heat flow[′hēt ‚flō]
the amount of heat transferred across an isothermal surface in a unit time. Heat flow has the same dimensions as power and is measured in watts (W) or kilocalories per hour (kcal/hr); 1 W = 0.86 kcal/hr.
The amount of heat transferred across an isothermal surface of unit area in a unit time is called the heat flux. It is usually designated
by q and is measured in W/m2 or kcal/(m2·hr). Heat flux is a vector. The magnitude of any component of this vector is equal to the amount of heat transferred in a unit time across a surface of unit area perpendicular to the direction of the component. In English, the term “heat flux” is sometimes used in the sense of “heat flow.”