最新刊期
- 摘要：We investigated the quality changes of ready-to-eat pomegranate arils during storage at 5， 15， 25， and 35 ℃. The kinetic parameters of each quality index were fitted using quality degradation kinetic equations， and a shelf life prediction model was developed by integrating the fitting results with the Arrhenius equation. The results demonstrated that the anthocyanin content exhibited an optimal fit with the first-order kinetic model， exhibiting the highest fitting accuracy. A first-order kinetic model with anthocyanin content as the characteristic index was subsequently combined with the Arrhenius equation to construct a shelf-life prediction model. Validation experiments revealed that the mean absolute error between the predicted and actual values was less than 10%， confirming the high accuracy and reliability of the model. This model can effectively predict the shelf life of pomegranate arils over the temperature range of 5-35 ℃， providing theoretical support and methodological guidance for quality maintenance during the circulation and marketing of the product.关键词：ready-to-eat;pomegranate arils;shelf temperatures;shelf life prediction model0|0|0更新时间：2026-04-27
- 摘要：Against the backdrop of the "dual carbon" goals， in this study we aimed to achieve efficient recovery and reuse of low-grade waste heat generated by high-voltage direct current （HVDC） converter valves. Using R515b as the system refrigerant， thermodynamic models and economic models were established. Through experimental testing， the thermodynamic performance variations and economic analysis of evaporative compression heat pumps versus ejector compression heat pumps were compared at different evaporation and condensation temperatures. The results indicate that the COP of the injection compression heat pump was， on average， 8.75% higher than that of the vapor compression heat pump， with the compressor power consumption reduced by 4.78% and the system heating capacity increased by 3.50%. The total friction losses in the injection compression heat pump were primarily concentrated in the condenser and injector， accounting for 32.6% and 27%， respectively. Economically， the net present value of the injection compression heat pump system increased by approximately 10.9% compared to traditional systems， with a dynamic payback period of 4.08 years. The results show that injection compression heat pumps effectively recover expansion losses， enhance the system energy efficiency and economic performance， and provide an efficient and economical solution for recovering waste heat from inverter valves.关键词：converter valve;waste heat utilization;ejector compression heat pump;heating system0|0|0更新时间：2026-04-27
- 摘要：ObjectiveTo address the demand for high-efficiency heat dissipation in railway transportation and aerospace equipment under variable gravity environments， we systematically investigated the flow boiling heat transfer characteristics of water-glycol mixtures in microchannels and developed data-driven predictive models. Although microchannel flow boiling offers a compact cooling solution， its characteristics under variable gravity are not well understood， and traditional empirical correlations lack prediction accuracy. In this study， we aimed to fill this gap and provide a theoretical basis for optimizing cooling systems for both railway and aerospace applications.MethodsBoth experimental and machine-learning approaches were employed to evaluate flow boiling heat transfer performance. A variable gravity experimental platform based on a centrifugal rotating table was established， capable of simulating gravity environments from 1.00g to 3.16g. The experimental system featured closed-loop circulation with a 200 mm-long， 2 mm-inner-diameter copper microchannel test section. Experiments were conducted across mass fluxes of 50-500 kg/（m2·s）， heat fluxes of 100-800 kW/m2， system pressures of 0.1-0.3 MPa， and inlet subcoolings of 10-30 ℃. T-type thermocouples with ±0.1 ℃ accuracy were used for temperature measurements， while pressure transducers and differential pressure sensors monitored system pressures. Three machine learning algorithms—Random Forest （RF）， Support Vector Machine （SVM）， and Extreme Gradient Boosting （XGBoost）—were developed using 80% training and 20% testing data splits with 5-fold cross-validation for hyperparameter optimization.Results and DiscussionsThe results demonstrate significant gravity-induced enhancement of flow boiling heat transfer. As gravity increased from 1.00g to 3.16g， the heat transfer coefficient （HTC） improved by 60%-80%， while the critical heat flux （CHF） increased by 20%-35%. In the region of low vapor quality （x<0.3）， gravity enhancement reduced bubble departure diameter according to the relationship Db ∝ g-0.5， leading to increased departure frequency and enhanced microlayer evaporation. In the medium quality region （0.3<x<0.7）， gravity intensification resulted in thinner and more uniform liquid films， with peak HTC values reaching 23 000 W/（m2·K） at 3.16g compared to 14 100 W/（m2·K） at 1.00g. In the high-quality region （x>0.7）， hypergravity delayed the onset from x=0.75 to x=0.8. A comparison with ten classical correlations showed that traditional models exhibit large prediction errors under variable gravity， with the best-performing Fang model achieving only a 9.6% mean absolute error （MAE）. In contrast， the XGBoost model achieves an MAE of 3.1% across all gravity conditions， with particularly superior performance at 3.16g （MAE=3.35%） compared to the Fang model （MAE=18.61%）.ConclusionsThis study confirms that gravity is a critical factor in flow boiling heat transfer， significantly enhancing both HTC and CHF through mechanisms such as bubble dynamic optimization and liquid film redistribution. The XGBoost machine-learning model demonstrates superior accuracy in predicting heat transfer performance under variable gravity compared to traditional methods. These findings provide a crucial theoretical basis for the optimal design of cooling systems for railway-vehicle-mounted aerospace airborne equipment that operate in complex gravitational environments.关键词：variable gravity environment;micro-channels;boiling heat transfer;critical heat flux;machine learning7|14|0更新时间：2026-04-24
- 摘要：Condensers， a critical component in refrigeration and heat pump systems， require rapid and accurate performance prediction， which is crucial for system selection and design optimization. Conventional condenser performance evaluation methods， such as computational fluid dynamics simulations and experimental testing， suffer from computational inefficiency and prolonged cycle times. To address their technical limitations， this study developed a synergistic optimization framework integrating genetic algorithms with the simulation modes of the condenser. This approach refined the heat transfer correlations in the single-phase region to enhance the predictive accuracy of the model. The results show that under this optimization method， the average absolute errors in the degree of under subcooling for the plate and finned tube condensers are 1.83 ℃ and 2.23 ℃， respectively. In addition， validation results based on 32 sets of experimental data covering a wide range of operating conditions showed that the average relative errors for both the heat transfer capacity and outlet temperature of the refrigerant were maintained within 5%. This method improved the prediction accuracy of simulation models to some extent， providing effective technical support for the rapid simulation and engineering applications of refrigeration systems.关键词：condenser;thermodynamic model;genetic algorithm;fast prediction6|61|0更新时间：2026-04-24
- 摘要：To investigate the heating performance characteristics of R290 refrigerants in electric vehicle compressors under low-temperature conditions， a comprehensive performance testing system for electric vehicle air-conditioning compressors was established. The variation patterns of power consumption， heating capacity， isentropic/volumetric efficiency， COP， oil circulation rate， and discharge temperature of R290 compressors under low-temperature operating conditions were investigated. The results demonstrate that power consumption and heating capacity increase linearly with rotational speed， with heating capacity decreasing by 13.6%-15.3% for every 5 ℃ reduction in evaporation temperature； isentropic efficiency decreases by 6.2%-9.3% with increasing speed and is more significantly affected by evaporation temperature than by condensing temperature； volumetric efficiency initially increases and then decreases， dropping by 3.5%-4.9% for every 10 ℃ decrease in evaporation temperature and only 0.4%-1.2% for every 10 ℃ increase in condensing temperature； COP decreases with rotational speed， with reductions of approximately 0.15-0.40 and 0.25-0.45 every 5 ℃ decrease in evaporation temperature and every 10 ℃ increase in condensing temperature， respectively； oil circulation rate increases monotonically with speed， being significantly influenced by evaporation temperature while being less affected by condensing temperature； and discharge temperature rises with increasing speed， although the temperature rise induced by speed variation is considerably smaller than that caused by thermal operating condition changes. In this study， we demonstrate that R290 compressors maintain satisfactory heating performance under low-temperature conditions， while validating the feasibility of R290 as an environmentally friendly refrigerant for electric-vehicle air conditioning systems.关键词：R290;compressor;worst cold case;heating performance5|14|0更新时间：2026-04-24
- 摘要：In this study， we analyzed the flow-boiling heat transfer behavior of a copper microchannel heat sink with a high geometric aspect ratio of 18. An experimental platform was established to systematically evaluate the thermohydraulic response and heat dissipation capability under two heating regimes： continuous and intermittent. In the continuous mode with a heat flux of 300 W/cm² and in the intermittent mode with 750 W/cm² for 90 s， the heat sink successfully maintained the heat-source surface temperature below 75 ℃， while the inlet-outlet pressure drop remained around 18 kPa， indicating excellent two-phase thermal and hydraulic performance. In addition， the flow rate and microchannel pressure drop exhibited a strong positive correlation.关键词：thermal management;heating modes;high aspect ratio microchannels;flow boiling heat transfer5|12|0更新时间：2026-04-24
- 摘要：Refrigerant hydrates have potential applications in air-conditioning systems as phase-change cold-storage materials. However， refrigerants are insoluble in water， the nucleation of hydrates in static systems is slow， and the actual cold storage density is low. Surfactants can improve the refrigerant hydrate formation. In this study， fatty acid polyoxyethylene esters （LAE-4 and LAE-9） and fatty alcohol polyoxyethylene ethers （AEO-4 and AEO-9） were used to accelerate the hydrate formation. It was found that the amount of surfactant added affected the hydrate formation. The hydrate-formation induction time with a mass fraction of 2.5% AEO-9 was the shortest （63 min）. Hydrate exhibited the largest cold storage density （246.10 kJ/kg） and its growth rate reached 4.47 kJ/（kg·min） when the mass fraction of AEO-9 added was 2.5%. Surfactants with short hydrophilicities caused the droplets of the emulsion to become large and stratified， whereas surfactants with long hydrophilicities improved the stability of the emulsions. The hydrophobic ester bonds in LAE-9 promoted rapid hydrate formation. Hydrate showed a “memory” effect. There was no evident induction time for hydrate reformation. The stability of emulsions played a pivotal role in hydrate formation. The LAE-9 emulsion system exhibited the best stability in the hydrate formation/dissociation cycle.关键词：hydrate;surfactant;Induction time;cold storage;cycle stability3|12|0更新时间：2026-04-24
- 摘要：For an office building in Zhengzhou， the ground-source heat pump （GSHP） system meets only the heating demand， cannot provide cooling， and its long-term operation leads to soil thermal imbalance and performance degradation. Based on measured data， we first verified the accuracy of the TRNSYS dynamic model， providing a reliable basis for subsequent operational analysis and control strategy research. On this basis， the operation process of a single GSHP system was analyzed， an air-source-ground-source heat pump （ASHP-GSHP） coupling scheme was proposed， and a hybrid PSO-GPS algorithm was used to optimize a dual-threshold control strategy with the goals of system economy and soil thermal balance. The results show that under the temperature control strategy， the annual average system COP remained basically stable at about 3.24 over the 10-year operating period， with a cumulative soil temperature rise of 0.35 °C； under the load control strategy， the annual average system COP remained basically stable at about 3.05， with a cumulative soil temperature rise of 0.38 ℃， and the economic performance was the best， with a payback period of about 4.26 years. Compared with the original heating-only system， in which the COP declined and the soil temperature dropped by 7.47 ℃， the coupling scheme effectively improves system efficiency， maintains soil thermal balance， and reduces CO₂ emissions by approximately 11 000 kg annually. This study provides a reference for the optimal design and efficient operation of cooling and heating cogeneration systems in office buildings located in cold regions.关键词：ASHP–GSHP coupling;combined heating and cooling system;operational control logic;PSO–GPS optimization algorithm9|23|0更新时间：2026-04-24
- 摘要：To promote the development of high-efficiency tubular condensation heat exchangers， we studied R134a flow-condensation heat transfer characteristics in six micro-fin tubes with different structures， evaluated the prediction performance of four correlations （Koyama et al.， Miyara et al.， Cavallini et al.， and Oliver et al.）， and explored the influence mechanisms of experimental conditions and tube structural parameters. The results show that the R134a heat transfer coefficient increases with the increase of mass flux （500~1 100 kg/（m²·s）） and the decrease of condensation temperature （35~45 ℃）； the Koyama et al.'s correlation exhibits the best prediction concentration （deviation range of -43.6% to -27.4%）， the Cavallini et al.'s correlation has the optimal overall prediction performance but poor concentration， the Miyara et al.'s correlation overestimates （deviation range of 21.3%~56.4%）， and the Oliver et al.'s correlation underestimates （deviation range of -31.4% to -52.5%） the heat transfer characteristics. Therefore， based on the prediction performance of the Koyama et al.'s correlation for the flow-condensation heat transfer characteristics in micro-fin tubes， the dimensionless variable characterizing the fluid turbulence in the model was redefined. The obtained model can accurately predict R134a flow-condensation heat transfer characteristics in 1# （14.6%） & 2# （-11.0%） & 3# （4.9%） & 4# （-12.0%） & 5# （8.4%） & 6# （2.7%） micro-fin tubes. The average prediction deviation， which ranges from -12.0% to 14.6%， sufficiently validates practical values provided by the model developed.关键词：R134a;micro-fin tube;flow condensation;heat transfer coefficient;correlation3|14|0更新时间：2026-04-24
- 摘要：Efficient recovery of industrial waste heat is crucial for achieving the industrial "dual-carbon" goals. In this study， we addressed the challenges associated to low- and medium-temperature waste heat， such as low utilization rates， demand for high-temperature lift， and temporal mismatch. We focused on recovering continuous waste heat from an air compressor station to meet intermittent high-temperature industrial heat demand. We also researched on the design and performance of a transcritical high-temperature heat pump system based on a zeotropic mixture and cascaded phase-change thermal storage. First， via single-objective optimization， the optimal zeotropic mixture R290/cis-Butene （0.5/0.5） was selected， achieving a coefficient of performance （COP） of 3.31 and a volumetric heating capacity （VHC） of 5 975.63 kJ/m³. Subsequently， the structural parameters of the thermal storage unit were obtained， and the optimized configuration of the cascaded phase-change materials （PCMs） was determined to be a volume ratio of 25∶35 for high-temperature to low-temperature paraffin. Finally， the operational performance of the system was investigated. The results show that the cascaded PCM configuration （Case 1） reduces temperature non-uniformity within the PCM during both charging and discharging processes， maintains a higher average outlet temperature during discharge， and achieves optimal performance with an average COP of 2.88 and the lowest compressor power consumption.关键词：transcritical;high-temperature heat pump;zeotropic mixture;cascade phase change thermal energy storage5|15|0更新时间：2026-04-24
- 摘要：To evaluate the reliability and increase the accuracy of dynamic energy efficiency testing of room air conditioners， uncertainty quantification of the dynamic test is essential. In this study， we categorize the uncertainty sources of dynamic testing into three types： systematic， random， and time-delay errors. The uncertainty resulting from systematic and random errors was evaluated using the GUM and MCM methods， with the error limits set based on the steady-state measurement uncertainty requirements specified in GB 7725—2022 Room Air Conditioners. The time-delay error was modeled and analyzed using a first-order model， with the sensor response time set based on common values. Using an air conditioner with a rated cooling capacity of 3.5 kW as an example， the uncertainty calculation results showed that the relative expanded uncertainty caused by systematic and random errors was 3.8%， and the uncertainty due to the time delay was 1.0%， leading to a total uncertainty of 3.9% in the dynamic energy efficiency. Extending to other air conditioners with various capacities， the total uncertainty should be in the range of 3.2% to 5.4%. Contribution analysis revealed that the uncertainty in capacity measurement caused by systematic error is the primary factor affecting the uncertainty in dynamic energy efficiency testing. Concerning the capacity measurement， the accuracy of the inlet and outlet wet-bulb temperatures of the indoor side makes the most significant contribution.关键词：dynamic testing;uncertainty;room air conditioner;air-enthalpy method;time delay6|14|0更新时间：2026-04-24
- 摘要：To explore the refrigeration performance of the ternary mixed refrigerant R600a/R1150/R50， an experimental setup was established based on the Linde-Hampso cycle refrigeration principle for experimental research， and the refrigeration characteristics of the ternary mixed refrigerant were comparatively analyzed. The experimental results indicate that when the optimal charging amount of the ternary mixed refrigerant （R600a/R1150/R50） is 161.8 g/26.2 g/2.0 g， the throttling temperature after stable operation is -94.6 ℃， the ambient temperature in the box is -87.1 ℃， the cooling capacity is 22 W， and the coefficient of performance （COP） is 0.043. In the ternary mixed working medium， with an increase in the high-temperature working medium （R600a）， the performance of the regenerator is improved， and both the throttling temperature of the system and exhaust temperature gradually decrease. Under the premise of sufficient precooling， when the temperature before throttling does not reach the liquefaction temperature under the corresponding exhaust pressure of R1150， the addition of R1150 can reduce the pressure ratio， throttling temperature， and refrigeration flow rate of the system. Because the liquefaction temperature of R50 is too low under the exhaust pressure of a conventional refrigeration system， the pressure ratio increases and the mass flow rate decreases after adding the system. The experimental results have a certain guiding significance and reference value for the performance analysis of the Linde-Hampso cycle and the selection of mixed refrigerant charge ratios and system commissioning.关键词：Linde-Hampso cycle;low temperature;mixture;R600a/R1150/R507|82|0更新时间：2026-04-16
- 摘要：High-temperature auto-cascade heat pumps exhibit a simple and compact structure and reliable operating performance and can achieve heating at relatively high temperatures. Currently， the research and application of high-temperature auto-cascade heat pumps remain relatively immature， and most studies are still in the theoretical stage. Although their heating capacity and coefficient of performance （COP） are relatively low， they still hold significant promise for development in the field of high-temperature heating. This paper first introduces the research status of auto-cascade technology in the fields of refrigeration and heating and then reviews the research progress of auto-cascade heat pumps from two aspects： research advances in refrigerants and the optimization of system processes. The analysis showed that the replacement of refrigerants with a low global warming potential （GWP） is the current research focus. Refrigerants with high critical temperatures， such as R1233zd（E） and R1224yd（Z）， enable auto-cascade heat pumps to achieve high-temperature heating. R290 and R1234yf are more suitable for heating in areas with low ambient temperatures， whereas R1234ze（Z） and R1234ze（E） exhibit excellent thermodynamic performance. The proportion of mixed refrigerants has a significant impact on the performance of auto-cascade heat-pump systems. Online cycle concentration measurement methods and active control strategies for mixed refrigerants can maintain the system at an optimal proportion at all times. In terms of the optimization of heat-pump system processes， the application of vapor injection technology for increasing enthalpy is the most mature and widespread. Technologies such as multistage evaporation and ejection show potential for development. Multi-system coupling is conducive to improving system performance but may affect the stability of system operation.关键词：high-temperature auto-cascade heat pump;zeotropic mixed working fluid;process optimization;research progress9|68|0更新时间：2026-04-16
- 摘要：Vapor injection technology can effectively enhance the heating performance of heat pump-type multi-unit air conditioning systems （heat pump VRF） under low-temperature conditions. However， complex system configuration and component coupling necessitate a more general steady-state simulation approach for VRF heat pumps. This study proposes an improved graph-theory-based steady-state simulation method for a multiunit air-conditioning system with vapor injection. By abstracting the components into computational units， a graph-theory-based description method guided by the refrigerant flow paths was established. A directed graph of computation units was employed to characterize the adjacency relationships in cooling/heating modes， with mode switching achieved using a four-way valve model. A dual-layer path generation method for system pressure and flow paths is proposed， along with a decoupled iterative algorithm for flow pressure calculation. Validation based on experimental data from a heat pump VRF system with vapor injection （four indoor units） shows that the model prediction error is within ±5% under rated cooling/heating conditions. A steady-state simulation platform with customizable system configurations was developed based on the proposed method， providing a convenient digital tool for the VRF system design.关键词：multi-unit air conditioning systems;heat pump;vapor injection;steady-state simulation;graph theory6|42|0更新时间：2026-04-16
- 摘要：Current evaporative cooling air conditioning systems adopt traditional HVAC design parameters as their design conditions， using extreme weather conditions as design day parameters， which overlooks the coupling between the diversity of evaporative cooling operation modes and meteorological factors. This study considers data centers as the research object and proposes a new method for generating design days based on the operational characteristics of indirect evaporative cooling air-conditioning systems in dry， wet， and mixed modes. First， a TRNSYS model was established for an indirect evaporative cooling air-conditioning system in data centers， with the supply air temperature serving as the criterion for determining the operation mode. The climatic features corresponding to the hourly outdoor dry- and wet-bulb temperatures under the three switching modes were extracted. By combining conventional principal component analysis and the weighted dynamic time warping method， the meteorological days most similar to these characteristic sequences were identified from historical weather data， thereby generating design-day parameters for different operation modes. The results show that， compared with the original design parameters， the peak cooling loads generated by the new method under the three operating modes exhibit relative deviations from the actual design loads of 0.15%， 0.03%， and 0.41%， respectively. The design-day parameters proposed in this study effectively mitigated the design redundancy issues associated with the original parameters， thereby better satisfying the accuracy requirements of the engineering design.关键词：data center;indirect evaporative cooling;supply air temperature;meteorological parameters;energy-saving optimization5|72|0更新时间：2026-04-16
- 摘要：Absorption refrigeration is one of the most promising methods for recovering waste heat in data centers. However， the conventional method demands high driving temperatures （>85 ℃） and occupies substantial space， rendering it incompatible with the waste heat （<70 ℃） and high-density deployment requirements of data centers. To address these problems， for the first time， to the best of our knowledge， a novel compact absorption refrigeration experimental prototype was developed based on the working pair R32/DMF， which was selected for its suitability as a low-temperature driving heat source. Furthermore， compact plate heat exchangers were employed for the absorber， generator， and solution heat exchangers to minimize the overall system footprint. Experimental results indicated that under a driving heat source temperature range of 50-70 ℃ and an absorber cooling water inlet temperature of 25 ℃， the novel system achieved an evaporating temperature of approximately 13.1 ℃ and a coefficient of performance （COP） of up to 0.57. By adjusting the expansion valve opening on the refrigerant side， the evaporating temperature was reduced to 10.4 ℃， with a corresponding increase in COP to 0.69. Meanwhile， gradually reducing the expansion valve opening on the weak solution side caused the COP to increase slightly. Moreover， a reduction in the evaporator inlet air temperature led to a corresponding decrease in the system COP. The proposed compact， low-temperature， waste-heat-driven R32/DMF absorption refrigeration prototype presents a novel technical solution for the decarbonization of data centers.关键词：absorption refrigeration;waste heat recovery;data center cooling;organic working pair;compact design5|49|0更新时间：2026-04-16
- 摘要：Inspired by the drag-reducing effect of natural riblet-like structures on shark skin， this study proposes a biomimetic shark skin denticle structure and evaluates its heat transfer enhancement and drag reduction performance in a single-phase tube flow. The bio-inspired denticles consist of longitudinally protruding riblets and streamlined auxiliary riblets arranged in an interlocking， staggered pattern along the inner tube surface. This configuration forms well-organized flow channels that effectively confine near-wall vortices within the grooves， preventing the transverse migration of wall-flow vortices and reducing the momentum exchange caused by vortex cross-flow， thereby achieving drag reduction. Furthermore， denticles generate flow disturbances that enhance the wall convective heat transfer， leading to improved heat transfer coefficients. The primary factors affecting drag reduction and thermal performance were the denticle height and arrangement density. As the denticle height increased and the arrangement became more compact， the flow disturbance intensified， resulting in a greater heat transfer enhancement. However， the drag reduction effect initially improved and then deteriorated， indicating the existence of an optimum denticle height and arrangement density. For the studied tube with a 7-mm outer diameter at Reynolds numbers ranging from 4 500 to 9 500， the optimum denticle height was determined to be 0.07 mm， with optimal riblet spacings D2 and P of 2.3 mm and 0.6 mm， respectively. Compared to a smooth tube， the sharkskin denticle tube achieved an approximately 3.0% reduction in drag and an 8.0% improvement in heat transfer capacity.关键词：bio-inspired shark skin denticles;turbulent flow in tubes;convective heat transfer;drag reduction and thermal enhancement28|124|0更新时间：2026-03-25
- 摘要：Ortho-para hydrogen conversion is a key process in hydrogen liquefaction that reduces energy consumption and improves storage efficiency. Understanding the catalytic reaction kinetics and achieving real-time concentration monitoring are crucial for optimizing liquid hydrogen production. Among available techniques， Raman spectroscopy enables rapid， accurate， and efficient in situ measurement of ortho-para hydrogen concentration. Compared with traditional indirect methods that use gas chromatography， this technique meets the dynamic detection needs of the process and provides precise measurements， such as reaction kinetics， making it an advanced measurement technique. This study reviews the Raman scattering spectroscopy-based ortho-para hydrogen concentration measurement technique. Accordingly， the principle and composition of the optical detection system for this measurement technique are systematically explained. This study highlights the advantages and disadvantages of Raman spectroscopy compared with the methods of gas chromatography， nuclear magnetic resonance， and sound velocity by reviewing the development and evolution of the ortho-para hydrogen conversion measurement technique from its early use for macroscopic thermal conductivity measurements to its use for modern， in situ spectroscopic analyses. Finally， the study highlights the advantages of Raman spectroscopy in terms of its self-calibration and nondestructive， in situ， and rapid response capabilities. Overall， this study provides a theoretical basis and technical reference for the high-precision monitoring of ortho-para hydrogen in large-scale applications of hydrogen energy.关键词：Raman scattering spectroscopy;hydrogen liquefaction;ortho-para hydrogen catalytic conversion;in-situ measurement techniques;quantitative measurement para-hydrogen27|232|0更新时间：2026-03-25
- 摘要：Thermochemical energy storage is a promising solution for addressing the temporal， spatial， and intensity mismatch between solar energy supply and demand. This study experimentally investigates the crystallization-based energy storage characteristics of lithium bromide solution， focusing on the energy storage density， rate， and efficiency， along with a sensitivity analysis of key parameters. The results showed that the energy storage rate and efficiency increased with the source temperature. At a 55% mass fraction， increasing the heat source temperature from 100 ℃ to 140 ℃ enhances the energy storage rate and efficiency by 89.1% and 18%， respectively. The performance response to the solution mass fraction was nonlinear， with an optimal mass fraction range； as the initial mass fraction increased from 55% to 63%， the average storage density decreased by 15.9%， while the efficiency increased by 31%. Storage characteristics are negatively correlated with cooling water temperature； as it increases from 10 ℃ to 30 ℃， the energy storage rate and efficiency decrease by an average of 46.7% and 35.4%， respectively. Of all the factors， the cooling water temperature exerts the most consistent and significant negative impact on system performance， making it the primary limiting factor under current operating conditions.关键词：lithium bromide;Solution;Crystallization;energy storage26|187|0更新时间：2026-03-24
- 摘要：Efficient fault diagnosis of metro air-conditioning systems is essential for reducing energy consumption and ensuring passenger comfort. This paper proposes an unsupervised transfer learning method based on a domain-adversarial neural network （DANN） to address the challenges involving diverse feature distributions and complex faults. Data obtained from three single faults （condenser fouling， ventilation fouling， and refrigerant leakage） and their concurrent combinations are collected from a multifunctional test vehicle under various operating conditions and compressor frequencies. The DANN achieved accuracy values ranging from 97.30%-98.90% for single faults and 77.80%-86.70% for concurrent faults. Uniform Manifold Approximation and Projection （UMAP） and SHapley Additive exPlanations （SHAP） analyses revealed the underlying reasons for the less accurate concurrent fault diagnosis. Compared with the two baseline transfer learning models， DANN exhibited markedly smaller performance fluctuations， maintaining high accuracy even under large feature distribution shifts and overlapping concurrent fault features.关键词：subway air conditioning;fault diagnosis;transfer learning;domain-adversarial neural network24|174|0更新时间：2026-03-24
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