This section presents methods and examples of computing the steady-state heating and cooling loads of aircraft compartments. In a steady-state process the flows of heat throughout the system are stabilized and thus do not change with time. In an aircraft compartment, several elements compose the steady-state air conditioning load. Transfer of heat occurs between these sources and sinks by the combined processes of convection, radiation, and conduction in the following manner: 1) convection between the boundary layer and the outer airplane skin; 2) radiation between the external skill and the external environment; 3) solar radiation through transparent areas directly on flight personnel and equipment and on the cabin interior surfaces; 4) conduction through the cabin walls and structural members; 5) convection between the interior cabin surface and the cabin air; 6) convection between cabin air and flight personnel or equipment; and 7) convection and radiation from internal sources of heat such as electrical equipment.
