Radiation heat transfer between black bodies

Now reconsider two bodies each with a flat black surface at absolute temperatures T and Tz separated l distance apart in a vacuum, as shown in Fig. 1.15(b). Surface 1 has emissive power Ebi, surface 2 has emissive power Ebz, and the radiation heat transfer between these bodies is... 

The emissivity accounts for the properties of a radiating surface. An ideal radiator, or black body, has a value of e = 1. The rate of radiative heat transfer between two bodies is proportional to the difference between the fourth powers of their temperatures. In most commercial apparatus, not all the radiation from one body reaches the second. Radiation goes out in all directions, and only some of it reaches the intended receiver. The fraction that does is called the area factor or the view factor. Thus,... 

Radiation is the rate of heat transfer by electromagnetic waves emitted by matter. Unlike conduction and convection, radiation does not require an intervening medium to propagate. The basic rate of radiation heat-transfer equation between a high temperature (Th) black body and a low temperature Tf) black body is Stefan-Boltzmann s law ... 

In catalytic channels, the flat plate surface temperature in Eq. (3.32) is attained at the channel entry (x O). As the catalytic channel is not amenable to analytical solutions, simulations are provided next for the channel geometry shown in Fig. 3.3. A planar channel is considered in Fig. 3.3, with a length L = 75 mm, height 21) = 1.2 mm, and a wall thickness 5s = 50 pm. A 2D steady model for the gas and solid (described in Section 3.3) is used. The sohd thermal conductivity is k = 6W/m/K referring to FeCr alloy, a common material for catalytic honeycomb reactors in power generation (Carroni et al., 2003). Surface radiation heat transfer was accounted for, with an emissivity = 0.6 for each discretized catalytic surface element, while the inlet and outlet sections were treated as black bodies ( = 1.0). To illustrate differences between the surface temperatures of fuel-lean and fuel-rich hydrogen/air catalytic combustion, computed axial temperature profiles at the gas—wall interface y=h in Fig. 3.3) are shown in Fig. 3.4 for a lean (cp = 0.3) and a rich cp = 6.9) equivalence ratio, p = 1 bar, inlet temperature, and velocity Tj = 300 K and Uin = 10 m/s, respectively. The two selected equivalence ratios have the same adiabatic equilibrium temperature, T d=1189 K. 

Radiation is the transfer of heat between surfaces of solids not in contact with each other and at different temperatures. A so-called black body absorbs all radiation heat, whereas a white body reflects part of it. Radiation (see Figure 5.17c) is described by the equation ... 

A plate. 1 m in diameter at 750 K, is to be heated by placing it beneath a hemispherical dome of the same diameter at 1200 K the distance between the plate and the bottom of the dome being 0.5 m, as shown in Figure 9.42. If the surroundings are maintained at 290 K, the surfaces may be regarded as black bodies and heat transfer from the underside of the plate is negligible, what is the net rate of heat transfer by radiation to the plate ... 

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