Quasi-adiabatic Conditions Research Articles

Experiment and Simulation for REBCO Superconducting Tape in Different Temperature and Current on Quasi-Adiabatic Condition

Experiment and Simulation for REBCO Superconducting Tape in Different Temperature and Current on Quasi-Adiabatic Condition

A finite deformation formulation for amorphous glassy polymers under moderate and impact strain rates: Application to adhesive films

This work describes a novel finite strain hypo-elastic formulation for amorphous thermoset polymers working in the glassy regime. The constitutive formulation is able to describe time and pressure-dependent behaviour under loading rates ranging from quasi-static to impact-type loading conditions and to account for thermo-mechanical coupling effects. A non-linear pressure dependent potential function is introduced to capture the non-associative visco-plastic potential flow for volumetric plastic strain control. The formulation also incorporates an internal state or deformation resistance variable to enable the description of the polymer hardening — softening behaviour, as well as a novel relation for the dissipative fraction of the plastic work in terms of the equivalent accumulated plastic strain. The constitutive model is formulated within a finite strain kinematics framework, and full details of its numerical implementation into the finite element method using a fully implicit Euler Backward algorithm are given. Model calibration is carried out for three different thermosetting resins (PR520 and RTM6 Epoxies, and MMA adhesives).To illustrate the model capabilities, two case studies are investigated: (i) the de-formation behaviour of epoxy under moderate and impact-type loading conditions under isothermal and fully adiabatic conditions, and (ii) the fracture behaviour of adhesive layers used to bond stiff metallic substrates. Results on RTM6 epoxy show that at, e.g., 60% true strain, 48.5% of the rate of plastic work is dissipative, and that the corresponding predicted increase in temperature due to the locally dissipated heat is consistent with published calorimetry data on a similar thermoset polymer. It was also found that, by coupling the proposed constitutive model with a cohesive zone model, it was possible to predict accurately the effect of an MMA adhesive layer thickness and pressure-dependency on the growth of an interfacial crack between the MMA adhesive and the metallic substrates. The proposed model should constitute a generic phenomenological formulation for the mechanical behaviour prediction of a wide range of thermoset polymers under confined and quasi-adiabatic conditions such as in composites and adhesive joints.

How Cyclic Aging at Different Temperatures Affects Safety of Li-Ion Pouch Cells

Li-ion battery safety behavior is critical and should be examined carefully. However, safety testing is typically performed only on pristine cells. This neglects the significant effect of aging conditions, such as ambient temperature, on safety behavior. For example, aging at low temperatures results in Li plating and thus drastically reduces safety [1–3]. Cells aged at higher temperatures with a pronounced solid-electrolyte-interface (SEI) layer on the anode show an increased onset of self-heating leading to improved safety [3,4].The temperature dependent cyclic aging behavior of commercial Li-ion pouch cells is evaluated using an Arrhenius plot. Further Post-Mortem analyses of aged cells from both branches of the V-shaped Arrhenius plot confirm two dominant aging mechanisms: Li plating and SEI growth for the low and high temperature ranges, respectively.Heat-wait-seek (HWS) tests under quasi-adiabatic conditions in an accelerated rate calorimeter (ARC) are used to evaluate safety behavior and identify critical temperatures such as the onset of self-heating. Multiple sensors (voltage, resistance, temperature, strain, and ultrasonic transmission) are placed on the pouch cell to provide a better understanding of the processes taking place during HWS tests. These sensors show that some critical events, such as the onset of swelling, venting, or separator melting, are only slightly affected by aging. In contrast, the onset of self-heating depends on the aging mechanism and state of health (SOH) of the cell, as a more pronounced aging has a greater impact on the change in safety. This knowledge can be used, for example, by cell manufacturers to estimate the minimum safety of aged cells based on tests of new cells.

Safety Evaluation of Temperature-Dependent Aging Mechanisms of Li-Ion Batteries Using ARC Tests with Multiple Online Sensors

Compared to many other characteristics of Li-ion batteries, the safety behavior is a critical property and should be examined carefully. Especially manufacturers and most studies only focus on the safety of pristine cells. However, the safety behavior can drastically change dependent on the prior aging conditions such as ambient temperature. Especially low temperature aged cells with Li plating show a drastically decreased safety behavior [1]. Moreover, cells aged at higher temperatures with a distinct solid-electrolyte-interface (SEI) layer on the anode show an increased onset of self-heating leading to improved safety [2]. Post-Mortem analysis of aged cells confirmed the two dominating aging mechanisms: Li plating and SEI growth for low and high temperature range, respectively.Heat-wait-seek (HWS) tests under quasi-adiabatic conditions in an accelerated rate calorimeter (ARC) are a well-known method to evaluate the safety behavior of Li-ion batteries and can reveal critical temperatures such as the onset of self-heating. HWS tests on cells aged at different temperatures until different state-of-health (SOH) reveal the trend that a more pronounced aging increases or decreases the onset of self-heating depending on whether SEI growth or Li plating is the dominating aging mechanism.In addition to the temperature measurement, multiple sensors for voltage, resistance, strain, and ultrasonic transmission and reflection were placed on the pouch cell for a better understanding of the ongoing processes while the HWS tests. The benefit of these sensors is that they are cheap, allowing them to be widely implemented. Furthermore, an externally coupled mass spectrometer provides information about the gases produced and released after venting of the cell [3]. By Correlating different sensors signals, critical events on the way to the thermal runaway can be reliably identified or even predict in an early stage.Hence, the HWS tests on Li-ion batteries aged at different temperatures in combination with the multi sensor study provide a comprehensive understanding of the influence of temperature dependent aging state on the safety behavior of Li-ion pouch cells. Acknowledgment We gratefully acknowledge the German Federal Ministry of Education and Research (BMBF) for the financial support of the projects AnaLiBa (03XP0347C) and MiCha (03XP0317C) within the AQua cluster.

Magnetocaloric Effect, Structure, Spinodal Decomposition and Phase Transformations Heusler Alloy Ni-Mn-In.

Ni46Mn41In13 (close to 2-1-1 system) Heusler alloy was studied by magnetization measurement dependence on the temperature in magnetic fields of up to 13.5 T. The magnetocaloric effect measured by the direct method in quasi-adiabatic conditions showed a maximum value of ∆Tad = -4.2 K at a temperature T = 212 K in a magnetic field of 10 T in the region of martensitic transformation. The structure of the alloy was studied by transmission electron microscopy (TEM) as a function of the temperature and the thickness of the sample foil. In the temperature range from 353 to 215 K, at least two processes were established. The results of the study indicate that the concentration stratification occurs according to the mechanism of spinodal decomposition (conditionally spinodal decomposition) into nanoscale regions. At a temperature of 215 K and lower, martensitic phase with 14 M modulation is observed in the alloy at thicknesses greater than 50 nm. Some austenite is also observed. In foils with thickness of less than 50 nm in a temperature range from 353 to 100 Km only the initial austenite, which has not transformed, was found.

Thermal Behaviors and Interaction Mechanism of Ammonium Dinitramide with Nitrocellulose.

The initial interaction mechanism is very important for the design and safety of nano-scale composite energetic materials composed of ammonium dinitramide (ADN) and nitrocellulose (NC). The thermal behaviors of ADN, NC and an NC/ADN mixture under different conditions were studied by using differential scanning calorimetry (DSC) with sealed crucibles, an accelerating rate calorimeter (ARC), a self-developed gas pressure measurement instrument and a DSC-thermogravimetry (TG)-quadrupole mass spectroscopy (MS)-Fourier transform infrared spectroscopy (FTIR) combined technique. The results show that the exothermic peak temperature of the NC/ADN mixture shifted forward greatly in both open and closed circumstances compared to those of NC or ADN. After 585.5 min under quasi-adiabatic conditions, the NC/ADN mixture stepped into the self-heating stage at 106.4 °C, which was much less than the initial temperatures of NC or ADN. The significant reduction in net pressure increment of NC, ADN and the NC/ADN mixture under vacuum indicates that ADN initiated the interaction of NC with ADN. Compared to gas products of NC or ADN, two new kinds of oxidative gases O2 and HNO2 appeared for the NC/ADN mixture, while NH3 and aldehyde disappeared. The mixing of NC with ADN did not change the initial decomposition pathway of either, but NC made ADN more inclined to decompose into N2O, which resulted in the formation of oxidative gases O2 and HNO2. The thermal decomposition of ADN dominated the initial thermal decomposition stage of the NC/ADN mixture, followed by the oxidation of NC and the cation of ADN.

Experimental Comparison of Methods to Evaluate Heat Generated by Magnetic Nanofluids Exposed to Alternating Magnetic Fields

The paper aims to compare different methods able to estimate the specific loss power (SLP) generated by three different types of magnetic nanoparticles, MNPs, dispersed in a suspension fluid, e.g., octane or water. The nanoparticles were characterized morphologically in terms of shape and size, chemically for composition and their physical properties like magnetization and SLP were studied. We evidenced the differences in SLP evaluation due to the applied method, particularly in the presence of thermally induced phenomena such as aggregation or precipitation of MNPs that can affect the heating curve of the samples. Then, the SLP determination methods less sensible to this phenomenon appear to be the ones that use the initial slope when the sample is in quasi-adiabatic condition. Finally, we propose a comparison of those methods based on the pros and cons of their use for the SLP determination of magnetic nanofluids. In particular, the analysis of the behavior of the heating curve is useful to evaluate the useful amplitude of the interval analysis for the initial slope methods.

Experimental evaluation of isentropic efficiency in turbocharger twin-entry turbines

Turbocharging plays a fundamental role not only in improving the performance of automotive engines, but also in reducing the fuel consumption and exhaust emissions of spark-ignited biofuel, diesel, liquid, and gaseous engines. Dedicated experimental investigations on turbochargers are therefore needed to evaluate a better understanding of its performance. The availability of experimental information on the steady flow performance of the turbocharger is an essential requirement to optimize the matching calculation. It is interesting to know the isentropic efficiency of the turbine in order to improve the coupling with the engine, in particular it is difficult to identify the definition of the turbine efficiency through a direct evaluation. In a radial turbine, the isentropic efficiency, evaluated directly starting from the measurement of the thermodynamic quantities at the inlet and outlet sections, can be affected by significant errors. This inaccuracy is mainly related to the incorrect evaluation of the turbine outlet temperature, due to the non-uniform distribution of the flow field in the measurement section. For this purpose, a flow conditioner was installed downstream the turbine. Tests were performed at different values of the rotational speed, and in quasi-adiabatic conditions. The flow field downstream the de-coupler was analysed through a hand-made three-hole probe with an exposed junction thermocouple inserted in the pipe with different protrusions. Thanks to this experimental campaign, it was possible to measure pressure, velocity, mass flow and temperature profiles necessary to examine the homogeneity of the flow field. As the turbocharger is fitted with a twin entry turbine, the thermodynamic quantities have been properly taken into account referring to each sector.

Maximum Possible Cooling Rate in Ultrafast Chip Nanocalorimetry: Fundamental Limitations Due to Thermal Resistance at the Membrane/Gas Interface

Ultrafast chip nanocalorimetry opens up remarkable possibilities in materials science by allowing samples to be cooled and heated at extremely high rates. Due to heat transfer limitations, controlled ultrafast cooling and heating can only be achieved for tiny samples in calorimeters with a micron-thick membrane. Even if ultrafast heating can be controlled under quasi-adiabatic conditions, ultrafast controlled cooling can be performed if the calorimetric cell is located in a heat-conducting gas. It was found that the maximum possible cooling rate increases as 1/r0 with decreasing radius r0 of the hot zone of the membrane. The possibility of increasing the maximum cooling rate with decreasing r0 was successfully implemented in many experiments. In this regard, it is interesting to answer the question: what is the maximum possible cooling rate in such experiments if r0 tends to zero? Indeed, on submicron scales, the mean free path of gas molecules lmfp becomes comparable to r0, and the temperature jump that exists at the membrane/gas interface becomes significant. Considering the limitation associated with thermal resistance at the membrane/gas interface and considering the transfer of heat through the membrane, we show that the controlled cooling rate can reach billions of K/s, up to 1010 K/s.

Effect of Li plating during formation of lithium ion batteries on their cycling performance and thermal safety

The presented work focuses on the effect of different applied C-rates within the formation procedure on the performance and the thermal safety of lithium ion battery cells. The formation procedure is based on constant-current constant-voltage charging and constant-current discharging. Here, two different formation procedures were used characterized by the applied current rate of either 0.2C or 2C. The cells were investigated via electrochemical, microscopic and spectroscopic methods. Applying a C-rate of 2C shortens the formation to 1.5 h compared to 10.5 h at 0.2C for one formation cycle. However, also the occurrence of Li plating with an amount corresponding to (7.8 ± 0.3) mAh g−1NMC was observed. Based on those results, thermal safety properties of cells after 0.2C or 2C formation was analyzed under quasi-adiabatic conditions in an accelerated rate calorimeter. Within the margin of error, no influence of the C-rate during formation on the thermal safety could be detected. In addition, no difference in cell cycling performance could be observed. Therefore, the here determined amount of Li plating originating solely from the formation process does not lead to significant differences in cycling performance and thermal safety behavior for the here considered lithium ion battery cells.

Progress in Thermal Management and Safety of Cells and Packs By Testing in Battery Calorimeters

With increasing energy density the safety and the thermal management of Li-ion batteries is becoming more and more important, because the thermal runaway can cause an ignition or even explosion of the battery with simultaneous release of toxic gases. In the last nine years we have established battery calorimetry as a powerful and versatile electrochemical-thermal characterization technique, which allows both advancements for the thermal management and the safety of batteries. With six adiabatic Accelerating Rate Calorimeters (ARC) of different sizes and two sensitive Tian-Calvet calorimeters, all of them combined with cyclers, the IAM-AWP now operates Europe’s largest battery calorimeter center, which enables the evaluation of thermodynamic, thermal and safety data on material, cell and pack level under quasiadiabatic and isoperibolic environments for both normal and abuse conditions (thermal, electrical, mechanical). It will be shown how sophisticated battery calorimetry allows finding new and quantitative correlations between different critical thermally and safety related parameters that will help to design safer systems. For an optimized design with regard to safety cells and packs have to be characterized not only for their temperature behavior but also for the heat dissipation and the pressure development in a quantitative manner.Calorimetry allows the collection of quantitative data required for optimum battery performance and safety. This information can then be used to define the requirements for cooling and thermal management and adapt them accordingly. The battery calorimeters can be used for studies on heat generation and dissipation of Li-ion cells and are coupled to a battery cycler in order to perform the measurements during charging and discharging of the cells under defined thermal conditions. Isoperibolic (constant temperature of the calorimeter) or quasiadiabatic (no heat exchange with the calorimeter) ambient conditions are adjusted by heaters and thermocouples that are located in lid, bottom and side walls of the calorimeter chamber, in which the cell is inserted. For improving the thermal management system, the measured temperature data are converted into generated and dissipated heat data [1] by determination of specific heat capacity and heat transfer coefficient using heat flux sensors.Concerning safety aspects it will be presented how battery calorimeters provide thermal stability data on materials level, e.g. of anodes, cathodes or electrolytes or there combinations and to perform safety tests on cell and pack level by applying thermal [2], mechanical or electrical [3] abuse conditions. The studies on materials level are especially important for Post-Li cells, which make use of more abundant materials, such as sodium or magnesium instead of Li, nickel and cobalt, because these data help to develop safe cells from the beginning all along the value chain. For the advanced Li-ion technology, a holistic safety assessment is in the focus, because the thermal runaway can have multiple interacting causes and effects. A test in the calorimeter is much more sensitive than a hotbox test and reveals the entire process of the thermal runaway with the different stages of exothermic reactions. Self-heating, thermal stability and thermal runaway are characterized and the critical parameters and their thresholds for safe cell operation are determined. As a result of the different tests quantitative and system relevant data for temperature, heat and pressure development of materials and cells are provided. In addition it will be explained how calorimeters allow studying the thermal runaway propagation in order to develop and qualify suitable countermeasures, such as heat protection barriers, which is currently becoming a very hot topic, because a global technical regulation (GTR) on electric vehicle safety is being developed, which includes thermal propagation. There is still the open question, which is the best initialization method to become a standard. We hope that the research in the Calorimeter Center will help to make progress in this field as well. Reference s : [1] C. Ziebert et al., in: L.M. Rodriguez, N. Omar, eds., EMERGING NANOTECHNOLOGIES IN RECHARGABLE ENERGY STORAGE SYSTEMS, Elsevier Inc., ISBN 978032342977, 195-229. 2017.[2] B. Lei, W. Zhao, C. Ziebert, et al., Experimental analysis of thermal runaway in 18650 cylindrical cells using an accelerating rate calorimeter, Batteries 3 (2017) 14, doi:10.3390/batteries3020014.[3] A. Hofmann, N. Uhlmann, C. Ziebert, O. Wiegand, A. Schmidt, Th. Hanemann, Preventing Li-ion cell explosion during thermal runaway with reduced pressure, Appl. Thermal Eng. 124 (2017) 539-544. Figure Caption: Different sizes of accelerating rate calorimeters at the IAM-AWP Calorimeter Center (upper part) and X-Ray tomography image of 18650 cell showing position of pressure line and pressure vs. temperature curves for external and internal pressure measurement during thermal abuse test in an ARC (lower part). Figure 1

A Methodology for Measuring Turbocharger Adiabatic Maps in a Gas-Stand and Its Usage for Calibrating Control Oriented and One-Dimensional Models at Early ICE Design Stages

Abstract In this work, a methodology is proposed to standardize turbochargers testing based on measuring the maps twice: in close to adiabatic and in diathermal conditions. Along the paper, it is discussed with special detail the impact of the procedure followed to achieve said quasi-adiabatic conditions in both the energy balance of the turbocharger and the testing complexity. As a conclusion, the paper proposes a methodology which combines quasi-adiabatic tests (cold and hot gas flow) with diathermal tests (hot gas flow) in order to extract from a turbocharger gas-stand all information needed by engine designers interested in controlling or one-dimensional-modeling the internal combustion engine (ICE). The methodology is completed with a guide for calibrating said control-oriented turbocharger models in order to separate aerodynamic efficiency (adiabatic) from heat transfer (HT) losses and from friction losses in the analysis of the turbocharger performance. The outsourced calibration of the turbocharger model allows avoiding uncertainties in the global ICE model calibration, what is very interesting for turbochargers benchmarking at early ICE-turbo matching stages or for global system analysis at early control design stages.

Very high-resolution modelling of submesoscale turbulent patterns and processes in the Baltic Sea

Abstract. In order to simulate submesoscale turbulent patterns and processes (STPPs) and to analyse their properties and dynamics, the Regional Ocean Modeling System (ROMS) was run for June 2016 in a subregion of the Baltic Sea. To create a realistic mesoscale environment, ROMS with 500 m horizontal resolution (referred to as R500) is one-way nested into an existing operational model, and STPPs with horizontal scales <1 km are resolved with a second nest of 100 m resolution (R100). Both nests use 10 terrain-following layers in the vertical. The comparison of the R500 results with a satellite image shows fair agreement. While R500 is driven by realistic air–sea fluxes, the atmospheric forcing is turned off in R100 because it prevents the generation of STPPs and blurs submesoscale structures. Therefore, R100 provides deep insight into ageostrophic processes and associated quantities under quasi-adiabatic conditions that are approximately met in no-wind or light-wind situations. The validity of the results is furthermore limited to the selected region and the time of the year. STPPs evolve rapidly within a about a day. They are characterized by vertical speeds of 𝒪(10) m d−1 and relative vorticities and divergences reaching multiples of the Coriolis parameter. Typical elements of the secondary circulation of two-dimensional strain-induced frontogenesis are identified at an exemplary front in shallow water, and details of the ageostrophic flow field are revealed. The conditions for inertial and symmetric instability are evaluated for the whole domain, and the components of the tendency equation are computed in a subregion. While anticyclonic eddies are generated solely along coasts, cyclonic eddies are rolled-up streamers and found in the entire domain. A special feature of the cyclones is their ability to absorb internal waves and to sustain patches of continuous upwelling for several days, favouring plankton growth. The kinematic properties show good agreement with observations, while some observed details within a small cyclonic eddy are only partly reproduced, most likely due to a lack of horizontal resolution or nonhydrostatic effects.

Further Understanding and Modeling of the Thermal Runaway of High Energy Density Lithium-Ion Batteries

Since the commercialization of Lithium-Ion Battery (LIB) by Sony Inc. in 1991 until today, recurrent incidents involving LIBs have been reported worldwide. During these incidents, the most energetic catastrophic failure of a LIB system is a cascading thermal runaway event. It is characterized by a deficit of energy dissipation versus energy accumulation in the cells leading to uncontrollable overheating of the battery system [1,2]. This complex event involves multi-scale phenomena ranging from internal parallel or cascading physico-chemical to battery components reactions (electrodes, electrolytes & separator) and further to the thermal propagation of cell core & safety features. Complexity of the comprehensive understanding of the thermal runaway hazard also lies in the fact that both normal operation (through aging and relating medium/long term degradation effects) and abuse conditions can contribute to a thermal runaway event, as recently discussed by [2] or [3].Battery safety is becoming even more critical with the emergence of highly reactive Ni-rich LIBs in the market. These batteries are commercialized to meet novel energy- or power-demanding applications and are expected to dominate the market in the coming years, likely until the occurrence of a new technological breakthrough. Therefore, these newly introduced LIBs presenting such high energy density characteristics and integrating more intrinsically reactive materials could possibly lead to more catastrophic events subsequent to the thermal runaway. Therefore, there is a clear need to better understand the underlying specific electrochemical and thermal behaviors of these technologies in both normal and abuse conditions across their lifetime. Inspired by the former collaborative IFPEN/INERIS research works on the thermal runaway of LIBs (essentially focused on LFP/Graphite and relating batteries) [2], this work aims to go deeper into the understanding & modeling of this complex phenomenon at cell scale, taking into account the influence of novel highly reactive technologies and the influence of aging with 2 target degradation mechanisms: SEI growth and Li Plating, in order to understand what the keys are towards inherently safer design and operation of highly reactive LIBs. It is a matter of establishing the link between the materials used (electrodes, electrolytes) in high energy density & intrinsically reactive LIB technologies, the degradation products during cell calendar and cycling aging (mainly analyzed through SEI evolution during cell lifetime and Li deposition during cold recharges) as well as the thermal runaway kinetics.The selected technologies studied in this research are two commercial 18650 Ni-rich LIBs, namely a Panasonic NCR GA and a LG HG2, which were based on Li(Ni0.8Co0.15Al0.05)O2 (NCA) and Li(Ni0.8Mn0.1Co0.1)O2 (NMC811), respectively, for positive electrodes, in combination with graphite-SiOx composite negative electrodes.With the goal of finding the keys factors that can improve the safety of these highly reactive LIBs during usage, the research strategy relies on the achievements of the previous projects and on the synergism offered by combined experimental and modeling studies as illustrated in Figure 1.The experimental study includes the 3 interconnected experimental processes here after specified: a complete multi-scale cell analysis in order to analyze the pristine, aged and thermally abused cells;a safety-focused aging campaign in order to artificially age battery samples, focusing on each target mechanism (SEI growth, Lithium plating) in a controlled and measurable way;accelerating rate calorimetry (ARC)thermal abuse tests in quasi-adiabatic conditions at cell level in order to qualifying the thermal runaway phenomenon as well as calibrating the thermal runaway model. The modeling study leads to the development of an extended thermal runaway model in order to predict the behaviors of different LIBs nearby and during thermal runaway under field conditions. This coupled multi-physics model will improve and extend the initial thermal runaway model built by [2] by integrating the impact of Li plating & SEI-driven cycling aging.The final result will be a multi-dimensional multiphysical model of LIB capable of accounting for the triggering of runaway under different thermal and electrical conditions and as a function of the state of aging. The predictions of the models will be validated based on other thermal abuse tests. This model will further be implemented to understand the electrical or thermal initiation of the phenomenon of thermal runaway and its propagation within a battery pack regarding its design. They will eventually be transposed into tools enabling the best design of the packs and avoidance of this undesirable phenomenon.

Thermal Simulation of Rolled Concrete Dams: Influence of the Hydration Model and the Environmental Actions on the Thermal Field

Mathematical models for the simulation of the thermal evolution of roller-compacted concrete (RCC) dams during construction constitute an important tool for preventing excessive temperature rise, which may lead to cracking and losses of functionality. Here, we present a framework for the simulation of the thermal process. We define the boundary conditions of the problem using a careful description that incorporates the main heat exchange mechanisms. We adopt both a non-adiabatic and an adiabatic heat generation model for the simulation of the cement hydration. Our numerical framework lets us study the effect of the adopted heat generation model on the thermal field. Moreover, we study the influence of the weather conditions on the evolution of the hydration, and on the starting date of construction. Our simulations have shown that the hydration model has an important influence over the temperature field during the construction and the heat generation rate. Moreover, the hydration process and the temperature evolution are driven by the weather conditions. Once the next lift is cast, its thermal insulation effect makes the hydration take place under quasi-adiabatic conditions. As expected, dams built in cold months are prone to dissipate more heat than those built in warm seasons.

High-temperature CO2 methanation over structured Ni/GDC catalysts: Performance and scale-up for Power-to-Gas application

This paper investigates the performance of 25 wt% Ni/GDC catalyst supported on ceramic monolith (MO) and open-cell foam (FO) towards the conversion of CO2 to CH4 at bench-scale level (CO2 flow rate = 78–319 NL·h−1). Both structured catalysts were prepared by the In Situ-Solution Combustion Deposition (IS-SCD) method to coat thin, uniform and high-resistance catalytic layers (Ni/GDC). Catalysts were characterized by XRD, TEM, SEM, and adhesion tests. Temperature profiles in axial and radial direction were registered and discussed. The experimental results highlighted the effect of the geometry of the support on the thermal profile of the catalytic bed and, consequently, on the catalytic performance towards CO2 methanation. For the investigated quasi-adiabatic conditions, the monolith-supported sample enabled a favourable temperature distribution, leading to higher performances (χCO2 = 70.3%; FCH4, OUT = 2.6 NL·cm−3·h−1) compared to the foam-based catalyst (χCO2 = 52.0%, FCH4, OUT = 2.2 NL·cm−3·h−1). Besides, Ni/GDC-MO catalyst showed high stability for 50 h of time-on-stream under daily start-up and shut-down cycles.

Understanding the Thermal Runaway of Ni-Rich Lithium-Ion Batteries

The main safety issue pertaining to operating lithium-ion batteries (LIBs) relates to their sensitivity to thermal runaway. This complex multiphysics phenomenon was observed in two commercial 18650 Ni-rich LIBs, namely a Panasonic NCR GA and a LG HG2, which were based on L i ( N i 0.8 C o 0.15 A l 0.05 ) O 2 (NCA) and L i ( N i 0.8 M n 0.1 C o 0.1 ) O 2 (NMC811), respectively, for positive electrodes, in combination with graphite-SiOx composite negative electrodes. At pristine state, the batteries were charged to different levels of state of charge (SOC) (100% and 50%) and were investigated through thermal abuse tests in quasi-adiabatic conditions of accelerating rate calorimetry (ARC). The results confirmed the proposed complete thermal runaway of exothermic chain reactions. The different factors impacting the thermal runaway kinetics were also studied by considering the intertwined impacts of SOC and the related properties of these highly reactive Ni-rich technologies. All tested cells started their accelerated thermal runaway stage at the same self-heating temperature rate of ~48 °C/min. Regardless of technology, cells at reduced SOC are less reactive. Regardless of SOC levels, the Panasonic NCR GA battery technology had a wider safe region than that of the LG HG2 battery. This technology also delayed the hard internal short circuit and shifted the final venting to a higher temperature. However, above this critical temperature, it exhibited the most severe irreversible self-heating stage, with the highest self-heating temperature rate over the longest duration.

AC elastocaloric effect as a probe for thermodynamic signatures of continuous phase transitions.

Studying the response of materials to strain can elucidate subtle properties of the electronic structure in strongly correlated materials. Here, we focus on the elastocaloric coefficients, forming a second rank tensor quantity describing the relation between entropy and strain. In contrast to the better-known elastoresistivity, the elastocaloric effect is a thermodynamic quantity. Experimentally, elastocaloric effect measurements are demanding since the thermodynamic conditions during the measurement have to be well controlled. In this work, we present a technique to measure the elastocaloric effect under quasiadiabatic conditions. The technique is based on oscillating strain, which allows for increasing the frequency of the elastocaloric effect above the thermal relaxation rate of the sample. We apply the technique to Co-doped iron pnictide superconductors and show that the thermodynamic signatures of second order phase transitions in the elastocaloric effect closely follow those observed in calorimetry experiments. In contrast to heat capacity, elastocaloric effect measurements allow for the electronic signatures to be measured against a small phononic background even at high temperatures and in addition give information on the symmetry of the involved order parameters. This establishes the technique as a powerful complimentary tool for extracting the entropy landscape as a function of strain proximate to a continuous phase transition.

Experimental approach for the characterization and performance analysis of twin entry radial-inflow turbines in a gas stand and with different flow admission conditions

In an internal combustion engine, twin entry turbine operates under different unequal admission conditions by feeding the turbine with a dissimilar amount of flow in each entry for a majority of the time. Despite of the impact on turbine performance, normal characteristic maps of these turbines are usually available only for full admission conditions. The current study investigates the best way of building characteristic maps of twin entry radial inflow turbines working under different admission conditions. The mass flow conditions are varied independently for each entry and results are examined to characterize the turbine performance parameters. The new methodology provides a practical approach regarding the reduced turbine speed; mass flow ratio; pressure ratios and efficiencies of a twin entry turbine. The most important conclusion of this work is the protocol of data analysis itself, which allows systematizing the testing procedure of this type of turbines with different steady flow admission and in quasi-adiabatic conditions. By sorting the experimental data in an orderly manner through proposed analysis, the readers can get benefit of this procedure to calibrate their own quasi-steady models for both: mass flow rate and efficiency; or to build new quasi-steady models with clear merit functions for fitting.

Magnetic moment inversion at giant flux jump: dynamical property of critical state in type-II superconductors

Experimental evidence of tremendous magnetic moment dynamical inversion, from metastable trapping state to the state with essentially the same moment oriented in the opposite direction, appearing during giant flux jump connected to thermomagnetic avalanche process in superconducting YBa2Cu3O7−δ single crystal, is presented. Magnetization inversion takes place in the system, without thermal contact between sample and sample holder, with a tremendous stored energy once the avalanche process is completed in quasi-adiabatic conditions. A model of magnetic moment inversion, caused by the jump between two metastable states of superconductor with the same energy storage, is presented and discussed in terms of the critical state with peculiar evolution of the critical-current spatial distribution. Importantly, knowledge of conditions of the appearance of such a phenomenon is crucial for applications of bulk superconductors as “permanent” magnets, for example, in superconducting levitation devices, etc.