Quantity of heat divided by area and time.
Source: ISO 14692-1:2017, Petroleum and natural gas industries — Glass-reinforced plastics (GRP) piping — Part 1: Vocabulary, symbols, applications and materials, Second Edition, August 2017. Global Standards
Heat Flux (heat density)
The rate of heat transfer per unit area normal to the direction of heat flow. A convenient unit is kW m-2 (1 kW m-2 = 317 Btu ft-2 h-1). It is a total of heat transmitted by radiation, conduction and convection.
Source: API RP 2FB, Recommended Practice for the Design of Offshore Facilities Against Fire and Blast Loading, First Edition, April 2006. Global Standards