| 摘要: |
| 在实际应用中，通常采用管道输送的方式将冰浆运送至待冷却区域进行热交换，因此，研究冰浆的流动特性具有重要意义。本文基于冰浆制备及流动特性测试实验台，以质量分数为5%的尿素溶液制备的冰浆为研究对象，通过可视化观测冰浆中冰粒的尺寸及分布并测量冰浆的运动黏度，分析了管径、含冰率（IPF）、流动压降以及管道摩擦阻力系数与雷诺数(Re)之间的关系，同时分析了不同管径水平不锈钢管内冰浆摩擦阻力系数的实验值(λ)与将冰浆看做牛顿流体计算得到的理论值(λ0)的比值偏离1的程度与IPF和Re的关系。研究结果表明：λ/λ0随IPF的增加而增大，随Re的增加而降低，即在高Re情况下冰浆更接近于牛顿流体，而高IPF的冰浆却与牛顿流体偏差较大。利用幂律模型分析冰浆的流动特性，发现流动特征指数n'随着IPF的增大而降低，在管径为6 mm管内，当IPF从6%增至26%，n'从1.006降至0.611；而稠度系数K'与IPF呈现正相关，在管径为8 mm管内，当IPF从6%增至26%，K'从0.015增至0.274。当IPF介于5%~30%范围内，n'随着管径的增大略有减小，K'随着管径的增大而逐渐增大。通过研究修正雷诺数和范宁摩擦阻力系数的关系，发现随着IPF的增加，管径为4、6和8 mm管道内的转折修正雷诺数ReMR的范围分别为2 500~3 200、1 600~2 300和1 500~1 900。 |
| 关键词: 冰浆 尿素溶液 水平直管 流动特性 含冰率 |
| DOI： |
| 投稿时间：2020-06-08 修订日期：2020-08-12
|
| 基金项目:国家博士后创新计划（BX201700166） |
|
| Study on Flow Characteristics of Ice Slurry Generated from Urea Aqueous Solution |
| Zhang Shengshi,Zhao Yanjie,Li Zhaoning |
| (Key Laboratory of Efficient Utilization of Low and Medium Grade Energy;School of Mechanical Engineering, Tianjin University) |
| Abstract: |
| In practical applications, pipeline transportation is usually used to transport ice slurry to the area to be cooled for heat exchange. Therefore, it is important to study the flow characteristics of ice slurries. This article is based on an ice slurry preparation and experiment in a flow characteristics test platform. The ice slurry was prepared with a 5% mass fraction urea solution, and the size and distribution of ice particles in the ice slurry were visually observed. The kinematic viscosity of the ice slurry was measured, and the relationships between the pipe diameter, ice packing factor (IPF), flow pressure drop, pipe frictional resistance coefficient, and Reynolds number (Re) were analyzed. The ratio of the experimental value (λ) of the friction resistance coefficient of the ice slurry in horizontal stainless-steel pipes with different pipe diameters to the theoretical value (λ0) was calculated by taking the ice slurry as a Newtonian fluid, and the relationship between the ratio and IPF and Re was analyzed. It was found that λ/λ0 increases with the increase in IPF and decreases with the increase in Re. That is, the ice slurry is closer to a Newtonian fluid under a high Reynolds number, whereas the deviation in ice slurry with high ice packing factor from a Newtonian fluid is larger. A power-law model was used to analyze the flow characteristics of the ice slurry. It was found that the flow characteristic index n' decreased with the increase in IPF. In a pipe with a diameter of 6.0 mm, n' gradually decreases from 1.006 under IPF = 6% to 0.611 under IPF = 26%; however, the consistency coefficient K' is positively correlated with the IPF. In a pipe with a diameter of 8.0 mm, K' increases from 0.015 under IPF = 6% to 0.274 under IPF = 26%. When the IPF is within the range of 5%–30%, n' decreases slightly with the increase in pipe diameter, whereas K' increases gradually with it. To better describe the complex flow characteristics of non-Newtonian fluids, a modified Reynolds number was introduced to quantitatively analyze the slurry. By exploring the relationship between the modified Reynolds number and Fanning friction coefficient, it was found that with the increase in the IPF, the range of transition Reynolds numbers in 4 mm, 6 mm, and 8 mm tubes were 2 500–3200, 1 600–2 300, and 1 500–1 900, respectively. |
| Key words: ice slurry urea aqueous solution horizontal straight tube flow characteristics ice packing factor |
