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61.
浆液池搅拌器固液两相三维数值模拟 总被引:1,自引:0,他引:1
对固-液悬浮搅拌槽中的固液两相流场进行研究,进而讨论固体浓度对搅拌槽内液相流场的影响规律,是固液搅拌研究工作的重要组成部分.本文应用商业计算流体力学软件fluent对浆液池中的流场进行模拟,基于N-S方程和标准的k-ε紊流模型,模拟出浆液池中液体的流动情况和浓度的分布,分析垂直面内和水平面内液相流的流场分布规律、固相颗粒浓度特点,并分析产生这种情况的原因,为搅拌器的设计和池液的改形提一些建议. 相似文献
62.
A 3-D computational fluid dynamics (CFD) model of airflow and heat transfer processes within packed horticultural produce was developed. The model included explicit geometries of the product and package. Model results showed that airflow and temperature inside produce bulk were heterogeneous. The regions near the package vents showed relatively higher cooling air velocity and turbulence intensity. The coldest region was located behind the entrance vents. Pressure drops through entrance and exit vents were 51.1% and 45.2%, respectively. As the cooling air passed through the package vents and produce bulk, there was an increase in turbulence intensity. Validation of the model was conducted using experimental results. There was a good agreement between the predicted and measured results, average relative errors of predicted pressure drop and produce temperature were 13.80% and 16.27%, respectively. 相似文献
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基于CFX的猪舍内温度和气流场模拟研究 总被引:2,自引:0,他引:2
为了探讨猪舍内温度场和气流场的模拟方法,以保育猪舍为模拟对象,以Navier-Stokes方程作为控制方程组,采用标准k-ε湍流模型,运用计算流体力学(computational fluid dynamics,简称CFD)软件CFX对猪舍内的温度场和气流场进行模拟,并对模拟结果进行实际检测验证。结果,模拟得到的舍内气流温度和速度变化规律与实测值相同;各检测点的空气温度误差最大值不超过1.3℃,平均绝对误差为0.24℃,平均相对误差为0.7%;各检测点的气流速度误差最大值不超过0.2 m/s,平均绝对误差为0.04 m/s,平均相对误差为20%。表明使用CFD模拟方法能够真实表达猪舍内气流状态,对猪舍内温度场和气流场的模拟是一种有效的方法。 相似文献
65.
多级离心泵轴向力平衡装置的设计与分析 总被引:2,自引:0,他引:2
可靠的轴向力平衡装置是高压多级离心泵实现平稳可靠运行的重要机构。针对反渗透海水淡化高压泵对结构和运行可靠性的特殊要求,设计了一种用于节段式多级离心泵的新型轴向力平衡装置。基于计算流体力学(CFD)方法研究了平衡装置内部的流场结构及其轴向力平衡机理,分析了不同轴向间隙、径向间隙以及滑动轴承长径比条件下的轴向力平衡特性。结果表明,不同进出口压差条件下,滑动轴承间隙内流动结构存在明显区别,轴承支撑机理发生变化;平衡力和相对泄漏量随轴向、径向间隙的增大呈非线性增大,平衡力随长径比增大近似呈线性增大,相对泄漏量随长径比增大近似呈线性减小。对径向、轴向间隙和长径比进行各种组合分析计算,得到轴向间隙0.2 mm、径向间隙0.3 mm、长径比为1的结构优化的新型机构,该机构既可以很好地平衡轴向力,又提高了多级泵的可靠性。 相似文献
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67.
沼气池搅拌的CFD模拟及温度场验证 总被引:3,自引:1,他引:2
为了对底侧入式搅拌的沼气发酵池内的流场进行研究,该文采用计算流体力学方法,以上海市崇明县某示范工程的主体沼气发酵池(69.3 m3)为对象,对流场和温场进行计算模拟,并通过温度测量来验证温度数值模拟的可靠性,从而间接验证流场数据准确性。通过温度场的模拟和实测数据对比,整体温场模拟和实测数据在0.05水平下无显著差异;通过流场模拟和工程运行的观察,都反映此发酵池中设计的底侧入式搅拌不能充分实现发酵池的搅拌。但模型在相关设定上仍有与实际不符之处,模型仍有待完善。 相似文献
68.
The numerical simulation for dynamic characteristics of the flow field of a novel twin screw kneader is carried out. The numerical simulation model of twin screw kneader is established,and the three dimensional,isothermal and steady numerical analyses of non newtonian fluid are presented based on computational fluid dynamics(CFD)theory,and the characteristics under the conditions of different speeds and center distances,such as the distribution of pressure and velocity field,the maximum shear stress,the mass flow rate and so on,are studied. The research results show that:with increasing speed,the maximum flow pressure,the mass flow rate and the maximum shear stress increase; the maximum shear stress increases first and then decreases with increasing of center distance of the screw rotors,while the mass flow rate increases with increasing of center distance; but when the center distance reaches a certain degree,the mass flow rate is negative and the material appears serious reflux which can make the kneader stop working. The results provide a theoretical basis for performance prediction and reasonable designing for the novel twin screw kneader. 相似文献
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70.
A 3-D computational fluid dynamics (CFD) model was applied to study the effect of package vent design on airflow and heat transfer during postharvest handling of horticultural products. The effect of vent area, shape, number and position on airflow and heat transfer characteristics was studied. An increase in vent area decreased the total pressure drop and increased the uniformity of airflow and temperature. Total pressure drop was expressed as a function of vent area in the form of a Darcy–Forchheimer equation and the results showed that vent area affected both Darcy and Forchheimer terms. Half and seven eighths cooling times and cooling rate of fruit were expressed as a function of vent area ratio and the results showed that vent number, position and shape mainly affected the uniformity of airflow and cooling. Cooling rate increased with an increase in vent area but the sensitivity of the increase in cooling rate decreased with an increase in vent area. With an increase in vent area up to 7%, there was a reasonable increase in cooling rate; however, further increase in vent area showed a relatively low increase in cooling rate. To optimize package venting, there is a need to combine such airflow and heat transfer studies with analysis of package mechanical integrity. 相似文献