Study on Flow Characteristics of Ice Slurry Generated from Urea Aqueous Solution

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.