Expansion ratios cryogenics

Cryogen Name Vapor Pressure, MPa Gas Density, g/1 Liquid/Gas Expansion Ratio Heat Capacity Cp, J/(kg K) Heat Capacity Cv, J/(kg K) Thermal Conductivity x 10-2 w/(m-K) Viscosity Pa-sec x 105 (cP) Solubility in Water, 0°C, v/v... 

The column 8 elements are all nonhazardous gases however, they can displace the oxygen in the air inside of buildings or in confined spaces and cause asphyxiation. Inert gases are commonly shipped and stored as compressed gases or cryogenic liquids. These materials are quite cold and can cause thermal bums. They also have large expansion ratios. DOT does not place them in a hazard class unless they are under pressure. 

Cryogenic liquids have large expansion ratios, some as much as 900 or more to 1 (see Figure 4.22). Because of this expansion ratio, if the cryogenic liquid is flammable or toxic, these hazards are intensified because of the potential for large gas cloud production from a small amount of liquid. As the size of a leak increases, so does the size of the vapor cloud. 

Assure adequate ventilation. Since liquified cryogenic gases have a high volume expansion ratio (see Table 17.1) when evaporated (in other words, a very small amount of liq-... 

Cryogenic fluids (hquified gases) are characterized by extreme low temperatures, ranging from a boiUng point of -78.5 C (-109 F) for carbon dioxide to -269.9 C (-453.8 F) for an isotope of hehum, e. Another common property is the large ratio of expansion in volume from liquid to gas, fixrm approximately 553 to 1 for carbon dioxide to 1438 to 1 for neon. Table 4.13 contains a more complete summary of the properties of cryogenic fluids. 

Temperature Correction. A temperature correction factor, must be used to account for any change of the area of section A 2 of the primary element when the operating temperature differs appreciably from the ambient temperature at which the device was manufactured and measured. If the meter is to be used under temperature conditions within the range of ordinary atmospheric temperatures, any difference between the thermal expansion of the pipe and the primary element may be ignored and the diameter ratio, p, may be considered to be unaffected by temperature. At cryogenic temperatures, the material for the throat liner of a Venturi tube, a flow nozzle, or an orifice plate should have a coefficient of thermal expansion as close as possible to that of the pipe. 

---