Underground cryogenic cavities - Field measurements and numerical methods

The storage of liquified gases in underground cavities and the construction of pipe-lines in permafrost are concerned by problems of heat transfer with change of phase. A two-dimensional finite element numerical method using enthalpy as variable is used to treat the problem around a buried cylindrical cavity placed at a finite depth in ground subjected to a sinusoidal temperature at the upper horizontal surface. A numerical study was made for a period of one year and the results compared with experimental observations at a liquified gas storage pilot station built in Belgium. In addition, the vertical rate of advance of the phase change interface on the upper side of the cavity computed with the two-dimensional model is compared for different depths of the cavity with that computed with one simple axisymetrical numerical model. This comparison establishes the range of depths of the cavity for which the axisymetrical approximation is acceptable.