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氧化铝溶出不凝气的影响及处置的探讨
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作者 李伟 杨再明 《中国金属通报》 2023年第21期7-9,共3页
我国氧化铝厂溶出工序经过多年的技术迭代和升级,大部分溶出工序的加热装置使用套管加热器。目前普遍采用蒸汽作为热源,蒸汽来源于氧化铝厂配套的电厂锅炉,锅炉在启动时可能会吸入空气,锅炉给水若除氧或除盐不足时也会带入空气和二氧化... 我国氧化铝厂溶出工序经过多年的技术迭代和升级,大部分溶出工序的加热装置使用套管加热器。目前普遍采用蒸汽作为热源,蒸汽来源于氧化铝厂配套的电厂锅炉,锅炉在启动时可能会吸入空气,锅炉给水若除氧或除盐不足时也会带入空气和二氧化碳,这些气体进入到蒸汽中就会成为不凝气。由于不凝气传热系数很低,随蒸汽到达溶出加热装置,含有不凝气的区域局部温度降低,在蒸汽冷凝放热时会起到阻碍作用,降低系统传热系数;不凝气无法冷凝,而且密度低且可压缩,又容易造成蒸汽系统的水锤和汽锁。目前热静力型排气阀通过精密的温度感应部件,感应到局部温度降低即可自动开阀将不凝气排出,为了减轻不凝气对溶出传热装置的不良影响,应采用这种自动化设备将不凝气及时从系统内排出,让系统传热保持高效率。 展开更多
关键词 氧化铝 溶出 不凝气 热静力排气阀 蒸汽传热系数
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Fluid-solid coupling numerical simulation of charge process in variable-mass thermodynamic system 被引量:8
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作者 胡继敏 金家善 严志腾 《Journal of Central South University》 SCIE EI CAS 2012年第4期1063-1072,共10页
Abstract: A joint solution model of variabk:-mass flow in two-phase region and fluid-solid coupling heat transfer, concerned about the charge process of variable-mass thermodynamic system, is built up and calculated... Abstract: A joint solution model of variabk:-mass flow in two-phase region and fluid-solid coupling heat transfer, concerned about the charge process of variable-mass thermodynamic system, is built up and calculated by the finite element method (FEM). The results are basically consistent with relative experimental data. The calculated average heat transfer coefficient reaches 1.7~105 W/(m2. K). When the equal percentage valve is used, the system needs the minimum requirements of valve control, but brings the highest construction cost. With the: decrease of initial steam pressure, the heat transfer intensity also weakens but the steam flow increases. With the initial water filling coefficient increasing or the temperature of steam supply decreasing, the amount of accumulative steam flow increases with the growth of steam pressure. When the pressure of steam supply drops, the steam flow gradient increases during the maximum opening period of control valve, and causes the maximum steam flow to increase. 展开更多
关键词 steam accumulator variable-mass control valve fluid-solid coupling numerical simulation
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External Heat Transfer in Moist Air and Superheated Steam for Softwood Drying 被引量:2
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作者 PANGShusheng 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2004年第6期762-766,共5页
In kiln drying of softwood timber, external heat and moisture mass transfercoefficients are important in defining boundary temperature and moisture content at the woodsurface. In addition, superheated steam drying of ... In kiln drying of softwood timber, external heat and moisture mass transfercoefficients are important in defining boundary temperature and moisture content at the woodsurface. In addition, superheated steam drying of wood is a promising technology but this has notbeen widely accepted commercially, partially due to the lack of understanding of the dryingphenomena occurred during drying. In this work, experimental investigation was performed to quantifythe heat transfer between wood surface and surrounding moist air or superheated steam. In theexperiment, saturated radiata pine sapwood samples were dried using dry-bulb/wet-bulb temperaturesof 60℃/50℃, 90℃/60℃, 120℃/70℃, 140℃/90℃, 160℃/90℃, 140℃/100℃ and 160℃/100℃. The lasttwo schedules were for superheated steam drying as the wet-bulb temperature was set at 100℃. Thecirculation velocity over the board surface was controlled at 4.2m·s^(-1). Two additional runs(90℃/60℃) using air velocities of 2.4 m·s^(-1) and 4.8 m·s^(-1) were performed to check theeffect of the circulation velocity. During drying, sample weight and temperatures at wood surfaceand different depths were continuously measured. Prom these measurements, changes in woodtemperature and moisture content were calculated and external heat-transfer coefficient wasdetermined for both the moist air and the superheated steam drying. 展开更多
关键词 wood drying external heat transfer coefficient moist air moisture content softwood timber superheated steam
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Boiling Heat Transfer in Circulating Fluidized Beds 被引量:1
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作者 张利斌 李修伦 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2001年第3期235-241,共7页
A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. T... A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39mm ID and 2.0m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data. 展开更多
关键词 boiling heat transfer circulating fluidized bed three-phase flow
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An Experimental Investigation of Heat Transfer Characteristics for Steam Cooling in a Rectangular Channel with Parallel Ribs
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作者 MA Chao CHEN Xiaoling +2 位作者 WANG Jianfei ZANG Shusheng JI Yongbin 《Journal of Thermal Science》 SCIE EI CAS CSCD 2014年第5期454-464,共11页
An experimental study of heat transfer characteristics in superheated steam cooled rectangular channels with parallel ribs was conducted.The distribution of the heat transfer coefficient on the rib-roughed channel was... An experimental study of heat transfer characteristics in superheated steam cooled rectangular channels with parallel ribs was conducted.The distribution of the heat transfer coefficient on the rib-roughed channel was measured by IR camera.The blockage ratio(e/Dh) of the tested channel is 0.078 and the aspect ratio(W/H) is fixed at3.0.Influences of the rib pitch-to-height ratio(P/e) and the rib angle on heat transfer for steam cooling were investigated.In this paper,the Reynolds number(Re) for steam ranges from 3070 to 14800,the rib pitch-to-height ratios were 8,10 and 12,and rib angles were 90°,75°,60°,and 45°.Based on results above,we have concluded that:In case of channels with 90° tranverse ribs,for larger rib pitch models(the rib pitch-to-height ratio=10 and12),areas with low heat transfer coefficient in front of rib is larger and its minimum is lower,while the position of the region with high heat transfer coefficient nearly remains the same,but its maximun of heat transfer coefficient becomes higher.In case of channels with inclined ribs,heat transfer coefficients on the surface decrease along the direction of each rib and show an apparent nonuniformity,consequently the regions with low Nusselt number values closely following each rib expand along the aforementioned direction and that of relative high Nusselt number values vary inversely.For a square channel with 90° ribs at Re= 14800,wider spacing rib configurations(the rib pitch-to-height ratio=10 and 12) give an area-averaged heat transfer on the rib-roughened surface about8.4%and 11.4%more than P/e=8 model,respectively;for inclined parallel ribs with different rib angles at Re=14800,the area-averaged heat transfer coefficients of 75°,60° and 45° ribbed surfaces increase by 20.1%,42.0%and 44.4%in comparison with 90° rib angle model.45° angle rib-roughened channel leads to a maximal augmentation of the area-averaged heat transfer coefficient in all research objects in this paper. 展开更多
关键词 Gas turbine cooling Steam cooling Rib-roughed channel Local heat transfer enhancement
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