3D Thermal Model Research Articles

Real-Time Average Junction Temperature Estimation for Multichip IGBT Modules With Low Computational Cost

The junction temperature of the insulated gate bipolar transistor (IGBT) modules is a vital parameter for the reliability of the power electronic system. For effective thermal management, it is necessary to estimate junction temperature in real time. However, existing thermal models have limitations to achieve fast temperature prediction for multichip IGBT modules. In this study, we investigate the real-time junction temperature prediction for multichip IGBT modules with low computational cost. According to the power module' structure, an average 2D thermal model with physical significance is proposed to predict the virtual junction temperature for multichip IGBT modules, which can be extracted from finite element model based on the least square method. To further improve the computational efficiency, a temperature predictor based on the staggered cycle-by-cycle calculation method is proposed and its prediction error under various extreme operation conditions is analyzed by enumeration method. Finally, the comprehensive experimental results verify the effectiveness of the proposed average thermal model and junction temperature prediction method.

Thermal Analysis of a Modular Permanent Magnet Machine under Open-Circuit Fault with Asymmetric Temperature Distribution

A modular permanent magnet machine is composed of several stator modules, and the three-phase winding of each module can be controlled independently. The novel modular permanent magnet machine has good abilities in terms of fault tolerance when the machine is exposed to fault conditions. The current of each phase is different and will result in uneven loss distribution in each phase. Heat transfer occurs in the circumferential direction and temperature distribution will be asymmetric in the circumferential direction. This paper proposes a 3D finite element thermal model to accurately calculate the rise in temperature under open-circuit conditions for modular permanent magnet machines. When two modules are in operation, the machine can output rated torque. When one module is in operation and the temperature is 150 °C, the output torque is 0.76 times the rated torque. The temperature of the machine under the one-phase open-circuit condition with a zero-temperature-difference control strategy will be 0.8 °C lower than that with a minimum copper loss control strategy. Finally, a prototype with three stator modules is manufactured and the calculation results are validated by experimental test. It holds great significance for the accurate calculation of a machine with asymmetric temperature distribution in the circumferential direction.

A comprehensive coupled 0D-ECM to 3D-CFD thermal model for heat pipe assisted-air cooling thermal management system under fast charge and discharge

Prediction of electrical and thermal behavior of lithium-ion capacitor (LiC) technology as an asymmetric technology is feasible by designing a precise model. Such a model should mimic the behavior of LiCs in heavy-duty applications where high current rates are applied. The developed model is used to design a management system based on efficient modeling tools, including 0D (zero-dimensional) electro-thermal models and 3D computational fluid dynamics (CFD) thermal models. A validated model is essential for LiCs as they operate at high dynamic current rates. In this article, the 0D second-order equivalent circuit model is developed to extract the electrical parameters of LiCs. Then, the thermal model is developed to be linked to the electrical model to make an electro-thermal platform capable of identifying the electro-thermal parameters. The characterization tests are performed within a wide range of temperatures, from the freezing temperature of −30 °C to the hot temperature of + 60 °C. Such a temperature range has never been carried out before. The validation is performed based on the owned experimental results. The applied current rates are from 0.1 A to 500 A, which shows the work's uniqueness in the field of electro-thermal modeling. Later, the extracted parameters have been set as inputs to the 3D CFD thermal model to design and develop a hybrid thermal management system (TMS) based on air cooling and heat pipes. Such a hybrid TMS maintains the maximum temperature at 24.6 °C when the temperature difference between the hottest and coldest cells is only 0.5 °C.

An Integrated Approach for the Thermal Maturity Modeling Re-Assessment of an Exploration Well in the Hellenides Fold and Thrust Belt

Utilizing geological and geochemical data, we re-assessed the thermal maturity of the Lower Cretaceous Vigla shales of the AY-3 well, located in the Internal Ionian geotectonic zone of Greece, using 1D thermal maturity modeling. Vigla shales primarily containing kerogen type I to II, incorporated within alternations of carbonates, cherts, and marly limestones, were selected as the main source rock intervals. Biomarkers and Rock-Eval data were used on top of vitrinite reflectance data for the calibration of the 1D model. Hopane and sterane isomerization ratios for the Vigla shales appear to hold values of 58–64% and 44–49%, respectively, while vitrinite reflectance ranges from 0.61% to 0.71% and Tmax between 431 and 451 °C. One-dimensional thermal maturity modeling suggests that lower Cretaceous Vigla shales entered the oil window in early Miocene times and reached the expulsion onset during the middle Miocene. Additionally, thermal modeling estimates the overburden eroded thickness to range between 2.1 and 2.6 km. This unravels the pre-eroded shape of this part of the belt of Miocene times alongside the burial history of the area and its evident relation to the hydrocarbon potential. This assessment comprises a step towards the understanding of the belt and the different timings of hydrocarbon generation in the External Hellenides.

Thermoelectric analysis of different vacuum-based photovoltaic semitransparent skylights

In commercial buildings with large glazing facades, transparent facades and skylights play a considerable impact on energy consumption. In this study, three different photovoltaic (PV) -based skylights are compared to save energy in these buildings. The first skylight uses a vacuum glazing sample as a substrate at the backside of the PV layers. The second design integrates a vacuum glazing layer in front of the PV layers. And lastly, the PV layers are attached to a single layer of glazing with a solar cells covers 25% of the whole area. A 3D thermal model is developed and validated with data from the literature to compare these designs. it is concluded that using a vacuum layer at the backside of the PV layer is favorable for thermal insulation and attains relatively similar power generation to the case without a vacuum layer. In more detail, replacing the single glazing PV skylight with the first skylight design reduces the total U-value of the glazing from 6.3 to 1.9 W/m2.K for a glazing sample with an area of 0.4 m by 0.4 m at ASTM boundary conditions. Furthermore, at received solar irradiance of 1000 W/m2, an ambient temperature of 25 °C, and a wind speed of 1 m/s, replacing the third skylight design with the first skylight design slightly reduced the electricity generation from 37.4 W/m2 to 36.4 W/m2, significantly decreased the heat flux transfer from 91.1 W/m2 to 50.5 W/m2 and lowers the indoor surface temperature from 32.1 °C to 27.1 °C.

Multi-Stage Thermal Modelling of Extrusion-Based Polymer Additive Manufacturing

Additive manufacturing is one the most promising fabrication strategies for the fabrication of bone tissue scaffolds using biodegradable semi-crystalline polymers. During the fabrication process, polymeric material in a molten state is deposited in a platform and starts to solidify while cooling down. The build-up of consecutive layers reheats the previously deposited material, introducing a complex thermal cycle with impacts on the overall properties of printed scaffolds. Therefore, the accurate prediction of these thermal cycles is significantly important to properly design the additively manufactured polymer scaffolds and the bonding between the layers. This paper presents a novel multi-stage numerical model, integrating a 2D representation of the dynamic deposition process and a 3D thermal evolution model to simulate the fabrication process. Numerical simulations show how the deposition velocity controls the spatial dimensions of the individual deposition layers and the cooling process when consecutive layers are deposited during polymer printing. Moreover, numerical results show a good agreement with experimental results.

3D Multi-Modality Medical Imaging: Combining Anatomical and Infrared Thermal Images for 3D Reconstruction.

Medical thermography provides an overview of the human body with two-dimensional (2D) information that assists the identification of temperature changes, based on the analysis of surface distribution. However, this approach lacks spatial depth information, which can be enhanced by adding multiple images or three-dimensional (3D) systems. Therefore, the methodology applied for this paper generates a 3D point cloud (from thermal infrared images), a 3D geometry model (from CT images), and the segmented inner anatomical structures. Thus, the following computational processing was employed: Structure from Motion (SfM), image registration, and alignment (affine transformation) between the 3D models obtained to combine and unify them. This paper presents the 3D reconstruction and visualization of the respective geometry of the neck/bust and inner anatomical structures (thyroid, trachea, veins, and arteries). Additionally, it shows the whole 3D thermal geometry in different anatomical sections (i.e., coronal, sagittal, and axial), allowing it to be further examined by a medical team, improving pathological assessments. The generation of 3D thermal anatomy models allows for a combined visualization, i.e., functional and anatomical images of the neck region, achieving encouraging results. These 3D models bring correlation of the inner and outer regions, which could improve biomedical applications and future diagnosis with such a methodology.

2D Restorations and Basin Modeling Provide Insight Into Formation Maturation

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 2021-5434, “Delaware Basin Wolfcamp Formation Maturation and Post-Permian Basin Evolution Based on 2D Restorations and Basin Modeling,” by Rachel Hoar, Mauro Becker, and Alan Yu, Texas A&M University. The paper has not been peer reviewed. _ The Permian Delaware Basin is a complex system in which the maturation of organic matter is affected by events not evident in the post-Permian available data. In this study, the authors aim to identify the effect of various geologic controls on hydrocarbon maturation in the Delaware Basin by restoring regional cross sections and performing simulations of organic-matter maturity. Integration of these data with seismic interpretation of the stratigraphic intervals present in the basin is used to refine the structural restorations and calibration of resulting 2D thermal models. Methods As a direct source of information for the initial evaluation of the post-Permian layers, surface geological maps, residual thickness maps, and structural information collected from the literature were examined. Next, four regional cross sections were selected and restudied with this objective. For the cross-sectional analysis, the data sets available were surficial geological and shallow-formation-thickness maps, subsurface seismic interpretation of the main stratigraphic intervals (proprietary data in the Delaware Basin sector), well logs, vitrinite reflectance evaluations, and apatite fission track analysis (AFTA) data available from the literature. In this Delaware Basin thermal-maturity study, the Wolfcamp formation was the unit selected and analyzed; however, the whole stratigraphic column needed to be included to produce the most-accurate and consistent model. With a major objective of this work being to evaluate the controls that post-Pennsylvanian depositional and erosional history have had on Delaware source-rock thermal maturity, this study focused on constraining the syn- and post-tectonic phase of the Ouachita/Marathon thrusting event. As such, the deformed rocks of the “known” phase (Carboniferous and older formations) were not considered, except for the paleogeomorphology resulted from the tectonic deformation and inherited by the lower Permian depositional phase. Previous work in the literature presented a comprehensive revision of the post-Permian sedimentary rocks and the patterns of erosion for the major post-Permian unconformities. The thickest post-Permian unit is the Triassic Dockum Group, a nonmarine red bed succession that paraconformably covers the Permian rocks. The Wichita paleoplain, an extensive unconformity, is recognized as an important exhumation and nondepositional period between the Triassic and the Cretaceous (Albian) in the area. Later Cretaceous carbonate strata also were deformed and exhumed at the Laramide contraction (Maastrichtian to Paleocene). The latest deformations that affected the area were the Miocene Basin Range event and Rio Grande Rift faulting complex. The work detailed in the complete paper details the cross section named the Diablo Platform/Central Basin Platform (CBP). All other cross sections followed the same methodology.

Conceptualization of the micro research reactor cooled by heat pipes (MRR-HP), part-II: safety analyses

ABSTRACT The safety of the novel Micro Research Reactor cooled by Heat Pipes (MRR-HP) design is explored. This is achieved by developing a 3D thermal conduction model using STARCCM+ software, besides, coupling it with the 3D neutronics model for reactor dynamics. The MRR-HP has a unique design characteristic, which is the implementation of dual-sets of heat pipes (HPs) in the monolithic-block: Water-HPs for operation, and Potassium-HPs for accident/post-accident scenarios. Water-HPs cool the reactor effectively, allowing for maximum fuel temperature (K). However, water-HPs may suffer from: Loss-of-heat-Sink-Accident(LOSA), which may occur due to blackout, since it requires forced convective cooling in the condenser. Non-Condensable-Gases-Generation-Accident (NCGGA), due to radiolysis. These events cause significant melting in the monolithic-block and fuel rods after 3 and 6 hours, respectively. This paper proves the reliability of potassium-HPs as a passive countermeasure against LOSA and NCGGA, while natural convective cooling in the condenser is applied. Cold-state no-scram Reactivity-Insertion-Accident (RIA) scenarios with an insertion of 2.35$ are investigated, showing that no partial or significant melting occurs, due to the negative reactivity feedback of the MRR-HP. Besides, Potassium-HPs are essential in removing the decay heat, for warm-state RIA, after water-HPs dry out. This paper proves the robustness of the MRR-HP and encourages its utilization for remote operation.

Rift thermal inheritance in the SW Alps (France): insights from RSCM thermometry and 1D thermal numerical modelling

Abstract. Conceptual models of orogenic accretionary prisms assume that peak temperatures (Tmax⁡) increase towards the internal domains as crustal rocks are accreted from the lower to the upper plate. However, the recognition of pre-orogenic heating events in mountain belts questions the magnitude of thermal overprint during nappe stacking. Using Raman spectroscopy on carbonaceous material (RSCM) to calculate Tmax⁡, we have investigated the thermal record of Lower Jurassic to Eocene strata exposed along six stratigraphic sections at the front of the Digne Nappe (SW Alps), from the Devoluy Massif to the Castellane Arc. Our results highlight two groups of depth-dependent temperatures: (1) a regionally extensive and constant Tmax⁡ up to 300–330 ∘C measured in the Jurassic succession and (2) regionally variable lower temperatures (<150 ∘C) recorded either in the Upper Mesozoic or the syn-orogenic sequence. Modelling shows that the highest palaeotemperatures were achieved during the Early Cretaceous (∼ 130 Ma), associated with the Valaisan–Vocontian rifting, while the lowest Tmax⁡ reflect post-rift thermal relaxation in the Alpine foreland basin. This study provides a striking new example where mid-crustal palaeotemperatures measured in sediments accreted from the downgoing plate are inherited. An estimated peak thermal gradient of 80–90 ∘C km−1 requires a crustal thickness of 8–10 km during the Early Cretaceous, hence placing constraints for tectonic reconstruction of rift domains and geophysical interpretation of current crustal thickness in the SW Alps. These results call for the careful interpretation of palaeothermal data when they are used to identify past collisional thermal events. Where details of basin evolution are lacking, high-temperature records may be misinterpreted as syn-orogenic, which can in turn lead to an overestimation of both orogenic thickening and horizontal displacement in mountain belts.

Passive thermal control of a triple-junction solar cell at high concentrations using various finned heat sink configurations

Designing an effective heat sink that is light, inexpensive, and simple to manufacture and install, is crucial in developing a heat control strategy for high concentrated triple-junction (TJ) solar cells to maintain the cell operating temperature below the maximum allowed limit. Such heat sinks ensure better electrical output power and efficiency at a cheaper cost. Thus, the present research focuses on the passive thermal regulation of a triple-junction solar cell utilizing four different finned heat sink configurations; (A) flat plate, (B) straight fins, (C) pin fins, and (D) flared fins heat sink. A comprehensive 3D thermal and electrical model is developed and computationally simulated, incorporating the cell module layers coupled with the aluminium heat sink. The performance of the proposed system with different heat sink designs is investigated at various concentration ratios (CR) of the solar irradiance ranging from 50 suns to 1250 suns, air temperatures ranging from 25 °C to 40 °C, and wind speeds ranging from 1 m/s to 5 m/s. In hot climatic conditions (40 °C and 1 m/s), the integration of the proposed heat sink configurations A, B, C, and D enables the cell to operate safely (below 110 °C) at high concentration ratios of 440 suns, 1435 suns, 1250 suns, and 1775 suns, respectively, and produce large electric power of 15.2 W/cm2, 49.7 W/cm2, 43.3 W/cm2, and 61.4 W/cm2. In contrast, the maximum permissible concentration ratio of an uncooled cell operating in the same conditions is limited to 77 suns with an electrical output of 2.7 W/cm2. Although the flared fins heat sink is the heaviest, weighing about 0.6 kg, and the flat plate one is the lightest with 0.05 kg, the environmental analysis revealed that utilizing the former for cooling concentrated photovoltaic systems could reduce annual CO2 emissions by 1475.2 tons/m2 compared to 364.5 tons/m2 for the latter if both are operated at the maximum permissible solar concentration ratio.

Combined film and pulse heating of lithium ion batteries to improve performance in low ambient temperature

Low ambient temperatures significantly reduce Lithium ion batteries’ (LIBs’) charge/discharge power and energy capacity, and cause rapid degradation through lithium plating. These limitations can be addressed by preheating the LIB with an external heat source or by exploiting the internal heat generation through the LIB's internal impedance. Fast external heating generates large temperature gradients across the LIB due to the low thermal conductivity of the cell, while internal impedance heating (usually through AC or pulse charge/discharging) tends to be relatively slow, although it can achieve more uniform temperature distribution. This paper investigates the potential of combining externally sourced resistive film heating with bidirectional pulse heating to achieve fast preheating without causing steep temperature gradients. The LIB is modeled with the Doyle Fuller Newman (DFN) electrochemical model and 1D thermal model, and reinforcement learning (RL) is used to optimize the pulse current amplitude and film voltage concurrently. The results indicate that the optimal policy for maximizing the rate of temperature rise while limiting temperature gradients has the film heating dominate the initial phases and create the ideal conditions for pulse heating to take over. In addition, the pulse component shares the heating load and reduces the energy rating of the auxiliary power source.

Case study on thermal optimization of oil immersed transformer used in solar power plant based on genetic algorithm and computational fluid dynamics

Transformers are one of the most capital investments in the solar power generation. Their safe and stable operations in the electrical networks are important. The main failure factor of transformers is the high temperature generated by the losses during operation, which increases the probability of insulation damage that significantly affects the useful life of transformer. Considering the importance of oil temperature and its effects on the life of the transformer, a numerical method is developed in this paper to optimize the cooling system of the transformer. In this regard, genetic algorithm is used as an optimization method to minimize the total cost of the cooling system while maintaining the required thermal conditions of the transformer. A comprehensive parametric study is carried out among the effective cooling geometry parameters using 3-D electromagnetic and thermal models of the photovoltaic transformer to evaluate and analyze the temperature distribution. The accuracy and feasibility of the proposed method is established by comparing the numerical results with those obtained from the experimental test. The results of the proposed method are found to be in a good agreement with the experimental and simulation results.

COMBINATION OF THERMAL INFRARED IMAGES AND LASERSCANNING DATA FOR 3D THERMAL POINT CLOUD GENERATION ON BUILDINGS AND TREES

Abstract. The thermal infrared study of urban environments is of growing interest. It allows to observe the variations of surface temperatures on objects over time and therefore the microclimate at the scale of a street. To facilitate the analysis of thermal interactions between urban elements, it is necessary to provide a 3D visualization of the thermography of a street. For this purpose, 3D thermal models combining geometric and thermal infrared (TIR) measurements are required. The chosen format for 3D thermal models is a point cloud with a temperature attribute. In our approach, two types of urban components are considered: buildings and trees. The geometric data of each component are acquired with a static laser scanner and the surface temperature is acquired with a thermal handheld camera. For the building, the approach consists in georeferencing TIR images and colorize the point cloud by projection. For trees, the approach consists of the colorization of each laser scan prior to the registration. The spherical panoramic images acquired with the Terrestrial Laser Scanning (TLS) are used as references to automatically georeferenced the TIR and thus to save time. The 3D thermal models obtained highlight the impact of sunlight on buildings and trees. At building scale, this thermal representation also helps to emphasize thermal bridges, as well as the shadow generated by surrounding trees. At tree scale, this representation is useful for monitoring the temporal and spatial variability of trunk’s and leave’s temperatures. Obviously, the thermal models underline the impact of trees on the urban environment.

Optimization of electrode loading amount in lithium ion battery by theoretical prediction and experimental verification

Lithium ion battery is a complex system, and any change in device parameters may significantly affect the overall performance. The prediction of battery behavior based on theoretical simulation is of great significance. In this work, the battery performance with LiNi1/3Co1/3Mn1/3O2 electrodes of different active material loading amounts was theoretically investigated, such as battery rate performance, capacity decay rate, energy and power density, SOC (State of Charge) change, temperature response, and heat source distribution. A 1D electrochemical–3D thermal coupling model was established, and the accuracy and predictability of the model were verified by experiments. An in-depth analysis of batteries under different discharge rates and batteries with different electrode loading amounts is carried out. The results show that the rate performance and capacity change with different electrode loading amounts, which is attributed to the variation in lithium ion diffusion. At the same time, the change in load affects the growth of lithium dendrites and the distribution of SOC, resulting in the thermal runaway of the battery and shortening the battery life.

3D thermal model of Sicily (Southern Italy) and perspectives for new exploration campaigns for geothermal resources

Quantification of the subsurface geothermal potential primarily relies on the assessment of the thermal and mechanical configuration of the lithosphere. Such investigations require a detailed knowledge of the geological and tectonic forcing on the regional thermal, stress and hydraulic regimes and their counter feedback mechanisms. This approach becomes even more relevant in complex and active tectonic settings. In this regard, the Sicily region, which is located in the Central-Western Mediterranean, is an exceptional case study due to its almost unexplored geothermal potential hosted in a complex geodynamic setting. The present-day geological configuration resulted from the collision between the African and European plates, which led to the coexistence of compressional phases, beginning with the Oligocene-Miocene clockwise rotation of Corsica-Sardinia and alternated extensional phases in the Tyrrhenian basin due to the southward progression of the Sicilian-Maghrebian chain towards areas of the internal foreland (Hyblean domain). In this study, we attempt a reconstruction of the present-day lithospheric state of Sicily to quantify its thermal regime at shallow and intermediate depths. We have carried out a 3D lithospheric-scale gravity modelling in order to define the main geological units and their lithology-dependent rock properties, then integrated into a 3D geological model consistent with available borehole and seismic datasets. We have used the constructed geological model with its lithology-dependent density, thermal conductivity, and radiogenic heat production to derive the present-day conductive thermal field as a whole and for individual tectonic or geological units, thereby considering different boundary conditions. We have finally validated results of the modelling against a shallow temperature dataset derived from hydrocarbon explorations. Our results indicate that the thermal field at depths shallower than 10 km is largely controlled by variability in sedimentary thickness in the foreland and the orogen, while deeper temperatures are primarily controlled by the distribution of the heat transferred from the mantle together with the radiogenic contribution of the shallow crystalline basement rocks and deeper crustal layers. The thermal modelling portrays a rather heterogenous Moho heat flow, locally higher than 80 mW/m2, revealing a particular geodynamic setting with specific areas characterized by high-to-medium enthalpy geothermal potential. As such, our modelling provides new perspectives for the exploration of geothermal resources in Sicily and helps to better constrain the thermal structure of the complex Sicilian collisional setting.

Basin-scale estimates of thermal stress and expelled petroleum from Mesozoic-Cenozoic potential source rocks, southern Gulf of Mexico

The Campeche and Yucatan salt basins remain two of the least explored areas of the Gulf of Mexico basin. This study uses a grid of 23,600 line-km pre-stack depth migrated (PSDM) 2D seismic reflection profiles, shipborne gravity data, and open-source geologic information to model the thermal stress of four potential source intervals (Oxfordian, Tithonian-centered, Cenomanian-Turonian, lower Miocene). We performed map-based, and 1D thermal modeling along two margin-perpendicular transects, each consisting of five pseudo-wells tied to the regional grid of seismic reflection data. Our modeling takes into account thermal stress variations related to the depth of base lithosphere, crustal type and thickness, paleo-water depth, Jurassic salt thickness, and the transient heat flow effects related to recent clastic sedimentation. We predict that deeply-buried, salt-related minibasins along the outer marginal trough are mature for petroleum expulsion with deeply-buried Mesozoic source rocks within the oil window from late Paleogene to early Neogene time. The ‘lag time’ required for vertical oil migration explains why oil maturation occurred during the late Paleogene to early Neogene but active oil seeps are observed today at the sea surface. We predict that oil is present in subsurface traps in the deepest part of the outer marginal trough and we calculate that the Oxfordian source interval has expelled a cumulative 20 million bbl of oil equivalent [BOE]/km2 and that the Tithonian-centered source interval has expelled 67 million bbl of oil equivalent [BOE]/km2.

Thermal Modelling Utilizing Multiple Experimentally Measurable Parameters

This paper presents three equivalent thermal circuit models with multiple input parameters, namely, the state of health (SOH), state of charge (SOC), current and temperature. Typical physiochemical models include parameters such as porosity and tortuosity, which are not easily experimentally available; this model allows for model parameters such as the internal impedance to be easily estimated using more practical inputs. The paper models the internal impedance resistance of a LiFePO4 battery at five different ambient temperatures (5, 15, 25, 35, 45 °C), at three different discharge rates (1C, 2C, 3C) and at three different SOHs (90%, 83%, 65%). The internal impedance surface fit experimental measurements with a Pearson coefficient of 0.945. Three thermal models were then created that implemented the internal resistance model. The first two thermal models were 0D models that did not include the influence of the thermal conductivity of the battery. The first model assumed simple heating through internal resistance and convection energy loss, while the second also included the Bernardi Reversible heat term. The final third model was a 2D model that included all previous heat source terms as well as tab heating. The 2D model was solved using a simple Euler method and finite center difference. The R2 values for the 0D thermal models were 0.9964 and 0.9962 for the simple internal resistance and reversible heating models, respectively. The R2 value for the 2D thermal model was 0.996.

Three-dimensional thermal modeling of high-temperature primary lithium battery with nickel disulfide cathode

Thermal modeling is significant for high-temperature primary lithium batteries (thermal batteries) widely used in military hardware and aerospace equipment. Herein, the three-dimensional (3D) thermal model of a thermal battery with the novel cathode NiS2 and 48 cells is performed to observe the thermal behavior within 500 s from the single cell to the whole battery. From the perspective of unit cell, the Li–B/LiF–LiCl–LiBr/NiS2 cell shows exothermic reaction with the potential temperature coefficient of −0.405 mV K−1, so double heat sources exist in the cell during discharge. From the thermal field of battery stack, the temperature uniformity of the battery stack is the worst at the start of the discharge with a significant temperature gradient (about 90 °C) in the lead-out disks, but then improves with increasing discharge time. According to the thermal balance of the entire battery, the total heat generation is greater than the heat dissipation for the first 325 s and then becomes negative, as the increase in Joule heat is insufficient to offset the decrease in reversible reaction heat with decreasing temperature. This study could provide theoretical guidelines for the thermal design and management of thermal batteries with NiS2 cathodes and other novel materials.

Strain localization at brittle-ductile transition depths during Miocene magmatism and exhumation in the southern Basin and Range

Feldspar dominates the middle and lower continental crust. Models of crustal rheology depend on our knowledge of feldspar deformation mechanisms. To learn more about natural feldspar deformation, we conducted a multidisciplinary investigation of a brittle-ductile transition (BDT) hosted within a Cretaceous pluton in the Colorado River Extensional Corridor, southern Nevada. Here, a distinct BDT was observed at ∼10 km paleo-depth, where brittle faulting transitioned to discrete, localized ductile shearing. Field relationships confirm this BDT to have deformed and exhumed in the Miocene, temporally associated with the intrusion of two surrounding ca. 16 Ma plutons and subsequent footwall rotation in an east-directed normal-fault system. We established the overall structural framework, strain rates, and thermal histories through field traverses, aluminum-in-hornblende barometry to reconstruct paleo-depth, zircon (U–Th)/He thermochronology (ZHe) to constrain temperature-time histories, and 1D thermal models to further resolve deformation temperatures. Localized shear zones within the BDT formed ca. 16.2–15.5 Ma at temperatures of ∼500–600 °C, which continued deforming as they cooled both conductively and advectively to ∼200 °C by ca. 14 Ma, as constrained by ZHe dates. Strain was concentrated in fine-grained (7–10 μm) feldspar-rich ultramylonites that were interpreted to have primarily deformed via grain-size-sensitive diffusion creep. Grain-size reduction that allowed activation of diffusion creep likely resulted from brittle cataclasis, fluid-assisted fracturing and neocrystallization, and dislocation creep mechanisms, thus emphasizing the importance of these processes to localize deformation at relatively strong mid-crust conditions to facilitate the development of diffusion-creep shear zones. Grain-size piezometers suggest stresses of ∼50 MPa, which are significantly weaker than peak strength in quartz-rich BDTs that deform via dislocation creep. This integrated process allows relatively low viscosities (∼1018–1019 Pa s) at lower crust temperatures and explains a coherent process of strain localization at near-BDT conditions in feldspar-dominated lithologies. We suggest that this naturally deformed feldspar shear zone was preserved due to the unique geologic history with fast heating and exhumation, which froze both brittle vs crystal-plastic structures to provide valuable insights into mechanisms of feldspar deformation.