Small concentric annular heat exchangers are widely used in compact thermal systems, but their performance is limited by weak convective mixing in the annulus. Constructal T-Y-fins have improved heat removal in flat and single-side geometries; however, their behavior in a conjugate annular configuration, together with the thermal-hydraulic trade-off, remains unclear. This study introduces constructal T-Y-fins into a small concentric annular heat exchanger and evaluates their thermal-hydraulic performance under parallel- and counter-flow conditions. With fixed total volume and fin material, two-degree-of-freedom constructal design is performed, and multi-objective optimization is carried out using an artificial neural network, the NSGA-II algorithm and three decision-making approaches. Under parallel-flow, the optimal composite function value is 0.941, which is 5.9% lower than the reference and 25.2% lower than the model without fins. Under counter-flow, the corresponding value is 0.920 (8% lower than the reference and 27.1% lower than the model without fins), indicating superior performance. The Shannon Entropy DMA yields the smallest deviation indices (0.3816 for parallel-flow, 0.3920 for counter-flow). The maximum thermal driving force concentrates at the branched-fin tips, where the temperature gradient increases by order of magnitude, indicating that flow-field redirection and boundary-layer thinning, rather than surface extension alone, dominate the enhancement.
To achieve the 150 ± 2 °C temperature-uniformity design target adopted in this study for photovoltaic (PV) module lamination, this study proposes an induction heating scheme using built-in perforated coils for a large-scale heating plate (4750 × 2900 × 45 mm). An equivalent finite element model was established to reduce the computational cost of large-scale multiphysics coupling, with accuracy validated via a physical prototype. Baseline excitation parameters were optimized by balancing heating cycle time and surface temperature difference. Numerical results identified significant corner overheating, prompting an electromagnetic-thermal collaborative optimization strategy. Specifically, a stepped aluminum shielding design was introduced to redistribute magnetic flux, supplemented by asymmetric current compensation to mitigate regional heating disparities. Furthermore, a non-linear variable-current control strategy based on a second-order smooth function was designed to mitigate thermal overshoot associated with heat-conduction lag in large-heat-capacity systems. Full-scale prototype tests showed that the measured temperatures at all 13 monitoring locations were within 148–152 °C, with a maximum measured temperature difference of approximately 3.1 °C, indicating a substantial improvement in temperature uniformity at the monitored locations.
Transverse flux induction heating (TFIH) offers distinct advantages in the field of metal strip heat treatment. However, optimizing its heating performance and ensuring the stable operation of the inductor requires a comprehensive multiphysics coupled analysis. To address the excessive inductor temperature rise caused by narrow air gaps in novel coil designs during high-temperature strip processing, this paper proposes a thermal protection strategy that combines active internal water cooling with passive composite thermal insulation. Forced water passages inside the hollow copper turns evacuate internal ohmic dissipation, while thin multi-layer ceramic-vacuum boards intercept intense radiative and convective heat fluxes from the moving strip. A finite element model of TFIH for moving strips is developed, accounting for strip motion, temperature-dependent material properties, water cooling, and thermal insulation. This modeling approach is experimentally validated using a low-power diamond-coil prototype. Subsequently, the validated method is applied to simulate a TFIH system featuring a novel dual-hexagonal-coil structure. Results demonstrate that the dual-hexagonal-coil structure significantly improves the thermal uniformity of the strip. Furthermore, the proposed protection measure not only prevents inductor overheating but also minimizes heat loss from the strip, producing a measurable rise in the delivered strip temperature without increasing input power. This study provides a valuable technical framework for the design and optimization of TFIH devices.
Internally heated liquid pools undergoing wall solidification occur in molten-salt systems, latent-heat thermal storage, metallurgical processing, and severe-accident in-vessel retention. Their behaviour is governed by the coupled interaction of natural convection, phase change, porous-layer mobility, turbulent mixing, internal heat generation, conjugate wall conduction, and competing heat-removal paths. While these mechanisms are individually well established, their relative influence on phase structure, thermal stratification, and angular wall loading is difficult to separate within a single phase-changing calculation. The present study addresses this problem through a verified assessment of porous-phase transport, turbulence treatment, boundary-condition sensitivity, and numerical uncertainty within a common computational framework.A two-dimensional conjugate molten-salt/steel semicircular pool is analyzed using a multi-region OpenFOAM enthalpy–porosity formulation. The study systematically varies mushy-zone resistance, turbulence treatment, turbulent Prandtl number, liquid-fraction formulation, phase-dependent turbulence attenuation, and boundary heat-loss parameters. Numerical credibility is established through independent grid and time-step studies, comparison across two mesh families, conservation and interface checks, and external comparisons with RASPLAV-Salt and the finite-freezing-interval LIVE-L4/L5L experiments.The analysis shows that the wall-attached solid and mushy regions behave as active thermo-hydraulic layers rather than purely passive conductive resistances: internal heat generation, phase state, and hydraulic accessibility jointly determine their interaction with the convecting pool and the cooled wall. Porous resistance primarily influences basal mush development, crust–mush partitioning, local mobility, and bottom-wall heat transfer, while numerical verification distinguishes these robust responses from mesh-dependent upper-wall effects. The LIVE benchmark provides complementary model-selection evidence: the phase-gated SST formulation strongly mixes the stably stratified lower pool, reducing melt superheat and altering crust development, whereas the corresponding calculation without an eddy-viscosity model reproduces substantially more of the measured stratification, melt temperature, downward wall flux, and wall-power partition. Boundary-condition variations significantly affect the global heat-path distribution but have a weaker influence on the principal basal phase-layer response.Relative to earlier internally heated enthalpy–porosity studies, including Xi et al., the present work extends the analysis by examining how porous resistance, turbulence treatment, boundary effects, and discretization propagate through the same conjugate phase-changing system. The results indicate that total solid inventory or a single permeability parameter is insufficient to characterize local wall loading; phase partition, local mobility, thermal stratification, turbulence treatment, and angular heat-flux redistribution must be considered together. These findings provide a physics-based basis for interpreting model behaviour and for improving reduced-order descriptions of internally heated solidifying pools in molten-salt, thermal-storage, and nuclear-safety applications.
Understanding the thermo-mechanical response of rock salt at high temperatures is important for the stability assessment of deep salt cavern gas storage. Uniaxial compression tests with synchronous acoustic emission (AE) monitoring were conducted on rock salt at 40–110 °C. The mechanical response, energy evolution, and AE characteristics were analyzed during the pre- and post-dilatancy stages. An AE-based damage variable was defined using cumulative AE counts, and its evolution was characterized using a normalized Weibull function. A distinct temperature-dependent transition in damage–dilatancy behavior is observed. At 40–80 °C, damage activity is concentrated predominantly in the post-dilatancy stage, with pre-dilatancy AE counts accounting for only 10.4% of the total pre-peak counts on average. By contrast, at 90–110 °C, the pre-dilatancy proportion increases to 54.2%, while the total strain energy density and dissipated energy density at the dilatancy point exceed 40% of their respective peak values. Low-frequency AE signals also become dominant during the pre-dilatancy stage. The normalized Weibull function can effectively characterize the pre-peak evolution of the AE-based damage variable in rock salt. These results indicate that substantial inelastic deformation and damage can accumulate while the specimen remains macroscopically compacted at high temperatures, revealing increasing damage–dilatancy decoupling. Tensile cracks remain dominant throughout the temperature range, indicating that temperature primarily redistributes crack activity across loading stages and alters its accumulation path without fundamentally changing the dominant crack type. These findings provide useful insights into the stability and safe operation of deep salt cavern energy storage.
