共查询到18条相似文献,搜索用时 814 毫秒
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本文详细研讨了螺带桨搅拌槽内给热系数及其与所需功率的关系.研究中使用了4个不同几何尺寸的螺带装以及8种不同稠度的假塑性非牛顿流体和高粘度牛顿流体.结果表明:在雷诺数小于0.1时,试验流体在槽内的给热系数与浆叶几何尺寸有关.通过回归分析法得到了4个对应于各螺带桨的给热系数关联式;雷诺数大于10时,给热系数和搅拌浆几何尺寸无关,从而得出一个适用于不同螺带浆的共同关联式.实验还研究了给热系数和所需搅拌功率的关系,并用多项式回归法得到了整个实验雷诺数范围的传热-搅拌功率关联式. 相似文献
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为使聚合釜内搅拌介质在湍流、过渡流及层流域都能达到良好的混合,对锚-三叶推进器、锚-内外单螺带、正交双层三角桨-单螺带、正交双层三角桨-内外单螺带等4种组合桨搅拌器,于φ300mm的有机玻璃釜中,测定了在牛顿流体和假塑性流体中的搅拌功率和循环特性。实验结果表明,4种组合桨中,含正交双层三角桨的2种组合桨功率消耗小,循环能力明显较强,具有较好的循环性能和剪切能力,能在粘度变化范围宽广的介质中获得良好的搅拌效果。假塑性流体(羧甲基纤维素水溶液)的过渡流域用lnN_p=A_1+A_2lnRe+A_3(lnRe) ̄2关联式,功率值精度高。 相似文献
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组合桨聚合釜内非牛顿流体的混合特性 总被引:6,自引:1,他引:5
在φ476mm的椭圆底有机玻璃聚合釜中,以羧甲基纤维素-甘油水溶液(前者质量分数为1.3%)为实验物系。利用酸碱中和法测定了9种不同的搅拌桨直径与聚合釜直径比接近于1的组合搅拌桨沿聚合釜轴向及径向的混合特性。结果表明:内外螺带-锚式组合桨的轴向混合最强,但径向混合较差。框板式搅拌桨的轴向混合较内外螺带-锚式组合桨弱,但比改进偏框式桨强,其径向混合较后者弱。改进偏框桨的7种不同组合方式沿径向的混合良好,多数组合桨沿轴向的混合较前2种组合桨弱,更接近于平推流。 相似文献
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分别以浓度为1%,2%,3%,3.5%的羧甲基纤维素溶液为实验,采用测温法,测定了正交双层三角桨-单螺带桨,正交双层三角桨-内外单螺带桨.锚式桨-三叶推进器.锚式桨-内外单螺带4种组合桨拌器的宏观混合时间,无量钢数C1,C2,C3,C4综合评判了它们的宏观混合性能,实验证明,前2种组合桨搅拌器在不同流域内都使搅拌介质达到良好的宏观混合,且功率消耗低,混合效率高,具有明显的节能优势,对搅拌变粘度体系 相似文献
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组合浆搅拌器搅拌特性的研究 总被引:1,自引:0,他引:1
为使聚合釜内搅拌介质在湍流,过渡流及层流域都能达到良好的混合,对锚-三叶推进器,锚-内外单螺带,正交双三角桨-单螺带,正交双层三角桨-内外单螺带等4种组合桨搅拌器,于φ300mm的有机玻璃釜中,测定了在牛顿流体和假塑性流体中的搅拌功率和循环特性。实验结果表明,4种组合桨中,含正交双层三角桨的2种组合桨功率消耗小,循环能力明显较强,具有较好的循环性能和剪切能力,能在粘度变化范围宽广的介质中获得良好的 相似文献
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研究了高粘度牛顿流体和非牛顿流体在螺杆-导流筒、螺杆-导流筒-直管组两种搅拌体系中的传热行为。结果表明,设置导流筒和直管组后,对夹套侧的传热膜系数α_j没有明显影响,导流筒侧和直管组直管外侧的传热膜系数α_d和α_c都较α_j大,传热面积比夹套增加一倍左右,从而增强了搅拌槽的传热能力。在所有几何因素中,搅拌桨径 d和导流筒内径 D_(ti)对传热膜系数影响最大。搅拌桨的转向对传热无明显影响。分析了传热关联式中 Re的方次的变化情况。用因次分析和回归分析得到的夹套、导流筒和直管组传热面的传热关联式和文献结果吻合甚好。 相似文献
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基于搅拌桨旋转扭矩和搅拌槽内所有壁面的平均扭矩近似相等的关系,引入流况系数,提出了计算非牛顿流体表观粘度的剪切速率模型.并对内蛇管、外蛇管和直管以及不同几何尺寸的MIG、透平、三叶后掠式、板式、锚和半椭圆片桨组成的多种搅拌体系,用该模型关联夹套侧和冷却管侧的给热系数,分别得到了统一不同几何尺寸搅拌桨的给热系数关联式.该模型适用于不同冷却构件.不同类型、不同几何尺寸的搅拌桨、过渡域和湍流域以及夹套侧和冷却管侧的非牛顿流体给热系数关联.另外,对多种剪切速率模型进行了比较和讨论. 相似文献
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Measurements of the circulation time during batch mixing of Newtonian and non-Newtonian fluids were used to analyse and compare the performance of six different helical-ribbon impellers and a screw impeller inside a draft coil. The distribution of circulation times obtained from two hundred repeated measurements is shown to depend markedly on the impeller geometry. Mixing time data with the helical-ribbon impellers are correlated with the mean value and the reduced standard deviation of the circulation times. Effective (rapid) mixing corresponds to a large circulation capacity and a wide distribution of the circulation times. The mixing mechanism of Newtonian fluids with the helical-ribbon impellers is qualitatively described by the Voncken model. The helical impellers' circulation capacities are not affected by the shear-thinning properties of non-Newtonian fluids. However, in highly shear-thinning fluids, the presence of important stagnant zones is responsible for much longer mixing times which consequently do not correlate with the circulation parameters. The relative efficiencies of the different impellers in Newtonian fluids are compared using a criterion based on the the total energy required to achieve a certain degree of mixing. The wide blade impeller is the most efficient of the helical-ribbon impellers but is considerably less efficient than the screw impeller in a draft coil. 相似文献
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Naoki Dohi Takanori Takahashi Kimio Minekawa Yoshinori Kawase 《Chemical Engineering Communications》2006,193(6):689-701
Gas dispersion with large-scale impellers consisting of modified large paddle impellers in stirred tanks, with rather large ratios of both impeller diameter and impeller height to tank diameter, was experimentally examined in transition and turbulent mixing ranges. Gas holdups and volumetric gas-liquid mass transfer coefficients with large-scale impellers, i.e., Maxblend and Fullzone impellers, were measured in 0.31 and 0.6 m I.D. stirred tanks, and the gas dispersion performance of large-scale impellers was compared with that of double conventional small-scale high-speed impeller systems, i.e., double four-flat blade disk turbine impellers and double four-flat paddle impellers.
The gas holdups of the large-scale impellers were comparable with those of the small-scale impeller systems at a given rotational speed. The volumetric gas-liquid mass transfer coefficients for large-scale impellers were also similar to those of the small-scale impeller systems. It was found that the large-scale impellers are not more energy efficient than the small-scale impellers in obtaining good gas dispersion.
Empirical correlations for gas holdups and volumetric gas-liquid mass transfer coefficients were developed. They fit the experimental data in transition and turbulent mixing ranges reasonably well, with correlation factors greater than 0.84. 相似文献
The gas holdups of the large-scale impellers were comparable with those of the small-scale impeller systems at a given rotational speed. The volumetric gas-liquid mass transfer coefficients for large-scale impellers were also similar to those of the small-scale impeller systems. It was found that the large-scale impellers are not more energy efficient than the small-scale impellers in obtaining good gas dispersion.
Empirical correlations for gas holdups and volumetric gas-liquid mass transfer coefficients were developed. They fit the experimental data in transition and turbulent mixing ranges reasonably well, with correlation factors greater than 0.84. 相似文献
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Naoki Dohi Takanori Takahashi Kimio Minekawa 《Chemical Engineering Communications》2013,200(6):689-701
Gas dispersion with large-scale impellers consisting of modified large paddle impellers in stirred tanks, with rather large ratios of both impeller diameter and impeller height to tank diameter, was experimentally examined in transition and turbulent mixing ranges. Gas holdups and volumetric gas-liquid mass transfer coefficients with large-scale impellers, i.e., Maxblend and Fullzone impellers, were measured in 0.31 and 0.6 m I.D. stirred tanks, and the gas dispersion performance of large-scale impellers was compared with that of double conventional small-scale high-speed impeller systems, i.e., double four-flat blade disk turbine impellers and double four-flat paddle impellers. The gas holdups of the large-scale impellers were comparable with those of the small-scale impeller systems at a given rotational speed. The volumetric gas-liquid mass transfer coefficients for large-scale impellers were also similar to those of the small-scale impeller systems. It was found that the large-scale impellers are not more energy efficient than the small-scale impellers in obtaining good gas dispersion. Empirical correlations for gas holdups and volumetric gas-liquid mass transfer coefficients were developed. They fit the experimental data in transition and turbulent mixing ranges reasonably well, with correlation factors greater than 0.84. 相似文献
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肋形隧道表面多孔管强化沸腾传热的研究 总被引:3,自引:1,他引:2
本文报道了肋形隧道机械加工表面多孔管(JK-2管)单管管外池沸腾实验。实验工质为R-113和R-11。实验结果表明:对R-113和R-11工质,JK-2管沸腾给热系数分别比光滑管高2.5~15倍及1~10倍,比JK-1管高20%~150%,而且,当工质为R-113时,JK-2管比光滑管的临界热负荷高约100%。并建立了一个池沸腾膜传热系数的准数关联式,其预测值和实验值的相对误差在±15%以内。 相似文献