ABSTRACT
This chapter develops the concept of diffusion and chemical availability and the equations for their numeric calculation, and discusses their applications to various engineering processes such as those in heating, ventilating, and air conditioning (HVAC) and in combustion. The conditions of the environment play an important role in the calculation of thermomechanical availability. The thermomechanical availability will have different values for different choices of the environmental temperature and pressure. In the environmental state, there is no requirement for chemical equilibrium with the environment. It can also be interpreted that there is no interaction between the substance and the contents of the environment. The chapter also develops the concept of diffusion availability for a pure substance that exists as one of the components in the environment. The total flow availability for a mixture is important to many availability analyses. It consists of thermomechanical and diffusion availabilities.
