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Numerical Comparisons on Heat-Source-Targeted and Large-Area Spray Cooling for an Impinging Jet at High Temperature in a Confined Space 1

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11th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC 2019

作者： Zhi, Chengqiang Huang, Yixiang Zhang, Qianru Ye, Wei Zhang, Xu School of Mechanical Engineering Tongji University Shanghai China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai China

ISBN: (数字)9789811395208

ISBN: (纸本)9789811395192

Impinging jets with high temperature can be commonly found among industrial applications, such as exhaust gas from turbine engines that used for ships, heavy trucks or aircrafts. When the heating source is in a confined space, i.e., a garage or a machine room, additional cooling method, e.g., spray cooling, usually needs to be applied to decrease the temperature of the impinging jet, to minimize damages to the interior structure. In this paper, numerical simulation is used to study the cooling effect of water spray on an impinging jet at ~800 K. The confined space also incorporates an exhaust fan to remove the generated gas. The cooling effect of both local cooling (i.e., directly spraying at the heat source) and large-area cooling (i.e., spraying spread out the whole space) are investigated. Six cases were designed. In the first case, there were no nozzles were set. In the next 5 cases, the total number of nozzles were 65 and remained unchanged, by changing the number of nozzles used for larger-area cooling and local cooling, the cooling effect of different installation scheme of nozzles was obtained thorough computational method. For all the cases, the flow rate of the flue gas is 28.0 kg/s, and hourly water consumption of each nozzle is ~0.8 m3/h. The results show that increasing the number of nozzles that used for local cooling result in a better cooling effect, but the increment of cooling effect will be slightly when the number of local cooling nozzles up to ~20. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Cooling

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Performance analysis of a hybrid solar energy, heat pump, and desiccant wheel air-conditioning system in low energy consumption building 11th

Performance analysis of a hybrid solar energy, heat pump, an...

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11th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC 2019

作者： Tian, Shaochen Su, Xing School of Mechanical Engineering Tongji University Shanghai China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai China

ISBN: (纸本)9789811395239

In hot and humid climate zone of China, a huge amount of building energy is consumed by conventional air-conditioners (CACs) in dehumidification especially in low energy consumption buildings where sensible load can be largely reduced by adopting high-performance building envelopes, but the moisture load is not changed. In this paper, a hybrid solar energy, heat pump, and desiccant wheel (HSHDW) system was proposed and the performance of the system was analyzed based on simulation studies. It was found that the evaporation temperature of the system should be kept at 12.8 and 9.7 °C on a typical day of summer and transition season separately. Compared with CACs, HSHDW system can provide a more comfortable thermal and humid indoor environment. The daily energy consumption of the HSHDW system is lower than that of the CAC, achieving great energy savings, especially for a typical weekday in summer, when a 16.8% daily energy saving is obtained. © Springer Nature Singapore Pte Ltd 2020.

关键词： Solar energy

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A small-scale experimental study of CO_(2) enhanced injectivity methods of the high-rank coal

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Petroleum Science 2021年第5期18卷 1427-1440页

作者： Qing-He Niu Li-Wen Cao Shu-Xun Sang Wei Wang Wei Yuan Jiang-Fang Chang Xiao-Jun Jia Wei-Min Zheng Zeng-Xue Zhang State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang050043China Hebei Technology and Innovation Center on Safe and Efficient Mining of Metal Mines Shijiazhuang050043China School of Resource and Earth Science China University of Mining and TechnologyXuzhou221008China Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization China University of Mining and TechnologyXuzhou221008China Hebei Academy of Emergency Management Shijiazhuang050081China Hebei Iron and Steel Group Mining Co. LtdTangshan063000China Minmetals Mining Holding Co. LtdHefei241000China

The attenuation of CO_(2)injectivity has become the biggest technical barrier for the application of CO_(2)enhanced coalbed methane recovery(CO_(2)-ECBM).Commonly,the intermittent CO_(2)injection,N2 displacing CO_(2)and pre-fracturing are the potential CO_(2)enhanced injectivity methods for coal reservoirs,but their mechanism and effectiveness remain to be *** paper thus conducted small-scale experiments to simulate the working process of these engineering measures by an independently developed experimental *** show that the CO_(2)injectivity of coal is remarkably improved by the intermittent injection mode since the CO_(2)injection time is increased by folds and the loss of reservoir pressure can be complemented in *** N_(2)displacing CO_(2)method promotes the desorption of CO_(2)and reduces the swelling strain,with the result that the permeability of coal is improved by 74.82%and 64.95%compared with the methods of the primary subcritical CO_(2)(Sub CO_(2))and supercritical CO_(2)(Sc CO_(2))***,the permeability reduces again with the secondary CO_(2)*** permeability of the coal sample after pre-fracturing is averagely improved by 1-2 orders of magnitude,the irreversible permeability loss rate,average stress sensitivity coefficient and the permeability loss rate due to adsorption are averagely reduced by 95.885%,61.538%and 96.297%,*** indicates that the permeability of coal after pre-fracturing is no longer sensitive to both the effective stress and Sc CO_(2)adsorption,the injectivity is thus improved and *** CO_(2)enhanced injectivity effects of the intermittent CO_(2)injection,the N_(2)displacing CO_(2)and the pre-fracturing are various,which thus can be selected individually or jointly to improve the CO_(2)injectivity according to the reservoir physical properties and geological *** research deepens the understanding of the functional mechanism of CO_(2)enhanced injectivity method

关键词： Supercritical CO_(2) Permeability Intermittent injection N_(2)displacing CO_(2) Pre-fracturing

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A mechanism-data dual-driven approach for predicting profile changes in rails

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Wear 2025年 578-579卷

作者： Yang, Yadi Wang, Jianxi Li, Yang An, Wenjie Cai, Jiasheng State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory of Roads and Railway Engineering Safety Control Ministry of Education Shijiazhuang Tiedao University Shijiazhuang050043 China

Accurate prediction of rail profile changes is crucial for scientifically formulating rail wear mitigation strategies, maintaining track reliability, and ensuring economic benefit. However, traditional models based on rail wear mechanisms are limited in prediction accuracy due to their idealized assumptions. While possessing strong nonlinear fitting capabilities, data-driven models often lack interpretability and rely on large amounts of high-quality training data. To address these challenges, this paper proposes a novel method that integrates the advantages of both approaches to predict rail profile changes. Utilizing a prototype network, a rail profile change model is pre-trained with simulation data and then fine-tuned using measurement rail profile data through transfer learning. K-fold cross-validation and noise augmentation are employed to enhance the model's prediction accuracy and robustness. The study results indicate that for tracks with curve radii between 400 and 600 m, the precision of 10 random prediction trials exceeds 90 %, with standard deviations of Mean Squared Error (MSE), Root Mean Squared Error (RMSE), Mean Absolute Error (MAE), and Mean Absolute Percentage Error (MAPE) being 0.03397 mm2, 0.04261 mm, 0.0204 mm, and 0.175 %, respectively, demonstrating excellent predictive accuracy and stability. Compared to models using only measurement data, this method achieves reductions in average MSE, RMSE, MAE, and MAPE by 30.60 %, 11.76 %, 12.94 %, and 10.45 %, respectively. © 2025 Elsevier B.V.

关键词： Railroad transportation

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Experimental Study on Shear Strength Characteristics of Frozen Soil - Cast-in-Situ Concrete Interface

SSRN

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SSRN 2022年

作者： Sun, Tiecheng Dong, Chuangqi Zhang, Jiao Zong, Zihang Wu, Kai State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory of Roads and Railway Engineering Safety Control Ministry of Education Shijiazhuang050043 China Hebei Province Technology and Innovation Center on Intelligent Construction of Infrastructure Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China

The roughness of contact surface is closely related to the friction coefficient and shear strength characteristics of pile-soil interface. At present, there is no recognized and unified quantitative characterization method of contact surface roughness. In this paper, the roughness formula is corrected in combination with the proposed form factor, and the low temperature direct shear test of the frozen soil-cast-in-situ concrete interface is carried out. The influence of several test factors, such as contact surface roughness, normal pressure and moisture content of soil sample, on frozen shear strength of frozen soil-cast-in-situ concrete contact surface is analyzed. The test results show that: (a) The frozen shear strength at the contact surface is mainly determined by the cementation of ice cementation force, cohesion and the bite force between frozen soil and concrete. The roughness corrected by the form coefficient can accurately characterize the contribution of bite force to the frozen shear strength of the contact surface. (b) The primary and secondary order of the influence of test control factors on the frozen shear strength of contact surface is normal pressure > moisture content of soil sample > test temperature > roughness > dry density. The normal pressure and moisture content have a strong and significant influence on the test results, the influence of dry density is not significant, and the influence of test temperature and roughness is in the middle. (c) The frozen shear strength of the contact surface increases with the increase of roughness, but the increase of normal pressure can weaken the effect of roughness on the enhancement of shear strength. © 2022, The Authors. All rights reserved.

关键词： Temperature

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CFD Simulations on Temperature control for an Organic Glass Sphere with High-Heat-Flux Sources 11th

CFD Simulations on Temperature Control for an Organic Glass ...

引用

11th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC 2019

作者： Zhao, Wenxuan Ye, Wei Wu, Chao Zhang, Xu School of Mechanical and Energy Engineering Tongji University Shanghai China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai China

ISBN: (纸本)9789811395192

A sphere-shaped experimental setup is assembled by organic glass via mass polymerization in a layer-by-layer manner from top (north pole) to bottom (south pole) in a cylindrical experimental hall. For each layer, the thermal bonding joints of both inner and outer surfaces need to be annealed by a heating belt with heat flux density of approximately 4200 W/m2. Due to the requirements of the experiment, the temperature should be controlled within the range of 21 ± 1 °C to avoid physical deformation. In this paper, rapid release and diffuse process of high heat (0–300 s) is simulated using transient CFD method and the applicability of two ventilation schemes, e.g., general ventilation and push–pull ventilation, is investigated. The temperature distributions of all the areas above the layer under polymerization and heat exhaust efficiency are used to evaluate the effects of different ventilation schemes on heat dilution. The results show that, first, the high heat release and diffusion results in rapid buoyancy and general ventilation alone cannot maintain temperature increment. Second, the push–pull ventilation can effectively minimize the buoyancy caused by the heating sources and maintain thermal environment and increase the heat exhaust efficiency. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Ventilation

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A preliminary field study on using air cleaners to substitute mechanical ventilation in an open office in Shanghai 16

A preliminary field study on using air cleaners to substitut...

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16th Conference of the International Society of Indoor Air Quality and Climate: Creative and Smart Solutions for Better Built Environments, Indoor Air 2020

作者： Fan, Yujie Zhi, Chengqiang Chen, Zean Ye, Wei Zhang, Xu School of Mechanical Engineering Tongji University Shanghai201804 China Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education Tongji University Shanghai200092 China

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Passive thermal protections of smoke exhaust fans for a high-temperature heat source 1

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11th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC 2019

作者： Huang, Yixiang Zhi, Chengqiang Zhang, Qianru Ye, Wei Zhang, Xu School of Mechanical Engineering Tongji University Shanghai201804 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai200092 China

ISBN: (数字)9789811395246

ISBN: (纸本)9789811395239

Smoke exhaust fans (SEFs) are commonly used to directly remove high-temperature gas exhausted from fire accidents, or industrial applications such as gas turbines and product manufacturing. Most available SEFs used in a confined space can be working properly under specific temperature range for a short period of time. Therefore, thermal protection for the fans is a vital issue to prevent SEFs from failing and causing damages or disasters. In this paper, a linearly five-SEF-array is used to extract exhaust gas from a moving impinging jet at approximately 700 K. Three passive (as opposed to active spraying) measures, i.e., installing a dam board for a fan, changing the angle of inclination of the fans and reducing the running number of fans are studied using the computational fluid dynamics (CFD) method. Three indicators, i.e., gas temperature at the inlet of the fan (Ti), the area of high-temperature zone (Ah) and total space ventilation efficiency of the fans, are assessed by employing at least one of the passive measures. The results show that, first, on the one hand, passive thermal protections are effective tools in decreasing Ti, especially for the fan that is closest to the heat source. On the other hand, Ah will be enlarged with the passive protections, since the exhaust gas is not directly being extracted. Second, changing the angle of inclination of the fans can decrease the temperature of the smoke that enters the SEFs. Third, the smoke exhaust efficiency can also be significantly lowered by reducing the running number of fans. Last but not least, passive protection control strategy should be up to the location of heat source. © Springer Nature Singapore Pte Ltd 2020.

关键词： Smoke

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Determining Moist-Based Ventilation Rates for Residential Buildings with Low-Infiltration in China: A Preliminary Discussion 1

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11th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC 2019

作者： Tang, Shengyi Ye, Wei Su, Xing Zhang, Xu School of Mechanical Engineering Tongji University Shanghai200092 China Key Laboratory of Performance Evolution and Control for Engineering Structures of Ministry of Education Tongji University Shanghai200092 China

ISBN: (数字)9789811395208

ISBN: (纸本)9789811395192

There is a growing concern over whether ventilation rates (VRs) for building are health-based. For example, moisture-related problems, e.g., molds and mites, can pose adverse health effects on occupants. However, ventilation-induced moist indoors is an overlooked issue in China. In this paper, the effects of VRs, as well as typical building characteristics, on indoor humidity levels were investigated using EnergyPlus. 1008 residential models (with low infiltration, and various ventilation and climate scenarios) were simulated. Generally-agreed non-healthy humidity levels were used to analyze health risks. The results showed that, first, buildings in two hot summer zones were at risk of high indoor humidity, while buildings in two cold zones might experience higher risks of low humidity. Second, higher the VRs, higher the risk of low humidity in cold zones, and higher the risk of dampness in hot summer zones. Third, it can be easier to be more humid indoors for small-size, top-floor, or north orientation residences in China. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Ventilation

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Numerical simulations on buoyancy-driven plumes from various sphere-attached heating sources 16

Numerical simulations on buoyancy-driven plumes from various...

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16th Conference of the International Society of Indoor Air Quality and Climate: Creative and Smart Solutions for Better Built Environments, Indoor Air 2020

作者： Zhao, Wenxuan Ye, Wei Zhang, Xu School of Mechanical Engineering Tongji University Shanghai201804 China Key Laboratory of Performance Evolution and Control for Engineering Structures Ministry of Education Tongji University Shanghai200092 China

ISBN: (纸本)9781713823605

A spherical scientific facility is under construction, during which high-temperature buoyancy-driven plume would be released from surfaces. However, there is still knowledge gap on the temperature distributions for plumes along the sphere. In this paper, CFD simulations were employed to analyse the temperature profiles of the plumes from sphere-attached sources with various intensity and location. The results showed that, first, the buoyancy-driven plumes exhibited different flow patterns from that of the conventional sources, and source-attached location on the sphere has a great effect on the thermal environment. Second, dimensionless excess temperature t*(τ,θ ) of the plumes along the sphere were approximately the same when temperature ranging from 80-300 ℃. Third, temperature distributions on the radial sections did not fully conform to the Gaussian distribution during the developing period. The simulation can be useful in developing ventilation for heating sources on spherical surfaces. © 2020 16th Conference of the International Society of Indoor Air Quality and Climate: Creative and Smart Solutions for Better Built Environments, Indoor Air 2020. All rights reserved.

关键词： Computational fluid dynamics

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