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The heating value depends on the source of gas that is used and the process that is used to liquefy the gas. The range of heating value can span ±10 to 15 percent. A typical value of the higher heating value of LNG is approximately 50 MJ/kg or 21,500 BTU/lb. [2] A typical value of the lower heating value of LNG is 45 MJ/kg or 19,350 BTU/lb.
If a sufficient amount of liquid is vaporized within a closed container, it produces pressures that can rupture the pressure vessel. Hence the use of pressure relief valves and vent valves are important. [2] The expansion ratio of liquefied and cryogenic from the boiling point to ambient is: nitrogen – 1 to 696; liquid helium – 1 to 745 ...
Values are given in terms of temperature necessary to reach the specified pressure. Valid results within the quoted ranges from most equations are included in the table for comparison. A conversion factor is included into the original first coefficients of the equations to provide the pressure in pascals (CR2: 5.006, SMI: -0.875).
Lee [4] developed a modified form of the Antoine equation that allows for calculating vapor pressure across the entire temperature range using the acentric factor (𝜔) of a substance. The fundamental structure of the equation is based on the van der Waals equation and builds upon the findings of Wall [ 5 ] and Gutmann et al. [ 6 ] , who ...
A log-lin vapor pressure chart for various liquids. The higher the vapor pressure of a liquid at a given temperature, the lower the normal boiling point (i.e., the boiling point at atmospheric pressure) of the liquid. The vapor pressure chart to the right has graphs of the vapor pressures versus temperatures for a variety of liquids. [10]
Compressibility factor values are usually obtained by calculation from equations of state (EOS), such as the virial equation which take compound-specific empirical constants as input. For a gas that is a mixture of two or more pure gases (air or natural gas, for example), the gas composition must be known before compressibility can be calculated.
At ambient pressure the boiling point of liquefied helium is 4.22 K (−268.93 °C). Below 2.17 K liquid 4 He becomes a superfluid (Nobel Prize 1978, Pyotr Kapitsa) and shows characteristic properties such as heat conduction through second sound, zero viscosity and the fountain effect among others.
This is illustrated in the vapor pressure chart (see right) that shows graphs of the vapor pressures versus temperatures for a variety of liquids. [7] At the normal boiling point of a liquid, the vapor pressure is equal to the standard atmospheric pressure defined as 1 atmosphere, [1] 760 Torr, 101.325 kPa, or 14.69595 psi.