【作者】 何军峰；

【导师】 杨昭；

【作者基本信息】 天津大学 ， 制冷与低温工程， 2008， 硕士

【摘要】 冷藏是经营食品、水果保鲜、生物冷藏过程中必不可少的一种处理措施,此措施的经济性能如何,直接影响整个过程的效益。在冷藏过程中产生的结霜现象是影响食品品质以及冷库运行是否稳定的主要因素。在上述背景下,本课题开展了新型恒温恒湿冷库的结霜与除霜实验的研究。通过以PLC为核心的电气控制系统,本文进行不同了库温、湿度以及送风速度条件下的实验研究,并分析了在不同实验条件下,蒸发温度、翅片温度以及压差的变化情况。实验结果表明,在不同的库温、湿度以及送风速度的工况下,蒸发器侧的结霜情况有明显的差异,结霜量在一定范围内会随着库温的降低、湿度的升高以及送风速度的降低而增多。通过结霜实验得到了比较容易结霜的条件,针对此条件进行了除霜实验的研究。在除霜实验中,本文不仅分别进行了停机除霜与不停机除霜的实验,而且进行了在不停过程中不同时刻除霜的实验对比。通过对实验结果的分析,得出了适用的除霜方法。更多还原

【Abstract】 Refrigeration is the necessary step during storing food, keeping fruit and vegetable fresh, and refrigerating the biology. How to handle the economic application of this step has a huge effect on the whole process. The frosting phenomenon during the refrigeration plays a very important part in the quality of the food and the stability of the refrigeratory. According to this, research on the experiments about the frosting and defrosting of the constant temperature and humidity system has been made.Through the control system based on the PLC, the thesis has studied the evaporation temperature, the wing temperature and the difference of the pressure, which based on different storing temperature, different humidity and the blowing velocity. The experiments’results show that differences of the frosting quantity are obvious on the surface of the evaporator during different experiment conditions. With the fall of the storing temperature, the rising of the humidity, and the fall of the blowing velocity, the frosting quantity will rise in certain range.The conditions that frost easily have obtained through the experiments, which become the basis of the defrosting experiments. During the defrosting processes, many methods have been used to contrast, such as stopping the refrigerating and the non-stopping the refrigerating defrosting, and defrosting at different time. Finally, the right way of defrosting was obtained through analyzing the experiments’results.更多还原