Page 151 - Design of Solar Thermal Power Plants
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136 3. GENERAL DESIGN OF A SOLAR THERMAL POWER PLANT
1
0.9
Absorption efficiency factor Qa 0.6
0.8
0.7
0.5
0.4
0.3
670nm
0.2
870nm
936nm
0.1 440nm
1020nm
0
0 1 2 3 4 5 6 7 8 9 10
Particle size r /mm
FIGURE 3.8 Variation of absorption efficiency factor Qa over particle size r.
4. Extinction coefficient. Aerosol extinction coefficient is used to
describe the degree of solar direct radiation being weakened by
the atmosphere. Value of the coefficient is related to the category of
aerosols and wave band of solar direct radiation; yet in general, the
coefficient is comparatively stable.
Fig. 3.9 offers contributions of differently sized particles to
extinction coefficient, according to which, the overall extinction
coefficient of all particles is proportional to the area below the curve,
FIGURE 3.9 Variation of extinction coefficient b over particle size r.
