ABSTRACT
The equations governing heat and mass transfer and uid ow processes are based on the conservation principles for mass, momentum, and energy. The conservation principles are very general statements that may be applied in a local sense, leading to differential equations, or in a more global sense, leading to integral equations. In certain special cases the differential equations governing heat transfer and uid ow problems involve only one independent variable and are ordinary differential equations. In addition to a statement of the conservation equations, the formulation of a problem requires a complete speci cation of the problem geometry and appropriate boundary or initial conditions. The momentum and energy equations, the differential and integral forms represent local and global balances of momentum and heat. The differential and integral forms of the governing equations provide alternative starting points for a numerical solution.
