Definitions for "Heat Flow"
The movement of heat energy from the core of the Earth towards the surface.
The flow of heat from the interior of Earth.
Heat flow is measured as the amount of energy transferred per unit of time. In SI units this would be measured in Joules per second. A Joule per second is the same as a Watt (W), so heat flow should be expressed in Watts. Because thermal energy is often measured in non-SI units, heat flow is often reported in other units, too. Air conditioners are rated in BTUs per hour. You will sometimes see ergs per second or calories per second.
energy transfer through various materials and structures (usually refers to conduction, convection, and radiation combined)  Wärmeflu
the transfer of energy from a warmer object to a cooler object