Applied Thermal Engineering最新文献

{"title":"Comparative study on thermal-hydraulic performance of discontinuous-fin printed circuit heat exchangers for supercritical CO2 Brayton cycle","authors":"Wanlong Jin ,&nbsp;Limin Wang ,&nbsp;Lei Deng ,&nbsp;Lei Zhang ,&nbsp;Defu Che","doi":"10.1016/j.applthermaleng.2025.128490","DOIUrl":"10.1016/j.applthermaleng.2025.128490","url":null,"abstract":"<div><div>The flow resistance reduction and volume decrease of the printed circuit heat exchanger (PCHE) are important for the supercritical CO₂ (S-CO₂) Brayton cycle. However, the performance evaluation methods for drag reduction and compactness of heat exchangers are inadequate. In this study, the recently proposed generalized performance evaluation plot is used to assess comprehensive flow performance. A volume factor combining heat transfer characteristics and geometry parameters is proposed to represent compactness. The thermal–hydraulic performances of four discontinuous-fin PCHE channels including rectangle fin channel (RTFC), airfoil fin channel (AFFC), rhombus fin channel (RBFC) and slotted fusiform fin channel (SFFC) are numerically compared. The pressure drop of RTFC is the largest and that of SFFC is the smallest. The flow separation and flow stagnation are the main reasons for flow resistance. Suppressing separated flow is the principal way for PCHE drag reduction. The comprehensive hydraulic performance of SFFC is the best, followed by the AFFC and RBFC, and that of RTFC is the worst. The SFFC is more compact than the AFFC and RBFC. The fin slotting contributes to enhancing PCHE compactness. The SFFC PCHE with low pressure loss and compact structure is preferred for the S-CO₂ cycle.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"281 ","pages":"Article 128490"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145264399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and numerical study on conjugate heat transfer in additively manufactured straight duct featuring Kagome-shaped unit cells","authors":"Youssef Aider ,&nbsp;Prashant Singh ,&nbsp;Karthik Nithyanandam","doi":"10.1016/j.applthermaleng.2025.128565","DOIUrl":"10.1016/j.applthermaleng.2025.128565","url":null,"abstract":"<div><div>An experimental and numerical study was conducted to characterize the conjugate heat transfer in an additively manufactured straight duct featuring an inline arrangement of Kagome-shaped unit cells made of stainless steel 316. Steady-state heat transfer experiments were conducted using air as the working fluid for Reynolds number ranging from 6,000 to 25,000. The convective heat transfer coefficient for a unit cell which lies in the periodic heat transfer regime is reported for the two asymmetric end walls of the Kagome lattice. Complementary numerical simulations were conducted for Reynolds number of 10,000 to elucidate the flow and thermal transport within a periodic unit cell. The study reveals that the end wall with two forward facing struts inclined toward the incoming flow (Wall A) exhibited consistently higher heat transfer compared to the end wall with a single forward-facing strut (Wall B). The velocity and turbulence field data along with normalized temperature distributions in both solid and fluid domains are presented to provide insights into the local heat transfer characteristics at the endwalls. The key contributions of this work include the thermal transport characterization of inline arrangement of Kagome unit cells and detailed description of the local differences in the conjugate heat transfer characteristics of the two asymmetrical walls. Such properties make the Kagome topology suitable for applications which require high rates of heat dissipation on one of the walls, while the opposite wall is not directly subjected to heat load, for example, in heat sinks for electronics thermal management. Furthermore, the k-ω SST turbulence model is recommended for further studies related to Kagome unit cell due to its accuracy in predicting global flow and thermal transport quantities.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"280 ","pages":"Article 128565"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparing spray and microchannel as evaporators of a compact refrigeration system for electronics cooling","authors":"Marcus Vinícius P. Carneiro ,&nbsp;Pedro Cavicchioli ,&nbsp;Michel R.P.M. Tavares ,&nbsp;Daniel Alexandre Rolón ,&nbsp;Dirk Oberschmidt ,&nbsp;Jader R. Barbosa Jr.","doi":"10.1016/j.applthermaleng.2025.128526","DOIUrl":"10.1016/j.applthermaleng.2025.128526","url":null,"abstract":"<div><div>This study presents a unique experimental comparison of a multi-jet spray cooling unit and a parallel microchannel evaporator, both integrated into the same compact R-1234yf vapor compression refrigeration system with an oil-free linear compressor. Previous studies have not compared these technologies side-by-side under identical conditions. This work fills that gap by testing both configurations in the same facility, with matched heat transfer surface areas and calibrated flow restrictions to ensure an unbiased comparison. The spray unit merges evaporator and expansion functions, delivering subcooled refrigerant through oblique orifices to form impinging two-phase jets on a heated surface. The microchannel system employs a needle valve and a copper evaporator with 34 channels (<span><math><mrow><mn>260</mn><mo>.</mo><mn>7</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> hydraulic diameter), with the valve configured to match the spray unit’s flow coefficient. Tests covered refrigerant charges from 29.9 to 143.6 g and thermal loads from 25 to 250 W. Both systems maintained surface temperatures below 70 °C. The spray unit outperformed at high heat fluxes, achieving higher critical heat flux and lower surface temperatures, while the microchannel unit was more effective at low to moderate loads. Maximum heat transfer coefficients on the order of 43 kW/(m<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>K) were achieved with spray cooling, versus 37 kW/(m<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>K) for the microchannel system, though at significantly lower wall heat flux. Thermal performance was benchmarked against classical pool boiling correlations, which serve as reference standards for immersion cooling. Both systems exceeded these baselines, with the spray unit maintaining higher heat transfer coefficients up to critical heat flux levels.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"281 ","pages":"Article 128526"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145264215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic evaluation of deep Q-networks for multi-chiller system reinforcement learning control","authors":"Jae Hwan Cha ,&nbsp;Jeong Woo Chae ,&nbsp;Sang Hun Yeon ,&nbsp;Jun Kyu Park ,&nbsp;Kwang Ho Lee","doi":"10.1016/j.applthermaleng.2025.128578","DOIUrl":"10.1016/j.applthermaleng.2025.128578","url":null,"abstract":"<div><div>The building sector accounts for a significant share of global greenhouse gas emissions, with HVAC systems, particularly those employing multi-chiller configurations, serving as major energy consumers. This study systematically evaluates the performance of Deep Q-Networks (DQN) for multi-chiller control through co-simulation with EnergyPlus. The analysis covers four aspects: hyperparameter optimization, baseline DQN performance, evaluation of control timesteps, and assessment under diverse climate scenarios. An optimal set of hyperparameters (learning rate 0.01, discount factor 0.8, and exploration decay 0.9999) enabled stable convergence and measurable energy savings. Compared to the conventional Uniform Load (UL) method, the DQN approach achieved up to 7.1% reduction by operating chillers in efficient part-load ratio ranges. In addition, despite unexpected constraints, the model autonomously learned from data to achieve stable and efficient control, delivering additional savings compared to UL and SL, maximizing COP under low-load conditions, and substantially reducing inefficient operating hours. Shortening the control timestep from 60 to 10 min yielded an additional 1% of savings but increased computation time by over 300%, highlighting the trade-off between precision and cost. Across climate zones, the framework delivered savings ranging from 2.0% to 17.4%, demonstrating better performance under low-load conditions. Moreover, model trained in 4A climate zone generalized effectively to others, with performance differences within 11.8% of locally trained models, demonstrating strong transferability. Overall, this study illustrates the performance of DQN and underscores its key characteristics across different scenarios, providing insights into effective parameter choices and achievable performance. Ultimately, it establishes a practical evaluation framework that advances reinforcement learning design and supports its real-world deployment in HVAC energy control.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"280 ","pages":"Article 128578"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combinations of Lauric acid phase change material and hybrid nanofluid on energy storage and thermal behaviour of solar heat exchanger","authors":"Vijaya Rajan V ,&nbsp;N. Nagabhooshanam ,&nbsp;Yogendra Thakur ,&nbsp;Ankur Kulshreshta ,&nbsp;M.D. Anto Praveena ,&nbsp;U.L. Nagendra Kumar ,&nbsp;Ramya Maranan ,&nbsp;T. Thirugnanasambandham ,&nbsp;Gopal Kaliyaperumal","doi":"10.1016/j.applthermaleng.2025.128560","DOIUrl":"10.1016/j.applthermaleng.2025.128560","url":null,"abstract":"<div><div>The solar thermal heat exchanger combined with a parabolic trough collector (PTC) demonstrated improved thermal performance, ease of integration with hybrid nanofluid systems, reduced carbon monoxide emissions, and higher temperature output. However, its overall efficiency can be limited under cloudy weather conditions. The present research aims to enhance the thermal behaviour of a solar thermal heat exchanger with PTC by incorporating a water/Lauric acid phase change material (PCM) and varying the volume percentage of a hybrid nanofluid containing copper and titanium dioxide. The combined effects of PCM and hybrid nanofluid concentrations on thermal characteristics were investigated. It was found that the system with PCM and 5 vol% hybrid nanofluid exhibited a higher thermal conductivity (0.99 W/m·K), reduced specific heat behaviour (4185 J/kg.K), an improved convective heat transfer coefficient of 491.4 W/m²·K, and increased thermal diffusivity (2.23 X 10⁻⁷ m²/s at 90 ⁰C). With the support of zeta potential, the stability behaviour of the hybrid nanofluid was analyzed and found to exhibit better stability. The Lauric acid PCM was capable of storing and releasing a maximum of 2567 kJ and 2501 kJ of thermal energy, respectively, along with enhanced melting and solidification durations. Furthermore, the current setup, featuring bio-based PCM and 5 vol% of hybrid nanofluid, has achieved an average energy saving of 0.712 kWh/day. These findings suggest that hybrid nanofluids are a promising strategy to improve thermal charging and discharging performance in solar thermal energy storage systems.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"280 ","pages":"Article 128560"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variable pulse width pulsed thermography: theoretical model and experimental validation","authors":"Rongbang Wang ,&nbsp;Andreas Mandelis ,&nbsp;Hai Zhang","doi":"10.1016/j.applthermaleng.2025.128557","DOIUrl":"10.1016/j.applthermaleng.2025.128557","url":null,"abstract":"<div><div>As an advanced non-destructive testing (NDT) technology, pulsed thermography (PT) plays a crucial role in fields such as aviation, automotive transportation, and construction. The classical PT theoretical model uses the Dirac delta function to describe the temporal distribution of heat source power density. However, the duration of this highly singular function is infinitesimal, which not only oversimplifies the actual heat input conditions but also violates the applicability conditions of Fourier’s law of heat conduction. This results in significant discrepancies between theoretical predictions and experimental results. To address this issue, this paper proposes an improved temporal distribution function for the pulse heat source power density. The work incorporates the effects of optical absorptivity and defect depth on the detection results. The Laplace transform method was employed to solve the one-dimensional (1D) transient heat conduction equation, leading to an improved PT theoretical model with a variable pulse width. To validate the accuracy and applicability of this model, PT detection experiments were conducted on metal additive manufacturing (MAM) components. The experimental results showed that the theoretical model more accurately reflects real-world conditions than the classical theoretical model. This work provides a more reliable theoretical foundation for optimizing PT system performance in practical NDT scenarios.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"280 ","pages":"Article 128557"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermodynamic analysis of a modified auto-cascade refrigeration cycle using mixture R290/R170","authors":"Xinmin Lin ,&nbsp;Fukang Yu ,&nbsp;Jianlin Yu","doi":"10.1016/j.applthermaleng.2025.128558","DOIUrl":"10.1016/j.applthermaleng.2025.128558","url":null,"abstract":"<div><div>Conventional auto-cascade refrigeration cycle (ARC) with single-stage compression faces significant challenges in larger pressure ratio and lower efficiency for low-temperature refrigeration applications. To solve this problem, a modified auto-cascade refrigeration cycle (MARC) using a vapor-injection compressor is proposed in this paper. In the modified cycle, the vapor-injection compressor could decrease the pressure ratios for each stage compression process, resulting in higher compressor efficiency. Furthermore, two vapor–liquid separators associated with two cascade heat exchangers are used to achieve much more effective phase separation for the low-boiling component, leading to performance enhancement. A thermodynamic evaluation of the MARC with zeotropic mixture R290/R170 was carried out under various operating conditions and compared with the conventional ARC. The analysis results show that under typical operating conditions, the conventional ARC demonstrates the coefficient of performance (COP_c) of 0.415, while the MARC exhibits the COP_c of 0.624, which achieves a 50.36% improvement. Additionally, the volumetric cooling capacity increases by 89.37%, and exergy efficiency improves by 50.47%. The compressor discharge temperature is reduced by 55.76%, contributing to enhanced compressor efficiency and a reduction in exergy destruction by 27.57%. By investigating the effect of different parameter variations on the two cycles’ performance, it was found that in the modified cycle, the vapor quality at the second separator inlet and the condenser outlet temperature have a considerable effect on the coefficient of performance and exergy efficiency. The findings demonstrate that the MARC offers a promising solution for low-temperature refrigeration, significantly outperforming conventional ARC systems in terms of both energy and exergy efficiency.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"280 ","pages":"Article 128558"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aerodynamic design of sink nozzle providing supersonic toroidal cooling film for hypersonic optical window","authors":"Zhang Bo,&nbsp;Lu Xiaoge,&nbsp;Zhao Yuxin,&nbsp;Yi Shihe,&nbsp;Yu Huang,&nbsp;Lin Juncan","doi":"10.1016/j.applthermaleng.2025.128575","DOIUrl":"10.1016/j.applthermaleng.2025.128575","url":null,"abstract":"<div><div>An aerodynamic design is developed for the sink nozzle that generates supersonic toroidal cooling film for nose-tip optical window and fuselage star sensor of hypersonic aircraft, serving to block high-temperature outflow. The governing equations and boundary conditions are determined. Compared to conventional nozzle, the sink nozzle is additionally governed by the sink flow. The throat transonic solution, exit characteristic line, and symmetry axis are different from those of the conventional nozzle. The sink nozzle is inversely designed by the method of characteristics. The boundary layer is corrected by von Kármán equation. The CFD results show a Mach number error of 0.08%, a temperature error of 0.27%, and a pressure error of 0.30%, validating the accuracy of the aerodynamic design.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"280 ","pages":"Article 128575"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Research on thermal performance and durability of ETICS under wind load in severe cold area","authors":"Shengkun Sun,&nbsp;Shui Yu,&nbsp;Jianyu An,&nbsp;Fuhong Han","doi":"10.1016/j.applthermaleng.2025.128530","DOIUrl":"10.1016/j.applthermaleng.2025.128530","url":null,"abstract":"<div><div>External thermal insulation composite systems (ETICS) are a primary building envelope type in cold climates. Hence, accurate prediction of their thermal performance and durability is essential. This study investigates the effects of dynamic outdoor wind speed and wind pressure on ETICS performance and longevity in extremely cold regions. Specifically, a heat-moisture-mechanical model is developed and experimentally validated, year-long COMSOL simulations for Shenyang are performed, and concrete fatigue life across various insulation configurations is estimated using rainflow counting and the Palmgren–Miner rule. The results indicate that wind significantly increases surface heat and moisture exchange; neglecting wind leads to an overestimation of the annual average exterior surface temperature by 1.84 °C (up to 9.4 °C in summer) and underestimation of moisture in the exterior finish and insulation by 1.48 and 0.32  kg·m⁻³, respectively. Owing to the compliance of expanded polystyrene (EPS), neglecting wind results in a 19 % underestimation of the concrete layer’s fatigue life. Comparative analysis reveals that insulation type markedly affects concrete service life; for long-term durability, EPS and extruded polystyrene (XPS) outperform foamed concrete. The study confirms that wind-boundary effects have significant and wide-ranging impacts on hygrothermal performance and durability and should be explicitly included in design practices and simulations. These findings provide essential theoretical and practical insights for high-precision building design and improved sustainability performance.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"281 ","pages":"Article 128530"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145264721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance differences of open refrigerated display cabinet under different package layouts","authors":"Shengchun Liu ,&nbsp;Peiyao Wang ,&nbsp;Yifan Zhang ,&nbsp;Dewei Meng ,&nbsp;Zhongyao Zhang ,&nbsp;Xueqiang Li","doi":"10.1016/j.applthermaleng.2025.128573","DOIUrl":"10.1016/j.applthermaleng.2025.128573","url":null,"abstract":"<div><div>Open refrigerated display cabinets (ORDCs) are widely implemented in retail environments. Although there are many works focusing on improving its performance, the role of package layouts is often neglected. To clearly illustrate the performance difference caused by package layouts, this study initially designs 245 unique package layouts. By using the validated model, their impacts on average temperature, energy consumption, and thermal entrainment factor (TEF) from the <em>X</em> , <em>Y</em>, and <em>Z</em> directions are discussed. Results show that, the package layouts markedly impact the ORDC performance, which comes from the interplay among ambient air, the cold air emitted from the perforated back panel, and the generation of vortices. The variation of package layouts in <em>X</em> direction would affect the average temperature, energy consumption, and TEF by 2.76 °C, 13.95%, and 22.56%, respectively. Similarly, the variation of package layouts in <em>Y</em> direction would affect the average temperature, energy consumption, and TEF by 2.78 °C, 18.3%, and 28.6%, respectively. Considerable oscillations in the average temperature, particularly at Shelves 4–5, could ascend to 4.14 °C. The average temperature, energy consumption, and TEF may experience oscillations of up to 3.06 °C, 20.9%, and 34.1%, respectively, when contrasting optimal and worst package layouts.</div></div>","PeriodicalId":8201,"journal":{"name":"Applied Thermal Engineering","volume":"281 ","pages":"Article 128573"},"PeriodicalIF":6.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145264402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}