Jakob Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Jakob number, abbreviated as Ja, a dimensionless number, is the ratio of sensible latent heat absorbed or released during liquid vapor phase change.

Jakob Number formula

 $$\large{ Ja = \frac{ c_p \; \left( T_s \;-\; T_{sat} \right) }{\Delta h_f} }$$

Where:

 Units English Metric $$\large{ Ja }$$ = Jakob number $$\large{ dimensionless }$$ $$\large{ c_p }$$ = constant pressure at specific heat $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ \Delta h_f }$$  = evaporation enthalpy change $$\large{\frac{Btu}{lbm}}$$ $$\large{\frac{kJ}{kg}}$$ $$\large{ T_{sat} }$$ = temperature saturation point $$\large{F }$$ $$\large{ K }$$ $$\large{ T_s }$$ = total stagnation temperature $$\large{F }$$ $$\large{ K }$$