Phenomenology and modeling of liquefied natural gas vapor dispersion

Technical Report · Sun Apr 01 04:00:00 EST 1984

OSTI ID:6194858

Morgan, Jr, D L; Morris, L K; Chan, S T; Ermak, D L; McRae, T G; Cederwall, R T; Koopman, R P; Goldwire, Jr, H C; McClure, J W; Hogan, W J

The purpose of the Burro series of spill experiments, in 1980, and one of the purposes of the Coyote series, in 1981, was to investigate the atmospheric dispersion of cold, dense LNG vapor resulting from an LNG spill onto water. The atmospheric dispersion of LNG vapor differs from that of passive pollutants. Analysis of the LNG vapor concentration data obtained in these spill experiments shows the effects of three physical phenomena that are particularly important in the dispersion of a dense cryogenic gas: (1) reduction in the turbulent mixing rate with air due to stable density stratification, (2) gravity flow of the cloud, and (3) ground heating of the cloud. These phenomena affect the maximum distance to the lower flammability limit (LFL), an important quantity which indicates the potential extent of an accidental combustion. The LFL distance also depends on the spill parameters and meteorological conditions. Our analysis indicates two additional phenomena, rapid-phase-transition (RPT) explosions and differential boiloff (producing increased ethane-to-methane ratio), that can lead to significant increases in the LFL distance. Both the SLAB and FEM3 computer codes incorporate mathematical models of the physics that governs the dispersion phenomena. SLAB is a one-dimensional, crosswind-averaged, conservation-equation model that calculates cloud height and width, and then uses these values to determine the crosswind distribution of LNG vapor concentration. FEM3 is a fully three-dimensional, conservation-equation model that can include variable terrain. Both models are time-dependent. In spill simulations, both give results that are in agreement with the experimental data for downwind extent and duration of the flammable region and other cloud features. In addition, FEM3 can simulate the complicated three-dimensional structure of a cloud where heavy-gas dispersion and terrain effects predominate. 24 refs., 48 figs., 6 tabs.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• OSTI ID: 6194858
• Report Number(s): UCRL-53581; ON: DE86005299
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030800* -- Natural Gas-- Environmental Aspects
500200 -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
CLOUDS
COMPUTER CODES
COMPUTERIZED SIMULATION
DISPERSIONS
DISTRIBUTION
ENERGY SOURCES
ENVIRONMENTAL TRANSPORT
EXPLOSIONS
F CODES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GAS SPILLS
GASES
LIQUEFIED GASES
LIQUEFIED NATURAL GAS
MASS TRANSFER
MATHEMATICAL MODELS
NATURAL GAS
ONE-DIMENSIONAL CALCULATIONS
S CODES
SIMULATION
SPATIAL DISTRIBUTION
THREE-DIMENSIONAL CALCULATIONS
TIME DEPENDENCE
TURBULENCE
VAPORS
WIND