One can note that in the special case of a small area A and surrounded completely by a high temperature heater Te, which are the conditions of e_e=1, the net radiation power will now be approximately equal to (e_a)sA(Te⁴-Ta⁴). Note that the radiative power follows a power law that is T⁴. (T is in Kelvin).

MHI heating elements and microheaters are designed for high emissivity. 

Elements like the nanostructured GAXP™, No-Age ™ or MP1900™, Microheaters™ and Magnacoils™ .  These are best free (open) radiating heating elements and materials.