Search Results (335)

Magmatic–hydrothermal systems transport heat through coupled conduction and buoyancy-driven fluid flow in porous rock, behavior conventionally modeled with grid-based finite-difference simulators such as HYDROTHERM. We demonstrate that a physics-informed neural network (PINN), built on the NVIDIA PhysicsNeMo framework using automatic differentiation and mesh-free collocation, can produce a stable two-dimensional time-dependent solution for a magma-chamber configuration based on the Rio Pisco pluton in the Peruvian Coastal Batholith. Boundary conditions and material parameters are taken from a prior HYDROTHERM study of the same pluton, and 28 temperature samples digitized from that study are used as a supervised constraint. The PINN couples Fourier conduction, advective heat transport, Darcy flow with a temperature-dependent permeability law, and a mass-conservation formulation; the mass-conservation equation is written in two-phase form, but in the regime studied here, the simulation remains below the boiling curve, so the steam-phase saturation stays at zero and the formulation reduces to its single-phase liquid–water limit. The network reproduces the conductive temperature gradient and a directionally consistent buoyancy-driven flow field, with weaker and less organized circulation than the reference simulation, and a cooling time of approximately $1.6\times {10}^5$ years, comparable to the ∼175,000 years reported for the matching $k={10}^{-16}{\mathrm{m}}^2$ HYDROTHERM reference scenario from which the supervised training data was digitized. We discuss the conditions under which the mesh-free, automatically differentiable PINN approach offers a useful alternative to grid-based solvers. Full article

To address the difficulty of simultaneously achieving effective heat dissipation and adequate humidification in open-cathode air-cooled proton exchange membrane fuel cells (PEMFCs) under medium and high power operation, this study proposes a hydrothermal management strategy based on coordinated ultrasonic atomization humidification and fan speed regulation. A three-dimensional single-cell multiphysics model is developed and validated using a 300 W experimental platform. The effects of atomization frequency and water temperature on stack performance and internal hydrothermal distribution are systematically investigated. Results show that ultrasonic atomization provides inlet precooling, latent heat absorption, and active region humidification, thereby improving hydrothermal uniformity within the stack. Under the optimal condition of 100 kHz and 55 °C, the peak stack power increases by 21.0% to 319.00 W, while voltage consistency and surface temperature uniformity are also improved. Analysis based on the Stokes number and Dalton’s law of partial pressures indicates that the optimum results from a balance between suppressing droplet agglomeration and inertial deposition, and limiting oxygen dilution caused by excessive water vapor. The proposed strategy provides a compact and practical approach for improving the stability, uniformity, and efficiency of air-cooled PEMFCs. Full article

Biodiesel fuel produced through transesterification is mainly used in blends with conventional diesel fuel (D100). The analysis of the combustion process parameters for each specific biodiesel fuel represents the basis for a rational approach to the utilization of available motor fuel quantities. In this study, the differential and cumulative heat release laws during the combustion of D100 and blends of biodiesel fuel made from waste grape seed oil and D100 were analyzed. In addition, the engine efficiency and economy for the cases of using the aforementioned fuels were analyzed. The tests were conducted on a single-cylinder, air-cooled diesel engine with direct fuel injection. The engine testing was conducted for two engine loads; that for which the brake was a mean effective pressure of 4.2 bar, and for the full load, that for the brake was a mean effective pressure of 5.6 bar at engine speeds of 1635 rpm, 1937 rpm, and 2239 rpm. All experimental work was conducted for conventional diesel fuel D100 and for biodiesel diesel blends B7 and B14. The combustion rates of D100, a blend containing 7% of biodiesel by volume (B7), and a blend containing 14% of biodiesel by volume (B14) were examined. However, the higher combustion rate of the B14 blend, particularly during the combustion of the first 50% of the fuel mass per cycle, could have a positive impact on the fuel economy of the working cycle and the brake thermal efficiency (BTE). The maximum heat release rates for D100, B7, and B14 at full load and an engine speed of 2239 rpm are 115.65 J/deg, 148.01 J/deg, and 152.99 J/deg, respectively. At full load and engine speeds of 1635 rpm and 2239 rpm, the brake thermal efficiencies (BTEs) for D100, B7, and B14 were 0.301, 0.285, and 0.296 and 0.281, 0.273, and 0.277, respectively. Under other tests, the highest BTE was observed for the B14 blend. Therefore, from the perspective of brake thermal efficiency (BTE), the most favorable blend for application is B14. Full article

To investigate the effect of cooling rate on the phase transformation behavior and mechanical properties of 9Ni steel, a 7 mm thick industrial 9Ni steel plate was selected as the research object in this study. The JMatPro software was employed to simulate and calculate key parameters, including the thermodynamic phase diagram, CCT curve, and mechanical properties. Meanwhile, static thermal simulation experiments at cooling rates ranging from 0.5 to 30 °C/s were conducted on a Gleeble-3500 thermal simulation testing machine. Microstructure characterization and property tests were carried out using a metallographic microscope, scanning electron microscope (SEM), and Vickers hardness tester, and the experimental CCT curve was subsequently plotted and compared with the simulation results. The results revealed that the microstructure of 9Ni steel changed regularly with the cooling rate. With the increase in cooling rate, the ferrite content decreased continuously, the bainite content increased initially and then decreased, and the martensite content increased continuously. At a cooling rate of 30 °C/s, the martensite content reached approximately 90%. The microhardness of 9Ni steel initially sharply increased and then stabilized with the increase in cooling rate, stabilizing at 359 HV₁ at a cooling rate of 30 °C/s. The phase transformation law of the measured CCT curve is highly consistent with the simulation results, verifying the reliability and accuracy of JMatPro for predicting the phase transformation behavior and mechanical properties of 9Ni steel. This study provides a theoretical basis and data support for the precise optimization of the heat treatment process of 9Ni steel and has important practical significance for enhancing its service performance in cryogenic engineering applications. Full article

Large-diameter axial-flow fans are predominantly used for cooling purposes, such as in air-cooled heat exchangers. Since it is difficult to experimentally test large-scale fans in the controlled environments provided by fan test facilities, smaller scaled-down versions of the fans are tested instead. Scaling laws, also called affinity laws, are then used to determine the performance characteristics of the large-scale fan. The size difference between the two scaled fans means that it is not possible to match their Reynolds numbers when testing with the same test fluid. A comparison is conducted using experimental results and four numerical models for two different fans, which are scaled to different fan sizes: 0.63 m, 1.542 m, 3.658 m and 7.315 m, to determine the effect of Reynolds number on the performance characteristics of an axial-flow fan. The numerical geometries are based on the M- and B2a-fans, and are tested in the A-type experimental setup fan test facility at Stellenbosch University, which is used to obtain the experimental results. It was found that the numerical approach discussed within this paper, namely a Reynolds-Averaged Navier–Stokes (RANS) approach, can predict the performance of multiple fan sizes without relying on turbomachinery or blade-specific empirical correlations. This approach accelerates the evaluation of fan performance while enabling the parameterization of fan configurations. Full article

With the core advantages of high energy efficiency, high power density, and reliable operation, high-voltage permanent magnet motors have become the mainstream development direction of modern motor technology. However, the risk of demagnetization caused by excessive temperature increases in permanent magnets has become a key bottleneck restricting motor performance and operational reliability, which makes research on the flow and heat transfer characteristics of motor cooling systems of great engineering value. Taking the 710 kW high-voltage permanent magnet motors as the research object, this study established a global flow field mathematical model covering the internal and external air duct cooling systems of the motor based on the theories of computational fluid dynamics and numerical heat transfer, and systematically analyzed the flow characteristics and distribution laws of cooling air. The thermal–fluid coupling numerical method was employed to simulate the temperature field of the motor, and the overall temperature distribution of the motor, temperature gradient of key components, and maximum temperature value were accurately obtained. To verify the validity of the established model, a test platform for the cooling system performance was designed and built. Measuring points for wind speed, air temperature, and component temperature were arranged at key positions, such as the stator radial ventilation ducts, and experimental tests were conducted under the rated operating conditions. The results show that the flow field distribution of the internal and external air ducts of the motor is reasonable and that the cooling air flows uniformly, with the external and internal circulating air volumes reaching 1.2 m³/s and 0.6 m³/s, respectively, which meets the heat dissipation requirements. The maximum temperature of 95 °C occurs in the stator winding area, and the maximum temperature of the permanent magnets is controlled within the safe range of 65 °C. The simulation results were in good agreement with the experimental data, with an average relative error of only 4%, which fell within the engineering allowable range, thus verifying the accuracy and reliability of the established global model and thermal–fluid coupling calculation method. This study reveals the thermal–fluid coupling transfer mechanism of high-voltage permanent magnet motors and provides a theoretical basis and engineering reference for the optimal design, precise temperature rise control, and reliability improvement of motor cooling systems. Full article

In the process of using the freezing method to uncover coal from stone gates, the thermal evolution profiles of the coal body during the freezing process tend to be complex due to the presence of gas and moisture. To investigate the temperature response of coal containing gas under different freezing temperature conditions, a self-developed low-temperature freezing test system for coal containing water and gas was used to conduct freezing and cooling tests at different freezing temperatures (−5 °C to −30 °C). The temperature changes at various measuring points inside the coal over time were monitored in real time, and the temperature distribution, cooling law, and strain evolution process of the coal in the axial and radial directions were analyzed. The experimental results show that the cooling process of the center point of the coal can be divided into four stages: rapid cooling, extremely slow temperature drop, relatively slow cooling, and stable constant temperature. The time required to reach the stable constant temperature stage is inversely proportional to the freezing temperature, and corresponding prediction formulas have been established based on this. The standardized coal briquettes exhibit a gradient distribution characteristic of gradually increasing temperature from outside to inside in both axial and radial directions, with the radial temperature distribution being well matched by an exponential decay model. The strain of coal is affected by both thermal shrinkage and ice-induced expansion. The occurrence time of frost heave is positively correlated with freezing temperature, while the strain of frost heave is negatively correlated with freezing temperature. The axial frost heave effect is significantly stronger than the radial effect, but the radial frost heave occurs slightly earlier than the axial effect. This study reveals the thermal-mechanical coupling response mechanism of gas-containing coal during the low-temperature freezing process, and the research results can provide theoretical support for parameter optimization and engineering application of low-temperature freezing anti-outburst technology. Full article

This paper analyzes the potential application of Physics-Informed Neural Networks (PINNs) in solving equations that describe thermal–electrical processes in thermoelectric systems. Combining machine learning with the laws of physics, the PINN method can serve as an alternative to traditional numerical methods, particularly in the context of the miniaturization of cooling systems, heat pumps, and systems that convert thermal energy (heat flow) into electrical energy (e.g., heat recovery), as well as the implementation of models in embedded systems. The article presents a model of thermoelectric equations, explains how PINNs work, provides numerical results, and assesses the advantages and disadvantages of the proposed approach. Full article

Bi-doped low-silver Sn-Ag-Cu solders are increasingly gaining attention in advanced electronic packaging due to their cost-effectiveness and enhanced mechanical properties. However, the thermo-mechanical reliability mechanisms of such modified solders, particularly Sn-0.3Ag-0.7Cu-3Bi (SAC0307-3Bi) within Ball Grid Array (BGA) assemblies, remain insufficiently understood. To address this gap, this research proposes a comprehensive assessment framework integrating constitutive parameter calibration with finite element analysis (FEA) to accurately characterize the mechanical behavior and fatigue durability of SAC0307-3Bi solder joints under cyclic thermal loads. The Anand viscoplastic parameters were first calibrated via the Norton creep law and virtual tensile tests. Subsequently, a 3D quarter-symmetry model was constructed to replicate thermal cycling conditions between 25 °C and 125 °C. Simulation data reveal a strong correlation between stress concentration and the Distance to Neutral Point (DNP), pinpointing the chip-side interface of the corner joint as the critical failure site. Moreover, creep strain was observed to accrue in a “step-wise” pattern, predominantly during the heating and cooling ramps, reflecting distinct temperature sensitivity. Utilizing the Syed model, the fatigue life was estimated at approximately 2239 cycles. These insights serve as a crucial benchmark for designing robust packages using Bi-doped, low-silver lead-free solders. Full article

In the global wave of energy transition, ground-source heat pump (GSHP) systems are widely adopted for their ability to efficiently provide space heating and cooling. By utilizing stable shallow geothermal energy, these systems significantly reduce operational energy consumption in buildings, playing a crucial role in enhancing building energy efficiency and achieving low-carbon strategies. However, large-scale ground heat exchanger (GHE) clusters with non-identical circuits often face hydraulic and thermal imbalances, leading to degraded system performance. This study investigates the hydraulic and thermal behavior of a large-scale GHE system in Shandong Province, China. Hydraulic and thermal models are first developed based on Kirchhoff’s laws and the principle of energy conservation, and then used to simulate and analyze the influence of the number and depth of boreholes on hydraulic and thermal conditions. The results indicate that the flow imbalance rate and pipe length ratio follows a power-law relationship, δ_f = a (L_v/h)^{^b} + d, with fitted coefficients, a = 0.0677–0.1294, b = −0.7086 to −1.0805, d = 0.0036–0.0921, while the heat exchange imbalance rate follows a linear relationship, δ_q = kδ_f + o, with k = 0.0906–0.265 and o = 0.0028–0.0039. Increasing the number of boreholes or decreasing depth exacerbates flow imbalance (10–58%), but soil thermal resistance dominates, limiting the increase in the heat exchange imbalance rate (2.2–9%). The formula and the quantitative relationship proposed in this paper aim to provide guidance for the engineering design of large-scale non-identical circuit GHE clusters. Full article

This article presents an improved formulation of Newton’s law of cooling using the conformable fractional derivative to model long-term thermal behavior more accurately. A key feature of our approach is the use of the fractional time variable $t^{\gamma }$, which introduces a simple scaling symmetry: the structure of the model remains unchanged even when time is proportionally stretched or compressed. This symmetry-based property provides additional flexibility compared to the classical formulation and enables the derivation of analytical solutions under both constant and non-constant ambient temperature. In particular, we incorporate sinusoidal models for ambient temperature to capture realistic environmental fluctuations over extended periods. Experimental measurements confirm that the conformable model achieves significantly better accuracy than traditional integer-order models. These results highlight the relevance of symmetry and fractional calculus in describing physical processes and demonstrate the potential of conformable methods for improving long-term thermal predictions. Full article

Urban heat islands are among the most intense and unequal climate impacts in Mediterranean cities, with direct effects on health, thermal comfort, and habitability. This reality calls for the incorporation of binding and verifiable climate criteria into spatial planning and urban planning law. This article examines the extent to which the Spanish legal framework—at national, regional, and municipal levels—incorporates measurable standards to mitigate urban heat islands and how it might evolve towards operational climate-responsive urbanism. A legal–analytical and comparative methodology is applied, based on multilevel normative content analysis and a comparison of four autonomous communities, four Spanish cities, and four international reference cases with consolidated metrics. The results show that, despite progress in recognising adaptation, territorial asymmetries persist, enforceable parameters remain scarce, and there is a prevailing reliance on strategic or voluntary instruments. In response to these gaps, the study proposes a coherent set of urban climate standards (urban vegetation, functional soil permeability, roof albedo/cool roofs, green roofs and façades, plot-scale performance indices, urban ventilation, and thermal diagnostics) and a multilevel integration model aimed at guiding legislative reforms and strengthening cities’ adaptive capacity and thermal equity. Full article

This work presents a straightforward procedure for constructing the solution to the steady-state energy-transfer process in a system of two convex, opaque, gray bodies, with the aim of determining the temperature distribution within these bodies when separated by a vacuum. The methodology proposed in this work combines a sequence of elements that are functions obtained from the solution of uncomplicated, well-known linear, uncoupled heat transfer problems, thereby enabling solutions to be obtained using tools found in basic engineering textbooks. Specifically, these well-known problems resemble classical conduction-convection heat transfer problems, in which the boundary condition is described by the noteworthy Newton’s law of cooling. The limit of sequences of elements that are solutions to straightforward linear problems corresponds to the original, complex, coupled nonlinear problem. The convergence of these sequences is mathematically proven. The phenomenon (considered in this work) encompasses those involving black bodies. Since each element of the sequence arises from a well-known linear problem, numerical approximations can be used to obtain it, yielding a simple and powerful tool for simulations. Some presented results highlight the importance of considering thermal interaction between the two bodies, even in the absence of physical contact. In particular, the alterations in the temperature distributions of two separate gray bodies are explicitly shown to result from their thermal interaction. Full article

In assessing the strength properties of stone materials, especially in historic structures, ultrasonic measurements are widely used as a non-destructive testing (NDT) method. Actual stone degradation in situ is estimated based on various laboratory tests which allow researchers to correlate the number of artificial ageing cycles of stone specimens with ultrasonic wave velocity measured on these specimens. This paper presents the results obtained for granite, marble, limestone, travertine and sandstone which underwent various cyclic ageing tests including freezing and thawing, high temperature and salt crystallization. Analysis of the obtained results shows that, independent of the stone type tested and independent of the ageing test applied, a rate of change in the stone elastic properties is described by an ordinary differential equation whose solution is an exponential law analogue to the Newton’s law of cooling. The degradation function model can be used for further research on expected residual strength and dynamics of the heritage materials degradation processes. Full article

Understanding the factors influencing temperature variations in natural ecosystems is crucial for processes such as species distribution, phenology, and carbon cycling. This article presents a theoretical framework that investigates the impact of relative humidity ($RH$) on these variations. Previous analyses based solely on environmental thermodynamics governed by radiation and the Stefan–Boltzmann law, named the dry model, revealed a nocturnal cooling rate of approximately 0.9 °C/h in low-relative-humidity conditions (<85%) using data of three distinct Brazilian forests within the Amazonian biome. However, this rate decreased significantly at higher $RH$, suggesting an additional heating effect, which is likely attributed to the coalescence of water molecules in the air. In this study, a novel humid model is developed, integrating terms proportional to $RH$ and its time derivative. This model is based on the premise that clusters of water molecules and latent heat depend on the quantity of water molecules and intermolecular forces. The findings demonstrate a superior fit to the data using the proposed model, with ${\mathrm{R}}^2$ values ranging from 0.7 to 0.95, effectively capturing both the nocturnal temperature decline and diurnal variations. This advancement is significant as it underscores the importance of considering water molecule clusters in developing a more precise model that improves upon the dry model methodology. Full article