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

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


 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 \(\large{F }\) \(\large{ K }\)


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Tags: Heat Transfer Equations Vapor Equations