Heat flow

Heat flow describes heat per unit of time in J/s or W; it is also a measure of power. Heat flow is a scalar, therefore not directed and not affected by changes of the co-ordinate system.

Applied to a building element, however, heat flow turns into a heat flow rate in W/m². It looses is undirectedness, becoming a vector. The heat flow rate is proportional to the temperature difference at both ends of the system, for example at building element surfaces.

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