All Electro-Flex Heat products are designed using these heat transfer principles:

**Conduction Heat Transfer**: heating process whereby heat energy is transferred from a body of higher temperature to a body of lower temperature by direct contact of the two bodies, or within one body when the heat flows from a higher-temperature zone to a lower-temperature zone.

where,

H = heat flow, (Btu/hr)

k = conduction coeffiecient, (Btu-in./hr.-ft^{2} -°F)

A = area of contact surface, (ft^{2})

t_{H} = higher temperature, (°F)

t_{L} = lower temperature, (°F)

d = depth (thickness), (in.)

**Convection Heat Transfer**: heating process whereby heat is transferred by the motion of a heated medium (gas or liquid) over the body to be heated. Free convection exists where motion is due to gravity. Forced convection is where the medium is moved with blowers or pumps.

where,

H = heat flow, (Btu/hr)

h = convection coefficient, (Btu-in./hr.-ft^{2} -°F)

A = area of contact surface, (ft^{2} )

t_{H} = higher temperature, (°F)

t_{L} = lower temperature, (°F)

**Radiation Heat Transfer**: heating process whereby heat is emitted from a higher-temperature surface into space and absorbed by a lower-temperature surface through the natural radiation of heat waves.

where,

H = heat flow, (Btu/hr)

S = Stefan-Boltzmann constant, (Btu/hr.-ft^{2} -°R^{4})

e = radiation factor

A = area of contact surface, (ft^{2} )

T = absolute temperature, (°R)