Eckert Number

Eckert number, abbreviated as Ec, a dimensionless number, is used in thermodynamics and fluid dynamics to characterize the ratio of kinetic energy to thermal energy in a fluid flow.  It is defined as the ratio of the kinetic energy per unit mass to the specific enthalpy increment per unit temperature difference.  It is used to study the behavior of high speed fluid flows, such as those found in supersonic aircraft or rocket engines.  A high Eckert number indicates that the flow is dominated by kinetic energy, while a low Eckert number indicates that the flow is dominated by thermal energy.

 

Eckert Number formula
\( Ec \;=\; U^2 \;/\; 2 \; c \; \Delta T \)     (Eckert Number) \( U \;=\; \sqrt{ 2 \; Ec \; c \; \Delta T }   \) \( c \;=\; U^2 \;/\; 2 \; Ec \; \Delta T \) \( \Delta T \;=\; U^2 \;/\; 2 \; Ec \; c \)
Symbol	English	Metric
\( Ec \) = Eckert number	\(dimensionless\)	\(dimensionless\)
\( U \) = characteristic flow velocity	\(ft\;/\;sec\)	\(m\;/\;s\)
\( c \) = specific heat	\(Btu\;/\;lbm-F\)	\(J\;/\;kg-K\)
\( \Delta T \) = temperature change	\(F\)	\(K\)