The Ansys Chemkin software includes the file tran.dat in the System Data directory of the standard installation. This data file contains transport data for over 200 species. This compilation is something of a historical record and should be considered a starting point only and used with some caution. Some of the numbers in the standard tran.dat file were determined by computing "best fits" to experimental measurements of a macroscopic transport property (for example, viscosity), while in other cases the Lennard-Jones parameters were estimated.

Users will often need additional transport data for their particular simulations. User data can be provided in a supplemental TRANSPORT...END data block in their gas-phase mechanism file. When adding a new species to this block of data, the species name needs to exactly match that in the corresponding thermochemical data and in the chemical-kinetic mechanism SPECIES...END block, and should have the same format as the standard tran.dat file. More information about transport data is available in the Chemkin Input Manual.

Previous modeling work is often a good source of transport parameters; they are often provided along with thermochemical and kinetic data in established reaction mechanisms. Some data on Lennard-Jones parameters can be found in standard references such as Hirschfelder, Curtiss and Bird [25], or chemistry and chemical engineering handbooks. In some cases, however, transport parameters will have to be estimated. Svehla [26] outlines methods for estimating the needed force constants based on physical properties such as molar volumes or boiling points, as well as empirical and combining rules for extrapolating amongst related molecules.