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.

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.

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.

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.

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.

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°.

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.

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.

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.

Detonation engines, compared with traditional aviation engines that adopt the Brayton cycle, have higher unit thrust and lower fuel consumption rate, and thus have broad application prospects. Rotating detonation engines have attracted significant attention in the global aerospace field in recent years due to their advantages such as high operating frequency, single ignition and low start Mach number. The funding intensity and engineering application progress of various countries in this research field are all in a state of rapid development. In view of this, this paper conducts a comprehensive review of the research progress of rotating detonation in the international community. It analyzes the current research status of multiple key technical problems in turbine-based rotating detonation engines, and elaborately describes the breakthrough progress made by our research team in these fields. Finally, it looks forward to the future development of turbine-based rotating detonation engines and puts forward development suggestions for each research direction. The subsequent research work on turbine-based rotating detonation engines will focus on three application directions: internal/external afterburning detonation and turbine-ramjet rotating detonation combined engines. Key technical challenges such as reliable initiation of combustor over a wide range, modulation and propagation stabilization of detonation wave modes, optimization of combustor and injection structures, suppression of pressure feedback, efficient thermal protection of combustor, and stable matching of engine will be overcome to accelerate the engineering application of rotating detonation engines.

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.

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.

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.

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. 

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.

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.

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.

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.

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. 

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.

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.

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.

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.

Global warming is one of the major challenges for the mankind. In order to reduce CO₂ emissions, it is necessary to build a new low-carbon/carbon-free and sustainable energy system. Ammonia, with its excellent fuel properties and carbon-free characteristics, as well as its ease of liquefaction and storage, shows great potential for development in the energy transition. However, there are challenges in the ammonia combustion process, including flame instability and high NO_x emissions. This paper reviews options to improve the flame stability and reduce NO_x emissions of ammonia through the addition of reactive small molecules, hydrogen-ammonia co-combustion, oxygen-enriched combustion technology, plasma-assisted combustion, and mild combustion. When hydrogen-ammonia fuel is used in combustion engine oriented, the ammonia combustion flame is more stable at high pressure, and the rich and lean combustion blowout equivalence ratio can be slightly prolonged by increasing the pressure due to the enhanced combustion intensity and denser flame at high pressure. Liquid ammonia has energy consumption and cost issues for combustion engine applications, but the stability of its spray flame can be improved by preheating the air and co-firing small molecule fuels.

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.

Membrane electrode assembly (MEA) is a key part of electrocatalytic carbon dioxide reduction (eCO₂RR), which converts carbon dioxide into valuable chemicals and fuels. This paper proposes a structural design of a CO₂ reduction electrolyser based on a membrane electrode assembly to simultaneously achieve the diffusion of CO₂ and the timely discharge of the product carbon monoxide (CO). The experiment investigated the effects of different flow channel configurations on the catalytic activity, product distribution and current density of the reaction system. The results showed that the vein-shaped bionic flow channel achieved a CO Faraday efficiency of up to 96.72 % at a cell voltage of 2.5 V and a current density of 115 mA·cm⁻². Combined with numerical simulation, the coupling relationship between CO₂ mass transfer and electrochemical reaction was established. 

To deeply investigate the distribution of liquid water in the proton exchange membrane fuel cell, a two-dimensional model of non-isothermal two-phase flow including gas-water-heatelectricity-force multi-physical fields was developed in this paper to simulate the cell performance and liquid water distribution of two different types of gas diffusion layer (GDL) materials at the operating conditions of 80°C, 200 kPa abs, and 80% RH. Performance tests and neutron radiograph experiments were also conducted and compared with the simulation results. The results show that the cell with Freudenberg GDL have a better performance compared to the cell with Toray GDL, especially at high current density. The peak liquid water saturation using Toray GDL occurs in catalyst layer under the ribs, and it can reach to 0.4. The peak liquid water saturation using Freudenberg GDL occurs in the gas diffusion layer under the ribs, and it can reach to 0.25.

With the development of electric vehicles and electronic devices, the two-phase immersion cooling technology using dielectric coolants has gradually attracted attention due to its significant advantages in temperature control performance and integration. The demand for the application of this technology in low-temperature conditions is also increasing. However, there is currently limited research on the boiling heat transfer of dielectric coolants, especially at low temperatures. This study investigates the effect of liquid static pressure on the boiling heat transfer characteristics of Novec 7100 on a smooth copper surface under low saturation pressure conditions using an airtight experimental system with controllable saturation pressure (temperature). The experiment reveals a unique trend of critical heat flux decreasing first and then increasing with decreasing saturation pressure. After the saturation pressure drops below 8.34 kPa, the pool boiling process exhibits “intermittent boiling” and “self-induced subcooled boiling” as two distinct heat transfer modes, and the critical heat flux increases with the liquid height. When the saturation pressure is 0.741 kPa, the critical heat flux values at liquid levels of 23 mm and 35 mm show the greatest difference, approximately 39 kW/m².

The electrode structure plays a vital role in mass transfer processes within Proton Exchange Membrane Fuel Cell (PEMFC) systems. This study involved the reconstruction of an orderly graded porous micro-porous layer (MPL) and stochastic gas diffusion layers (GDLs), giving rise to a graded mesoporous structure and uniform microporous gas-liquid separation channels in the MPL. Leveraging the Lattice Boltzmann Method (LBM), the Shan-Chen multiphase pseudopotential model was employed to investigate the mechanisms of liquid water transport within the orderly graded porous architecture. Subsequently, the liquid water saturation in the GDL and gas content in the MPL under various operating conditions were examined. The findings revealed that an ordered positive gradient porous structure can efficiently remove liquid water while retaining more reaction gases at appropriate driving pressure differences and flow rates. Conversely, wetting gradient designs struggle to strike a balance between water removal efficiency and gas retention. Consequently, by optimizing operational conditions, an ordered positive gradient MPL can significantly enhance liquid water management in PEMFCs, thereby boosting their electrochemical performance. 

As concerns about climate change continue to grow, the conundrum of how to produce carbon-neutral fuel needs to be addressed. This paper proposes a multi-energy co-generation system with solar thermochemical cycle based on chemical-looping cycle oxygen removal, which uses chemical-looping cycle to absorb oxygen generated by thermochemical cycle to improve the reduction degree of oxygencarrier Through the combined cooling, heating and power system, the hightemperature thermal energy generated by chemical-looping cycle is utilized in a cascade manner to output electricity, cold energy and low-grade thermal energy. The results show that NiO/Ni is more suitable as oxygencarrier in chemical-looping cycle. When the pressure ratio of chemical-looping cycle is 5 and the thermal chemical cycle reduction temperature is 1500°C, the solar utilization efficiency and exergy efficiency reached 28.5% and 23.5% respectively, and when the reduction temperature rose to 1600°C, these efficiencies rose to 32.2% and 25.5% respectively. The use of multi-energy cogeneration system can save 57.4% of methane and reduce carbon emissions. Theoretical calculation shows that if the energy supply of the multi-energy cogeneration system is completely relied on, the annual energy consumption per capita of Beijing and Shanghai residents needs 12.1 m² and 7.3 m² of concentrating area.

The conventional single-stage compression auto-cascade heat pump (SACHP) has tough issues such as high compressor discharge temperature and low heating efficiency at the low ambient temperature. Therefore, the concept that the graded compression of high and low boiling point component matches with the fractionation of low boiling point component is presented to develop a double-stage compression auto-cascade heat pump (DACHP) with R290/R600 as the working fluid, which helps reduce the compressor discharge temperature and power consumption, and improve the heating performance of the proposed DACHP. Based on the thermodynamic mathematical model, the cycle performance of DACHP is compared with SACHP. The results indicate that there is an optimal composition ratio for DACHP to obtain the highest heating coefficient of performance (COP), with the maximum COP of 2.44 at the R290 mass fraction of 0.61. When the evaporator outlet temperature varies from −24°C to −10°C, the average discharge temperature of DACHP decreases by 24.09°C, and the average compressor power consumption of DACHP reduces by 55.49%, compared with the SACHP. The compressor power consumption of DACHP is 52.82%∼56.61% lower than that of SACHP, while its COP increases by 0.90∼0.95 as compared with DACHP, as the condenser outlet temperature ranges from 50°C to 65°C. Double-stage compression auto-cascade heat pump is suitable for application in cold areas or severe cold areas.

Based on the decisive relationship between material structure and physical properties, a method for regulating thermal properties of materials was proposed by generating microstructures through 3D printing technology. The 304L stainless steel with different 3D printing scanning speeds was prepared, and the correlation between porosity, thermal conductivity and scanning speed was established by microstructure characterization and thermal property measurement, and the nonlinear relationship equation k = 14.43 + 4.25 exp(−v/1187.7) between thermal conductivity and scanning speed was obtained based on the experiment. The prediction and experimental verification of the thermal conductivity of the new sample with a scanning speed of 1500 mm/s and the error of 0.6% indicates the validity of the above correlation between thermal conductivity and scanning speed. In addition, a two-dimensional heat transfer model of the microporous structure of the 3D printed samples was established, and the effect of the pore structure on the overall thermal properties of the material was investigated in detail.

Heat dissipation with high heat flux has always attracted much attention. In this paper, a heat dissipation scheme of liquid metal jet impinging cooling is proposed in order to achieve efficient heat dissipation on the surface with high heat flux density. Using Ga₆₈ln₂₀Sn₁₂ and Na₂₂K₇₈ as working fluids, the numerical simulation of impinging heat transfer of liquid metal jet was carried out, and compared with water jet. In addition, the firing distance and inlet velocity were changed to explore their effects on the heat transfer performance of liquid metal jet. The results show that under the same working conditions, the average heat transfer coefficient of Na₂₂K₇₈ jet and Ga₆₈ln₂₀Sn₁₂ jet is 3.7 and 6 times higher than that of water jet, respectively. And the heat transfer performance is the best when the firing distance is less than 2 times the jet aperture. Changing the firing distance in the jet core area has little effect on the heat transfer performance. While continuously increasing the firing distance beyond the core area will not be conducive to heat transfer. The inlet flow rate has a significant effect on the heat transfer performance. So increasing the flow rate can enhance the heat transfer, but the enhancement effect will gradually weaken. The research results of this paper are of reference value for the study of heat dissipation with high heat flux.

In order to eliminate the influence of the discontinuous curvature on the performance of the compressor airfoil and improve the optimal design capability of compressor cascade, a parameterization method with a continuous-curvature surface was proposed. The curvature continuity condition of the two Bezier curves at the connection point can be achieved, by using the connection of the endpoint guide vector and the control point of the Bezier curve to make the corresponding control point satisfy a specific relationship. Based on this property of the Bezier curve, the leading edges and trailing edges of the compressor blade are reconfigured. In order to remove discontinuous curvature at the connection point between the leading edge and the airfoil，the least squares method was used to fit the suction section and pressure section of compressor airfoil in the parameterization process. The numerical simulation method is used to calculate the flow field, and the aerodynamic performance of the parameterization airfoil and the original airfoil are compared. The results show that the parameterization method can obtain a continuous-curvature surface, which can effectively improve the flow condition of the leading edge and improve the aerodynamic performance of the compressor airfoil.

A combined cooling, heating and power(CCHP) system with solid oxide fuel cell (SOFC) coupled with chemical chain combustion (CLC) carbon capture is proposed. After methanol reforming, H₂ is separated by membrane separation technology to drive SOFC to generate electricity, and the remaining syngas is burned into the chemical chain to achieve carbon capture, and supercritical carbon dioxide (SCO₂) Brayton cycle, absorption refrigeration system (ARS) and heating system are integrated to realize cascade utilization of energy. The performance analysis models of key components and the whole CCHP system are constructed, and the effects of key parameters such as reforming reactor temperature, water-carbon ratio, SOFC operating pressure and temperature on the system performance are studied. A combination of energy analysis and analysis was used to comprehensively evaluate the performance of the system. The energy efficiency and exergy efficiency of the new system reach 66.29% and 57.70%. Compared with the reference system of traditional CCHP system with SOFC without integrated with chemical chain combustion, after achieving a CO₂ capture rate of more than 99%, the power generation efficiency of new system is about 1.95% higher than that of the reference system and the exergy efficiency of new system has an increase of 0.75%.