at ≈380 K. Specifically, for Δp ≈ 0.23 (0.10) GPa, |ΔSrev| = 280 (200) J K−1 kg−1 and |ΔTrev| = 32 (10) K are measured, which individually rival with state‐of‐the‐art BCE figures. Furthermore, pressure shifts of the order of 0.1 GPa yield huge reversible barocaloric strengths of ≈2 J K−1 kg−1 MPa−1. Molecular dynamics simulations are performed to quantify the role of lattice vibrations, molecular reorientations, and ion diffusion on the disclosed BCE. Interestingly, lattice vibrations are found to contribute the most to |ΔS| while the diffusion of lithium ions, despite adding up only slightly to the entropy change, is crucial in enabling the molecular order–disorder phase transition. [ABSTRACT FROM AUTHOR]

The effects of hydrogen (H 2) addition on the freely-propagating acetylene-oxygen (C 2 H 2 –O 2) flames in a doubly-infinite domain are investigated, considering separate and coupled chemical and transport phenomena. Results show that increasing proportions of H 2 enhance the laminar flame speeds of C 2 H 2 –O 2 mixtures. Moreover, H 2 promotes the C 2 H 2 –O 2 flame to contain both light (H, H 2) and heavy (C 2 H 2) species. Compared with the Soret diffusion and radiation effect, the unity Lewis number assumption can induce substantial inaccuracies. Sensitivity analysis indicates that the key elementary reaction H + O 2 O + OH exerts stronger influences on the laminar flame speed. Additionally, due to the effective enthalpy of C 2 H 2 being greater than H 2 , adding H 2 decreases both adiabatic flame temperature and enthalpy of C 2 H 2 –O 2 flames. Notably, reactions C 2 H 2 + O H + HCCO and C 2 H + H 2 H + C 2 H 2 in the C 2 H 2 sub-mechanism are identified as important exothermic- and endothermic-reactions respectively. Furthermore, it is demonstrated that dilution effects from CO 2 have a larger impact compared to those from H 2 O and Ar. Finally, the effects of initial pressure and temperature on the laminar flame speeds are also discussed. The results of the present work provide guidance for the effective use of binary fuel and risk control as well as fire suppression. • The effects of hydrogen additions on acetylene-oxygen flames are numerically studied. • Different flame diffusion models are characterized. • Chemical and thermal structures are revealed separately. • The effects of different dilution gases and initial conditions are considered. [ABSTRACT FROM AUTHOR]

In the current work, the thermodynamic properties of equiatomic and non-equiatomic Ni-Ti were estimated using Factsage Software for the "self-propagating high temperature synthesis (sHs) method. To calculate behind the pure substance model, the sublattice model was used. For the various ratios of the nickel in the B2 ordered phase and second intermetallics, the values of adiabatic temperature, Cp, Gibbs free energy, enthalpy of formation, products, and liquid-solid ratio were computed (Ni3Ti, Ti2Ni). These proporties play a crucial role in understanding the nature of propagating behavior since they affect the final product's micro/macrostructure, mechanical characteristics, and stable or metastable phases. The results were compared with the literature. It was also discussed why the existing studies could not reach the theoretical adiabatic temperature and the effect of the ignition W wire on the sample was investigated with the experimental study. [ABSTRACT FROM AUTHOR]

A large adiabatic temperature change along with a wide operating temperature region is usually required for the electrocaloric materials to fulfill their refrigeration function. In general, doping foreign ions into BaTiO3 is the frequently utilized strategy in order to obtain excellent electrocaloric materials for the practical application. In the current paper, BaTiO3 lead‐free ferroelectric ceramics were doped by Ca2+ and Sn4+ simultaneously in order to generate a coexistence state at room temperature, where ferroelectric domains and nanodomains exit. As a result, a large polarization and a wide operating temperature range were finally induced. It is found that Ba0.9Ca0.1Ti0.85Sn0.15O3 has a maximum adiabatic temperature change of 0.85 K and an excellent working temperature region (65 K, ∆T > 90% Tmax) was achieved under an electric field of 50 kV/cm. The above phenomenon indicates that the modified BaTiO3 ceramics can be a good potential electrocaloric material in the state of cross‐existence of ferroelectric domains and nanodomains. [ABSTRACT FROM AUTHOR]

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In the present study, first, the environmental challenges and cracking characteristics during the construction of plateau concrete on the Sichuan–Tibet route were revealed. Then, using a multi-field coupled shrinkage model with hydration temperature humidity constraints, the early and long-term cracking risks in the core of plateau pier bodies were investigated. Later, the effects of tensile strength, pouring interval age and adiabatic temperature rise on the cracking risk were analyzed. Finally, various control measures for high-altitude concrete cracking were proposed. The results indicated that the complex environment of the plateau led to different forms of cracks in the pier body, especially vertical cracks in the straight sections. The long-term risk of core cracking in the plateau pier body is significantly greater than the risk of early cracking. This risk was strongly influenced by factors such as the concrete tensile strength, pouring interval age and adiabatic temperature rise, which should be given more attention. Deformation compensation can significantly enhance the peak and residual deformation capacities of plateau concrete, with peak values greater than 900 με and residual deformation greater than 200 με at day 60, as well as its resistance to cracking. Strategies such as adopting radiant cooling techniques, improving construction techniques and implementing effective management measures can all play a vital role in improving the cracking resistance of highland concrete. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectric polymers exhibiting a giant electrocaloric effect (ECE) can potentially be used to create next‐generation solid‐state coolers. Under an electric field, poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) terpolymer goes through a large dipolar entropy change producing a high adiabatic temperature change (ΔTECE). This work resolves the molecular origins of the large entropy change behind the electric field‐induced dipole switching. A Fourier transform infrared spectroscopy equipped with a high voltage source is used to operandoly observe the characteristic molecular vibrational modes. A short‐range trans (T) conformation of the CF2‐CH2 dyads interrupted by a gauche (G) conformation, e.g., TTTG in the terpolymer chain, undergoes a dynamic transformation that leads to a corresponding ΔTECE whenever an electric field is applied. The molecular dynamics simulation also proves that the energy barrier that the transformation from TTTGs into a long T sequence overcomes is smaller than that for all other conformations. A mixed solvent system is used to obtain T3G‐enriched terpolymer films exhibiting a 4.02 K ΔTECE at 60 MV m−1 and these films are employed to manufacture a 2‐layer‐cascaded cooling device that achieves a 6.7 K temperature lift, the highest reported value for a 2‐layer cascaded device made of fluoropolymers. [ABSTRACT FROM AUTHOR]

The catalytic combustion of ultralean air-hydrogen mixtures is a technique for generating thermal power without emissions at the stack with inherently safe systems. The technology utilizes mixtures beyond flammability limits and conducts combustion in catalyst-coated monoliths. This work develops a numerical model of an adiabatic channel of a catalytic combustor and provides data for its validation obtained with an experimental test rig operating with ultralean stoichiometry. The focus is on the superadiabatic temperature hotspot over the walls of the monolith as well as the fuel conversion in the device. Both these factors are numerically estimated and experimentally measured under various operational conditions by varying the inlet flow rate and the inlet hydrogen fraction. Furthermore, the numerical model is utilized to evaluate the impact of the heat conduction coefficient and of the channel diameter of the monolith on the parameters presented above. Finally, the start-up time is measured and compared against the numerical estimation. A 30 mm long, 400 CPSI, Pt- and Pd-based catalytic honeycomb monolith with square channels is exploited. The results reveal that despite significant adiabatic hotspots, the highest catalytic surface temperature measured is 692 K, with an adiabatic combustion temperature of 543 K, and with greater than 99% H 2 conversion. The numerical and experimental results show that a catalytic combustor can be reliably operated with hydrogen outside the flammability limits and that the process can cold-start without external ignition. • H 2 ignition at room temperature and complete conversion with ultralean mixtures. • Superadiabatic temperatures on the catalyst are both modelled and measured. • Surface temperatures measured in the catalytic combustor with a coated thermocouple. • Measured temperature hotspot always below 692 K with <3% H2/air at combustor inlet. • Monoliths with small channels and high thermal conductivity are less stressed. [ABSTRACT FROM AUTHOR]

A series of high-pressure multi-anvil experiments were conducted in the MgO-Al 2 O 3 system between 15 and 50 GPa and at temperatures up to 2623 K, to determine the solubility of Al 2 O 3 in periclase in the stability fields of coexisting spinel, corundum, the Mg 2 Al 2 O 5 modified ludwigite phase, the MgAl 2 O 4 calcium ferrite phase, and the MgAl 2 O 4 calcium titanate phase. The Al 2 O 3 solubility in periclase is strongly temperature-dependent over the conditions investigated. Conversely, periclase Al 2 O 3 solubility exhibits a negative relationship with pressure. Experiments with up to 40 mol.% FeO in ferropericlase show Al 2 O 3 solubilities that are near identical to those of periclase, within experimental uncertainties. A simple thermodynamic model incorporating significant literature on ambient pressure measurements is able to describe periclase Al 2 O 3 solubility up to 40 GPa. This model is used to investigate the Al 2 O 3 contents of ferropericlase inclusions observed in natural diamonds, which vary up to 0.35 mol. %. Pressure–temperature curves along which particular inclusions formed can be produced if equilibrium can be assumed with Al-bearing minerals found in the same diamond. Alternatively, the maximum possible Al 2 O 3 content in ferropericlase can be determined for a certain pressure–temperature profile and inclusions with Al 2 O 3 contents that exceed this curve can be excluded from those conditions. To obtain such solubility curves, calculations are performed for periclase coexisting with the Al-rich phases spinel, garnet, bridgmanite and the MgAl 2 O 4 calcium ferrite phase. The calculations indicate that periclase, and by inference ferropericlase, Al 2 O 3 -contents cannot be greater than 0.5 mol.% under present day adiabatic mantle temperatures and go through a minimum at mantle transition zone conditions. This excludes a number of Al-rich ferropericlase inclusions found in natural diamonds from being formed in the transition zone, unless temperatures were super-adiabatic. This subset of inclusions likely formed either at the base of the upper mantle or the top of the lower mantle, but must have formed at near adiabatic temperatures. The majority of ferropericlase inclusions have Al 2 O 3 contents that would be consistent with formation in the transition zone at near slab temperatures, but could still have been formed at higher temperatures if Al 2 O 3 activities were low. [ABSTRACT FROM AUTHOR]

We report the effect of configurational entropy (CE) on the electrocaloric (EC) effect of Ba x Sr y Ca z (Bi 0.5 Li 0.5) 1- x - y - z TiO 3 (BSCBLT) (0.627≤ x ≤ 0.66, 0.0716≤ y ≤ 0.1993, 0.0145≤ z ≤ 0.1758) ceramics. All samples were designed to show different CE but the same A-site cation average radius, tolerance factor and cationic size disorder. The samples with x ≤ 0.64 show ferroelectric (FE) relaxor behavior, while x ≥ 0.65 are normal FEs. x = 0.65 shows the maximum EC effects among all samples. Both maximum adiabatic temperature change (ΔT m) and CE vary almost in the same way with increasing x. The anomalous enhancement of ΔT m in x = 0.65 with relatively lower CE compared with that in x = 0.64 can be ascribed to an additional contribution of Ba concentration induced FE to relaxor FE transition in BSCBLT. Our results reveal important evidences of enhanced EC effects by CE and suggest that designing FEs or relaxor FEs with high CE might be an effective route to achieve high EC effects. [ABSTRACT FROM AUTHOR]

Blending of partially cracked ammonia with biosyngas is an attractive strategy for improving NH 3 combustion. In practice, products of biomass gasification and those of thermo-catalytic cracking of NH 3 are subject to some compositional uncertainties. Despite their practical importance, so far, the effects of such uncertainties on combustion systems remained largely unexplored. Hence, this paper quantifies the effects of small compositional uncertainties of reactants upon combustion of partially cracked NH 3 /syngas/air mixtures. An uncertainty quantification method, based on polynomial chaos expansion and a data-driven model, is utilised to investigate the effects of uncertainty in fuel composition on the laminar flame speed (S L) and adiabatic flame temperature (T ad) at different inlet pressures (P i). The analysis is then extended to the power output of a combined-cycle gas turbine fuelled by the reactants. It is found that 1.5% fuel compositional uncertainty can cause 12–21% of S L uncertainty depending on the inlet pressure. Furthermore, the effect of compositional uncertainty on T ad increases at higher ratios of H 2 to NH 3. Sensitivity analysis reveals that the uncertainty of CO contribution to S L uncertainty is higher than that of NH 3 , while the trend is reversed for the T ad uncertainty. In addition, the power output from the combined-cycle gas turbine system varies between 4 and 6% with 1.5% of fuel compositional uncertainty. This become more noticeable at elevated P i [5–10 atm], particularly when the fuel mixture contains high H 2 which is the main contributor to T ad variability. • PCE-UQ model to analyse compositional variability effects on flame properties (S L and T ad). • Additional UQ analysis examines the uncertainty impacts on a CCGT system. • H 2 variability is the strongest contributor to the uncertainty in the CCGT power output. • Richer fuel mixtures are most affected (6%) by minor fuel compositional variability. • Uncertainty impact is higher for high H 2 fuel mixtures combustion at elevated pressures. [ABSTRACT FROM AUTHOR]

Electrocaloric refrigeration technology has garnered significant attention due to its potential for next-generation solid-state cooling, which is miniaturized and efficient. However, achieving a substantial electrocaloric effect (ECE) and a wide working temperature range at low electric fields remains a challenge. In this study, a synergistic approach combining domain and defect engineering was used in transparent 0.88 Pb(Mg 1/3 Nb 2/3)O 3 -0.12PbTiO 3 - x Sm(0.88PMN-0.12 PT- x Sm) ceramics to improve ECE and temperature stability. Finally, a notable adiabatic temperature change (ΔT) of 2.07 K in the x = 0.01 ceramic, with ΔT exceeding 1.0 K across a broad temperature range from 30 to 180 °C was achieved. Piezoresponse force microscopy (PFM) and X-ray photoelectron spectroscopy revealed the presence of small domains and appropriate oxygen vacancies as contributors to the enhanced ECE and broad operation temperature range. This work introduces a promising candidate material for electrocaloric refrigeration. [ABSTRACT FROM AUTHOR]

Addressing burning characteristics of syngas under oxy-combustion conditions in substantially CO 2 -diluted combustion environment for gas turbine combustion applications has rarely been reported. A detailed modeling study was performed over a broad range of syngas compositions at fixed inlet flow velocity of 6 m/s, fixed equivalence ratio of 0.42, and fixed oxygen fraction (OF) of 60% (by vol.). For validating the numerical model, the calculated results were compared against experimental results recorded from the same physical combustion setup. The effects of syngas composition on flow field, laminar flame speed (LFS), flame thickness, adiabatic flame temperature (AFT), combustor power density (PD), thermal power (TP), and species distributions were investigated. Adiabatic flame temperature increased from 2312 to 2388 K, LFS increased from 0.53 to 1.32 m/s, PD reduced from 2854 to 2672 kW/m3, and TP decreased from 4.0 to 3.7 kW when the hydrogen fraction (HF) was changed from 0 to 80%.When the HF was reduced from 90% to 10%, with excluding CH 4 , the AFT increased from 2447 to 2560 K, the LFS decreased from 2.01 to 0.46 m/s, the TP increased from 3.64 to 4.1 kW, and the PD increased from 2620 to 2923 kw/m3. [Display omitted] • Study combustion characteristics of CH 4 /H 2 /CO syngas premixed flames. • Flame speed and temperature and power decreased increased with CO fraction rise. • Increase in H 2 fraction leads to rise in flame speed and temperature but power decreases. • Increase in CH 4 leads to decreases in flame speed and temperature but power increases. • Excluding CH 4 leads to decreases in flame speed and temperature but power increases. [ABSTRACT FROM AUTHOR]

The peak explosion pressure and maximum rate of pressure rise of explosions in confined spaces are key safety parameters to evaluate the hazard of processes running in closed vessels and to design enclosures able to withstand explosions or of their vents used as relief devices. These properties are examined in the present paper, for hydrogen-hydrocarbon-air mixtures at sub-atmospheric pressures, using propane and n -butane as test fuels and variable hydrogen ratios between 0 and 0.3. The experimental study was carried out in a sphere and a cylindrical chamber at room temperature and sub-atmospheric pressures (between 0.3 and 1.0 bar). On the basis of pressure recordings, the characteristic explosion indices, i.e., the maximum explosion pressure (p max), maximum rate of pressure rise ((dp/dt) max), deflagration index (K G), and time to peak pressure (θ max) were derived. Numerical simulations were used to determine the adiabatic explosion pressures and adiabatic flame temperatures of isochoric combustion. The effects of initial pressure (p 0), hydrogen concentration, and shape and size of the explosion vessel on explosion indices are discussed. For each hydrogen concentration of the blended fuels, linear correlations p max = f(p 0) and (dp/dt) max = f(p 0) were found. In addition, the heat loss to the walls during explosion propagation was estimated on the basis of the difference between the adiabatic and experimental explosion pressures. The amount of heat lost increases with the increase of hydrogen blending ratio and vessel asymmetry. • Hydrogen-blended propane-air and butane-air explosions were studied in two closed vessels. • The experiments were performed at various initial pressures between 0.3 and 1.0 bar. • As Hydrogen blending ratio increases, the explosion pressure, the maximum rate of pressure rise, and the severity factor increase. • The increase of hydrogen blending ratio results in the decrease of the explosion times. • The observed variations depend largely on the volume and shape of the explosion vessel. [ABSTRACT FROM AUTHOR]

Root-finding methods solve equations and identify unknowns in physics, engineering, and computer science. Memory-based root-seeking algorithms may look back to expedite convergence and enhance computational efficiency. Real-time systems, complicated simulations, and high-performance computing demand frequent, large-scale calculations. This article proposes two unique root-finding methods that increase the convergence order of the classical Newton-Raphson (NR) approach without increasing evaluation time. Taylor's expansion uses the classical Halley method to create two memory-based methods with an order of 2.4142 and an efficiency index of 1.5538. We designed a two-step memory-based method with the help of Secant and NR algorithms using a backward difference quotient. We demonstrate memory-based approaches' robustness and stability using visual analysis via polynomiography. Local and semilocal convergence are thoroughly examined. Finally, proposed memory-based approaches outperform several existing memory-based methods when applied to models including a thermistor, path traversed by an electron, sheet-pile wall, adiabatic flame temperature, and blood rheology nonlinear equation. [ABSTRACT FROM AUTHOR]

The effect of pulsating jet on the unsteady film cooling performance was studied by experimental and numerical simulation. The FLIR thermal infrared thermal camera was used the measure the adiabatic temperature of the surface. The large eddy simulation was conducted for analyzing the adiabatic film cooling effectiveness at four different jet non-dimensionalized pulsated frequency of St = 0, 0.1, 0.2, and 0.3. The analysis of the dynamic model decomposition of both the velocity and temperature fields obtained by numerical calculation was performed to obtain the coupling relationship between the flow and heat transfer. Results show that the cooling effectiveness of steady film cooling (St = 0) decreases with the increase of blowing ratio. At low blowing ratio (M = 0.65), the cooling efficiency of the pulsating jet is significantly lower than the steady-state jet. At the blowing ratio of 1.0 and 1.5, the cooling efficiency of the low frequency pulsating jet (St = 0.1) is a little higher than the steady-state jet, indicating that the low frequency pulsation under the high blowing ratio can improve the coverage of the cooling air. At high pulsating frequency (St = 0.3), the cooling effectiveness is obviously declined. [ABSTRACT FROM AUTHOR]

Comprehensive characterizations of the superelastic and elastocaloric effects of NiTi and NiTi-based shape memory alloys (SMA) in the operation temperature region are highly desirable for using them in elastocaloric coolers with a large temperature lift. In this article, we report the superelastic and elastocaloric effects of a commercially available superelastic polycrystalline NiTi SMA tube with an outer diameter of 5 mm and a wall thickness of 1 mm between 293 and 330 K. The NiTi tube sample was subjected to a training of 250 cycles to stabilize its superelastic and elastocaloric effects. We observed that temperature dependencies existed for both superelastic and elastocaloric effects of the NiTi tube, and stress–strain curves differed much between isothermal and adiabatic loading conditions. The largest temperature rise and temperature drop measured at 293 K under an applied strain of 3.66% and a strain rate of 0.1 s−1 during loading and unloading were 21 and 11 K, respectively. The loading conditions (loading function and holding time) also impacted the superelastic effect of the NiTi tube. We identified two major reasons for the irreversibility of the adiabatic temperature change: the hysteresis heat dissipation and the temporary residual strain after unloading, and they affected the cooling performance of the elastocaloric cooler in different ways. We investigated the dependencies of the superelastic and elastocaloric effects on the maximum applied strain and the temperature distribution on the NiTi tube during loading and unloading. The results are beneficial to the modeling of elastocaloric coolers with large temperature lifts. [ABSTRACT FROM AUTHOR]