超声波对水冻结及脱冰影响的研究

发布时间：2018-01-29 12:17

本文关键词： 超声波加快冻结速率耦合计算脱冰　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：在溶液冻结过程中,超声波具有降低初始成核的过冷度、促进二次成核的优点。但是,很少有关于超声波对水冻结速率影响的研究。在制冰及冰蓄冷过程中,能够加快冻结速率具有重要的现实意义和经济价值,尤其在冰蓄冷行业,加快冻结速率能够充分利用用电的低谷期;针对当前制冰机在制冰和脱冰过程中出现的弊端,提出了运用超声波脱冰的方法,探索了超声波运用于脱冰的可行性,超声波脱冰具有提高冰的卫生品质、降低二次能耗等优点。围绕超声波对水冻结速率的影响以及超声波脱冰这二个方面本文做了以下工作:(1)对冰晶成核和冰晶生长的热动力学条件进行了论述;对冰层的生长速率以及超声波作用于水结冰过程的机理做了概述和分析。(2)本文在水冻结过程中施加超声波,并且对不同功率超声波的作用效果做了对比实验研究,结果表明超声波能够加快水的冻结速率,在45W(40kHz)条件下,加速冻结效果最佳,自来水完全冻结的时间提前了16min。(3)探究了超声波脱冰的作用机理,建立结冰冰盘的实体模型,利用有限元分析软件ANSYS,对结冰冰盘进行了耦合计算,得到了冰盘的应力云图和各节点的应力值,在与冰在冰盘的最大粘附力0.85MPa进行比较后可知,运用超声波脱冰理论上具有可行性。(4)在模拟计算的基础上对超声波脱冰展开了实验研究,当施加超声约165s时冰盘中的冰除了边角处没有脱去外,其它部分的冰都脱离了冰格,验证了超声波脱冰的可行性。然而在脱冰过程中产生了部分水,水的产生不利于冰的贮藏;此外,有些冰的结构被破坏,所以超声波应用于脱冰还需进一步的探索。
[Abstract]:In the process of solution freezing, ultrasonic has the advantages of reducing the undercooling of initial nucleation and promoting secondary nucleation. However, there is little research on the effect of ultrasonic on the freezing rate of water. It has important practical significance and economic value to speed up the freezing rate, especially in the ice storage industry, the freezing rate can make full use of the low period of electricity consumption. In view of the disadvantages of the current ice maker in the process of ice making and deicing, the method of ultrasonic deicing is put forward, and the feasibility of ultrasonic application in deicing is explored. Ultrasonic deicing can improve the hygiene quality of ice. The effect of ultrasonic wave on water freezing rate and ultrasonic deicing are discussed in this paper. The thermal kinetic conditions of ice crystal nucleation and ice crystal growth are discussed. The growth rate of ice layer and the mechanism of ultrasonic wave acting on the process of water freezing are summarized and analyzed. 2) in this paper, ultrasonic wave is applied in the process of water freezing. The results show that ultrasonic can accelerate the freezing rate of water, and the acceleration effect is the best under the condition of 45W ~ 40kHz. The mechanism of ultrasonic deicing was explored, and the solid model of ice plate was established, and the finite element analysis software ANSYS was used. The coupling calculation of ice sheet is carried out, and the stress cloud diagram of ice plate and the stress value of each node are obtained. The results are compared with the maximum adhesion force of 0.85 MPA. The ultrasonic deicing is theoretically feasible. (4) on the basis of simulation calculation, the experimental study of ultrasonic deicing is carried out. When ultrasonic wave is applied for about 165s, the ice in the ice plate is not removed except at the corner. Other parts of the ice are separated from the ice grid, which verifies the feasibility of ultrasonic deicing. However, some water is produced in the process of deicing, which is not conducive to the storage of ice. In addition, some ice structures have been destroyed, so ultrasonic application in deicing needs further exploration.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB559

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