The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ruzhuang Wang - One of the best experts on this subject based on the ideXlab platform.
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Thermal shock resistance of ultra-high temperature ceramics under active Cooling Condition including the effects of external constraints
Applied Thermal Engineering, 2017Co-Authors: Haibo Kou, Tianbao Cheng, Ruzhuang WangAbstract:Abstract A model has been established according to practical applications that ultra-high temperature ceramics are used as parts of the thermal protection system. Taking HfB 2 as an example, the effects of convective heat transfer coefficient, thermal shock initial temperature and external constraints on the thermal shock resistance of ultra-high temperature ceramics under active Cooling Condition have been studied through numerical simulation. This model has also considered about sensitivities of thermo-physical properties to temperature changes. The results indicate that with the increase of thermal shock initial temperature and convective heat transfer coefficient, there are dangerous regions where the critical rupture temperature difference is the lowest. Some measures can be taken to pass the dangerous region safely in practical engineering applications. Besides, external constraints can improve the thermal shock resistance of ultra-high temperature ceramics under active Cooling Condition, which is very significant in practical applications.
Shuangfeng Wang - One of the best experts on this subject based on the ideXlab platform.
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an investigation on optimal external Cooling Condition for an ultra thin loop thermosyphon based thermal management system
Energy Conversion and Management, 2018Co-Authors: Sihui Hong, Yongle Tang, Shuangfeng WangAbstract:Abstract Thermal management system plays a critical role in dissipating heat and guaranteeing the safety of facilities. Among the various thermal management technologies, thermosyphon receives increased attentions owing to the fast developing demands in high-efficient Cooling technology. In this paper, the heat transfer performance of an air-Cooling assisted thermal management system (AATM) with ultra-thin loop thermosyphon (UTLT) is investigated with experimental method and theoretical analysis. Specifically, the effects of the assisted Cooling Conditions including the placement of the condenser and the consumed fan power on the start-up characteristics, operating temperature and thermal resistance of the ULLT-based system are respectively discussed. During the experiments, conventional point measurement and IR thermography are both adopted to detect the temperature variation and capture the vapor-liquid interface formed in the loop pipeline of the UTLT. By revealing the movement of vapor-liquid interface under various Cooling Conditions, it is verified that there always exists an optimal Cooling Condition for the UTLT-based AATM to start up most quickly and operates with the highest efficiency. Simply raising the Cooling capacity leads to the liquid stagnation in the pipeline and triggers adverse temperature excursion. A proper regulation on the coupled Cooling Condition could significantly improve the operational safety and reliability of the UTLT-based AATM. In the present work, the operating temperature of the UTLT under the optimal Cooling Condition can be decreased by 5.2 K and the thermal resistance can be reduced by 24.2% to only 0.169 K/W. In addition, an effective model to predict the thermal performance of the UTLT-based AATM has been established with 93.6% of the experimental data in the ± 15% error band.
Zhengjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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Effect of surface heat transfer coefficient gradient on thermal shock failure of ceramic materials under rapid Cooling Condition
Ceramics International, 2018Co-Authors: Chen Limin, Anzhe Wang, Xiangbo Suo, Xinghong Zhang, Zhengjun ZhangAbstract:Abstract A rapid thermal processor (RTP) device as well as quenching technique is employed to systematically investigate the effect of surface heat transfer coefficient (h) gradient on thermal shock failure of a hot-pressed ZrB2-based ceramic. Two typical kinds of quenchant with different surface h gradients during quenching tests, water and boiling water, are used for this study. When water as the Cooling medium, two different Cooling modes of indirect contact Cooling by RTP device and direct contact Cooling by quenching are also studied. The experimental results and related numerical simulations illustrate that surface h gradient plays an important role in thermal shock failure. This study confirms the previous presumption that the combination of body temperature gradient and surface h gradient leads to thermal stress damage and thermal shock failure. Under water quenching Condition, water phase changes form bubbles randomly and produce great surface h gradient. Accordingly, critical body temperature gradient (V(max)c) is small (~ 270 °C s−1). Under aqueous polymer quenching Condition, the introduction of polymer chains into water lowers the random formation of steam bubble and mediates the surface h gradient. The corresponding V(max)c hence become larger (~ 500 °C s−1). Under boiling water quenching Condition, there is no surface h gradient and V(max)c is even larger (> 600 °C s−1). This study provides useful complementary information for understanding the thermal shock behavior and gives suggests for predicting materials performance in actual service.
Wei Zhao - One of the best experts on this subject based on the ideXlab platform.
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tig cladding in situ nano vanadium carbide reinforced fe based ultra fine grain layers under water Cooling Condition
Surface & Coatings Technology, 2018Co-Authors: Hui Zhang, Kai Chong, Guangchun Xiao, Zhiping Sun, Wei ZhaoAbstract:Abstract In-situ vanadium carbides reinforced Fe-based TIG cladding layers were obtained under air Cooling and water Cooling Conditions. The effects of the different Cooling Conditions on carbides size, grain size and properties of cladding layers were comparatively studied. The results showed that in-situ nano vanadium carbide reinforced Fe-based ultra-fine grain layers could be obtained under the water Cooling Condition. This cladding layer showed a narrower heat affected zone and a lower dilution rate. The average grain size of the cladding layer is 1.90 μm. Carbide has two morphologies, one consists of submicro/nano particles with an average particle size of 0.15 μm, and the other consists of rod-like particles with an average diameter of 0.09 μm. High resolution transmission electron microscope results indicated that the nanoscale carbides were V6C5 and VC. The hardness of the water Cooling cladding layer was significantly increased by 375 HV0.2 to 905 HV0.2. The corrosion rate indicated that the corrosion resistance was approximately 5.6 times greater as compared with the air Cooling cladding layer. The passive film formed on the air Cooling cladding layer were Fe3O4 and V2O5, and that formed on the water Cooling cladding layer was Fe2O3 and Fe3O4.
Haibo Kou - One of the best experts on this subject based on the ideXlab platform.
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Thermal shock resistance of ultra-high temperature ceramics under active Cooling Condition including the effects of external constraints
Applied Thermal Engineering, 2017Co-Authors: Haibo Kou, Tianbao Cheng, Ruzhuang WangAbstract:Abstract A model has been established according to practical applications that ultra-high temperature ceramics are used as parts of the thermal protection system. Taking HfB 2 as an example, the effects of convective heat transfer coefficient, thermal shock initial temperature and external constraints on the thermal shock resistance of ultra-high temperature ceramics under active Cooling Condition have been studied through numerical simulation. This model has also considered about sensitivities of thermo-physical properties to temperature changes. The results indicate that with the increase of thermal shock initial temperature and convective heat transfer coefficient, there are dangerous regions where the critical rupture temperature difference is the lowest. Some measures can be taken to pass the dangerous region safely in practical engineering applications. Besides, external constraints can improve the thermal shock resistance of ultra-high temperature ceramics under active Cooling Condition, which is very significant in practical applications.