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Effect of baffles on bubble behavior in a bubbling fluidized bed for chemical looping processes

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Particuology 2020年第6期18卷 154-167页

作者： Xiao Zhu Xuan Feng Yuanyuan Zou Laihong Shen Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education Southeast UniversityNanjing 210096China

A bubbling fluidized bed is generally used as the fuel reactor in chemical looping ***,in sufficient gas-solid contact remains a steadfast *** such,we propose the use of in ternal baffles to split bubbles at a high gas velocity and to restrict the movement of large-scale solids in the fluidized *** investigated the effect of baffle arrangement on the bubble size and energy,pressure gradient,particle distribution,and particle velocity in a fluidized bed using a computational particle fluid dynamics simulation based on our experimental *** discuss the main influenci ng factors,which in elude presence of caps,number of baffles,and the baffle opening *** baffle structure with caps efficiently broke the large bubbles without creating jet *** baffles were deemed suitable in the bed owing to the small bubble size and uniform gas-solid distribution in each *** selected a baffle opening ratio of 20.5%,which improved the flow pattern without causing a significant increase in the pressure gradient and particle velocity through the *** also discussed the potential for sea ling up this baffled fluidized bed for industrial applications.

关键词： Baffle bubble behavior Fluidized bed Chemical looping CPFD simulations

Experimental Investigation on Flow Pattern and bubble behavior during Subcooled Flow Boiling of R1233zd(E)in Parallel Channels

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Journal of Thermal Science 2023年第6期32卷 2374-2385页

作者： FANG Yidong ZHANG Zhao XU Dan WANG Yuchen YANG Huinan HUANG Yuqi School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093China Key Laboratory of Clean Energy and Carbon Neutrality of Zhejiang Province Jiaxing Research InstituteZhejiang UniversityJiaxing314031China Key Laboratory of Smart Thermal Management Science&Technology for Vehicles of Zhejiang Province Taizhou317200China

In this study,the flow pattern and bubble behavior of R1233zd(E)during subcooled flow boiling in parallel channels are experimentally investigated with visualization and thermal *** test section is composed of 21 rectangular mini channels with the hydraulic diameter of 1.5 mm and the length of 140 *** flow,slug flow,churn flow and wavy-annular flow occur in sequence with the increase of vapor quality,while transient flow pattern transition process involving multiple flow patterns are also *** distribution of flow pattern is non-synchronized and axial-asymmetric,with earlier flow pattern transitions observed in peripheral channels away from the center *** initial nucleate site in each channel also show a random and axial-asymmetric distribution,while faster bubble growth can be noted in some channel under the comprehensive effects of liquid evaporation and bubble *** variation of heat transfer coefficient is correspondence to the flow pattern transition,showing different trends along the flow *** increase of mass flux can lead to delayed flow pattern transition and variation of heat transfer *** addition,higher heat transfer coefficient can be noted in channels away from the center axis.

关键词： flow boiling flow pattern bubble behavior parallel channel visualization

Numerical investigation of heat transfer performance and bubble behavior of nucleate pool boiling in a confined space under rolling conditions

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Energy Storage and Saving 2023年第1期2卷 336-347页

作者： Jianjie Cheng Jiangwei Sun Weihao Ji Yu Dong Wei Li Yurong Chen College of Urban Construction Nanjing Tech UniversityNanjing211816China

Nucleate pool boiling process is widely used in heat exchangers because of its excellent heat transfer *** the gradual increase of applications,more and more equipments work in a non-static state,but there is little research under rolling ***,it is necessary to investigate the influence of rolling motion on the nucleate pool boiling *** this study,a numerical investigation of the nucleate pool boiling process under static and rolling conditions is performed based on the volume-of-fluid(VOF)*** fields and phase distribution under static state and rolling motion are compared to investigate the effect of rolling motion on the nucleate pool boiling *** results show that rolling motion greatly influences the bubble behavior and void fraction owing to the differences between flow *** void fraction decreased by 11.84%,48.82%,and 56.87%as the maximum rolling angle increased from 15°to 45°,and by 11.84%,22.27%,and 21.81%as the rolling period increased from 1 s to 3 *** void fraction decreased by 11.84%,48.82%,and 56.87%as the maximum rolling angle increased from 15°to 45°.The heat transfer coefficients of different cases are compared,and it is found that the effects of rolling motion on heat transfer coefficients can be ignored.

关键词： Nucleate pool boiling Rolling condition bubble behavior Heat transfer characteristic

Single bubble behavior in Direct Current Electric Field

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Chinese Journal of Chemical Engineering 2008年第2期16卷 178-183页

作者：彭耀陈凤宋耀祖陈民 School of Aerospace Tsinghua University Beijing 100084 China

The investigation on bubble behavior in electric field helps to analyze the mechanism of electric enhancement of boiling heat transfer. Experiments were performed to investigate the bubble deformation in direct current （DC） electric field with bubbles attached to the orifice. The air bubbles were slowly generated in the transformer oil pool at different orifices, so that the effect of flow on bubble shape was eliminated. The results showed that the bubbles were elongated and the departure volume decreased when the electric field was intensified. The major and minor axes, aspect ratio and departure volume increased with increasing the orifice diameter. Both the electric field and orifice size have great influence on bubble behavior. The bubble deformation was also simulated to compare with the experimental results. The numerical and experimental data qualitatively agree with each other.

关键词： electrohydrodynamic enhancement multiphase flow bubble behavior direct current electric field

Mixing Characteristics and bubble behavior in an Airlift Internal Loop Reactor with Low Aspect Ratio

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Chinese Journal of Chemical Engineering 2014年第6期22卷 611-621页

作者：张伟鹏雍玉梅张广积杨超毛在砂 Key Laboratory of Green Process and Engineering National Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences

The present study summarizes the results of macro-and micro-mixing characteristics in an airlift internal loop reactor with low aspect ratio(H/D≤5) using the electrolytic tracer response technique and the method of parallel competing reactions respectively. The micro-mixing has never been investigated in airlift loop reactors. The dual-tip electrical conductivity probe technique is used for measurement of local bubble behavior in the reactor. The effects of several operating parameters and geometric variables are investigated. It is found that the increase in superficial gas velocity corresponds to the increase in energy input, liquid circulation velocity and shear rate, decreasing the macro-mixing time and segregation index. Moreover, it is shown that top clearance and draft diameter affect flow resistance. However, the bubble redistribution with a screen mesh on the perforated plate distributor for macro-mixing is insignificant. The top region with a high energy dissipation rate is a suitable location for feeding reactants. The analysis of present experimental data provides a valuable insight into the interaction between gas and liquid phases for mixing and improves the understanding of intrinsic roles of hydrodynamics upon the reactor design and operating parameter selection.

关键词： airliftloop reactor macro-mixing micro-mixing bubble behavior hydrodynamics

Space Materials Science in China:*** Studies under Microgravity

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空间科学学报 2020年第5期40卷 946-949页

作者： ZHANG Xingwang YIN Zhigang YU Jianding YUAN Zhangfu ZHAO Jiuzhou LUO Xinghong PAN Mingxiang Institute of Semiconductors Chinese Academy of SciencesBeijing 100083 Centre of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049 Shanghai Institute of Ceramics Chinese Academy of SciencesShanghai 200050 Collaborative Innovation Center for Steel Technology University of Science and Technology BeijingBeijing 100083 Institute of Metal Research Chinese Academy of SciencesShenyang 110016 School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016 Institute of Physics Chinese Academy of SciencesBeijing 100191 School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049 Songshan Lake Materials Laboratorij Dongguan 523808

The virtual absence of gravity-dependent phenomena in microgravity allows an in-depth understanding of fundamental events that are normally obscured and therefore are difficult to study quantitatively on *** particular interest is that the low-gravity environment aboard space provides a unique platform to synthesize alloys of semiconductors with homogeneous composition distributions,on both the macroscopic and microscopic scales,due to the much reduced buoyancy-driven *** the other hand,the easy realization of detached solidification in microgravity suppresses the formation of defects such as dislocations and twins,and thereby the crystallographic perfection is greatly ***,the microgravity condition offers the possibilities to elucidate the liquid/solid interfacial structures,as well as clarify the microstructure evolution path of the metal alloys(or composites)during the solidification *** by these facts,growths of compound semiconductors and metal alloys were carried out under microgravity by using the drop tube,or on the scientific platforms of Tiangong-2 and *** following illustrates the main results.

关键词： Space materials Microgravity bubble behavior Microstructural evolution