霜层生长初期冰晶体分布状况实验研究

Experiment Investigation on Distribution of Ice Crystal During Initial Period of Frost Growth

研究霜层的结构对于理解结霜现象有着重要的意义。利用自行研制的图像放大及采集系统,对霜层生长初期冰晶体的形态进行显微观测,得到了不同生长条件下冰晶体的图像。随后采用数字图像处理方法,将原图像转换为二值图。通过对图像的分析,发现霜层的生长初期冰晶体的分布与充分生长的霜层有所不同,此时霜层靠近冷表面固含率最大;随着高度的增长,固含率以近似线性的方式减小。实验还发现,对霜层生长初期影响最大的两个因素是冷表面的温度和空气的相对湿度。随着冷表面温度的降低,霜层的高度明显增长,冰晶体沉积量增加,而平均密度的变化则不明显;随着空气相对湿度的增加,霜层的高度、平均密度以及冰晶体总的沉积量都有所增加。空气温度对霜层生长的影响不明显。

With the picture magnifying and collecting system, ice crystal shape was observed and the picture of ice crystal at different circumstance was obtained. Then the digital image processing method was used to convert the initial picture into binary image. On the basis of analyzing this image, it is found that the distribution of ice crystal at the initial period of frost growth is different from that at fully growth period. In initial time, the maximum occupancy rate of ice crystal occurs near the cold plate, and it decreases linearly with the frost thickness. It is also found that the most important factors that influence the frost growth are the temperature of cold plate and relative humidity of air. Frost thickness and deposition of ice crystal increase with the decrease of cold plate temperature and the increase of air humidity, and the frost average density increases with the increase of air humidity. The influence of air temperature on frost growth is not obvious.