Radiation total flux

Radiation heat flux is graphically represented as a function of time in Figure 8.3. The total amount of radiation heat from a surface can be found by integration of the radiation heat flux over the time of flame propagation, that is, the area under the curve. This result is probably an overstatement of realistic values, because the flame will probably not bum as a closed front. Instead, it will consist of several plumes which might reach heights in excess of those assumed in the model but will nevertheless probably produce less flame radiation. Moreover, the flame will not bum as a plane surface but more in the shape of a horseshoe. Finally, wind will have a considerable influence on flame shape and cloud position. None of these eflects has been taken into account. 

Specific solar radiation conditions are defined by the air mass (AM) value. The spectral distribution and total flux of radiation outside the Earth s atmosphere, similar to the radiation of a black body of 5,900 K, has been defined as AM-0. The AM-1 and AM-1.5 are defined as the path length of the solar light relative to a vertical position of the Sun above the terrestrial absorber, which is at the equator when the incidence of sunlight is vertical (90°) and 41.8°, respectively. The AM-1.5 conditions are achieved when the solar flux is 982 Wm2. However, for convenience purpose the flux of the standardized AM-1.5 spectrum has been corrected to 1,000 Wm2. 

Consider the amount of radiation arriving on the surface of the Earth at a distance of 1 AU or 1.5 x 1011 m. The total flux of the Sun is distributed evenly over a sphere of radius at the distance of the planet, d. From the luminosity calculation of the Sun, F, the solar flux at the surface of Earth, FEarth, is F/47t(1.5 x 1011)2 = 1370 Wm-2 from the least-square law of radiation discussed in Example 2.4 (Equation 2.4). Substituting this into Equation 7.6 with the estimate of the albedo listed in Table 7.2 gives a surface temperature for Earth of 256 K. 

The radiation heat fluxes are exchanged between the internal and external surfaces of the cell slice and the surrounding surfaces. Moreover, fuel should not be considered as a transparent gas because of the significant partial pressures of CO2 and H2O. This means that radiation heat fluxes are exchanged between the external surface of the cell slice and the fuel volumes. The total net flux exiting the ith cell slice can be expressed as (see Figure 7.21) ... 

Effects of Radiation. LA exposed to gamma radiation by Warren et al and by Kosen-wasser, as reported in Ref 139, exhibited post-irradiation gas evolution as measured by vac stab test appar. Bowden Singh (Ref 135) irradiated Pb, Ag and Cd azides with electrons, neutrons, fission prods and x rays. All azides were exploded by an intense 75-kv electron scream. Thermal neutron irradiation did affect the subsequent decompn of Li and Pb azides. Muraour Ercaud (Ref 129) also subjected LA to a neutron flux. Raney (Ref 158) reported that a total flux of 7.5 10 ... 

The total flux available at a given wavelength is estimated from the product of the on-axis brightness with the solid angle of the radiation, i.e. 

Unlike absorption, scattering does not result in a loss of radiation. While the direct flux of incoming solar radiation is attenuated, the diverted light undergoes multiple scattering and is available as a diffuse component, which must be added to the direct flux. In addition, some radiation is reflected at the Earth surface (or from clouds, although clouds are rarely considered). Thus, the total flux may be written... 

Radiation contributes about 28 percent of the total flux, but the velocity of 2 m/s is relatively low. At lOm/s the convective flux would be 1870 W/m and radiation would contribute only 10 percent of the total flux. 

In the case of extended detector areas, the total power received by the detector is obtained by integration over all detector elements dA (Fig. 2.8). The detector receives all the radiation that is emitted from the source element dA within the angles -u<6<- -u. The same radiation passes an imaginary spherical surface in front of the detector. We choose as elements of this spherical surface circular rings with dA = 2nrdr = 2iiR sin cos d. From (2.29) one obtains for the total flux 0 impinging onto the detector with cos 9 = I... 

---