Technical Reports

Thermodynamic Properties of Liquefied Petroleum Gases

  • 01
  • Apr
  • 1980
AUTHOR: Sallet and Wu
OFFICE: RPD
REPORT NUMBER: DOT/FRA/ORD-76/299
SUBJECT: Hazardous Materials
KEYWORDS: hazardous materials; propane; thermodynamic data; data of hydrocarbons; propylene; n-butane; maximum flow rates of propane; liquefied petroleum gases; safety relief valves
ABSTRACT: The thermodynamic properties of several liquefied petroleum gases (with particular emphasis on propane) are discussed in detail. It is concluded that the widely used propane data by Stearns and George are too inconsistent and too inaccurate to be used for mass flow calculations of propane and propane mixtures through safety valves of rail tank cars. Accordingly, the thermodynamic properties of propane, propylene, n-butane, and a mixture of 65% (by mole) propane, 25% propylene, and 10% n-butane, are recalculated using equations of states proposed by Benedict-Webb-Rubin (BWR) and by Starling. It is shown that Startling’s equation results in thermodynamic properties which are more consistent and compare better with measured values than the BWR equation. Thermodynamic data for the four liquefied petroleum gases discussed above are calculated and presented in tabular form. In addition, predictions of pure propane mass flow rates (based upon isentropic, homogeneous equilibrium flow) are given. The influence of the thermodynamic data upon the predicted mass flow rates is demonstrated.

####