Question

Compute the equilibrium temperature of a thin, polished copper plate 1 m x 1 m x 1 mm under the following conditions: a In earth orbit, with solar radiation normal to a side of the plate. Neglect the 3.7 influence of the earth. See Table 4.7.1 b Just above the earth's surface, with solar radiation normal to the plate and the sun directly overhead. See Table 4.7.1 Assume the following: the sky is clear and transmits 0.80 of the solar radiation. the equivalent blackbody sky temperature is 10 C less than the ambient temperature, the ambient air temperature is 25 C, the wind heat transfer coefficient is 23 W/m C, and the earth's surface is effectively a blackbody at 15 C. type, emittance and absorptance values can be fould from e qauuns Ul materials. The data are Table 4.7.1 gives data on surface properties for a few common total hemispherical or total normal absorptance at room temperature. Most of these data were calculated from monochromatic data as was done in Example 4.6.1. Table 4.7.1 was compiled from Volumes 7, 8, and emittances at various temperatures and normal solar Table 4.7.1 Radiation Properties Emittance Temperature 0.102 0.130 0.113 Mate 573 773 873 0.09-0.10 296 484 574 012-0.16 Aluminum, pure 0.842 0.720 0.669 Aluminum, anodized Aluminum, Sio, coated Carbon black in acrylic binder Chromium 0.366 0.384 0.378 263 293 324 0.83 278 0.290 0.355 0.435 722 905 1072 0.041 0.036 0.039 338·463 . 80- 0.025 0.040 0.048 275 468 668 0.071 0.110 0.175 199 468 668 0.89 298 0.73 0.68 0.53 380 491 755 0.10 0.10 0.12 310 468 668 0.11 0.94 0.415 0.35 Copper, polished 0.20-0.23 0.44 Lampblack in epoxy Magnesium oxi Nickel Paint 0.96 0.14 0.36-0.43 Parson's black Acrylic white White (ZnO) 0.981 0.981 240 462 0.90 298 0.929 0.926 0889 295478 646 0.98 0.26 0.12 0.18 H is total hemispherical emittance. N is total novrmal emittance "The numerator is the emittance at the temperature KKyof the denominator Normal solar absorptance

Answer 1

m tab 2 al a:0、01005 b:-0.000 t

ant On P, b Gse .rah, dsel :04.(Ст.:..а.) und.nb