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.

Carnot battery (CB) is a novel electricity storage technology which could realize electricity storage and waste heat recovery simultaneously. The thermal integrated CB (TI-CB) only utilizes the waste heat energy during the charging process in previous study. The waste heat energy utilization is insufficient. A CB with thermal integration during charging and discharging process (DTI-CB) is proposed in this paper. The waste heat energy is effectively integrated with DTI-CB in all periods through being coupled to the Organic Rankine cycle (ORC). A thermo-economic evaluation of the proposed DTI-CB is conducted. Compared with TI-CB, the power output capacity could be increased 95.67% and the Levelized cost of storage could be reduced 30.90%. The thermoeconomic performance of the proposed DTI-CB performs better than those of the single ORC and CB under the conditions with relatively higher heat utilization load. 

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.

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%.

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. 

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.

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.

Northwest China is rich in wind and solar resources. In recent years, new energy power generation systems based on wind and solar energy have developed rapidly. However, due to factors such as productivity and population, the power load in the northwest region is low. In addition, the random and unstable characteristics of new energy make the phenomenon of abandoning wind power and solar power seriously. Some studies have shown that the problem can be solved by new energy power generation coupled with hydrogen energy storage technology. Based on the concept and structure of the combined wind and solar power generation coupled electrolyzer hydrogen production system, take the hydrogen production rate of system as the research goal. A hybrid architecture model including wind power generation system, photovoltaic power generation system and electrolyzer was established under the MATLAB/Simulink. Through this model, the characteristics and laws of hydrogen production in the natural environment of the northwest region were explored.

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.

A Kalina-organic Rankine combined cycle model is built in this paper. Constructal thermodynamic optimization of the combined cycle is conducted under the condition of the fixed total heat transfer area of the heat exchangers by combing constructal theory with finite time thermodynamics. The combined cycle thermal efficiency is chosen as the optimization objective, and the structural parameters of the components in the combined cycle are employed as the optimization variables. The optimal performances among the combined cycle, single Kalina cycle and single organic Rankine cycle are compared under the same conditions. The results show that the combined cycle thermal efficiency after optimization is improved by 40.83% compared with the initial design point. Compared to single Kalina cycle and single organic Rankine cycle, the combined cycle net power output of the combined cycle is improved by 49.89% and 66.82%, respectively, while the combined cycle thermal efficiency is improved by 57.76% and decreased by 4.69%, respectively. The optimization results can be used to guide the optimal designs of low-temperature waste heat resource utilization systems.

A two-dimensional axisymmetric mathematical model was developed for an adiabatic hydrogen storage reactor based on the magnesium hydride and magnesium hydroxide. A sandwich reactor was proposed and compared with conventional sleeve reactor, the effect of hydrogen pressure and Mg(OH)₂ thermal conductivity on hydrogen storage and thermal storage performance of the sandwich reactor was investigated. The results show that the sandwich reactor exhibits a larger heat transfer area and lower heat transfer thermal resistance than conventional sleeve reactor, which results in faster heat transfer and hydrogen storage rates. Increasing the hydrogen pressure can enhance the heat transfer between metal hydride and thermal storage material and accelerates the hydrogen and heat storage rates. In addition, improving the thermal conductivity of Mg(OH)₂ is essential to further improve the performance of the sandwich MgH₂-Mg(OH)₂ reactor.

In this paper, the ion diffusion coefficients and thermal conductivity of solid polymer electrolytes (SPE) containing poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonylimine) salt (LiTFSI) with different end group of PEO are investigated and the structural properties are analyzed to study the ion transport and heat conduction mechanisms. The results showed that the poly(ethylene glycol) dimethyl ether (PEGDM) based SPE has better ion transport performance because more free lithium ions can be transported. However, the thermal conductivity of PEGDM is worse because the phonon spectrum is shifted to higher frequencies, which suggests that enhanced high-frequency phonon scattering leads to lower thermal conductivity. These findings provide valuable guide for PEO-LiTFSI electrolyte design.

As derived concepts of exergy, the application of the energy quality and energy grade has achieved great success in the practice of thermal science in the past four decades. However, their concepts and calculations have not been fully clarified, and the summary and induction of relevant applications are very rare in the literature database. Based on literature research, this paper explains the history of the energy quality and energy grade concepts, and expands the calculations and corresponding environmental reference states in detail. Moreover, analysis methods derived from the concepts and their applications are reviewed to better understand the functions of energy quality and energy grade. In addition, the concept of energy potential in the context of thermodynamics is preliminarily sorted out. This paper clearly shows the history and progress of the research in the field of energy quality, energy grade, and energy potential, which is helpful for the definition and thinking of related concepts.

In order to obtain the optimum design parameters of the supercritical carbon dioxide power system, this paper establishes a thermal analysis model of system and main equipment. parameter performance analysis and multi-objective optimization design of the supercritical carbon dioxide power generation device system with a heat pipe reactor is carried out. We develop an optimal solution set of power generation device system parameters with an output power of 1 MW(e), and conduct system sensitivity analysis. The research results indicate that increasing system parameters can achieve the goal of improving system cycle efficiency, but it also increases the size and scale of the equipment, which is unfavorable for improving compactness. The sensitivity of various main thermal parameters to system efficiency and volume varies greatly. The final optimization solution can be selected from the optimum solutions set in this article, based on the size of the available space, in order to obtain the optimum design parameters with better efficiency and compactness.

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).

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.

A novel concentrating solar photovoltaic and thermal (CPVT) system using multi-plate mirror concentrator and water-based Ag/CoSO₄ nanofluid spectrum splitter is designed in this paper. The water-based Ag/CoSO₄ nanofluid is prepared and measured. The results reveal that the absorption and transmission rates of the Ag/CoSO₄ nanofluid are 42.3% and 57.7% in the full spectrum range. The optical analysis results of the CPVT system show that the optical efficiency of the system is 96.34%. The thermodynamic analysis reveals that the photoelectric efficiency of the PV module and that of the CPVT system are 28.9% and 16.7%, and the thermal and exergy efficiencies of the CPVT system are 40.9% and 22.3%. With the inlet nanofluid flow velocity increased from 0.004 m/s to 0.008 m/s, the exergy efficiency of the CPVT system decreases from 24% to 21%, while when the inlet nanofluid temperature increases from 278 K to 298 K, the exergy efficiency increases from 22% to 23.2%.

Accurately obtaining the thermal properties of high-temperature gas is the basis for numerical simulation of rocket engine nozzles. Since it is extremely difficult to obtain the thermal conductivity of gas at high temperature by experimental methods, it is a better choice to predict the thermal conductivity of gas at high temperature based on theoretical calculation methods. In this study, the thermal conductivities of H₂, CO, and N₂ gases in the temperature range of 300 K to 4000 K were calculated using the Istomin correction considering high-temperature electronic excited states. Combined with the Wassiljewa equation, a theoretical prediction model for the thermal conductivity of multi-component gas mixtures at high temperatures was constructed, and the thermal conductivity of the gas mixtures of the two combustion gases in the temperature range of 300 K to 4000 K was predicted, providing gas reference thermal property data for the refined simulation of the rocket engine nozzle.

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.

The infrared radiative signature of the military target is determined by the emissivity of the infrared atmospheric window and the temperature level. Conventional infrared stealth coatings exhibit low emissivity across the whole infrared band but lack effectively radiative cooling through non-atmospheric window. This work designs a set of infrared stealth multilayered films structure based on deep neural network, incorporating germanium, platinum, and silicon arranged in order for compatible radiative cooling. The analysis reveals that the structure achieves a low average emissivity of 0.20/0.23 within the infrared atmospheric window detection bands of 3∼5 μm and 8∼14 μm, while maintaining a high average emissivity of 0.87 within the non-atmospheric window band of 5∼8 μm, thus facilitating efficient radiative cooling. Furthermore, the designed structure shows strong robustness regarding the polarization and incidence angle of the incoming electromagnetic wave. The spectral selectivity of the structure is attributed to the selective transmission of the germanium layer, the Fabry-Perot resonance generated by the Pt-Si-Titanium alloy TC4, as well as the intrinsic absorption of the Pt layer and TC4 substrate.

The application, screening, evaluation and funding of National Natural Science Foundation of China programs in Engineering Thermophysics and Energy Utilization Discipline in 2023 are summarized and statistically analyzed. The strategic research, funding proposals in the field of energy conversion and utilization under the carbon peaking and carbon neutrality goals are introduced. The outstanding achievements funded by the discipline in 2023 and future work in 2024 are introduced as well.

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.

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.

Proton exchange membrane fuel cells are widely used in the field of electric vehicles, and the flow field design has an important impact on the performance of the battery. In this paper, the effects of three different flow fields on the gas distribution, temperature distribution and water removal performance of the battery were studied through three-dimensional multiphase and multiphysical field numerical simulation. The results show that the slot flow field design can significantly enhance the lateral mass transfer under the ribs. Compared with the parallel flow field, the uniformity of the distribution of gas, temperature, current density and liquid water is significantly improved, and the performance is improved.

As a typical kind of air pollutants, VOCs has hazardous effects on both the gas environment and impair human health. Abatement of VOCs is the major requirement of China’s ecological environment. Simultaneously, it is the significant content of China’s 14th five-year plan. Based on the economic development, emission source of VOCs in China has been illustrated. Furthermore, the national, local and industrial regulations of VOCs emissions have been concluded. Abatement techniques of VOCs have been compared and analyzed, including various recovery and destruction techniques. The multi-technique characteristics has been concluded. Finally, the dominant abatement technique in the future was prospected.

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.

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.

Gas-solid fluidized beds have been widely studied and applied in chemical, metallurgical and pharmaceutical fields. An in-depth study of the kinetic behavior of gas-solid two-phase flow in fluidized beds is beneficial to the design and performance optimization of fluidized bed equipments. In this study, a data-driven full 3D deep time-series model is constructed using the deep learning technology to learn the complex kinetic behavior of 3D gas-solid two-phase temporal flow fields in the fluidized bed. With this model, it is able to achieve a reasonable prediction of the velocity fields of gas and particle phases in the fluidized bed under unknown incoming flow velocity conditions. The test results show that the prediction results of this full 3D intelligent model are highly consistent with the CFD calculation results, and have good generalization ability. In addition, the model is hundreds of times faster than the traditional numerical simulation and can be used for fast prediction of the flow field to alleviate the time-consuming issue of numerical simulation.

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.

This work investigates the heat transfer performance of a porous thermal storage wall (PTSW) based on a composite sorbent of hydrates for the solar energy direct storage and conversion process under dynamic variations in solar irradiance and ambient temperature. The results indicate that during the charging phase with solar irradiation, the temperature of the PTSW and the outlet air temperature of the channel first increase and then decrease, reaching their maximum values at 14:30, approximately 67.5°C and 47.9°C, respectively. Before 20:00, the outlet temperature remains above 30°C, and the desorption conversion rate at this time is 0.82. During the discharging phase, the temperature initially increases and then stabilizes. The adsorption conversion rate at 09:00 the next day is approximately 0.75, and the outlet temperature during the stable period is around 39.7°C. This PTSW enables the efficient utilization of solar heat with extended heating periods.

Utilizing 70◦C low-grade heat sources discharged by low-temperature proton exchange membrane fuel cells for the efficient supply of cooling capacity is the key to enhance the efficiency of combined cooling and power systems. In this paper, a hybrid adsorption refrigeration system using solid desiccant cooling system is designed and experimentally studied to recover 70^◦C low grade heat and realize efficient cooling and dehumidification. Results show that the hybrid system can be operated effectively under a heat source temperature of 70^◦C. Increasing inlet air temperature or relative humidity can facilitate the system performance promotion. The cooling capacity and COP are up to 3.95 kW and 0.539, respectively. Using such hybrid system to exploit 70^◦C low-grade heat sources can significantly improve the overall efficacy of proton exchange membrane fuel cells, reaching 67.3%.

R1234ze(E) and R600a are considered as promising environmental-friendly alternative refrigerants and accurate heat transfer data is essential when R1234ze(E) and R600a are applied in engineering practice. In this study, heat transfer coefficient prediction models are developed by using R1234ze(E) and R600a experimental data through a back-propagation (BP) neural network. The prediction result of new models is better than the classical heat transfer model in the literature. To expand the prediction ability of the model, a more general heat transfer prediction model based on R1234ze(E) and R600a is also developed. For R1234ze(E), the average relative deviation (ARD) of prediction results is 4.08%, average absolute relative deviation (AARD) is 8.46%, λ10% is 70.2%; for R600a, the ARD of prediction results is −3.59%. AARD is 6.98%, λ10% is 76.4%. The ARD range of the prediction results for six works of literature is −17.9% to 26.8%, AARD is no more than 27.6%, and λ30% is not less than 60.0%, which shows that the model in this study has certain prediction accuracy and universality.

With the improvement of the integration and power density of electronic devices, the high power consumption and high integration of electronic chips will make the heat dissipation of electronic devices continue to increase. Therefore, heat dissipation has become one of the main bottlenecks in the performance development of high-performance electronic devices. In this paper, a microchannel heat sink with airfoil ribs is proposed, and the airfoil ribs can enhance heat transfer by locally accelerating of fluid flow and mixing of fluid flow. ANSYS FLUENT was used to analyze the influence of the main geometric parameters of airfoil rib such as attack angle, exit angle, length and number on the flow and heat transfer characteristics of microchannel. It is found that the influence of rib length and rib number on the flow resistance and heat transfer performance of the microchannel is more significant than that of the attack angle and the exit angle. Compared with smooth microchannel, the proposed microchannel with airfoil ribs shows better comprehensive heat transfer enhancement performance under the constrain of same pressure drop.

In this paper, the high-temperature structure in stretched turbulent flames of hydrogenrich gaseous fuel are studied. The Laser Tomographic Visualization (LTV) and numerical simulation methods are used to quantitatively characterize the structural changes in the high-temperature region in laminar and turbulent cases. The results show that the thickness of the high temperature zone in the flame increases with the increase of equivalent ratio. With the increase of the outlet flow rate, the strain rate of the flame is increase, and the thickness of the high temperature zone decreases. The laminar flame is relatively stable, so the position and shape of boundaries of the high temperature region are relatively steady. The turbulent vortexes will destroy the structure of the high temperature region, resulting in drastic fluctuations and bends of the high temperature boundary. With the increase of turbulence intensity, the thickness of flame high temperature zone also increases. Compared with the changing trend of flame high temperature zone boundary in high turbulence intensity and the energy spectrum analysis results, the results show that flame enters the Thin Reaction Zone (TRZ) combustion mode. 

In this paper, the electrothermal characteristics and failure mechanism of lithium-ion batteries during external short circuit were analyzed, and the performance of batteries without thermal runaway in subsequent use and the potential thermal runaway risk were explored. The results indicated that the temperature and voltage changes of the battery during external short circuits were related to the internal resistance which changes with SOC and short-circuit current. Further external short-circuit batteries were accompanied by phenomena such as electrolyte evaporation, lithium metal deposition, electrode particle rupture, and membrane closure, which affect the internal Li⁺ transport process. The battery without Thermal runaway was tested in the cycle. The battery capacity was recovered in the cycle, and the polarization internal resistance was reduced to the initial level, but the ohmic internal resistance was higher than the initial value. The potential risk of Thermal runaway inside such batteries was analyzed through the secondary short circuit.

In order to investigate the influence of buoyancy effect on heat transfer characteristics of supercritical water, a 3-D numerical model was developed to predict the heat transfer of supercritical water in a vertical smooth tube. This numerical model was used to predict the heat transfer characterisitics of supercritical water under the conditions of system pressure of 25 MPa, mass flux of 600∼800 kg·m⁻²·s⁻¹, and inner wall heat flux of 400∼500 kW·m⁻². The influence of heat flux and mass flow flux on buoyancy effect and the influence of buoyancy effect on heat transfer characteristics were also analyzed. The results show that when the mass flow flux is 800 kg·m⁻²·s⁻¹, the buoyancy effect causes local heat transfer deterioration. After the heat transfer deterioration occurs, the heat transfer coefficient rebounds rapidly. When the mass flow flux is 600 kg·m⁻²·s⁻¹, the influence of buoyancy effect on heat transfer is related to heat flux. When the mass flow flux is 600 kg·m⁻²·s⁻¹ and the heat flux is 400 kW·m⁻², supercritical water heat transfer shows enhanced heat transfer; when the mass flow flux is 600 kg·m⁻²·s⁻¹ and the heat flux is 500 kW·m⁻², the buoyancy effect causes local heat transfer deterioration, and the heat transfer coefficient did not recover after the heat transfer deterioration occurred.

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 make the dynamic modeling and simulation of the utility boilers perform better potential in the applications of flexibility transformation, life extension transformation and control strategy optimization, this paper systematically reviews the current research progress in the field of dynamic modeling and simulation of coal-fired utility boilers. First, the dynamic modeling methods and dynamic simulation tools of utility boilers are analyzed. Then, the research progress of dynamic simulation modeling for steam-water system, combustion system and pulverizing system is introduced in detail, the advantages and disadvantages of different modeling methods for each subsystem are discussed. Next, the application status of the utility boiler flexibility is summarized, including dynamic modeling and simulation of low-load operation, start-up process optimization, residual life prediction and simulation of ‘coal-fired+’ coupled power generation systems. Finally, from the aspects of domestic simulation software, modeling methods, model refinement, system coupling and model validation, the future development trends of dynamic modeling and simulation of coal-fired utility boilers are provide references for subsequent research.