Above a few hundred degrees — furnace walls, radiant panels, hot process equipment — radiation stops being a correction and becomes the dominant mode. Exchange between two surfaces needs exactly two ingredients: a view factor for the geometry and emissivities for the surfaces. These four tools provide both for the standard configurations.
What's in this suite
- Aligned Parallel Plates — two equal gray rectangles face-to-face, the classic analytical view-factor expression.
- Aligned Parallel Square Plates — the equal-square special case.
- Coaxial Parallel Disks — directly-opposed disks of possibly different radii (lamp-to-target, furnace port geometries).
- Perpendicular Plates — Common Edge — two rectangles meeting at a right angle (wall-to-floor, wall-to-ceiling exchange).
Method
The view factor F12 — the fraction of radiation leaving surface 1 that arrives at surface 2 — is pure geometry, evaluated from the exact analytical expressions for each configuration. For coaxial disks, for example:
F12=21{S−[S2−4(r2/r1)2]1/2}Net exchange between two gray, diffuse, isothermal surfaces forming an enclosure then follows the two-surface network:
Q12=ε1A11−ε1+A1F121+ε2A21−ε2σ(T14−T24)with temperatures in kelvin and σ=5.67×10−8 W/m²·K⁴. An emissivity table for common industrial finishes (polished and oxidised metals, painted surfaces) is built in.
Assumptions
Gray, diffuse, isothermal surfaces; non-participating medium between them (air is effectively transparent at these path lengths). Convection is not included — add it from the convection suites for a total heat balance.