Heat Flow Rate

Written by Jerry Ratzlaff on . Posted in Thermodynamics

Heat Flow Rate

Heat flow rate ( \(Q_f\) ) is the rate at which heat moves from an area of higher temperature to an area of lower temperature.  Btu/hr (W/hr). Heat flow is generally used to quantify the rate of total heat gain or heat loss of a system.

Heat Flow Rate FORMULA

\(heat \; flow \; rate \;=\;   -\; thermal \; conductivity \;\; \left( \; \frac { area \; of \; body } { length \; of \; material } \; \right)  \;\;  temperature \; differential  \)

\(Q_f = -\lambda  \left( \frac {A} {l} \right)   \Delta T  \) 


\(Q_f\) = heat flow rate

\(\lambda\) (Greek symbol lambda) = thermal conductivity

\(A\) = area of the emitting body

\(l\) = length of the material

\(\Delta T\) = temperature differential


Tags: Equations for Heat Equations for Flow Rate