Vaporisation of liquefied gases

Claim 1

PROCESS FOR THE VAPORISATION OF LIQUEFIED OXYGEN OR NITROGEN WITH SUBSEQUENT HEATING OF THE VAPOR FORMED TO A TEMPERATURE NOT ABOVE THE AMBIENT TEMPERATURE, WHICH COMPRISES PASSING A STREAM OF THE LIQUEFIED GAS THROUGH AN EVAPORATOR, PASSING A STREAM OF ATMOSPHERIC AIR EXTERNALLY OF THE EVAPORATOR IN INDIRECT HEAT EXCHANGE WITH THE LIQUEFIED GAS PASSING INTERNALLY THERETHROUGH AT A VELOCITY SUCH THAT THE FALL IN TEMPERATURE OF THE AIR IN ITS PASSAGE PAST THE EVAPORATOR IS MAINTAINED AT A VALUE SUFFICIENTLY SMALL TO PREVENT THE OUTER SURFACE OF THE EVAPORATOR FROM FALLING BELOW THE FREEZING POINT OF WATER AT ATMOSPHERIC PRESSURE, AND PERIODICALLY REVERSING THE DIRECTION OF FLOW OF THE LIQUEFIED GAS THROUGH THE EVAPORATOR WHILE MAINTAINING CONSANT THE DIRECTION OF FLOW OF THE STREAM OF ATMOSPHERIC AIR EXTERNALLY OF THE EVAPORATOR.