The Eckert number (Ec) is a dimensionless number used in continuum mechanics. It expresses the relationship between a flow's kinetic energy and the boundary layer enthalpy difference, and is used to characterize heat transfer dissipation.^[1] It is named after Ernst R. G. Eckert.

It is defined as

${\displaystyle \mathrm {Ec} ={\frac {u^{2)){c_{p}\Delta T))={\frac {\mbox{Advective Transport)){\mbox{Heat Dissipation Potential))))$

where

• u is the local flow velocity of the continuum,
• c_p is the constant-pressure local specific heat of the continuum,
• ${\displaystyle \Delta T}$ is the difference between wall temperature and local temperature.