Hongtao Li

Traditional fluid network theory often underestimates pressure losses in complex pipe-bundle systems operating under vortex-dominated flow conditions, with deviations exceeding 20% in many cases. To address this limitation, this study proposes a vortex-based correction method. Three-dimensional simulations were performed on a multidirectional parallel pipe bundle to analyze vortex formation and to quantify the effects of fluid properties (viscosity and inlet velocity) and structural parameters (branch diameter, manifold cross-sectional ratio, and manifold arrangement) on pressure loss. To account for vortex-induced energy dissipation that is overlooked by conventional one-dimensional network models, an additional vortex-induced loss coefficient, α, is introduced to modify the pressure-loss formulation. Results indicate that higher viscosity, larger branch diameter, a higher manifold cross-sectional ratio, and a co-flow arrangement improve flow uniformity and prediction accuracy. Conversely, higher inlet velocities and counter-flow arrangements intensify vortex effects and increase prediction deviations. Least-squares fitting indicates that α ranges from 1.15 to 1.37. Implementation of the proposed correction reduces pressure-loss prediction errors to within 5%, demonstrating the method’s effectiveness and extending the applicability of fluid network theory to vortex-dominated flows.

Single-material thermoelectric generators (TEGs) often face performance degradation across broad temperature gradients because the transport properties of thermoelectric materials vary strongly with temperature. To improve temperature-gradient utilization, this study investigates a Bi2Te3/PbTe segmented TEG using multiphysics simulation and machine-learning-assisted performance prediction. Rectangular and cylindrical thermoelectric-leg configurations were constructed under identical geometric and thermal-electrical boundary conditions to examine the influence of leg geometry on temperature distribution, electric-potential distribution, output power and conversion efficiency. A two-segment n-type leg was designed by placing Bi2Te3 near the cold side and PbTe near the hot side, while the p-type leg, overall geometric constraints, and segment ratio were kept unchanged. A three-dimensional thermoelectric model was established in COMSOL Multiphysics 6.3, and 270 steady-state simulation samples were generated by varying the operating current and hot-side temperature. The simulated output power and conversion efficiency were used to train an eXtreme Gradient Boosting (XGBoost) surrogate model for rapid performance prediction within the investigated current-temperature domain. The segmented rectangular configuration produced more uniform temperature and electric-potential distributions than the segmented cylindrical configuration, indicating a more favorable thermal-electrical transport behavior. Compared with the corresponding non-segmented rectangular model, the segmented rectangular model achieved 18.4% higher output power and 15.7% higher conversion efficiency under the same modelling assumptions. The regression-model comparison indicated that RF achieved the highest in-domain interpolation accuracy for the present current-temperature dataset, whereas XGBoost maintained competitive predictive performance for output power and conversion efficiency, with coefficients of determination of 0.9712 and 0.9697, respectively. Within the prescribed operating domain, the XGBoost surrogate was further examined as a regularized gradient-boosted model through learning-curve analysis, permutation-based feature attribution, and repeated-split stability assessment. These results demonstrate that, within a consistent multiphysics modelling framework and under identical thermal-electrical boundary assumptions, Bi2Te3/PbTe segmentation enhances the simulated performance of fixed-geometry TEGs, while XGBoost provides a representative regularized gradient-boosted surrogate prediction approach over the investigated current-temperature operating domain.

The geometric design of flow channels in bipolar plates is one of the critical features of proton exchange membrane fuel cells (PEMFCs), as it determines the power output of the fuel cell and has a significant impact on its performance and durability. The function of the bipolar plate is to guide the transfer of reactant gases to the gas diffusion layer and catalytic layer inside the PEMFC, while removing unreacted gases and gas–liquid byproducts. Therefore, the design of the bipolar plate flow channel is directly related to the water and thermal management of the PEMFC. In order to improve the comprehensive performance of PEMFCs and ensure their safe and stable operation, it is necessary to design the flow channels in bipolar plates rationally and effectively. This study addresses the limitations of existing bipolar plate flow channels by proposing a new coupling of serpentine and radial channels. The distribution of oxygen, water concentrations, and temperature inside the channel is simulated using the multi-physics simulation software COMSOL Multiphysics 6.0. The performance of this novel design is compared with conventional flow channels, with a particular focus on the pressure drop and current density to evaluate changes in the output performance of the PEMFC. The results show that the maximum current density of this novel design is increased by 67.36% and 10.43% compared to straight channel and single serpentine channels, respectively. The main contribution of this research is the innovative design of a new coupling of serpentine and radial channels in bipolar plates, which improves the overall performance of the PEMFC. This study provides theoretical support for the design of bipolar plate flow channels in PEMFCs and holds significant importance for the green development of energy.

Molten salt energy storage technology shows great potential in a sustainable energy integrated system for its excellent thermal energy storage efficiency and environmental adaptability, and it has received much attention from the academic community. To improve the efficiency of traditional dual-tank heat storage systems, a new distributed single tank thermal storage system with an internal heat source was proposed. The single tank was designed according to API 650 and EN 13445-3:2012 specifications, and the specific data of the storage tank was obtained by combining application examples. The results show the following: (1) the stress of the molten salt storage tank with internal electric heating increases during the heating process, and the peak stress appears at the connection position below the tank body and the electric heater sleeve. (2) The increasing electric heater sleeves lead to the increase in tank stress, and when the number of electric heater sleeves increases from four to eight, the tank stress increases by 24%. (3) The stress of the tank reduces with the increasing axial height of the electric heater sleeve. The stress of the tank is reduced by 8% when the position of the electric heater sleeve is increased from 400 mm to 800 mm. This study can provide some theoretical support for the design and optimization of a single-tank molten salt heat storage system and provide a reference for the design of such storage tanks with a built-in heat source.

Turbine energy recovery is a process energy saving technology, and understanding turbine efficiency has important operational and economic benefits for the operator of a power plant. There are three main areas of research into turbine energy efficiency: the structural performance of the turbine itself, the configuration of the recovery device and the regulation of operating conditions. This paper summarizes recent research advances in hydraulic turbine energy efficiency improvement, focusing on the design factors that can affect the overall efficiency of a hydraulic turbine. To quantify the impact of these factors, this paper investigates the effects of surface roughness, flow rate, head and impeller speed on overall efficiency. Methods for optimizing improvements based on these design factors are reviewed, and two methods, the Box–Behnken Design method and the NSGA-II genetic algorithm, are described with practical examples to provide ideas for future research.

Flexible multi-body dynamics of wind turbines is a subfield of structural mechanics that mainly studies the response of the coupling structure under dynamic loading, such as the transient changes of displacement and stress, in order to measure the load carrying capacity of the coupling structure and obtain the corresponding dynamic properties. Structural dynamics takes into account not only the damping and inertia forces generated by the vibration of the structure but also the elastic force generated by the deformation of the structure. With the continuous increase of individual power and tower height, the flexibility of the multi-body system of wind turbines also increases. The study of the influence of structural parameters on the coupled structural vibrations of tower blades of large wind turbines can provide a scientific basis for the flexible design of large wind turbines as well as important theoretical support for their safe, stable, and economic operation.

In order to reduce the influence of temperature fluctuation on heat treatment of regenerative forging reheating furnace, a scheme of improving traditional cascade PID controller to fuzzy PID controller was proposed in this paper. Taking the actual PID parameters of reheating furnace in forging workshop of a steel plant as reference object, the feasibility of the scheme is simulated by using MATLAB/SIMULINK. The results show that: 1) The control effect of fuzzy PID control is better than that of PID control in overshoot and adjusting time when the gain coefficient is perturbed 30%; 2) The dynamic performance of the system does not change significantly when the time constant is perturbed 20%; 3) The fuzzy PID shows better stability when the lag time is perturbed 20%.

Using CFD simulation technology, the influence of three kinds of operation modes (air change on the same side mode, cross air change mode and staged air change mode) on the temperature uniformity of regenerative heating furnace was studied. The results show that: 1) in the same side air exchange mode, the high temperature area is easy to form in the middle of the furnace, which makes the local temperature of the billet surface high; 2) in the cross air exchange mode, the high temperature area appears in the middle of the furnace, the heat exchange in the middle of the billet is strong, and the heating speed is fast; 3) in the staged air exchange mode, the high temperature area moves to both ends, and the temperature at both ends of the billet is higher than that in the middle. Therefore, in order to keep the temperature of billet constant, the best operation mode of regenerative heating furnace is alternating operation of cross air change mode and staged air change mode.

Adding coal additives in civil water heating coal furnace can effectively reduce coal consumption and has great economic benefits, but there is no standard method for testing energy-saving performance of coal additives in slime. Referring to GB/T 16155-2018 “Test Method for Performance of Civil Water Heating Coal Furnace”, this paper developed a measuring device for energy-saving performance of coal additives, and proposes a detection method based on the temperature of effluent and backwater as a measuring scale for heating capacity of slime combustion. The experimental results show that the energy-saving effect of coal additives on clean briquette is not obvious when it is sprayed on clean briquette and burned by dry clean briquette, while in wet mixed combustion, the cumulative heat of slime with coal additives increases by up to 50% compared with that of ordinary slime.

Biomass energy utilization can solve the contradiction between economic development and energy and environment. Biomass pyrolysis technology is not only one of the thermochemical conversion technologies, but also the necessary stage of biomass gasification, which has become a hot academic research topic. Firstly, based on the pyrolysis experimental data of cellulose, hemicellulose and lignin, the analytical expressions of pyrolysis gas mass yields of different biomass components varying with temperature were obtained; then, the prediction of pyrolysis products was obtained by mass component superposition method, and the correction coefficient of biomass pyrolysis gas yield model was obtained based on the comparison between the average yield of biomass pyrolysis gas and the predicted value of pyrolysis products; finally, the gas release mechanism model of biomass pyrolysis was obtained. This study provides theoretical basis and technical support for the development of biomass utilization technology.