| 摘要: |
| 纳米流体作为功能性材料在强化传热方面运用较广，但作为蓄冷剂时对其初始冻结温度的研究较少。本文选用500nm粒径的Al2O3颗粒,设定三种不同降温速率(1、5、10 ℃/min),配置了三种不同质量分数(0.01％、0.05％、0.1％)的Al2O3-H2O纳米流体，研究初始冻结温度和降温速率以及纳米流体质量分数之间的关系,试验分为九组，每组进行60次,记录初始冻结温度的数据得到其概率分布。结果表明:初始冻结温度值概率分布近似为高斯分布；增大降温速率会使冻结过程中流体初始冻结温度降低；而在不同降温速率下，初始冻结温度与纳米流体质量分数未呈现相同的变化趋势，随着降温速率的增大，初始冻结温度随纳米流体质量分数的增大由减小逐渐转变为增大，异质结晶对初始冻结温度的影响程度逐渐大于溶液黏度的影响程度。 |
| 关键词: Al2O3-H2O纳米流体 初始冻结温度 分布概率 降温速率 |
| DOI： |
| 投稿时间：2020-02-17 修订日期：2020-06-21
|
| 基金项目:国家自然科学基金青年项目(51906178)资助项目。 |
|
| Analysis of Initial Freezing Temperature of a New Cold Storage Material Al2O3-H2O Nanofluid |
|
Zhang Chensi, Liu Bin, Guo Heng, Chen Aiqiang, Zhao Songsong, Yang Wenzhe
|
| (Tianjin Key Laboratory of Refrigeration Technology，Tianjin University of Commerce) |
| Abstract: |
| As a type of functional material, nanofluids are widely used to enhance heat transfer; however, as a cold storage agent, there are few studies on its initial freezing temperature. In this study, Al2O3 particles with a particle size of 500 nm were used, and three different cooling rates (1, 5, and 10 ℃/min) and three different mass fractions (0.01%, 0.05%, and 0.1%) were used to study the freezing point of the Al2O3-H2O nanofluid. The relationship between the cooling rate and particle concentration was investigated. The samples were divided into nine groups, and each group was tested 60 times; the initial freezing temperature was recorded to obtain its probability distribution. The results show that the initial freezing temperature value is approximately Gaussian; increasing the cooling rate will reduce the initial freezing temperature of the fluid during freezing; however, at different cooling rates, the initial freezing temperature and nanofluid mass fraction do not show the same trend: with an increase in the cooling rate, the initial freezing temperature gradually changes, first decreasing and then increasing with an increase in the nanofluid concentration. Moreover, the degree of influence of heterogeneous crystallization on the initial freezing temperature is greater than that of the solution viscosity. |
| Key words: Al2O3-H2O nanofluid initial freezing temperature distribution probabilit cooling rate |
