# Exchanged Heat in a Heat Exchanger

Written by Jerry Ratzlaff on . Posted in Thermodynamics

## Exchanged Heat in a Heat Exchanger Formula

 $$\large{ Q = h \; A \; LMTD }$$

### Where:

 Units English Metric $$\large{ Q }$$ = exchanged heat duty $$\large{ \frac{Btu}{lbm}}$$ $$\large{ \frac{J}{kg}}$$ $$\large{ A }$$ = exchange area $$\large{ft^2}$$ $$\large{m^2}$$ $$\large{ h }$$ = heat transfer coefficient $$\large{\frac{Btu}{hr-ft^2-F}}$$ $$\large{\frac{W}{m^2-K}}$$ $$\large{ LMTD }$$ = logarithmic mean temperature differential $$\large{ \frac{Btu}{lbm}}$$ $$\large{ \frac{J}{kg}}$$