Radiation with refractory surfaces

The crude oil and atmospheric residue are heated in tubular heaters. Oil is pumped through the inside of the tubes contained in a refractory combustion chamber fired with oil or fuel gas in such manner that heat is transferred through the tube wall in part by convection from hot combustion gases and in part by radiation from the incandescent refractory surfaces. 

An adiabatic refractory surface of area Ar and emissivity er, for which Qr = 0, proves quite important in practice. A nearly radiatively adiabatic refractory surface occurs when differences between internal conduction and convection and external heat losses through the refractory wall are small compared with the magnitude of the incident and leaving radiation fluxes. For any surface zone, the radiant flux is given by Q = A(W - H) = tA(E - H) and Q = eA/p( - W) (if p 0). These equations then lead to the result that if Qr = 0,Er = Hr = Wrfor all 0 < er< 1. Sufficient conditions for modeling an adiabatic refractory zone are thus either to put , = 0 or to specify directly that Q, = 0 with , 0. If er = 0, SrSj = 0 for all 1 < j < M which leads directly by definition to Qr = 0. For er = 0, the refractory emissive power Er never enters the zoning calculations. For the special case of 0 and Mr = 1, a sin-... 

Most of the target surfaces were untreated. However, in some experiments the surfaces were treated or coated, to study a specific surface effect. Kilham [31] and Jackson and Kilham [32] coated the surface of their refractory cylinders with different oxides. The objective was to estimate the emissivities of the coatings. The surface temperature was approximately determined using a thermocouple imbedded inside the cylinder body. Radiation from the surface was measured with a thermopile. Using the temperature level and the radiation, along with an energy balance on the cylinder, the emissivity of the coatings was calculated as a function of temperature. 

The issue of material cleanliness is significantly greater for a lunar mission than a deep space mission and makes extensibility more challenging if materials are sensitive to this contamination. This was a concern with refractory materials in the pressure boundary. This is also a concern relative to coating heat transfer surfaces such as the radiator, as well as coating electronics and mechanisms. Similar concerns would exist for Mars which has a CO2 atmosphere and dusty conditions. 

Treatment of Refractory Walls Partially Enclosing a Radiating Gas Another modification of the results in Table 5-10 becomes important when one of the surface zones is radiatively adiabatic the need to find its temperature can be eliminated. If surface A9, now called A, is radiatively adiabatic, its net radiative exchange with Aj must equal its net exchange with the gas. 

The determination of metal purity and the elemental composition of alloys is of utmost importance to the metallurgical industry. Microwave-assisted digestion is often well-suited to metals and metallurgical samples that pose no difficulty and dissolve readily and safely with the aid of microwaves [148,186-196]. For example, hydrofluoric acid can be used in closed vessels to digest silicate matrices and stop the hydrolysis of refractory elements without loss of volatile fluorides or passivation. After cooling, boric acid can be added to complex unreacted hydrofluoric acid [14]. The solid sample itself may absorb microwave radiation, thus creating a heated surface on which the acid or acids can react. Microwave muffle furnaces are commercially available [197] based on oven linings made... 

Tositumomab and iodine I-tositumomab is a monoclonal antibody that blocks (complement-dependent cytotoxicity) CD20 antigen, which is found on the surface of normal and malignant B lymphocytes. Cell death is associated with ionizing radiation from the radioisotope. It is indicated in the treatment of patients with CD20-positive, follicular, non-Hodgkinr s lymphoma, with and without transformation, whose disease is refractory to rituximab and has relapsed following chemotherapy. 

In one version of this method, the heat flux is determined from an energy balance on the solid. It was used in two early flame impingement studies [17,18]. Refractory cylinders were coated with different oxides. These were heated until steady-state conditions were reached. Radiation from the cylinders, along with the gas and cylinder surface temperatures, were measured. The total heat flux to the cylinder was then calculated from an energy balance on the cylinder surface. The heat gained by the cylinder was assumed to be by convection and radiation from the flame. The energy lost by the cylinder was assumed to be solely due to radiation. A thermopile was used to measure radiation from the flame, both with and without the cylinder present. The surface radiation from the cylinder was calculated by subtracting the first measurement from the second. This value was assumed to be equal to the total heat flux from the flame to the cylinder. 

Laser evaporation was originally employed by von Gustorf the beam from a 200 W Nd-doped laser passed through a gas window (a stream of inert gas in the window area ensures that it remains uncoated with evaporant) and was focused on to the metal sample contained in a water-cooled copper crucible (i.e., another example of a containerless method). The main drawback of this method is that reflectivity of the incident laser radiation increases with surface temperature (thus requiring elevated power levels), so that it is not a generally useful method for the more refractory metals. 

Gas-fired radiators These radiators consist of a perforated plate (metal or refractory), which is heated by gas flames in one of the surfaces so the plate raises its temperature and anits radiant energy. The porosity of the plate determines the temperature of the other surface so as to ensure a safe process. Figure 19.6b shows a sketch of this type of radiator (van t Land, 1991, p. 250). The temperature of such a radiator is generally between 1500°C and 1700°C with wavelengths from 2.7 to 2.3 pm (van t Land, 1991, p. 249). The radiant efficiency of such radiators is typically about 60%. 

Step 1. Figure the radiation from hot refractory only. From figure 8.3, the normal exposure factor for rounds positioned with a spacing factor of 2.0 is 48% of the total peripheral surface area. Each of the side quadrants receives half of the refractory radiation into the 8 in. hearth space between rounds, so the effective refractory radiation receiving area of each side quadrant is only 25% x 0.48/2 = 6%. The bottom quadrant has 0% effective area thus, the total effective refractory radiation receiving area for the four quadrants is 25 + 6 -I- 6 + 0 = 37%. 

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