Featured Resource This radiation heat flow calculator is for a single heat shield between parallel plates. It figures the heat flow between two plates at given temperatures (if only you knew that ahead of time!) with a heat shield between. The heat flux between the plates is halved by the installation of the heat shield, even when all surfaces are treated as perfect emitters. (Think car-exhaust systems; it's common practice.)
I used the calculator to look at the effect of low emissivity coating on the various surfaces. It doesn't matter which surface you choose -- any one surface with low emissivity (I used 0.15 as an
estimate) cut the heat flux by almost 75% over having a black-body shield in place. Two surfaces cut it even further, by 85%. Compared with no heat shield between high-emissivity plates, a single
shield with low emissivity on both sides reduced the heat flow by 93%! Think about that next time you're contemplating outdoor equipment that's going to sit in the sun. |
