Calorimetric Measurements of Water Dissolved in Dielectric Fluids

In order to investigate how the water dissolved in dielectric fluids at room temprature behaves when subjected to cooling/heating, such dielectric fluids as alkyldiphenylethane and dimethyl silicone liquid in which various amounts of water were dissolved were investigated calorimetrically, using very precise Differential Scanning Calorimetry (DSC). Moreover, the degree of turbidity of the specimens which were cooled or heated at a constant rate in a low temperature bath, was observed visually to detect the appearance and disappearance of coagulation of dissolved water. As a result, it has been found that, whereas the water dissolved in alkyldiphenylethane appears to form an icy state, a coagulated state and a dissolved state at low temperatures, depending on its water contents, that on the other hand the water in dimethyl silicone liquid appears to form a coagulated state and a dissolvedstate, without any indication of formation ofice crystals. The author has succeeded in determining quantitatively the ice crystals produced from the water dissolved in a dielectric fluid at low temperatures using DSC. Thus, it has beenconcluded that this method has proved very useful for investigating the crystallization behavior of dissolved water existing in dielectric fluids at low temperatures.