Question

1.0 3) A diffuse surface at T = 1200K.has the spectral, hemispherical emissivity illustrated. Determine the following: o. E2 00 2. = 2 um 12 = 5 um 3 a. the total, hemispherical emissivity is a = (+0.001) E1 0.4 b. the total emissive power is E = kW/m² (+ 0.1%) 0 0 2 5 2. (um)

Answer 1

Solution known Spectral, hemispherical emissivity of a diffure surface at 1200k find - Total Hemispherical emissivity Total emissive power. Assumptions:- Surface is a diffuse emitter Analysis :- 6 The total Hemispherical emissivity is given by - So Ex Exo da E = Where the inte gration may Eb be perfomed in parts as follows & S² Exb dd E = Eb Eb Eb So Ex Exb di Ez sos Edbold => => E = Es Forum + Ez [Forum - Foorum where is Fosxum a fraction of the total emission from a black body that is in a certain wavelength interval op band (0+1). from the table [ Block body Radiation Functions], we obtain- at t, T = 2umx 1200 K = 2400 Mmok + Forzum 70.140 & at 3 T = SMM X 1200 K = 6000 Mm.k → For Sum= 0.7378 also given that E,=0.4 and Ep = 0.8+ { = 0.4x0.140 +0.8 (0.7378 -0.140) E = 0.5342 Answer z)

2 Total emissive power- E E Eb Stefenn's boltzmann constant O=5.67*108 W/m²kY E = 0.5342 X5.67x108x (120014 E = 62.807 kW/m² Answer E = EO T4 . =>