Molecular Weight#

Molecular Weight = CONSTANT <integer> <float>

Description / Usage#

This card specifies the molecular weight of a species. It is required when the Stefan- Maxwell flux model is used in modeling multicomponent transport of neutral or charged species. It is also required when vapor-liquid phase equilibrium is considered at the material boundaries. Molecular weight is used to convert units of mass fraction to mole fraction in a species material balance.


Molecular weight model type.

  • <integer> - species number

  • <float> - molecular weight of the species


The following is a sample input card:

Molecular Weight = CONSTANT 0 6.939

Technical Discussion#

This card originated from the development of a multicomponent diffusion model based on the Stefan-Maxwell equation. However, it has been generalized to include problems where mole fractions are necessary for the consideration of phase equilibria. For example, when YFLUX_EQUIL is invoked in the input deck, an equilibrium problem is solved rigorously which requires gas and liquid mole fractions. The conversion from mass fraction to mole fraction requires molecular weight information.


No References.