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. 

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 thermal conductivity of soil is a vital parameter in describing its heat transfer properties. Accurate prediction and sensitivity analysis of this parameter can aid in assessing the thermal response in geotechnical engineering and prevent deformation and damage in projects. Based on thermal conductivity experiments by Kersten’s team, we analyzed the factors influencing this parameter. we considered introducing a temperature variable into the traditional empirical formula and conducted validation, resulting in an improved formula with good applicability to clay. Using artificial intelligence algorithms, we established a prediction model for thermal conductivity. The model uses soil type, dry density, water content, and temperature as input variables. Our analysis showed that the Random Forest model, Radial Basis Function Neural Network (RBFNN), and Whale Optimization Algorithm Backpropagation Neural Network (WOA-BP) could all accurately predict thermal conductivity. Among these, the WOA-BP model demonstrated the best performance, followed by Random Forest and RBFNN.We tested the prediction model using a new sample set and found that the model still performed well, indicating a certain level of generalization ability. We employed a Monte Carlo simulation for parameter sensitivity analysis of the improved empirical formula. With the Random Forest model, we ranked feature importance to evaluate the impact of different input variables on model output. Finally, we calculated the sensitivity of influencing factors using a weighted product method combined with WOA-BP. The results from all three methods were consistent. They indicated that the sensitivity of thermal conductivity to changes decreases in the order of water content, dry density, temperature, and soil type.

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.

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. 

A total three-dimensional method for calculating mixing loss is proposed in response to the problem that existing methods for evaluating the mixing loss of film cooling cannot accurately calculate the loss between mainstream and coolant in the area affected by passage secondary flow. Film holes with different compound angles are set in the suction surface based on HS1A turbine guide vane. Under the premise of meeting the requirements from film cooling effectiveness, the loss mechanism is analyzed by controlling the mainstream and coolant parameters. Different models are analyzed by using the entropy creation of mixing as the basis for loss evaluation. The results show that film cooling effectiveness is improved by arranging subregional compound angle holes with entropy creation of mixing increasing. And the loss of film deflection caused by passage secondary flow and film detachment can be reduced by setting compound angles.

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.

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%.

Porous media play a key role in the fields of energy conversion, thermal management and energy storage due to their outstanding advantages such as large surface area, light weight and complex channels. In this paper, the homogeneous porosity and gradient porosity W type porous structure (porosity ε=0.3∼0.5, hydraulic diameter dh=1.33∼3.86 mm) were customized based on the triply periodic minimal surface (TPMS) method. A computational model of combustion reaction of porous media was established to investigate the range of flame stabilization within the W type porous structure and the SC-BCC cubic lattice structure, and the results showed that the flame blowout of W type structure limitation is higher (equivalence ratio φ=0.65 and inlet velocity V_in=0.6∼2.2 m·s⁻¹). Furthermore, the regulation of combustion and heat transfer processes by the W type porous structure with continuous gradient porosity was investigated, and the results showed that the continuous gradient porous structure would significantly broaden the range of flame stabilization by adaptively modifying the heat rejection rate. 

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.

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.

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.

Lignite has high water content, and direct combustion for power generation has problems of low efficiency and large investment. Therefore, the supercritical CO₂ lignite-fired power plant integrated with heat pump pre-drying lignite system was proposed and the coupled thermal calculation model for the supercritical CO₂ cycle power cycle and the heat pump pre-drying lignite system was established. Then, based on a 660 MW reference case, the thermodynamic performances of the lignite direct-fired power plant and the lignite-fired power plant integrated with heat pump pre-drying lignite system are compared and analyzed. The results show that the heat pump drying lignite can increase the power generation efficiency by 1.44% and reduce the standard coal consumption rate by 8.06 g·(kWh)⁻¹. Exergy analysis further shows that the heat pump drying lignite reduces the combustion exergy destruction of the boiler by 4.47% and reduces the boiler exhaust exergy loss by 0.35%, which increases the exergy efficiency of the lignite-fired power plant by 1.29%. And the reduction of the combustion exergy destruction and exhaust exergy loss of the boiler is the main reason for the energy saving. The higher the dryer efficiency, the lignite drying degree and heat pump COP, the more significant the energy-saving effect of the lignite-fired power plant integrated with heat pump pre-drying lignite system.

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.

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. 

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.

Turbine design is a complex and empirical process. To reduce the difficulty of turbine design, this paper proposed a method with uniform flux along radial direction and verified its advantages by the design case of E3 turbine. The results show that the through-flow design is basically consistent with the spanwise distribution of parameters in 3D CFD simulation. The results show that the through-flow prediction is basically consistent with the 3D CFD prediction. And the new design scheme reduces the secondary flow loss at the root of the first rotor and increases the turbine efficiency by 0.5%. The proposed through-flow design method has some advantages in improving calculating stability, reducing time cost and improving turbine aerodynamic performance.

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.

Numerical simulations were performed to study the effects of two factors, water content and contact angle of liquid bridges, on the fluidization characteristics, particle temperature, and particle concentration of wet particles in a spouted bed. Results shows that the number of fluidized particles increases with the height of the spouted bed. When the water content is 0, there is no particle agglomeration in the fountain region; as the water content increases, the flow velocity in the Z direction first increases and then decreases, and obvious agglomeration occurs in the fountain region. When the contact angle increases, the flow velocity in the Z direction first decreases and then increases, with the minimum velocity occurring when the contact angle is 30^◦. The larger the contact angle, the closer the core high-temperature region is to the spout region When the contact angle is 30^◦, the particle movement resistance reaches its maximum value, and the least number of particles escape from the bed layer with the airflow.

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 combination of spray flash and mixing evaporation (FME) was one of the most effective way to process wastewater with high aqueous salt concentration. In this paper, aqueous NaCl solution was selected as working fluid, a comprehensive calculation model for flow field of FME, including movement, evaporation and crystallization of droplets was set up on basis of previous experimental results. Numerical simulation was carried out with initial diameter of droplets between 20 and 200 μm, initial temperature between 100 and 120^◦C, initial mass fraction 0.26, initial speed 20 m·s⁻¹, and air speed of 15 m·s⁻¹, air temperature between 100∼300^◦C, and spray angle between 0 and 90◦ Results suggested that, during the increasing of spray angle from 0 to 90^◦ the main location of crystallization moved from the spray axis to the top of spray plume, making crystal easier to be separated. Besides, with the increasing of spray angle, superheat or air temperature, the average mass fraction of crystallization increased, but the average particle size and crystallization distance decreased. In order to measure the effect of crystallization within a given distance, complete crystallization efficiency was defined as the ratio of the mass flow rate of crystal salt of droplets to the mass flow rate of dissolved salt at inlet. Results suggested that this efficiency could be improved by increasing spray angle or air temperature. A semi-empirical formula for complete crystallization efficiency was proposed, and the main error between its calculated value and the simulated value was in ±35%. Above conclusion could provide technical support for design and operation of industrial desalination system.

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.

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.

Abundant compounds with different pore sizes can be synthesized by modifying the metal sites or inorganic pillar of SIFSIX hybrid microporous materials. The mechanism of the influence of TiF₆²⁻ pillar on the adsorption and charge transfer characteristic of CO₂ is still insufficient. In this study, TiFSIX-3-Fe and TiFSIX-3-Zn are constructed. The adsorption and charge transfer characteristic of CO₂ in TiFSIX-3-M (TiF₆²⁻ is inorganic pillar, M is metal atom, M=Fe, Zn) was analyzed by DFT. The adsorption sites, band structure, adsorption energy, differential charge density and Mulliken population were calculated. The results show that: TiFSIX-3-Fe and TiFSIX-3-Zn have smaller volume, which are 1.26×10⁵ nm³ and 1.22×10⁵ nm³, respectively. The addition of Ti atom improves the band structure of TiFSIX-3-Fe but has no obvious effect on Zn. The highest adsorption energy are −0.356 eV and −0.361 eV, respectively. The differential charge density indicates that the charge transfer is from F atom to C atom. Combined with Mulliken’s population, the charge transfer quantity increases to 0.072 e and 0.075 e, respectively. The addition of Ti atom significantly enhances the adsorption energy and charge transfer characteristics of CO₂. This work provides theoretical guidance for the development of hybrid microporous materials with high CO₂ capture characteristic.

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.

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.

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.

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 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.

For the future deep space exploration missions, the cryogenic propulsion engines are expected to be restartable for many times. Prior to the restart, it is required to chill down the cryogenic propellent pipe lines. Besides, for the cryogenic upper stage, there are also demands for the pipe line chilldown. During the chilling down, there is a tradeoff between the propellent consumption and chilldown time. It is necessary to conduct studies on the chilldown characteristics for cryogenic propellent pipe lines and find efficient chilldown methods. However, due to pipe wall temperature variation and cryogenic fluid properties, the chilldown process involves some complicated two-phase flow heat transfer mechanisms such as nucleate boiling, inverted annular film boiling and so on. In addition, some abnormal phenomenons are also observed. For example, transition boiling occurs at around 120 K of wall temperature, which is much higher than steady state experimental results. In this study, a transient numerical model for the liquid hydrogen pipe line chilldown is established. Different heat transfer mechanisms during the chilldown are analyzed. The numerical model simulation results agree well with NASA’s hydrogen experimental data. According to the model, during the chilldow, large amount of liquid hydrogen is entrained by the vapor, which results in the waste of liquid hydrogen. The wall heat flux comes to its local maximum valve when the wall temperature is around 115 K. This is due to the coexistence of nucleate boiling and film boiling. Thermal resistance of the pipe wall cannot be neglected. Using the multistep flow rate chilldown scheme can reduce the liquid hydrogen consumption of 27.5% without evident chilldown time extension.

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 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.

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.