Abstract:

Al₂O₃ nano particles were added into the water with xanthan and ultrasonic wave to prepare the well-distributed Al₂O₃-H₂O nanofluid. Based on the theory of flash evaporation, an experimental apparatus of dynamic ice-making under vacuum was designed. In the same flash pressure (300 Pa), it is investigated the vacuum flash experimental characteristics in different conditions,like solid adsorption,nanofluid concentration, particle size and diaphragm metering pump flow. The results shown that the adsorption action had obvious effect on keeping the stability of the pressure and it was useful to capture the water vapor in the system. When the temperature of the cooling medium is lower than the initial temperature of the adsorbent, the adsorbent had better adsorption capacity, but the cooling temperature should not be too low. The larger the concentraction of the nanofluid is, the smaller the particle size is,the better for getting the high ice packing factor of ice slurry. For the same concentration of nanofluid, ice packing factor of ice slurry can be gotten by reasonable to control the diaphragm metering pump flow. In 2%(mass) NaCl, the nanofluid concentration in different particle size should not exceed 0.05%(mass).

Key words: nanoparticles, ice-making, vacuum, adsorption, ice packing factor, phase change

摘要：

配制溶质为Al₂O₃纳米粒子、黄原胶为分散剂，经超声波振荡后分散均匀稳定的Al₂O₃-H₂O纳米流体。利用真空动态喷射制冰实验装置，设定初始压力300 Pa，研究在有无固体吸附作用、不同纳米流体浓度、不同纳米颗粒粒径和不同供液流量下的真空闪蒸制冰特性。结果表明，吸附作用对真空制冰系统稳压效果显著且有助于捕捉实验中的水蒸气；当冷却介质温度低于吸附剂初始温度时，吸附剂有更好的吸附能力但冷却温度不宜过低；纳米流体浓度越大、纳米粒子粒径越小，更利于制取高含冰率的冰浆；对于同一浓度的纳米流体，合理控制供液流量可以获得不同含冰率的冰浆；在2%（质量）NaCl下，各粒径的纳米流体浓度不宜超过0.05%（质量）。

关键词: 纳米粒子, 制冰, 真空, 吸附作用, 含冰率, 相变