Freezing Process of Solution in Two Cells Separated by a Semipermeable Membrane

实验研究了用玻璃纸膜隔开的两个细胞中溶液的混合和冷冻过程。采用高、长、宽分别为H=50 mm、L=30 mm、W= 38.4 mm的矩形容器，在容器宽度的中间平面贴附垂直膜，将容器分成两个细胞。通过将两个恒温槽中的卤水泵入壁后的容器，使左侧壁充满初始浓度为20%的NaCl-H2O浓溶液，右侧壁充满蒸馏水，从初始温度保持在40℃的条件下突然冷却，分别保持在-20℃和-5℃两个恒定但不同的温度。除了自由表面外，其他的墙壁都是绝缘的。制冷曲线由热电偶水平耙测量，该热电偶放置在距离电池底部H= 25mm的标高处。利用盐度传感器获得了浓度和温度的垂直分布。发现细胞内溶液的分层是通过溶质与溶质的混合而形成的。在冷冻过程中，在厚液侧的胞体中观察到双扩散界面。与薄金属壁相比，玻璃纸膜壁分离的细胞中树突的生长速度和过冷程度较小。

An experimental study on mixing and freezing process of solution in two cells separated by a cellophane membrane was performed. A rectangular container of which the height, length and width were H=50 mm, L=30 mm and W= 38.4 mm, dividing into two cells by attaching the vertical membrane at the midplane of width was used. The left-hand side wall of the cell filled with the thick solution of NaCl-H2O of which the initial concentration is 20% and the right-hand side wall of the cell filled with the distilled water were abruptly cooled from the initial condition kept at temperature 40 C and were maintained at two constant but different temperatures, -20 C and -5 C respectively by pumping brine from two constant temperature baths through container behind the walls. The other walls were insulated except for the free surface. The refrigerating curves were measured by a horizontal rake of thermocouple which was positioned at the location corresponding to the elevation of H=25 mm from the bottom of the cells. The vertical distributions of concentration and temperature were obtained by using a salinity sensor. It was found that the stratification of solution in the cells was formed by mixing solute of solvent which passed through the membrane. The double diffusive interfaces were observed in the cell of thick solution side with going on a freezing process. It appeared that the growth rate of dendrites and the degree of super cooling in the cells separated by the cellophane membrane wall were small in comparison with the thin metal wall.