Calorimetric analysis of water dissolved in dielectric fluids

Abstract

In order to investigate how the water dissolved in dielectric fluids at room temperature behaves in case of being subjected to cooling/heating, such dielectric fluids as alkyldiphenylethane and dimethyl silicone liquid of 50 cSt at 25°C in which various amounts of water were dissolved were investigated calorimetrically, using highly precise Differential Scanning Calorimetry (DSC). Moreover, the degree of turbidity of the specimens which were cooled or heated in a constant rate in a low temperature bath was observed visually to detect the appearance and disappearance of coagulation of the dissolved water in them. As a result, it has been found out that, whereas the water dissolved in alkyldiphenylethane appears to be led to an icy state, a coagulated state and a dissolved state at low temperatures, depending on its water contents, that in dimethyl silicone liquid appears to be led to a coagulated state and a dissolved state, without any indication of formation of the ice crystals. The authors have succeeded in determining quantitatively the ice crystals produced from the water dissolved in a dielectric fluid at low temperatures using Differential Scanning Calorimetry. Thus, it has been concluded that this method has proved very useful for investigating the crystallization behavior of dissolved water existing in dielectric fluids at low temperatures, although it goes without saying that this method is also available for their crystallization temperature and glass transition temperature measurements at low temperatures.