KNOWN: Spectrally selective, diffuse surface exposed to solar irradiation. FIND: (a) Spectral transmissivity, τλ, (b) Transmissivity, τS, reflectivity, ρS, and absorptivity, αS, for solar irradiation, (c) Emissivity, ε, when surface is at Ts = 350K, (d) Net heat flux by radiation to the surface.
KNOWN: Spectral transmissivity and reflectivity of light bulb coating. Dimensions, temperature and spectral emissivity of a tungsten filament. FIND: (a) Advantages of the coating, (b) Filament electric power requirement for different coating spectral reflectivities. ASSUMPTIONS: (1) All of the
KNOWN: Spectral transmissivity of a plain and tinted glass. FIND: (a) Solar energy transmitted by each glass, (b) Visible radiant energy transmitted by each with solar irradiation. ASSUMPTIONS: (1) Spectral distribution of solar irradiation is proportional to spectral emissive power of a blackbody
KNOWN: Thermocouple is irradiated by a blackbody furnace at 1500 K with 25 mm² aperture. Optical fiber of prescribed spectral transmissivity in sight path. FIND: (a) Distance L from the furnace detector should be positioned such that its irradiation is G = 50 W/m² and, (b) Compute and plot
KNOWN: Furnace wall temperature and aperture diameter. Distance of detector from aperture and orientation of detector relative to aperture. FIND: (a) Rate at which radiation from the furnace is intercepted by the detector, (b) Effect of aperture window of prescribed spectral transmissivity on the
KNOWN: Spectral emissivity of an opaque, diffuse surface. FIND: (a) Total, hemispherical emissivity of the surface when maintained at 1000 K, (b) Total, hemispherical absorptivity when irradiated by large surroundings of emissivity 0.8 and temperature 1500 K, (c) Radiosity when maintained at 1000 K
KNOWN: Power dissipation temperature and distribution of spectral emissivity for a tungsten filament. Distribution of spectral absorptivity for glass bulb. Temperature of ambient air and surroundings. Bulb diameter. FIND: Bulb temperature. ASSUMPTIONS: (1) Steady-state, (2) Uniform glass
KNOWN: Spectral distribution of surface absorptivity and irradiation. Surface temperature. FIND: (a) Total absorptivity, (b) Emissive power, (c) Nature of surface temperature change. ASSUMPTIONS: (1) Opaque, diffuse surface behavior, (2) Convection effects are negligible.
KNOWN: Spectral distribution of the absorptivity and irradiation of a surface at 1000 K. FIND: (a) Total, hemispherical absorptivity, (b) Total, hemispherical emissivity, (c) Net radiant flux to the surface. ASSUMPTIONS: (1) αλ = ελ.
KNOWN: Spectral, hemispherical absorptivity of an opaque surface. FIND: (a) Solar absorptivity, (b) Total, hemispherical emissivity for Ts = 340 K. ASSUMPTIONS: (1) Surface is opaque, (2) ελ = αλ, (3) Solar spectrum has Gλ = Gλ,S proportional to Eλ,b (λ, 5800 K).