Two well known laws that govern thermal radiation from surface Stefan’sLaw:A e(epsilon)o(sigma) P/a the power in watts radiated per square meter, E is a number, called the sur face emissivity(0-10)(Shiny Metal, ull Surface) Shiny metal surfaces have an emissivity at the lower end of this range under 0. 1. Dull surfaces will have values closer to 1.0 o is a number known as stefan-Boltzmann constant a=567×10-8W/m2.K4 Wien displacement law: /max (um) 2898 7(K) The sun's surface: a 2898 0.5 microns 5800 The black absorber surface: 2 2898 8.05 microns 360 复旦大学环境科学与工程系 Department of Environmental Science and Engineering, Fudan UniversityTwo well known laws that govern thermal radiation from surface: Stefan’s Law: ε(epsilon) σ(sigma) P/A the power in watts radiated per square meter, ε is a number, called the surface emissivity. (0~1.0) (Shiny Metal, Dull Surface) Shiny metal surfaces have an emissivity at the lower end of this range under 0.1. Dull surfaces will have values closer to 1.0. σ is a number, known as Stefan-Boltzmann constant. 4 T A P = εσ 18 2 4 = 5.67×10 W / m ⋅K − σ Wien displacement law: The sun’s surface: The black absorber surface: ( ) 2898 max ( ) T K λ µm = 0.5 micrions 5800 2898 λmax = = 8.05 micrions 360 2898 λmax = =