Solar radiation effective surface temperature

Another environmental issue important to low earth orbit materials is atomic erosion. At an altitude of 300 km, absorption of solar radiation produces atmospheric temperatures of 1150°C, and at these temperatures gas molecules decompose. Erosion of surface materials by oxygen atoms or nitrogen—oxygen radicals is a serious issue for low altitude orbiting satellites. Experiments conducted on early shuttle flights determined that organic materials that would normally be found on a heatshield erode more rapidly than metallic ones (15). Thus, the effects of atomic erosion must be considered for any vehicle that is subject to long term exposure at low earth altitudes. 

Thus hot bodies not only radiate more energy than cold ones, they do so at shorter wavelengths. The wavelengths for the maxima of solar and terrestrial radiation are 480 nm and 10,000 nm, respectively. The Sun, with an effective surface temperature of 6000 K, radiates about 2 x 105 more energy per square meter than the Earth does at 300 K. 

In our sample calculations (Example 3 1.1) we have chosen the colour of the outdoors surface as light grey and taking the vveathering effect into account, have considered the coefficient of both absorption and emission as 0.65. The manufacturer, depending on the colour and site conditions, may choose a suitable coefficient. It is, however, advisable to be conservative when deciding the temperature rise due to solar radiation to be on the safe side. 

Pollutant effects on the atmosphere include increased parhculate matter, which decreases visibility and inhibits incoming solar radiahon, and increased gaseous pollutant concentrations, which absorb longwave radiation and increase surface temperatures. For a detailed discussion of visibility effects, see Chapter 10. 

Thus, someone working near a window will receive hot solar radiation through the window in summer and cold radiation from the cold window surface in winter, causing uncomfortable radiant asymmetry even if the room temperature is perfect for personnel working away from the window. Ventilation will not be the correct solution for this problem - sun shading and double-glazing would be more effective. 

The rate of heat conduction is further complicated by the effect of sunshine onto the outside. Solar radiation reaches the earth s surface at a maximum intensity of about 0.9 kW/ m. The amount of this absorbed by a plane surface will depend on the absorption coefficient and the angle at which the radiation strikes. The angle of the sun s rays to a surface (see Figure 26.1) is always changing, so this must be estimated on an hour-to-hour basis. Various methods of reaching an estimate of heat flow are used, and the sol-air temperature (see CIBSE Guide, A5) provides a simplification of the factors involved. This, also, is subject to time lag as the heat passes through the surface. 

Calculate the beating due to solar radiation on the flat concrete roof of a building, 8 nr by 9 m. if the surface temperature of the roof is 330 K. What would be the effect of covering the roof with a highly reflecting surface such as polished aluminium ... 

The greenhouse effect is a natural phenomenon whereby the earth s atmosphere is more transparent to solar radiation than terrestrial infixed radiation (emitted by the earth s surface and atmosphere). Consequently, the planet s mean surface temperature is about 33 K higher than the planet s radiative equilibrium temperature (the temperature at which the earth comes into equilibrium with the energy received from the sun). 

If this excess absorption by clouds is ultimately shown to be a real phenomenon, then an increased cloud formation and extent due to anthropogenic emissions may alter the radiative balance of the atmosphere not only through increased reflectance but also through increased absorption of solar radiation. Such an effect could impact atmospheric temperatures, their vertical distribution, and circulation, as well as surface wind speeds and the surface latent heat flux (Kiehl et al., 1995). Hence establishing if this is truly excess absorption, and if so, its origins, is a critical issue that remains to be resolved. 

A greenhouse gas is any component of tbe atmosphere that allows visible solar radiation to reach the Earth s surface but prevents invisible infrared radiation (beat) from escaping back into outer space. This mimics the warming action of a greenhouse. If it were not for the atmosphere s greenhouse effect, Earth s average surface temperature would be a chilly -i8°C. 

Above the troposphere is the stratosphere, which reaches a height of 50 kilometers. At an altitude of 20 to 30 kilometers in the stratosphere lies the ozone layer. Stratospheric ozone acts as a sunscreen, protecting Earths surface from harmful solar ultraviolet radiation. Stratospheric ozone also affects stratospheric temperatures. At the lowest altitudes, the temperature is coolest because of the solar screening effect of ozone air at this altitude is literally in the shade of ozone. At higher altitudes, less ozone is available for shading and temperature increases all the way to a warm 0°C at the top of the stratosphere. 

The primary parameters affecting entrainment and evaporation are solar radiation, ambient temperature, storage or process temperature and pressure, liquid spill surface area, wind speed and the properties of the spilled material (such as vapor pressure, surface tension, and viscosity). Suppressing volatility by reducing containment temperature and constraining pool size or exposed surface area via a dike or berm are effective postmitigation approaches and are discussed in Chapters 3 and 5. 

A solar collector surface receives solar radiation at 1 kW/m2, and its other side is insulated. The absorptivity of the surface to solar radiation is a = 0.8 while its emissivity is e = 0.6. Assuming the surface loses heat by radiation into a clear sky at an effective temperature of 10°C, calculate the temperature of the surface. 

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