A finite time thermodynamic (FTT) model of HI decomposition membrane reactor under different sweep modes is established. The sweep flow rate, reaction inlet pressure, permeable membrane thickness and reactor length are taken as decision variables, and the multi-objective optimization is carried out to maximize HI conversion rate, H₂ recovery rate and total entropy generation rate. It is found that the HI conversion rate and H₂ recovery rate are consistent to some extent within a given range of decision variables, but they cannot reach the optimum with the total entropy generation rate at the same time. Compared with the co-current sweep mode, the target values of Pareto front have higher HI conversion and H₂ recovery in the countercurrent sweep mode. Different decision methods are used to select the optimal solution. TOPSIS decision point in cocurrent mode and LINMAP decision point in counter-current mode had smaller deviation factors and could be used as the optimal solution for reactor parameter design.

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.

Based on the quantum law of corresponding states and considering the structural differences between hydrogen isomers, a mathematical model was developed for predicting the transport parameters of low-temperature orthohydrogen and parahydrogen. The results were examined and analyzed, and it was found that the quantum correspondence state principle method could predict the viscosity and thermal conductivity of orthohydrogen and parahydrogen in the temperature range of 20∼100 K and pressure range of 0.01∼10 MPa with good accuracy. The pressure has a significant impact on the prediction accuracy of the model, and the prediction error of the correspondence state principle is basically controlled within 6% when the ambient pressure is less than 1 MPa. Further correction of the physical constants in the model is expected to improve the prediction accuracy of the correspondence state principle.

The optimal cogeneration share coefficient can guide the capacity configuration of cogeneration units and maximize the economic benefits of cogeneration. In this paper, a method for determining the techno-economic optimal cogeneration share coefficient considering the energy consumption characteristics of variable load conditions is proposed, the off-design working condition analysis model of cogeneration system is developed, and the variable load energy consumption characteristics of the case unit are calculated. The techno-economic cogeneration share coefficient is optimized. The results show that the optimal techno-economic heating coefficients are 0.750 and 0.702 respectively when considering and ignoring the energy consumption characteristics of variable load conditions, and the corresponding annual cost saving relative error without considering characteristics of variable load conditions reaches 22.0%. More accurate techno-economic benefits of cogeneration will be obtained by considering the energy consumption characteristics of variable load conditions.

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.

Based on the adaptive demand of the defrosting control method, the degradation of heating capacity (DHC) method was developed in this work to identify the frosty state, and the defrosting effect was evaluated adopting a fully connected neural network (FNN) classification model. Results indicated that in the monitoring case of the ASHP system, the proposed DHC method can effectively identify the frosty state, and the defrosting effect recognition accuracy achieved 91.3% for the trained FNN classification model in the testing data set. Compared with the original defrosting control method, the defrosting frequency, heating loss and power consumption were respectively reduced by 66.3%, 1775 MJ and 1829 MJ, and the SCOP was increased by 8.6% throughout the heating season. The promising results in this work will provide an innovative approach for the implementation and optimization of the defrosting control strategy of the ASHP system in practical operation.

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.

Based on a quasi-steady-state simulation model, a method to optimize the cooling-down rate of an auto-cascade refrigeration system operating with a rectifying column and multi-component mixed refrigerant is proposed in the paper. Targeted on the maximum cooling capacity, the optimal suction pressure-evaporating temperature curve for a specified mixed refrigerant concentration can be obtained, which can be matched by the sectional suction pressure adjustment in the practical applications to reduce the overall cooling-down time, and the concentration of mixed refrigerant can be optimized to further improve the cooling-down rate based on this way. The fastest overall cooling-down time is achieved using the R50/R1150/R290/R600a as the mixed refrigerant (0.35/0.25/0.15/0.25 by mole) and corresponding shifting parameters (including two shifting temperatures −20°C and −105°C) and three shifting suction pressure 700 kPa, 600 kPa and 550 kPa) for the sectional suction pressure adjustment, when the air temperature in the test chamber is dropped from 20°C to −100°C. Calculation results also show that the optimal concentrations are different for different evaporating temperatures, and the cooling-down rate can be improved further if the concentration of the mixed refrigerant can be adjusted during the cooling-down process. The optimization methods used in this paper can also provide references for researches on cooling-down processes of other refrigeration systems using multi-component mixed refrigerants.

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.

A three-dimensional mathematical model of steam condensation flow in a smooth tube based on Euler’s liquid film model was established by using ANSYS FLUENT software. The simulated pipe is 500 mm in length and 38 mm in diameter. Under simulated conditions, the saturation temperature of inlet steam is 70°C, the total heat transfer temperature difference is 5°C and 7°C, and the inlet steam speed is 14∼20 m/s. The simulation results show that the liquid film thickness increases with the increase of the flow distance at the bottom of the pipe, and the liquid film thickness increases first and then becomes stable at the top of the pipe. The larger steam inlet velocity produces higher liquid film thickness. The liquid film flow velocity increases with the increase of the flow distance at the bottom of the pipe, and the liquid film flow velocity increases first and then slowly decreases at the top of the pipe. A larger steam inlet velocity produces a higher liquid film flow velocity.

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.

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).

The safe operation of high-power electronic chips highly requires high-efficiency heat dissipation techniques. Flow boiling heat transfer has received widespread attention due to the high heat transfer coefficient. To accurately simulate the complex two-phase process of flow boiling in a microchannel, a phase change model based on the volume of fluid (VOF) method with phase interface temperature correction is proposed in this paper. The flow boiling heat transfer process in a single microchannel with a single microcolumn is simulated to investigate the effects of heat flux and inlet subcooling by analyzing the evolution of two-phase flow process and temperature field. The results show that due to the local vapor coverage, there is a turning point of thermal resistance for flow boiling in microchannel under different working conditions, and high heat flux corresponds to higher bubble growth rate and nucleation area. A high subcooling will delay the turning point, but the overall thermal resistance will increase.

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.

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. 

When the distance between solid walls is only a few nanometers, the self-diffusion coefficient of fluid is reduced by 1∼2 orders of magnitude due to the nanoconfinement effect, and the effects of pore size, temperature and pressure are significant and complex. It is of great significance to analyze the diffusion mechanism and law of nanoconfined fluid and establish a concise correlation formula. In this study, a wide range of fluid self-diffusion coefficient data in nanopores were obtained through careful calculation and analysis based on molecular dynamics simulation. The mechanism and law of the adsorption effect on fluid diffusion were analyzed, and a novel dimensionless diffusion coefficient, which can simply describe the fluid diffusion behavior, was proposed, and the corresponding correlation formula was established with Knudsen number, which has strong applicability.

In the field of active thermal utilization of nuclear energy, high temperature heat pipes (HTHPs) need to have a large length and ensure superior temperature uniformity. However, the existing research focuses on theoretical prediction of the performance and preparation of the HTHP with a relatively short length. In this paper, the HTHP with the length-diameter ratio of 67 is first prepared, the frozen start-up characteristic is theoretically analyzed, and the frozen start-up and steady heat transfer performance are experimentally studied, and a heating method that could give full play to the excellent heat transfer performance of the HTHP with a large length-diameter ratio is proposed. The HTHP with the length-diameter ratio of 200 is further prepared, and its heat transfer performance is qualitatively verified. The frozen start-up process is investigated by quantitative experiments, and the heat transfer law in the laryngeal region of the super-long HTHP is found.

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.

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.

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.

In the design process of modern turbine blades, the geometric parameters along the radial distribution need to be constantly adjusted, and the design cycle is long. In order to solve this problem, this paper constructs a one-dimensional design method of three-dimensional blade: the blade flow channel is divided into several sub-flow channels along the radial direction, and each sub-flow channel is designed in one dimension to obtain its optimal speed ratio and geometric angle. Then, the one-dimensional design results of each sub-flow channel are superimposed along the radial direction to construct a three-dimensional blade. Using the boundary conditions of the last stage of an F-class gas turbine, the blade is redesigned by this method, and the parameters such as the static blade outlet pressure and the backward angle in the numerical simulation results are used as additional constraints for fine design. The results show that compared with the original design, the optimized turbine has a slight increase in the loss in some areas of the rotor, the flow rate is reduced by 0.26%, but the outlet kinetic energy loss is significantly reduced. At the same time, the wheel efficiency is increased by 1.7%, the total-to-total efficiency is increased by 0.37%, and the shaft work is increased by 1.47%.

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.

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.

One-dimensional analysis of axial compressor plays an important role in the field of compressor design and rapid performance prediction. Based on the incidence angle, deviation angle and a serial of total pressure loss models obtained by classical experiments, a one-dimensional meanline program is established in this paper. The accuracy of the program is verified with a NASA 2-stage compressor from public literature. By comparing the prediction results of four stall boundary
models and three chock boundary models, the suitability of various models under different condition is analyzed, which provides guidance for one-dimensional prediction of compressor flow boundary. Meanwhile, a chock boundary prediction method based on velocity ratio is proposed with less error.

In order to explore the advantage mechanism and flow rate adjustment limit of the variable tandem stator compared with the conventional stator, the variable-angle performance of a two-stage fan under the condition of the conventional stators and the variable tandem stators is analyzed by numerical simulation. The results show that the flow angle at the exit of the stator determines the flow rate of the rotor components in next stage, the flow rate of the stator components can be increased by opening the front blades of the tandem stator, and the overall flow rate of the fan is limited by the flow rate of the stator components. For the intermediate stage, adjusting the conventional stator will cause the change of the inlet and outlet geometric angles to be unmatched. After changing to tandem stator, adjusting the appropriate front blade angle will greatly reduce the stator loss and increase the flow capacity under the same outlet geometric angle. For the exit stage, the tandem stator can adjust the front blade of the series to achieve higher flow capacity and less loss on the premise of ensuring the flow direction of the fan outlet. Compared with the conventional scheme, the efficiency of the tandem scheme is increased by 10%. 

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.

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 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.

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.

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.

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.

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 this paper, common flammable working medium is taken as the object. Based on M06-2X/6-311+G(d, p) optimization calculation of Gaussian 16 W, molecular descriptor data of working medium molecular structure under microscopic model are obtained. At the same time, three different machine learning methods, namely Multiple Linear Regression (MLR), Random Forest (RF) and Artificial Neural Network (ANN), were used to correlate the micro data with the macro experimental data, so as to predict the minimum ignition energy of these working media. The overall R² reached 0.853, 0.782 and 0.906, respectively. The results show that the prediction has good accuracy and robustness. The prediction results can provide theoretical basis for the practicability and safety of the new working medium.

Taylor flow in non-circular cross-section flow channels such as micro-heat sinks and micro-channel heat exchangers has received extensive attention due to its heat-enhancing properties. In this paper, under the boundary of constant heat flux density, air and water are used as working fluids to conduct an experimental study on the heat transfer characteristics of gas-liquid two-phase flow in horizontal pipes with cross-sections of 4 mm×4 mm and 5 mm×3 mm. The effects of different inlet gas and liquid inlet Reynolds numbers and liquid slug lengths on the wall temperature and Nusselt number of tubes and rectangular tubes are discussed. The results show that there are some differences between the liquid phase Reynolds number and the gas phase Reynolds number on the heat transfer coefficient of the rectangular tube and the rectangular tube. The results of this paper provide a reference for the design of microchannel heat exchangers and the establishment of mathematical models for heat transfer of rectangular and square tubes Taylor flow.

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.

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.

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.