RESEARCH ON THE HAZARDS ASSOCIATED WITH THE PRODUCTION AND HANDLING OF LIQUID HYDROGEN. Period covered: January 1958 to December 1959

The vaporization of liquid hydrogen from a surface is treated as a problem in heat transfer theory. Two extreme cases are briefly considered: (1) the transfer of heat occurs at constant temperature drop between the boiling liquid and the hot sunface, and (1) the transfer of heat is limited by the rate at which it can flow to the surface through a hot insulating medium. The available data indicate that case (1) is applicable when vaporizing from a conducting surface and initially, when vaporizing from an insulating medium; case (2) is applicable after initial flash vaporization has occurred from the insulating medium. The vaporization rate determines in part the rate at which flammable hydrogen vapor-air mixtures are formed above a spill area. However, the rate at which heat is transferred to the vapor is also important as is the rate at which air is brought in contact with the vapor. Accordingly, the distribution of flammable mixtures above a spill area was determined experimentally. In general, flammable mixtures were found to be both above and within the visible vapor cloud. The hazards associated with the ignition of hydrogen vapor-air mixtures above a liquid hydrogen spill area were determined by (1) ignitingmore » the vapors above a dewar and (2) igniting the vapor-air nuxtures above a spill area at various times following spillage of various quantities of liquid to 90 liters. Flame height and width measurements were made from motion pictures of the resultant flames. In addition, radiant energy and overpressure measurements were made at various distances from the flame. While the flame radiation was found to represent an appreciable amount of the available energy, the overpressure produced by the rapid combustion of hydrogen above a spill area was quite small. Burning rate measurements were conducted on pools of various liquid fuels including hydrogen. These were used to correlate burning rate with the heat feed-back to a pool to maintain steady vaporization and combustion. Finally, the results of this study were used to compile a table of distances for the storage of liquid hydrogen and outline emergency procedures for the protection of personnel and equipment when an accidental spillage of hydrogen occurs. (auth)« less