upstream over a minimum length of 10 times the diameter of the tube forming a rupture angle of more than about 5 degrees in relation to a portion of tube downstream fig4 shows that the change of direction can also take the form of a chicane 202 the rupture angle is thus equal to 90 degrees in this case fig5 shows that the change of direction can also be a change of section 203 of the tube 200 in the circulation circuit 20 the change of section 203 is preferably a shrinkage of the section the shrinkage 203 is preferably local with the section of the tube upstream and downstream of the shrinkage 203 being more or less the same the shrinkage takes place over a length which is more or less equal to 3 times the diameter of the tube 200 before the shrinkage fig9 shows that the obstacles 207 and 208 positioned within the tube 200 can form the supercooling rupture means the obstacles can take the form of plates for example or of fins 207 or 208 lying perpendicularly to the inner wall of the tube 200 or obliquely the obstacles 207 or 208 can have many different shapes they can also take the form of needles for example the obstacles 207 and 208 are attached or made from the material of the walls of the tube 200 the change of lining of the internal walls takes the form of a change of material and or a change of the surface state designed to interrupt the supercooling and allow the appearance of crystals the material of the rupture means.