Soft heat pipes have many potential applications in the thermal management of the human body and flexible electronic devices. However, the flexibility and heat transfer capability of the current soft heat pipes are limited, which cannot meet the requirements for engineering applications. In this work, according to the working principle of a pulsating heat pipe, a soft multi-branch heat pipe was fabricated by Teflon tubes, where acetone was used as the working fluid. As each heat transfer branch could deform independently, the proposed heat pipe exhibited excellent flexibility. Meanwhile, the proposed heat pipe also has high heat transfer performance with the apparent thermal conductivity being up to 4333 W·m⁻¹·K⁻¹. Therefore, the proposed soft heat pipe can contribute to the development of thermal management garments, cooling of electronic devices, low-grade waste heat recovery.

Sugar alcohols are gaining attention as highly promising medium-temperature phase change materials (PCMs) due to their superior overall performance. Currently, the evaluation of the comprehensive performance of sugar alcohol composite PCMs optimized for a single objective remains incomplete. In this study, erythritol (Ery) was used as a PCM, combined with expanded graphite (EG) and Al₂O₃ as additives. A ternary composite PCM was prepared using the melt blending method, and its comprehensive performance was assessed. The results showed that the components of the ternary composite PCM exhibited excellent physical compatibility. Among them, the ternary composite PCM with 0.5%(wt) Al₂O₃ / 1.5%(wt) EG/Ery demonstrated the best overall performance. This ternary composite PCM maintained a high melting enthalpy of 312.9 kJ/kg and, compared to Ery, achieved a thermal conductivity of 1.083 W/(m·K), an increase of 54%. In the isothermal cooling test, its supercooling degree was reduced by 9.3°C, in the non-isothermal cooling process, its supercooling degree was reduced by 16.7°C. The pyrolysis temperature increased by 20°C, and the maximum pyrolysis rate temperature increased by 8.3°C, significantly enhancing thermal stability. Additionally, after 40 isothermal cycling tests, its supercooling degree and melting enthalpy remained essentially unchanged, demonstrating excellent cycling stability.

Frosting usually has a negative impact on device, when ultrasound is used for frost retardation/defrosting, can realize no downtime defrosting, cooling and heating without interruption during defrosting time. But due to its mechanism is not clear, technical difficulties to pragmatize, failed to get popularization and application. This paper reviews the research progress of ultrasound in the field of frost retardation and defrosting from two aspects of its mechanism and pragmatization. Firstly, the ultrasound characteristics is introduced, including commonly used ultrasound wave types and their propagation, ultrasound effects on frost retardation and defrosting, distribution of equivalent force on the cold surface; then, the growth of frost is inhibited by delaying the generation of liquid droplets, delaying the freezing of droplets, crushing the frozen droplets and suppressing the frost branch growing; based on the frost crystal fracture breaking, defrosting effecting factors and defrosting enhancement methods, ultrasonic defrosting mechanism is summarized; and, from the equipment frost retardation/defrosting effects and its energy consumption comparison, practical difficulties and problems, the ultrasound frost retardation/defrosting practical applications is sorted; Finally, a outlook of the ultrasound used for frost retardation/defrosting in the future is given to provide reference.

Supercritical CO₂ Brayton cycles, due to their advantages in performance and compactness, hold promising prospects for hypersonic vehicles. However, the unique thermal environment of the aerospace scenario poses challenges to the cycle. In this paper, a model of a supercritical CO₂ Brayton cycle is established and validated. The study investigates the transient response of the Brayton cycle system under two operating conditions: a sudden increase in thermal load and a combined disturbance of thermal load and insufficient cold source. Dynamic simulation results indicate that both a sudden increase in thermal load and insufficient cold source can lead to a decrease in the thermodynamic performance of the cycle. Moreover, the combined disturbance may even result in controller failure, imposing higher demands on component design.

Microchannel heat sinks are highly favored in the thermal management of high-performance electronic devices due to their superior heat dissipation capabilities. To effectively enhance the heat dissipation performance of staggered ribbed microchannel heat sinks, this paper addresses the multi-objective optimization problem for such heat sinks by combining the Non-dominated Sorting Genetic Algorithm II (NSGA-II) with response surface methodology. The optimization is carried out under the conditions of minimizing both the pressure drop across the microchannel inlets and outlets and the maximum temperature difference on the heat exchange surface. The Box-Behnken experimental design method is employed, with the rib incidence angle, rib spacing, and rib height as design variables, and the pressure drop and maximum temperature difference on the heat exchange surface as objective functions, to conduct a numerical simulation study on the flow and heat transfer performance of the heat sink. To reduce the pressure drop and improve temperature uniformity, NSGA-II is used to optimize the geometric parameters of the microchannel heat sink. Compared to the original design, the Pareto optimal solution obtained using NSGA-II resulted in a 34.922% reduction in the maximum temperature difference on the heat exchange surface, with almost no change in the pressure drop, and an overall improvement in heat transfer performance by 9.415% under the same pumping power.

The photovoltaic-thermoelectric hybrid power generation system is a promising solar energy technology. However, traditional series-connected photovoltaic-thermoelectric system faces challenges such as mismatched device operating temperature and high thermal resistance. In this study, a bifacial type photovoltaic-thermoelectric hybrid power generation system with a sandwichlike configuration is proposed. An experimental setup is constructed to investigate the effects of different irradiance levels and cooling water flow rates on the performance of the new system under steady-state indoor conditions. Experimental data shows that the output power of photovoltaic module and thermoelectric device in bifacial type system is superior to that of traditional series system. Moreover, increasing irradiance levels can enhance the system’s power generation capacity but may reduce the photovoltaic power generation efficiency. Additionally, increasing the cooling water flow rate can further enhance the system’s output performance.

During the energy release phase of the compressed air energy storage (CAES) system, the air pressure in the storage device gradually decreases. When it falls below a certain threshold, the unit cannot maintain the rated total output power. To address this issue, the study proposes the applications of bypass systems in the CAES system expanders. In this paper, three types of bypass systems are designed for the expander unit of a CAES system: single-stage bypass systems (3 configurations), two-stage bypass systems (3 configurations), and three-stage bypass system (1 configuration), with a total of 7 configurations. By adjusting the openings of the main and bypass valves, the total inlet and outlet pressures of certain turbines are modified, thereby changing their mass flow rates and output powers to achieve the rated total output power. The results show that 5 configurations can achieve the desired performance. The three-stage bypass system enables the lowest terminal air pressure in the storage device, expanding the sliding pressure operation range of the unit. The optimal configuration is the two-stage bypass system that independently controls T1 and T2, which achieves the longest power generation duration and the highest energy density, representing a 71.25% improvement compared to the original unit. Therefore, adopting the bypass control methods can extend the power generation duration and increase the energy density of the CAES system.

In accordance with international environmental protection conventions, some high GWP HFCs refrigerants are facing obsolescence and destruction. Therefore, it is necessary to develop energy-saving, high-efficiency destruction way. In this paper, the performance differences of various catalysts in the photothermal catalytic degradation of R134a was compared based on existing technical route. Furthermore, the effects of material properties on the reaction rate, such as morphology, band structure and photoelectric properties, were obtained through characterization of catalysts. Based on the law of the effects, anatase TiO₂ was selected for modification. The modified catalyst achieved a degradation rate of over 98% within 30 minutes, with the reaction rate increasing by 3.8 times.

Ortho-para hydrogen conversion is an indispensable process in hydrogen liquefaction system. This paper summarizes the experimental research progress of ortho-para hydrogen conversion, comprehensively compares the advantages and disadvantages of various ortho-para hydrogen conversion schemes, analyzes the differences between typical ortho-para hydrogen catalysts, such as iron hydroxide and oxide catalysts and supported nickel catalysts, in terms of the activation methods and catalytic efficiencies, and further summarizes various measurement methods for ortho-para hydrogen concentrations as well as their measurement principles. Regarding the selection of catalysts for ortho-para hydrogen conversion, the literature findings indicate that supported nickel-based catalysts have higher catalytic efficiencies, but taking full consideration of catalyst preparation, activation, deactivation, and liquefier operating requirements, iron hydroxide as well as its oxide catalysts are still the mainstream catalysts for application-oriented catalytic choices. Among the measurement methods of ortho-para hydrogen fractions, compared with spectroscopy, acoustic velocity measurement, nuclear magnetic resonance, enthalpy measurement, etc., the ortho-para hydrogen concentration measurement based on thermal conductivity method has comprehensive advantages in terms of accuracy, response speed, economy and operability, which can be used as the preferred solution for the measurement of ortho-para hydrogen concentration. As large-scale hydrogen liquefaction plants are developing towards the direction of higher efficiency, compactness and reliability, continuous conversion is the mainstream solution for ortho-para hydrogen conversion in the future hydrogen liquefaction processes. However, at present, most of the domestic studies on continuous ortho-para hydrogen conversion remain in conceptual analysis and process application, lacking data on hydrogen conversion, flow and heat transfer under cryogenic conditions, as well as relevant high-precision correlation equations. Based on the measured data of continuous catalysis and cooling of orthopara hydrogen, the development of high-precision correlations for heat transfer, pressure drop and catalysis of hydrogen eat exchangers, and the accurate design of heat exchangers for continuous ortho-para hydrogen conversion, will be an urgent task to be carried out in the future.

The International Maritime Organization (IMO) and port States have increasingly stringent requirements for ship energy efficiency, and the improvement of ship energy efficiency based on waste heat recovery is one of the most effective ways to meet this challenge. TEG-ORC combined cycle is a new method to realize the utilization of multiple waste heat steps in ships, but the effect of bottom cycle ratio on the performance of combined cycle system has not been studied in detail. The theoretical model is optimized and the influence of variable bottom cycle ratio on the performance of the main parameters of the combined cycle system is studied experimentally. The experimental results show that under the conditions of ORC bottom cycle working medium R245fa, working medium mass flow rate m = 0.079 kg/s and evaporation pressure P = 0.7 MPa, with the gradual increase of bottom cycle ratio, the system output power and flue gas waste heat utilization rate of the main engine increase, and the cost of combined power generation decreases. When the bottom cycle ratio of TEG/ORC is 0.885, the flue gas waste heat utilization rate of the main engine is 85.07%, the total output power of the system is 688.4 W, the thermal efficiency of the system is 7.07%, and the power generation cost of the combined cycle system is 3.338 CNY/kWh.

Bag breakup is a typical breakup mode of the Supercooled Large Droplet (SLD) in the field of aircraft icing. The deformation and breakage processes of a water droplet in continuous airflow is studied by combining experimental and numerical simulation methods. A regime map is drawn to give the physical boundary of the bag breakup mode. The deformation ratio, velocity of the initial droplet and size distribution of the secondary droplets are analyzed, and the causes of droplet morphology evolution in each stage of the bag breakup mode are explained. The results show that the range of gaseous Reynolds number and Weber number corresponding to the bag breakage mode are 3100∼4250 and 12∼18, respectively. At the disk moment, the horizontal deformation ratio of the droplet is about 0.4, and it varies slightly with the increase of gaseous Weber number. While, the vertical deformation ratio of the droplet increases gently with the increasing gaseous Weber number. When the gaseous Weber number is 13.4, the droplet breaks in the bag breakup mode. The dimensionless size distribution of the secondary droplets ranges from 0 to 0.28, showing a unimodal distribution, and the peak value appears when the dimensionless size of the secondary droplet is 0.024. This study plays a crucial role in improving the physical model of SLD bag breakup and advancing the simulation accuracy of SLD icing.

The Cross-wavy primary surface recuperator has become the best choice for micro gas turbine regenerative devices due to its compact structure, high efficiency, and low resistance. However, there are few publicly available research results on the inlet and outlet structures of Cross-wavy primary surface recuperator based on heat exchange cores. This article constructs five comparative models based on the heat exchange core: considering the wall model of CW channel structure, not considering the wall model of CW channel structure, and inclination angle α= 60° model, inclination angle α=45° model and inclination angle α=30° model. Inclination angle of inlet and outlet structures α Compare and analyze the thermodynamic performance of CW channel structures, and then investigate the inclination angle α Conduct optimization. The results show that the inclination angle has a small impact on the temperature rise distribution of the CW channel structure, but a significant impact on the pressure drop near its inlet and outlet. By comparing and analyzing the five models from the perspective of the first and second laws of thermodynamics, the optimal tilt angle can be obtained α=45°.

In response to the high-stability low-temperature environment requirements for the primary thermodynamic temperature measurement of superfluid helium to liquid helium temperature range, this paper adopts a two-stage GM cryocooler pre-cooled closed 4He Joule-Thomson cooling method, and builds a 2∼5 K cryostat. The lowest temperature of the core component can reach 1.5 K, satisfying the requirement of the lowest operating temperature. Direct current and alternating current temperature control experiments were conducted in the 2∼5 K range. The results show that alternating current temperature control has advantages in the 2∼5 K temperature range. Temperature control stability better than 40 μK in the 2∼5 K temperature range has been realized. Typical results are 25.5 μK@2 K, 31.6 μK@3 K, 16.2 μK@4 K and 20.7 μK@5 K. This study provides a prerequisite for further upgrade and optimization of the cryostat and high-accuracy primary measurement of thermodynamic temperatures in the 2∼5 K temperature range. 

The three-fluid heat exchanger features a compact structure, enabling concurrent direct heat exchange among three distinct fluid, thereby presenting significant potential for diverse applications. However, a notable limitation is the scarcity of experimental data. This study established an experimental platform for performance testing of a three-fluid heat exchanger utilizing parallel flat tubes and conducted experimental tests to evaluate its heat transfer efficiency. The results show that the heat transfer performance of the three-fluid heat exchanger is primarily influenced by the refrigerant, air, and water flow rates, as well as the temperature differentials between them. When the refrigerant experiences superheating at the evaporator outlet, enhancing the refrigerant flow rate can notably enhance the heat transfer efficiency. However, once the dryness fraction falls below 1, further increasing the flow rate leads to minimal change in heat transfer performance. In the interaction between the refrigerant and water, an increment in the refrigerant flow rate from 15.6 kg/h to 40.5 kg/h results in a gradual rise in heat transfer capacity from 817.3 W to a plateau around 1100 W. The heat transfer capacity escalates linearly with the temperature difference between any two mediums. With the elevation of air temperature from 23.9°C to 30.0°C, the total heat transfer capacity increases from 1037.6 W to 1307.4 W, with the heat transfer efficiency bolstered by higher air speed and water flow rates.

Thermal conductivity is an important parameter reflecting the thermal properties of materials, whether it is used for heat dissipation or insulation. It is of great significance to accurately measure the thermal conductivity of materials. This paper reviews a thermal conductivity measuring method with strong adaptability, convenient testing, simple sample preparation, and low-cost— the 3ω method. Firstly, the basic principle of 3ω method was introduced. Then the analytical solutions for temperature of heat conduction mathematical models under different sample structures are provided, including semi-infinite substrates, thin film systems, multi-layer structures, and fine rod or filament-like sample. Various improved 3ω methods are introduced, including the anisotropy of thin film thermal conductivity, differential 3ω method that can reduce the influence of irrelevant factors, and the method of fitting thermal conductivity using impedance models through thermal penetration depth equivalence. At the same time, the application of 3ω in sensors are introduced. Finally, the possible errors in the experiment process and the methods to improve the accuracy are analyzed. This paper will help researchers to study the thermal conductivity measurement and provide guidance for the design and analysis of 3ω method.

In this study, the oxidation kinetics of Cu₂O was investigated using the micro-kinetics rate equation theory based on first principles. Firstly, the reaction paths and energy barriers of Cu₂O oxidation are obtained using DFT calculations based on first principles; secondly, the reaction rate constants are calculated using the results of DFT calculations to establish the surface reaction rate equations; finally, a kinetic model describing the oxidation process of Cu₂O is established by considering the surface reaction and the diffusion of the bulk phase. The model is validated using experimental data of Cu₂O oxidation in the literature. The results show that the model predictions are in good agreement with the experimental results.

In hydrogen liquefaction systems, the continuous catalytic conversion of ortho-para hydrogen is recognized as a key technology for achieving low energy consumption. The conversion heat of ortho-para hydrogen, which exhibits temperature dependence, is observed to vary significantly along the course of the heat exchanger, influencing the cooling process of hydrogen gas flow. This study investigates continuous conversion cryogenic hydrogen plate-fin heat exchangers, employing theoretical analysis and the development of a dynamic simulation model to explore the heat exchange and catalytic matching characteristics of such exchangers. Optimal cold fluid flow rates in various temperature zones have been determined. When helium is used as a cold fluid, optimal cold-to-hot mass flow rate ratios of 3.5 in the 80∼60 K range and 4.7 in the 60∼40 K range are identified. The dynamic simulation elucidates the heat transfer-catalytic matching relationship between normal hydrogen conversion and the cooling fluid in hydrogen heat exchangers, offering insights for the design and optimization of hydrogen liquefaction processes. These findings contribute to enhancing process efficiency, reducing energy consumption, and promoting sustainable development in the
hydrogen energy sector.

Research on non-Fourier heat transport in GaN transistors was conducted using both thermoreflectance thermal imaging and full-band multiscale simulations. Different-sized Au heaters are designed and fabricated on GaN epitaxial structures. Leveraging the high spatial resolution advantage of thermoreflectance thermal imaging, temperature field distributions of heat sources as small as 500 nm thermal observed, enabling more direct measurement of sample hot spot temperatures. Simulation results from three-dimensional multiscale simulations based on full-band phonon Monte Carlo and finite element methods are in good agreement with experimental values, indicating that phonon ballistic effects significantly increase hot spot temperatures. As the size of the heat source decreases, deviations from predictions based on Fourier’s law increase, highlighting the importance of combining high-resolution temperature field experiments with full-band multiscale thermal simulations to accurately predict device junction temperatures.

If the liquid water generated in the proton exchange membrane fuel cell (PEMFC) cannot be discharged in time, it will cause “water flooding”, thus hindering the mass transfer of reactant gas and leading to the degradation of cell performance. Flow field configuration is one of the decisive factors influencing the transport properties of reactants and products. In this study, the overall performance of 108 cm² large-scale PEMFCs with conventional parallel flow field configuration and modified parallel flow field configuration with divergent design are comparatively analyzed by a three-dimensional two-phase PEMFC numerical model. It is found that the modified parallel flow field configuration enhances the liquid water discharge performance and has a more uniform current density and oxygen distribution, thus enhancing the overall performance of the PEMFC. Compared with the conventional parallel flow field, the power density, current density uniformity, and temperature uniformity of the optimal modified parallel flow field design are improved by 2.31%, 15.31%, and 8.82%, respectively. In addition, a comprehensive evaluation by the entropy weighting method reveals that the optimal modified parallel flow field design improves the comprehensive evaluation index from 0.057 to 0.309.

Pre-chamber jet combustion technology is a crucial pathway for achieving breakthroughs in the thermal efficiency of spark-ignition engines. However, there are still many research gaps regarding the combustion mechanisms of pre-chamber engines. This paper reviews the development of pre-chamber engine jet combustion technology and reports recent advancements in laser diagnostics and numerical simulations of pre-chamber engine jet combustion. Research indicates that the ignition modes of pre-chamber engines can be categorized into “flame ignition” and “jet ignition”. In the flame ignition mode, flame quenching does not occur at the pre-chamber nozzle, resulting in good combustion stability and improved engine thermal efficiency. Due to the large flame quenching distance of ammonia fuel, pre-chamber ignition tends to exhibit the jet ignition mode, which can lead to reduced combustion stability and thermal efficiency of the engines.

To address the challenges of carbon dioxide capture in hydrogen production and electricity generation from fossil fuels, as well as the supply-demand mismatch in the utilization of intermittent and unstable solar energy, this paper proposes a solar-driven hydrogen and electricity cogeneration system with source decarbonization. The system employs an iron-nickel mixed oxygen carrier, which reduces the reduction reaction temperature while achieving efficient carbon dioxide capture. The results indicate that under a solar irradiance of 750 W/m², the system achieves a solar energy input ratio of 30.80%, with energy utilization rates of 67.23% and 59.47% for hydrogen production and electricity generation under design conditions, respectively. In addition, by regulating the sensible heat of the inlet oxygen carrier and its oxidation degree during the reaction process, the system can operate stably under varying irradiation conditions and flexibly adjust hydrogen and electricity outputs. When the solar irradiation intensity is 750 W/m², the adjustable hydrogen-toelectricity ratio ranges from 0.17 to 0.59 m³/kWh, demonstrating excellent adaptability to varying operating conditions. This study offers a novel technological pathway for highly efficient hydrogen and electricity co-production and source decarbonization through the complementary use of solar energy and natural gas.

As a natural refrigerant, CO₂ exhibits excellent environmental performance and low production costs, making it an ideal replacement for high-GWP refrigerants. To enhance system efficiency, vapor injection technology, characterized by its simple structure and reliable operation, has been widely employed in CO₂ heat pump systems. However, these systems still face significant challenges in practical applications due to inherent issues such as high operating pressures and substantial throttling losses. To address these challenges, this study incorporates three low-pressure refrigerants into the CO₂ heat pump system to improve operational efficiency and reduce system pressure. The research findings demonstrate that the CO₂/R161 system surpasses traditional CO₂ heat pump systems in terms of energy efficiency. The CO₂/R161 system achieves up to a 17.6% increase in efficiency under various thermal demand conditions and a maximum pressure reduction of 33.7% at an outlet water temperature of 85°C, compared to conventional CO₂ heat pump systems.

The infrared spectral properties of ZrB₂-SiC ceramic matrix composited with different microstructure were calculated based on the finite difference time domain (FDTD) method. The influences of SiC particle shape, volume fraction and material thickness on the infrared emissivity of the composites were discussed, and influences of SiC particle shape, volume fraction on the infrared stealth performance of the materials were also evaluated. The results show that the total emissivity of the composites doped with SiC particles is higher than that of bulk ZrB₂. The emissivity of the composites doped with whisker SiC particles is lower than doping with sphere and ellipse particles. The emissivity of the composites varies sharply with the increase of SiC volume fraction in the 10∼14 μm wavelength band. The spectral emissivity of the composite is mainly affected by the microstructure of the material near the surface. The largest influences of the above three parameters on the mean emissivity in the atmospheric window are 2.65%, 16.1% respectively. The results will be useful for realizing the regulation of the spectral radiative characteristics of ZrB₂-SiC ceramic matrix composites and improving the infrared stealth performance.

Capillary wick is the core component of heat pipe, which has important influence on the performance of heat pipe. In this paper, combined with the characteristics of parallel channel capillary wick and wire mesh capillary wick, different structure and different pore sizes of capillary wick were designed and samples were prepared by 3D printed method. Through experiments, the thermal conductivity and capillary performance of capillary wick and the influence of hydrophilic modified surface treatment were studied. The research results show that: the capillary wicks with non-circular sections such as rectangular and triangular sections can obtain lower friction coefficients. The effective thermal conductivity of capillary wick firstly increases and then decreases with the increase of temperature, and decreases with the increase of capillary wick porosity. The initial capillary pumping velocity increases with the pore size increase. The capillary performance of capillary wicks with circular section are the best and capillary wicks with triangular section are the worst. The performance of the modified capillary wick is improved. The performance of the modified capillary wicks with deionized water as the working medium are increased by 180%∼285%, and the performance of the modified capillary wicks with anhydrous ethanol as the working medium are increased by 108%∼119%.

The diagonal compressor is one of the important types of combined compressors for large-scale compressed air energy storage system (CAES). The off-design performance prediction is crucial in the research and development of the diagonal compressor. It can not only quickly evaluate the initial design parameters, but also select the overall optimal parameters according to the characteristics of the off-design operation of the compressor in CAES. The accuracy of the performance prediction model is essential. In this paper, a one dimensional performance prediction program for the diagonal compressor of the developing large-scale CAES is established by programming, and the optimal selection result of the loss model combination of the program is given through the design point parameters. Then, the off-design loss model is modified by using the flow coefficient, and the results are verified by CFD. The results show that this method can effectively predict the off-design performance of the diagonal compressor under different guide vane openings.

In order to solve the problem of mismatch between heat source temperature and evaporation pressure in low-pressure stage, a double gas-liquid separator (DS-DPORC) system was proposed based on the basic dual-pressure organic Rankine cycle (DPORC) system. The thermal performance of DPORC and DS-DPORC system is compared and analyzed. Both traditional and advanced exergy analysis methods were used to study the improvement potential and interaction relationship of the optimized DS-DPORC system and its components. It is shown that there is an optimal evaporation pressure at high and low-pressure stages, respectively, which enables the thermal performance of both systems to reach the optimal level. At that time, DS-DPORC had a 10.02% increase in net output compared to DPORC, while the exergy efficiency increase was 10.4%. There are differences between traditional and advanced exergy analysis methods. The former thinks that the preheater with the highest exergy destruction has the greatest potential for improvement, while the latter thinks that the high-pressure turbines has the highest priority for improvement considering both the exergy destruction rate and the exergy destruction. In addition, exergy destruction of various components in the DS-DPORC system mostly belongs to internal exergy destruction, and the exergy destruction of components is relatively poor in inter dependency.

Hydrogen production is considered to be a promising new hydrogen production method in the future. However, there are high overpotential and slow kinetic process of oxygen evolution reaction (OER), and corrosion of the electrode caused by chlorine evolution reaction (CER), which make the hydrogen production technology of seawater electrolysis face great challenges. In recent years, relevant studies have shown that coupling the anodic oxidation reaction of hydrazine, urea, sulfide, sugars, microplastics and other substances into the seawater electrolysis hydrogen production system can replace OER, avoid problems such as chlorine corrosion and achieve higher economic benefits. This paper systematically reviews the principle, challenges and the research status of related catalysts, focuses on the progress of the oxidation reaction of electrolytic seawater with lowenergy consumption in recent years, and finally discusses the problems that need to be breakthrough and the future research direction.

Dynamic stall of an airfoil causes aerodynamic fluctuations due to the formation of leading edge stall vortices on the suction surface, which seriously affects the wind energy capture efficiency and structural stability. Aerodynamic shape optimization provides an effective method to retard the dynamic stall characteristics. However, multiple evaluations using accurate but time-consuming computational fluid dynamics (CFD) simulations make the optimization process computationally expensive. Therefore, an surrogate-based optimization (SBO) technique is proposed in this paper to reduce the computational burden. The feasibility of the framework is verified by optimizing the S809 wind turbine airfoil. Due to the increase in thickness and leading edge radius of the optimized airfoil, the development of trailing edge vortices towards the leading edge is suppressed. Compared with the baseline airfoil, the average drag coefficient and bending moment coefficient of the optimized airfoil are reduced by 48.95% and 23.74% respectively, while the lift coefficient is improved. Finally, a global sensitivity analysis of the optimized design using Sobol’s index reveals the geometric parameters and their interactions that have the greatest influence on the dynamic stall characteristics of the airfoil.

Multi-energy co-generation systems are crucial for improving energy efficiency, enhancing system flexibility, and integrating various energy sources for end users. This paper proposes a largescale, cross-seasonal, and cross-regional CO₂-based combined cooling, heating, power and fuel system. A thermodynamic model of the system is developed to investigate the effects of parameters such as CO₂ mass flow coefficient, internal waste heat, compression/expansion stages, and intercooler outlet temperature on system performance. The results show that as the ratio of CO₂ mass flow rate within the CO₂ energy storage module to that captured by the direct air capture module increases from 200 to 600, the system energy utilization factor improves from 75% to 85%. When the expansion stage number is 3, 4, 5, 6, 8, 10, 11, 13 and 15, the system begins to generate cooling energy at higher compression stages. When the compression and expansion stages are 14 and 5, the system energy utilization factor reaches its maximum value of 105%. The optimal electrical roundtrip efficiency and system energy utilization factor are 70% and 105%, respectively.

Supercritical water gasification technology can realize the resource utilization of biomass waste. Formation and evolution of the pore structure of particles in supercritical water are different from that of the conventional state due to the unique physical properties of supercritical water. While pore structure affects the flow, heat transfer and chemical reaction of particles in supercritical water obviously, it is crucial to investigate the pore structure evolution. In this paper, biomass gasification experiment is carried out in the batch reactor first to obtain solid particles. Then the pore structure properties of the obtained solid particles are comprehensively characterized. The influence of different operating conditions on the formation and evolution of pore structure is obtained by analyzing the pore structure properties of the particles. It is found that the pore volume of biochar is about 57 times higher than that of raw material, and the specific surface area is enlarged about 86 times. 

The efficiency of the supercritical carbon dioxide (SCO₂) Brayton cycle is closely related to the parameters of the components in the cycle system. Based on the MATLAB/Simulink platform, a modularized calculation procedure for the SCO₂ Brayton cycle was established. The design and analysis of a large capacity coal-fired power generation system were carried out using split flow recompression and secondary reheating schemes, and the influence of relevant parameters of components was investigated, such as turbines, compressors, and flue gas coolers. The results showed that the optimal split ratio of the recompressor decreased with the increase of turbine inlet pressure; The power distributions of the heater exchangers in boiler were significantly affected by the split ratio of the flue gas cooler; The circulation efficiency of the system reached its highest level at 35 MPa and 600°C , when the primary reheat pressure and secondary reheat pressure were 25 MPa and 16 MPa, respectively, and the split ratio of the recompressor and the flue gas cooler is 0.3 and 0.05, respectively; As the inlet temperature and pressure of the compressor increased, the circulation efficiency gradually decreased. The research results of this article have important reference value for the establishment and optimization of the large-scale coal-fired SCO₂ power generation systems.

This paper employs the method of dissipative particle dynamics to construct a model of long-chain polymer motion within microchannels. The effects of polymer chain confinement, Reynolds number, and channel structure on the conformational changes and motion rules of individual polymer chains are systematically studied. The result shows that, in the Poiseuille flow in the straight channel, the distribution of the polymer chain’s center of mass is bimodal, and the position and peak value of the double peaks are closely related to the degree of confinement and Reynolds number. In addition, the period of different chain length polymers passing through the slit can be controlled by adjusting the slit width of the T-shaped channel. Based on this mechanism, the separation of different chain length polymers can be achieved, which has great potentials in biomedical field.

Inverse heat transfer problems involve the estimation of the internal characteristics or thermal boundary conditions by using the internal or surface temperature measurements in the heat transfer system. Inverse heat transfer problems widely exist in scientific and technological fields such as energy and power engineering, metallurgical engineering, intelligent mechanical manufacturing, biomedical engineering, and aerospace. In the past half century, research on the calculation methods and applications of inverse heat transfer problems have been very active. In this article, the research progress on the application of inverse heat transfer problems is surveyed and the research progress of calculation methods for inverse heat transfer problems is systematically elaborated; the current challenges and future development directions of the calculation methods and application research of inverse heat transfer problems have been laid out to promote the development of numerical calculation technology and applications for inverse heat transfer problems, empower production practice with research of heat transfer inverse problems, contribute to the construction of industrial digital twins, and contribute to the implementation of China’s digital transformation national strategy. 

With the increasing integration of renewable energy, the inherent uncertainty of energy sources and loads, coupled with the nonlinear coupling characteristics of multi-energy systems, poses significant challenges to the operation and management of distributed energy systems. This paper accounts for the nonlinear characteristics of electricity-heat transmission and conversion processes by incorporating a heat current model and a column-and-constraint generation algorithm, proposing a two-stage robust optimization model and a bilevel iterative optimization algorithm. Compared to a simplified robust optimization model that neglects nonlinear characteristics, the proposed approach reduces operating costs by 3.2%. Furthermore, the results demonstrate that in actual system operation, the proposed algorithm effectively mitigates the infeasibility risk of robust scheduling strategies caused by model simplifications, thereby verifying its economic efficiency and robustness. 

To investigate the impact of different definitions of dimensionless tip clearance on the performance evaluation of compressors, a numerical database of a single-stage subsonic compressor with four load coefficients, five aspect ratios, and five different tip clearances was utilized as the research foundation. A detailed analysis was conducted on the differences in the impact of different nondimensional tip clearance definitions on rotor tip performance, and a more reasonable nondimensional clearance definition method was identified for evaluating different performance parameters. Finally, the sensitivity empirical formula for the impact of compressor performance was summarized using nonlinear regression method. The results show that when analyzing the efficiency parameters of the compressor, the rotor blade height should be used as a nondimensional factor for the gap size, while when analyzing the pressure rise parameters, the rotor chord length should be used as a nondimensional factor. In terms of the sensitivity of various design parameters, the tip clearance has the greatest impact on performance sensitivity, followed by the load coefficient. The aspect ratio has the smallest impact on performance sensitivity.

Carnot battery is an emerging energy storage technology characterized by low cost and independence from geographical constraints. The use of latent heat thermal energy storage in Carnot battery results in high energy density, offering broad application prospects. This paper constructs a Carnot battery system based on a packed bed latent heat storage and establishes its dynamic model. The analysis includes the impact of heat transfer fluid flow rate and organic working fluid mass flow rate on system performance. A functional relationship for the mass flow rates of the heat transfer fluid and organic working fluid has been established at a design power of 1000 kW. Subsequently, using the NSGA-II algorithm for multi-objective optimization with roundtrip efficiency and energy density as optimization objectives. After balancing using the LINMAP method, the roundtrip efficiency and energy density obtained were 62.74% and 12.96 kWh/m³.

Thermoacoustic heat engines are a type of heat engine that utilizes the reciprocating oscillation of compressible gas to achieve the mutual conversion between sound energy and thermal energy. The core components are composed of static high and low temperature heat exchangers and regenerators, with a simple structure. In this paper, a three-dimensional local model is established for the core components of a thermoacoustic engine. In the three-dimensional local model, the heat exchanger uses the tube and sleeve model, and the recuperator uses Porous medium, in which the inertia drag coefficient and viscous drag coefficient of the recuperator are calculated by the pore method. Then, based on this three-dimensional model, this article establishes equivalent Fluent two-dimensional models and Sage one-dimensional models. By comparing the calculation results of the three models, it is found that the CFD calculation model and Sage calculation model are basically similar in capturing the distribution of time average temperature difference and time average heat flux. However, there is a significant difference in the calculation of resistance characteristics between the two, as Sage is a one-dimensional model software that cannot directly capture the local losses caused by complex flow changes. However, by comparing the calculation results of Fluent’s 2D and 3D models, it was found that the calculation results of the two models in terms of resistance characteristics are relatively close. Therefore, in engineering calculations, in order to simplify calculations and save time, a 2D Fluent model with equivalent topology can be used instead of a 3D model.

This study investigates integrating high thermal conductivity materials into the liquid chamber to decrease heat transfer resistance and examine the impact of fluid-degassing on the transmembrane resistance. These measures enhanced the efficiency of thermo-osmotic energy conversion (TOEC) system and the experimental water flux of a single-stage TOEC system reaches an attractive value of 56.69 L·m⁻²·h⁻¹. Furthermore, a theoretical model was built to forecast the performance. The results showed that a 34-stage system attained a maximum efficiency of 4.03% and a corresponding power density of 27.56 W·m⁻² at heating and cooling temperatures of 80°C and 40°C, respectively. This study exhibits a feasible approach for enhancing the efficiency of TOEC system.

During the operation of a dual fuel fuel chamber, the deterioration of combustion chamber performance is prone to occur during the mixed combustion process of gas/liquid fuel. This paper uses numerical simulation methods to study the fuel switching process of a dual fuel gas turbine combustion chamber used on offshore oil and gas platforms, and analyzes the impact of gas/liquid fuel ratio on the conventional performance of the combustion chamber during the fuel switching process under three switching strategies. The differences in performance fluctuations during fuel switching under different fuel supply strategies were compared, and a stable switching control strategy was obtained. Finally, the fast opening type was selected as the optimal switching strategy, and the rationality of the strategy was verified through full process switching simulation.

The physical processes of heat and mass transfer, including the diffusion of gases and liquids across interfaces and the mixing caused by convection, are extensively employed in various applications such as energy storage through phase-change, hydrogen storage, and geologic carbon sequestration. However, accurately predicting the diffusion coefficients and mixing rates of multiplecomponent fluids within porous structures, as well as understanding the mechanisms that enhance mass transfer, continues to present challenges. This work examines the mass transfer properties of gas-liquid phases in porous skeletons, specifically focusing on diffusion-convection dynamics. The equations used for calculations were enhanced to incorporate the effect of the dispersion of the injected solution. It was found that the disparity in the diffusion coefficients of the two linear molecular gases in the solution present in the water phase was contingent upon the effective size of the solute. The diffusion between the gas-liquid phases is mostly influenced by temperature, and the diffusion coefficients are nearly unaffected by pressure, which fits with the solvent’s low compressibility. The four manifestations of convective dissolution are additionally identified by NMR signals, revealing that the rate of convective dissolution is one to two orders of magnitude greater in comparison to the rate of diffusive dissolution.