A furnace with an aperture of 20-mm diameter and emissive power of 3.72 x 105 W/m2 is used to calibrate a heat flux gage having a sensitive area of 1.6 x 10-5 m2.

(a) At what distance, measured along a normal from the aperture, should the gage be positioned to receive irradiation of 1000 W/m2?

(b) If the gage is tilted off normal by 20°, what will be its irradiation?

(c) For tilt angles of 0, 20, and 60°, plot the gage irradiation as a function of the separation distance for values ranging from 100 to 300 mm.