A

= area, m ²

A

= albedo (reflected solar radiation off Earth), W/m ²

b

= dimension (width), m

C

= convection conductance, W/K

c

= specific heat (solids), W-h/kg K (also J/kg K)

c _o

= speed of light in vacuum, 3.0 10 ⁸ m/s

c _p

= specific heat at constant pressure (fluids), J/kg K

c _v

= specific heat at constant volume (fluids), J/kg K

D

= diameter, m

D _h

= hydraulic diameter, m

E

= modulus of elasticity (bending of tubular elements), N/m ²; voltage, V

E

= Earth [infra red (IR)] radiation, nominally 236 W/m ²

Ec

= Eckert number

e

= coefficient of expansion (composites; bending of tubular elements), /K

F

= shape factor; radiation factor, W/K ⁴; also W/m ² K ⁴; friction factor (heat pipe), N/W m ³

F

= radiation blockage factor (measure of ability to view)

F _A

= shape factor

F _E

= emissivity factor

f

= friction factor (Fanning); factor relating multilayered insulation properties to radiator's effective optical properties

f

= albedo factor, nominally 0.33

G

= radiation G factor, W/K ⁴

Gr

= Grashof number

g

= gravitational acceleration, m/s ²

H

= dimension; length (heat pipe in a radiator); height, m

HTF

= heat transport factor (heat pipe), W-m

h

= convection coefficient, W/m ² K; Planck's constant, 6.626 10 ^?34 J s

I

= radiation intensity, W/m ² ?m; moment of inertia,...