ABSTRACT
The effect of transpiration in numerical simulations, when the boundary layer is resolved, can be easily accounted for by application of the conservation principles to the wall surface. For engineering calculations, the effect of transpiration on friction, heat, or mass transfer can be accounted for by the Couette flow film model, or the stagnant film model. Transpiration cooling is a common and effective method of active cooling of a typically large surface that is exposed to a thermal load that includes a significant convective component. During transpiration cooling, a coolant passes through the heated wall and not only absorbs some of the internal energy in the solid structure, but also reduces the convective heat flux at the surface. Transpiration cooling by an inert gas or liquid can also prevent the oxidation of the heated surface by hot air. Higher coolant gas specific heat and lower molecular mass both improve the performance of a transpiration cooling system.
