Radiation:

  When heat is transferred through radiation, heat transfer rate, Q, is give as    

where F = factor depending upon the view emissivity factors.σ = Stefan-Boltzmann constant, 0.1713x10-8 Btu/(h·°F4). If the surfaces are normal to each other then the view factor is 1. The emissivity factor, Fε, can be calculated as

   

Where εi is an emissivity of body i having surface temperature Ti.

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Radiation through parallel surfaces

Radiation loss through a shield

Module for calculation of radiation losses:

L1 (insulation thickness 1, ft)
k1 (thermal conductivity 1, BTU per hr per ft per deg F)
L2 (insulation thickness 2, ft)
k2 (thermal conductivity 2, BTU per hr per ft per deg F)
L3 (insulation thickness 3, ft)
k3 (thermal conductivity 3, BTU per hr per ft per deg F)
hi (inside film coefficient, BTU per hr per ft2 per deg F)
ho (outside film coefficient, BTU per hr per ft2 per deg F)
Ta (Inside Temperature, deg F)
Tb (Outside Temperature, deg F)