VACUUM BREAK SAFETY OF LIQUID HYDROGEN & HELIUM TANKS

SAFETY OF VACUUM JACKETED CRYOGENIC VESSELS DEPENDS ON SIZING THE VENT LINE AND RELIEF DEVICES TO HANDLE VAPOR GENERATED DUE TO HIGH HEAT TRANSFER RESULTING FROM VACUUM BREAK TO ATMOSPHERIC AIR. HYDROGEN AND HELIUM TANKS CAN EXPERIENCE VERY HIGH AIR BREAK VENTING RATES IF AIR CONDENSES ON THE INNER SHELL. EXISTING GUIDELINES FROM THE COMPRESSED GAS ASSOCIATION DO NOT ADEQUATELY PREDICT VAPOR FLOW UNDER THESE CONDITIONS. THERE IS LITTLE EXPERIMENTAL HEAT TRANSFER DATA TO PROVIDE A BASIS FOR DESIGNING SAFE VENTING SYSTEMS, PARTICULARLY FOR MLI INSULATED DEWARS. FOCUS OF THE PROPOSED WORK IS DEVELOPMENT OF GENERAL CRITERIA FOR MLI AND ALTERNATE TANK COATINGS WHICH PREVENT AIR CONDENSATION UNDER VACUUM BREAK CONDITIONS. PHASE II OFTHE PROGRAM INVOLVES AN EXPERIMENTAL VACUUM BREAK PROGRAM WITH SPECIALLY DESIGNED HYDROGEN AND HELIUM VESSELS.