Chemical looping can achieve high product selectivity using lattice oxygen in oxygen carriers for partial oxidation of methane. Oxygen carrier La_1−xSr_xFe_0.8Al_0.2O₃ was prepared by sol-gel method for chemical looping dry reforming of methane. The reaction performance of the oxygen carrier doped with different proportions of Sr was tested by thermogravimetric and fixed bed reactor. The experimental results showed that the oxygen capacity of x=0.4 oxygen carrier in La_1−xSr_xFe_0.8Al_0.2O₃ is as high as 1.88 mmol·g⁻¹, with excellent reaction performance and less carbon deposition. The stability of the oxygen carrier La_0.6Sr_0.4Fe_0.8Al_0.2O₃ was further tested for 20 redox cycles. The oxygen carrier maintained excellent redox performance, achieving 61.2% methane conversion, 97.1% CO selectivity, and 1.81 H₂/CO. The material characterization results displayed that the morphology and crystal structure of the oxygen carrier were stable. The results show that La_0.6Sr_0.4Fe_0.8Al_0.2O₃ is an excellent oxygen carrier suitable for chemical looping dry reforming of methane.

The application, screening, evaluation and funding of National Natural Science Foundation of China programs in Engineering Thermophysics and Energy Utilization Discipline in 2024 are summarized and statistically analyzed. The strategic research, funding proposals in the field of energy and power under the carbon peaking and carbon neutrality goals are introduced. The outstanding achievements funded by the discipline in 2024 and future work in 2025 are introduced as well.

Heat pump heating technology can effectively reduce the energy consumption and environmental pollution caused by coal-fired heating. However, the low-temperature adaptability of commonly used heat pump heating systems is poor, making it difficult to meet the heating demand in cold regions. Considering that Stirling heat pump technology has a wide range of available temperature zones, an electrically-driven free-piston Stirling air source heat pump is developed in this paper to investigate its heating performance under different climatic conditions. The experimental results show that the overall coefficient of performance of the Stirling heat pump reaches 2.31, 1.97 and 1.78 for normal, cold and very cold regions, respectively. In addition, the relative Carnot efficiency of the Stirling heat pump gradually increases with rising heat-pumping temperature difference. Its advantage is more obvious at large heat-pumping temperature difference.

Aiming at the problems of low power generation efficiency and water high consumption in the chemical recuperated gas turbine cycle, a chemical reinjection gas turbine cycle is proposed in this study. It is proposed that part of the flue gas in the gas turbine was put back into the reactor, the reaction of methane self-reforming reaction, and realize the efficient transformation of methane conversion rate. The technology features fully realize the effect of improving the quality of gas turbine flue gas waste heat, and improving the circulation work. Through the improvement of the fuel energy conversion process and the optimization of the heat transfer process of the system, the power generation efficiency of the new system is increased by 9.12% compared with that of the chemical heat recovery system at the design point, the performance of the power generation of lower pressure ratio and high gas turbine inlet temperature is better. The economic analysis shows that the economic payback period of the system is 2.3 years, which has good economic benefits. 

The Brayton cycle is characterized by high efficiency and compactness, making it suitable for use in nuclear reactor thermal-electric conversion systems. In the present work, a system simulation model was built based on EBSILON software for four open Brayton cycle configurations: simple cycle, simple regenerative cycle, reheat regenerative cycle, and intercooled reheat cycle, and key parameters were analyzed. The cycle parameters were optimized with the objectives of cycle efficiency and power density, and compared with the closed Brayton cycle. The results revealed that among the four configurations, the reheating and recuperative cycle achieved the highest cycle efficiency at 25.44%, while the simple recuperative cycle demonstrated the highest power density, reaching 171.13 kW·m⁻³. Improving the open cycle into the closed Brayton cycle increased the maximum cycle efficiency by 12.56 percentage points and the maximum power density by 11.87 kW·m⁻³.

The common bulkhead tank is one of the most efficient forms for cryogenic propellants, and the non-loss storage technology in the common bulkhead tank is the key issue. A cold shield model designed for the common bulkhead and zero boil-off storage is built based on the liquid oxygen/liquid methane common bulkhead and zero boil-off storage experiment system. The coefficient of temperature variation that considers the location variation characteristic and time variation characteristic of the temperature during the transient heat transfer and flow process is proposed. Compared with the nonuniformity coefficient, the coefficient of temperature variation is more suitable to evaluate the thermal uniformity of the cold shield. The results show that the cold shield with coiler performs an excellent thermal uniformity, the maximum coefficient of temperature variation of the cold shield is 3.85%.

In this paper, a flow calorimeter was developed for the measurement of isobaric specific heat capacity (c_p) at low temperature. The calorimeter was composed of four parts: thermostatic bath, flow system, calorimeter and data acquisition system. The calorimeter can measure the c_p in the temperature range of 115 ∼ 340 K, and the pressure can reach 8 MPa. The uncertainty of temperature, pressure and heat capacity were 11 mK, 0.02 MPa and 0.9%, respectively. The c_p data of propane, isobutane, ethane and ethane + propane binary mixtures at low temperature were measured. The measured data showed a good agreement with the calculated values of high-precision Helmholtz equation of state. The average absolute relative deviations of propane, isobutane, ethane and ethane + propane was 0.26%, 0.32%, 0.31% and 0.38%, respectively, which verified the reliability of the device.

The exploitation of natural gas hydrate is a major strategic demand of the country, and further improvements in 
production and efficiency are needed before its commercial development. How to realize its efficient exploitation depends on the thermodynamic mechanism of the hydrates. Traditional hydrate thermodynamics studies are limited to phase equilibrium characteristics and lack the consideration of non-equilibrium thermodynamics in the hydrate decomposition process. At the same time, the hydrate decomposition process may be accompanied by icing and melting. The thermodynamic characteristics of hydrate exploitation under complex heat and mass transfer conditions need to be clarified. In this study, a 2 L natural gas hydrate depressurization decomposition experimental system was used to simulate the hydrate reservoirs with different distributions and perform long depressurization (to 1.0 MPa) at a constant exhaust rate of 0.55 L·min−1(normal conditions). The results show that there is a non-equilibrium thermodynamic relationship (T[°]=8533.8/{38.98−ln(1000p[MPa])}−275.25) between the temperature and pressure in the hydrate-bearing area during the depressurization process, which is only controlled by the hydrate decomposition and is not affected by the reservoir temperature gradient. According to the Gibbs phase law, the thermodynamic freedom of phase transition process is 1. As a result, the natural gas hydrate decomposition belongs to the phase transition process, and the quantitative relationship between temperature and pressure is consistent with the thermodynamic theory. When the hydrates depressurize to about 2.1∼2.3 MPa, instantaneous icing occurs in the reservoir, leading to a sudden increase in temperature and accelerating the hydrate decomposition. Due to the constant exhaust rate, the accumulated gas increases the pressure up to 2.36 MPa. It is found that the temperature and pressure of hydrate-bearing reservoir still satisfy the non-equilibrium thermodynamic phase diagram of hydrates before and after icing. This study illustrates the thermodynamic mechanism of phase transition in the presence of heat and mass transfer in the natural gas hydrate decomposition process, which can provide a more practical theoretical basis for the process of exploitation site monitoring.

In order to reduce the energy and water consumption of the cooling system in data center (DC), a DC cooling scheme coupled with radiative sky cooling (RSC) was proposed on the basis of mechanical cooling and direct air-side economizer, the corresponding system configuration and operation strategy were designed, and the mathematical model was established. A modular container DC in Xi’an coupled with the proposed scheme was simulated, and the energy and water saving effects as well as the environmental economic benefits were evaluated. In addition, the regional adaptability of the cooling scheme in 10 typical cities in China was analyzed. The results showed that, the energy saving and emission reduction rate of the proposed coupled cooling scheme (CM) can be attained 55% compared with the mechanical cooling (MCM), and increased by 5.2% compared with the outdoor air humidification scheme (OAHM). Meanwhile, the water consumption is reduced by 18.7%. Additionally, compared with MCM, the energy saving and emission reduction rate of CM in the studied 10 cities is between 42.9% and 78.1%, better energy saving and water saving benefits can be obtained.

District heating system is one of the important carriers for coordinating renewable energy and traditional energy and realizing flexible consumption of renewable energy. Considering the impact of the uncertainty of renewable energy output and user cluster heat load on the dynamic transportation process of district heating network, it is necessary to quantitatively analyze the uncertain variables on both sides of the source and load and the dynamic characteristics of the heating network. This paper first established a dynamic transportation model of the heating network to solve its heat loss and transmission delay characteristics. Secondly, the Gram-Chalier A algorithm was applied to calculate the probability distribution semi-analytical expression of the thermal power of the source and load nodes of the system, and Bayesian credible inference method was used to calculate the fluctuation interval of node thermal power. This paper selected a secondary heating network in Beijing for model accuracy validation and case analysis. The system has 90 nodes and 109 pipes. The results show that the proposed model and algorithm can effectively quantify the fluctuation interval of nodes’ thermal power.

A thermo-economic model was used to analyze the thermodynamic and economic characteristics of a geothermal ORC system. The evaporation and condensation temperatures of typical hydrofluoroolefins (HFOs) working fluids including R1224yd(Z), R1233zd(E) and R1336mzz(Z) were optimized to obtain the maximum net power. The thermo-economic characteristics were analyzed and compared with the traditional working fluids R601, R601a and R245fa. The results show that the evaporation and condensation parameters of R1224yd(Z) and R245fa are close under the optimal conditions. When the geothermal water inlet temperature is lower than 130°C, the net output power of R1336mzz(Z) is the maximum among the selected fluids, which is 1.47%∼1.89% more than that of R1233zd(E); but the heat exchanger area increases by more than 17%. When the geothermal water inlet temperature is higher than 130°C, the net output power of R245fa is the maximum, and the power generation cost is reduced by 15.5%∼16.8% compared with R1336mzz(Z).

Integrating direct air carbon capture (DAC) with renewable integrated energy systems (IES) provides an effective pathway to regional carbon neutrality. The reasonable configuration approach is a prerequisite for the stable, flexible, economic and zero-carbon operation of the overall system. Conventional configuration approaches cannot reflect the dynamic CO₂ mass transfer characteristics and energy consumption differences of DAC adsorption and desorption, resulting in suboptimal or infeasible configurations. To this end, this paper constructs the configuration-oriented DAC models to reflect its dynamic operation characteristics. Based on this, a DAC-IES configuration scheme is established with the annual total costs including investment costs, operation and maintenance costs, renewable curtailment penalties, and negative-carbon environmental benefits as the objective function to obtain the optimal capacity and collaborative operation strategy of each equipment, revealing the flexible operation mechanism of DAC under the background of intermittent fluctuation energy supply. The case study validates the effectiveness and superiority of the proposed configuration method. The analysis also indicates that the flexible operation of DAC systems enables better coordination with renewable energy and more cost-effective carbon capture. 

Constructing a high-efficiency refrigeration cycle is essential for developing efficient refrigeration systems and achieving energy savings and emission reductions in the refrigeration industry. The traditional approaches to constructing refrigeration cycles are often based on expert experience, resulting in subjective and suboptimal cycle structure. This paper proposes an automatic method for constructing a refrigeration cycle with an ejector based on graph theory and heat exchanger separation. The mathematical description of the ejector structure and cycle configuration are determined, and an algorithm for constructing a refrigeration cycle with an ejector is established. The proposed method is applied to construct a refrigeration cycle with an ejector and two-phase recuperator used for freezing. The constructed cycle improves the energy efficiency ratio by 23% compared to the classical refrigeration cycle with an ejector for recovering expansion work.

Entransy analytical model of heat transfer process in stacked porous medium is built, and a new utilization efficiency of Entransy is proposed, meanwhile wave function and field function characteristics of Entransy are found. Based on the model, coupling the cooling curve, surface temperature of cooling products in porous medium, internal temperature gradient, convective heat transfer coefficient along quick freezer, entransy dissipation rate during cooling process are predicted for the first time. Mesoscale characteristics of coupled heat transfer for conduction, convection and radiation in heat transfer process in porous medium have been found. Results show that, volume scale of internal heat transfer core and temperature gradient control heat flux and convective heat transfer coefficient on surface, and wavy characteristics of internal temperature difference decreasing rate affect tendency of heat flux convective heat transfer coefficient. Temperature change trend can be predicted accurately based on along heat transfer coefficient. Porous medium can enhance heat transfer, and scaling factor of heat transfer coefficient without and within porous medium is about 0.6, meanwhile radiation and convection have field synergy characteristics.

The flame fuel cell (FFC) is a novel kind of solid oxide fuel cell, which direct combines the fuel-rich flame and the SOFC. The FFC is a promising technology for small scale natural gas distributed power systems and mobile applications due to its simple setup, wide fuel flexibility and rapid start-up. The working principles and research status of the FFC were introduced at first. Then, the progress made on FFCs were reviewed from aspects of fuel-rich combustion characteristics, the cell performance in fuel-rich flames, as well as the stack integration and system analysis. At last, the development trends of FFCs were forecasted by discussing the super-high temperature fuel cells, the degradation mechanisms, and system scale-up issues.

In order to reduce the influence of alcohol-amine carbon capture system on thermal economy of coal-fired power plants, a carbon capture system was built based on rate model through ASPEN PLUS software, and built a novel carbon capture system integrating rich liquid split process, lean vapor compression process and steam superheat utilization. The results show that when the liquid-rich split ratio is 0.1 and the flash tank pressure is 0.16 MPa, the energy consumption of the novel carbon capture system is the lowest (3.09 GJ/t (CO₂)), which is 20.77% lower than that of the conventional carbon capture system. Among them, the utilization of steam superheat reduces the energy consumption of the system by 11.54%. In addition, EBSILON software was used to build the sub-critical unit thermal system coupled with the carbon capture system. The results showed that when the unit load is 127.55 MW and CO₂ capture capacity is 500000 tons/year, the boiler heat load of the novel carbon capture unit decreased by 1.87% and the coal consumption for power generation decreased by 7.22 g/kWh. It can be seen that the optimization measures adopted in this study can not only reduce the reboiler duty of the carbon capture system, but also greatly improve the thermal economy of the subcritical carbon capture unit.

In order to study the adsorption characteristics of materials with different pore sizes and microporous filling process, the pore adsorption during silicon-N2 adsorption was investigated using a combination of experimental and theoretical methods. The thermodynamic analysis of the adsorption isotherms of the nonporous materials was used to obtain the true Zeta adsorption isothermal constants of the materials, and it was found that the entropy of adsorption in the range of low pressure ratios first increased sharply and then decreased, and then began to increase again after reaching a pole. The molar latent heat is negative in this range, indicating the instability of the adsorbent at this time, from which the unstable interval determines the pressure ratio range of the microporous filling process. The pressure ratio and the corresponding cluster size at the beginning of the pore filling process of mesoporous silica materials were determined using the Zeta isothermal constant of the corresponding system. The cluster molecules were analyzed in relation to the pore size, and the scaling factor decreased with the increase of the pore size, and a physical model was proposed for the earlier merging of clusters at the adsorption sites due to the wall bending of the pores to start the pore filling process.

In this paper, a new solar photovoltaic/thermal system with parabolic trough concentrator and indium tin oxide/ethylene glycol nano-fluid beam splitting is proposed. Indium tin oxide/ethylene glycol nano-fluid is prepared and tested. The results show that the absorptivity and transmittance of the indium tin oxide nano-fluid are 30.9% and 69.1% in the full wavelength range. The optical behavior of the photovoltaic/thermal system is studied and the overall optical efficiency of the system is 89.38%. When the sun tracking error is less than 0.2 ̊, the photovoltaic/thermal system can have an overall optical efficiency which is greater than 84.14%. The operation performance analysis reveal that the photoelectric efficiency of the photovoltaic subsystem is 29.1%, and the overall photoelectric conversion and thermal efficiencies of the photovoltaic/thermal system are 19.1% and 19%. The thermal efficiency of the system can be improved by increasing the inlet indium tin oxide nano-fluid velocity, or by reducing the inlet indium tin oxide nano-fluid temperature and external convectional heat transfer coefficient.

In modern warfare, infrared stealth of military objectives plays an important role in improving their survival and breakout capabilities. In this paper, aiming at the multispectral infrared stealth, i.e., narrow-band high absorption at the active detection wavelength of near-infrared laser (1.54 μm), low emission in the two atmospheric window bands and taking into account the radiative heat dissipation requirements in the non-atmospheric window bands, we combine the rigorous coupled-wave analysis and deep learning methods to reversely design the Ge/Ag/Ge multilayer film circular hole metasurface structure. By analyzing the potential physical mechanisms and the emission and absorption characteristics at different angles for the optimized structure parameters, the multi-band synergistic stealth is achieved.

Sugar alcohols, as high-performance medium-temperature phase change thermal storage materials, have attracted significant attention, and their thermal stability is an important material property parameter that restricts their practical use. This study focuses on erythritol and comprehensively evaluates its thermal stability using three indicators: mass loss, melting point change, and melting enthalpy decay. Additionally, a kinetic model for assessing its thermal stability is established. The results show that the primary gaseous products of heated erythritol include various small molecules, while the solid products mainly consist of the formation of C=O bonds. A comparison of thermal stability characterization parameters such as mass loss, melting point, and melting enthalpy reveals that the melting enthalpy of erythritol decreases by 10.2% in the air atmosphere at 145°C for 48 h, which is significantly higher than the changes observed in the other two indicators. Therefore, melting enthalpy decay is chosen as the evaluation indicator for erythritol’s thermal stability. In a nitrogen (N₂) atmosphere, the activation energy of the melting enthalpy decay model is determined to be 80.0 kJ·mol⁻¹, with a logarithmic pre-exponential factor of 15.14 h−1. Based on the model, further analysis indicates that the half-life of erythritol’s melting enthalpy at temperatures ranging from 120 to 140°C is between 2401 to 7851 h.

As the core power component of the supercritical carbon dioxide (SCO₂) Brayton cycle, accurate analysis of the aerodynamic thermodynamic performance and loss characteristics of the compressor under near-critical conditions is crucial for the efficient operation of the cycle. The compressor is prone to condensation when working near the critical point, and the condensation process is non-equilibrium. In this paper, an SCO₂ non-equilibrium condensation model based on the Euler-Euler source term is established and compared with the equilibrium condensation model to evaluate the impact of the non-equilibrium condensation process on the aero-thermodynamic performance of the SCO₂ centrifugal compressor. The results show that the non-equilibrium condensation model is more accurate in predicting efficiency, and non-equilibrium condensation will cause the compressor to enchance the inlet flowrate and enter near-surge conditions faster.

In this paper, a visual experiment was carried out on the air-water two-phase flow in a vertical pipe with a diameter of 80 mm and a height of 11 m. The experimental condition was selected as the gas superficial velocity of 0.03<J_G<16.53 m·s−1 and liquid superficial velocity of 0.04<J_G<2.00 m·s⁻¹. Based on the data obtained by pressure and differential pressure sensors, the influence of inlet effect on two-phase flow was analyzed. In the bubble flow region, the downward trend of pressure is slow with the increase of gas velocity, and the downward trend is faster in the slug flow. When the flow turns into churn flow, the downward trend of pressure slows down again. With the increase of liquid velocity, the gas velocity corresponding to the trend of pressure drop from slow to sharp at each position increases gradually. When the gas velocity is greater than 10 m·s⁻¹, the gas void fraction near the entrance suddenly increases. With the increase of liquid velocity, the gas velocity corresponding to the gas void fraction surging phenomenon at the entrance decreases gradually.

A novel built-middle photovoltaic Trombe wall with vertical fins was proposed in this study. Based on the first and second laws of thermodynamics, the effects of fins spacing and height on the performance were numerically investigated, and the performance was compared with that of the built-middle photovoltaic Trombe wall without fins. The results show that the thermal efficiency can be effectively improved within a certain range of fins spacing and fin height. Decreasing the fins spacing and increasing the fins height can enhance the electrical efficiency. By introducing the overall exergy efficiency, it is found that the obtained electrical energy dominates the overall exergy efficiency compared to thermal energy. There exists the optimal fins spacing to maximize the overall exergy efficiency under higher fins, and increasing fins height can enhance the overall exergy efficiency of the system. The finned-built-middle photovoltaic Trombe wall has the overall exergy efficiency of 12.74% at 15.625 mm of fins spacing and 45 mm of fins height, which is an improvement of 11.29% compared to the system without fins, and has a great potential for application.

As an important cryogenic fluid with the lowest boiling point (4.21 K), liquid helium is used in various cryogenic systems and cryogenic laboratories. The film condensation efficiency of helium is the key for the performance improvement of small-scale helium liquefaction and recondensation systems using cryocoolers, but there is a lack of targeted theoretical and experimental researches. This study established a CFD model of helium film condensation on vertical surfaces at low temperatures based on existing experimental research. The helium film condensation process on vertical surfaces under different condensing temperature differences was simulated to reveal the heat transfer and liquid film distribution characteristics. This study aims to provide theoretical guidance for the design and optimization of helium condensers in small-scale helium liquefiers.

Based on traditional compressed air energy storage mode, this study proposes a novel cogeneration system integrated methanol chemical looping combustion with compressed air energy storage. In the new system, the air compressor power consumption of the chemical looping combustion is eliminated in discharging process by utilizing excess electricity. Compared with conventional compressed air energy storage, the CO₂ separation without energy consumption can be realized in discharging process of the new system. At the same time, the low temperature compression heat is stored in the charging process. Then the stored heat is used for low temperature methanol reduction reaction, improving low temperature thermal energy grade. The system was simulated in Aspen plus software. Additionally, the effects of oxidizer reaction temperature, pressure, and air flow rate on system performance were studied. Furthermore, based on the reference system of conventional chemical looping combustion, a comparative study of performance was carried out. Besides, compared with conventional chemical looping combustion, the thermal efficiency, electrical efficiency and exergy cycle efficiency of the new system were improved by 16.53%, 5.82% and 9.20%, respectively.

Ammonia has recently received much attention as a novel clean energy with broad application prospects. The paper focuses on the extinction limits of dimethyl ether/ammonia mixtures cool and hot diffusion flames by an atmospheric counterflow burner. The low and high temperature chemical kinetics of dimethyl ether/ammonia are analyzed. The results show that the extinction limits of dimethyl ether/ammonia mixtures cool and hot diffusion flames decrease with the increase of the ammonia blend ratios. For dimethyl ether/ammonia cool flames, the low temperature reactivity of dimethyl ether is inhibited mainly through three aspects: ammonia and dimethyl ether vie OH, DME + NO ⇐⇒ R + HNO and RO₂ + NO ⇐⇒ RO + NO₂. For dimethyl ether/ammonia diffusion hot flame, the high temperature reactivity of dimethyl ether is improved by the reaction of OH, H and O radicals generated by ammonia with dimethyl ether and the reaction of HCCO + NO ⇐⇒ HCNO + CO and HCCO + NO ⇐⇒ HCN + CO₂. Moreover, this research shows that the main oxynitrides in dimethyl ether/ammonia cold flame and hot flame are NO₂ and NO respectively.

In order to investigate the unsteady flow mechanism in the tip region of the axial compressor, a numerical simulation study was carried out to investigate the unsteady evolutionary characteristics of the tip leakage flow field. It was discovered that the dominant frequency of the unsteady flow at the blade tip region was 1863.3 Hz, and the tip leakage vortex formed at the leading edge of the suction surface broke down in one oscillation phase and formed a new vortex structure. Due to the combined effect of the differential pressure between the suction surface and the pressure surface and the leading edge excitation shock wave, the vortex structure gradually moved to the leading edge of the adjacent blades, and during this cross-cycle evolution, the vortex structure appeared to be maintained for about 1/9th of a cycle. In the subsequent cycle, the vortex structure formed by the tip leakage vortex breakdown dissipated while interacting with the broken vortex to form a blockage region in the passage. Along with the influence of the excitation shock wave, this blockage region exacerbated the generation of the “leading edge overflow”phenomenon. It was also hypothesized that the tip leakage vortex breakdown due to vortex wave interference was the key factor in the flow unsteadiness. After the tip leakage vortex broke down, a new vortex structure was formed at the leading edge of the adjacent blade, and a series of evolutionary processes occurred over time, which was the main cause of the unsteady flow in the blade tip region. 

Energy storage is the key technique to establish the new-type power system and achieve the dual carbon goal, and the compressed air energy storage is a highly promising option for largescale long-term energy storage. In this study, an afterburning-type compressed air energy storage system integrated with molten salt thermal storage was proposed, and thermodynamic models of the proposed system were developed. Then, influences of key parameters on system performance under different power loads were evaluated. The analysis results show that the four operation modes of the system can meet four power load demands, i.e., the high power load demand, the medium-high power load demand, the medium-low power load demand, and the low power load demand. Among them, the output power corresponding to high power load demand is 1573.93 kW, and the output power corresponding to low power load demand is 350.15 kW. The roundtrip efficiency of operation mode with low power load is the highest of 69.87%.

Proton exchange membrane electrolysis cells (PEMEC) are widely considered ideal devices for coupling renewable energy sources to produce green hydrogen. However, the local oxygen distribution characteristics within the electrolysis cell and the effect of assembly pressure on cell performance are not yet well understood, posing significant challenges for optimizing the cell structure and enhancing its performance. In this study, the ANSYS Fluent with the user-defined function code is first employed to simulate the three-dimensional multiphase and multi-physical fields of the electrolysis cell. The influence of porosity and contact angle on the oxygen distribution within the porous electrode is investigated. Then the accumulation characteristics of oxygen in the flow channel are determined by the volume of fluid (VOF) method and image recognition, and coupling iteration with the full cell model. Furthermore, a contact resistance model is proposed to analyze the performance of the electrolysis cell under different compression conditions. Results indicate that increasing porosity and reducing contact angle can enhance the mass transfer under the land, and oxygen bubbles tend to generate near the land, subsequently accumulating and growing towards the center of the channel, forming plug flow. When the current density is 0.8 A/cm², neglecting the contact resistance would underestimate the voltage by 0.17 V.

Organic Rankine cycle (ORC) technology can be used for low-grade thermal power generation, and has broad application prospects in renewable energy development and waste heat recovery. With the “double carbon” goal proposed, low-carbon energy and power system has become an inevitable trend. Therefore, the environmental performance index of ORC technology is more and more important. This paper summarizes the research status of the environmental protection performance of the ORC technology in the whole life cycle, summarizes the analysis process of the life cycle assessment (LCA) of the ORC technology, classifies the relevant research according to the type of heat source, summarizes its environmental impact characteristics, evaluates the environmental protection performance of common working fluids, and finally discusses the development trend of the life cycle research of the ORC technology. The study found that the existing inventory data in life cycle assessment is mostly secondary data, and the Recipe method is the most commonly applied evaluation method. The equipment production and substance leakage in the ORC system are important factors affecting its environmental performance.

In this paper, a finless micro-bare-tube heat exchanger with tube bundle diameter varying gradually in the range of 0.4 ∼ 1.0 mm is proposed. The air-side friction and heat transfer performance of micro-bare-tube heat exchangers with bundle diameters varying gradually were studied by CFD simulation. By using the relevant empirical formula and NSGA-II algorithm, the multiobjective optimization of the dynamic friction factor f and heat transfer performance factor j was carried out, and the optimal structural parameters of the micro-bare-tube heat exchanger with varied pipe diameter were determined. When the longitudinal tube wall spacing is 0.214 mm, the transverse tube wall spacing is 1.127 mm, and the tube bundle diameter is 0.876 mm, 0.746 mm, 0.697 mm and 0.550 mm from outside to inside, the heat transfer performance factor j reaches the maximum value of 0.04169, and the flow friction factor f reaches the minimum value of 0.01270. Compared with the equal-diameter finless micro-bare-tube heat exchanger, the new structure not only reduces the pressure drop, improves the heat transfer efficiency, but also saves the amount of metal manufacturing materials and refrigerant charge.

An integrated model of heat source and heat sink, in which circular section isothermal liquid cooling channels are embedded in a cylindrical heating body with uniform heat generation,is established. Based on the constructal theory, given the cross-sectional area of cylindrical heating body and the ratio of channel cross-sectional area as the constraints, the influence of the distribution of liquid cooling channels on the heat dissipation capacity of the integrated model is studied with the number and the radius of liquid cooling channels as design variables, and the optimal constructs with the different ratios of cross-sectional area of liquid cooling channels are obtained. When the ratio of channel cross-sectional area and the number of channels are given, there are optimal center distances, which make the overall heat dissipation performance of heat source-heat sink reach the optimal, but the optimal center distances corresponding to the two indexes are different. When the ratio of crosssectional area of channels is given, the dimensionless maximum temperature and the dimensionless entransy equivalent thermal resistance decrease with the increase of channel number. When the number of channels is given, the dimensionless maximum temperature and the dimensionless entransy equivalent thermal resistance decrease with the increase of the ratio of cross-sectional area of channels. The results obtained in this paper can provide theoretical guidelines for the thermal design of efficient cooling of cylindrical devices.

In view of the complex and variable characteristics of the turbine shroud in actual operating conditions, an impingement-film cooling test platform for turbine shroud with vertical gas-intake and adjustable aerothermal parameters was built in this paper. Infrared temperature measurement technology was used to conduct orthogonal experiment to study the correlation between mainstream Mach number, blower ratio and temperature ratio on turbine shroud cooling characteristics. The results show that the surface average overall cooling efficiency of the turbine shroud presents a trend of decreasing–increasing–decreasing with the increase of mainstream Mach number. In the research range of Mach number is 0.5∼0.8, the turbine shroud has the best overall cooling effect when Mach number is 0.6. By increasing the blowing ratio, the impingement and film cooling effects inside and outside turbine shroud can be gained by increasing the cool-gas flow rate and dynamic pressure. When the blowing ratio increases by 0.5, the surface average overall cooling efficiency of the turbine shroud increases by 1.46%∼9.08%. When the temperature ratio changes from 1.5 to 1.6, the surface average overall cooling efficiency of the turbine shroud decreases by 0.85%∼7.95%.

The applications of catalytic combustion technology cover a number of future strategic industries and therefore are of interests to both fundamental and applied combustion research. In many catalytic combustion processes, gas phase flames are ignited and intricately coupled with the catalytic reaction pathway. This article briefly reviews the latest research progress on premixed laminar combustion in catalytic channels coated with commonly used noble metals, including the controlling equations, numerical models, and conditions of flame ignition and propagation during coupled catalytic-gaseous combustion in microchannels. Several key fuels were reviewed, including hydrogen, syngas, methane, propane, n-decane, etc. Moreover, their distinct flame shapes, propensities of both fuel-lean and fuel-rich flames, and especially the determining factors of chemistry, flow and heat and mass transfer were discussed.

As an important component of the membrane electrode in proton exchange membrane fuel cell, the porosity of the gas diffusion layer has a significant impact on the cell performance. In this paper, a three-dimensional steady-state non-isothermal numerical model of the proton exchange membrane fuel cell (PEMFC) is established. Based on the variational principle, the optimized porosity distribution of the cathode gas diffusion layer is derived with the cathode diffusion layer water content as the optimization objective. The results show that the non-uniformly distributed porosity of the cathode gas diffusion layer is beneficial to the mass transfer of reactants and water in the cell, and meanwhile making the temperature distribution more even, which improves the cell performance. When the voltage is 0.3 V, the output cell current increased by 6.8% and the output power improved by 3.5%.

High-temperature heat pump is recognized as an effective solution for industrial decarbonization. R245fa has widely employed in high-temperature heat pump systems for its favorable thermal properties. Nevertheless, there is currently a dearth of reported research on the condensation heat transfer characteristics of R245fa under high-temperature conditions. This study experimentally investigated the condensation heat transfer characteristics of R245fa within a 9 mm horizontal circular tube at vapor quality range of 0.1∼0.9, mass flux range of 218∼393 kg·m⁻²·s⁻¹, saturation temperature range of 80∼100°C, and heat flux range of 11300∼22500 W·m⁻². Based on a comparison between experimental data and existing heat transfer correlations, modifications are made to the existing correlations. The revised correlations exhibited a mean prediction deviation of 6.11%, signifying a significant improvement in prediction accuracy.

The complex energy and heat conversion processes in microwave-assisted biomass pyrolysis have important effects on product properties. In this study, the thermal history and product distribution characteristics of microwave-assisted biomass pyrolysis under different operating conditions were investigated. To detect the mechanism, a numerical model coupled pyrolysis reaction kinetics and the equations of electromagnetic wave and heat transfer for the microwave-assisted biomass pyrolysis was established. The results indicate that, in comparison to conventional pyrolysis, the distinctive thermal profile of microwave-assisted pyrolysis results in a 0.71 to 7.43 times increase in the synthesis gas yield (CO+H₂) in the pyrolysis gas, along with a 4.87% to 18.8% rise in the selectivity of aromatic hydrocarbon components in bio-oil. By altering the dielectric properties and addition ratio of the microwave absorber, as well as the microwave power, we achieve a certain degree of directional control over the product composition by regulating the heat history during microwave-assistant pyrolysis of biomass.

In order to clarify the characteristics of different zooming strategies, and develop the algorithm of gas turbine hybrid-dimensional simulation for multistage compressor with high pressure ratio. For a split-shaft gas turbine and its 17-stage compressor, the hybrid-dimensional simulation models that coupled zero-dimensional engine model and compressor through-flow model were developed based on the De-coupled approach, conventional iterative coupled approach, fully coupled approach, and the improved iterative coupled approach proposed in this paper respectively. The variations of different zooming strategies were compared and analyzed, the results indicate that the De-coupled approach, iterative coupled approach and fully coupled approach can basically achieve the same simulation accuracy, the maximum relative error between simulation result and experimental data is less than 10%. Moreover, the De-coupled approach tends to converge easily, its simulation accuracy and efficiency are affected by factors such as the quality of characteristic map. Although the conventional iterative coupled approach exhibits high simulation efficiency, its robustness is difficult to guarantee in the zooming of multistage compressor with high pressure ratio. The fully coupled approach has relatively low simulation efficiency and high requirements for both the solving algorithm and the initial value of iterative variables. Meanwhile, the improved iterative coupled approach effectively utilizes the wide pressure ratio range of the 17-stage compressor, exhibiting both high robustness and high simulation efficiency, the effect is optimal.

The split vane impeller is widely used in the petroleum industry because the separation and offset of its blades can handle the gas-liquid flow well. In this paper, visualization and numerical simulation are used to study the gas-liquid flow characteristics in the split vane impeller. In the impeller, the gas pocket first appears at the inlet of the inner blade and the suction surface of the outer blade. The gas pocket is impacted by the fluid from the adjacent flow channel as it extends to the position where the blade is separated and offset. When the Eulerian-Eulerian model is used, the gas-liquid flow in the impeller obtained by numerical simulation is consistent with that obtained by visualization. In the impeller channel, the area occupied by the gas pocket loses the pressurization capability, while the area not occupied by the gas pocket still retains some pressurization capability.