ABSTRACT
Generation in mass transfer is easy to visualize since it involves the production or consumption of chemical species in the system. Generation in energy transport most often means the production or consumption of heat. The form of the generation term in the charge transport equation is essentially equivalent to the generation term in the species continuity equations for mass transfer. The boundary conditions involving generation in charge transport reflect the similarity between it and mass transfer. In momentum transport the generation terms result from forces acting to drive the fluid. Most commonly, these are pressure forces, body forces such as gravity, or surface forces. Heat generation may come from radioactive decay, chemical reaction, friction, electrical heating, absorption of radiation, phase changes, or from viscous dissipation in a fluid, where friction between the fluid molecules generates the heat.
