Péclet Number

a dimensionless number that is a similarity criterion for processes of convective heat exchange; named after the French physicist J. C. Péclet (1793–1857). The Péclet number Pe = vl/a = C_pρvl/γ, where l is the characteristic linear dimension of the surface of heat exchange, v is the fluid velocity relative to the heat exchange surface, a is the thermal diffusivity, C_p is the specific heat at constant pressure, ρ is the density, and λ is the thermal conductivity of the fluid. The number Pe characterizes the relationship between the convective and molecular processes of heat exchange in the flowing fluid. The process of molecular conduction predominates at low Pe values, and the process of heat exchange by convection of the fluid predominates at high Pe values. The relation between the Péclet number, the Reynolds number Re, and the Prandtl number Pr is given by the equation Pe = Re × Pr.