Surface emission coefficient

The Surface Emission Coefficient. During wood drying, particularly of thin wood such as veneers, flakes, and chips, the limiting rate factor may be the rate at which moisture can be removed from... 

It is useful to define an overall mass transfer coefficient as a function of the ambient conditions so that a surface emission coefficient gradient can be defined by... 

Radiation differs from conduction and convection not only in mathematical structure but in its much higher sensitivity to temperature. It is of dominating importance in furnaces because of their temperature, and in ciyogenic insulation because of the vacuum existing between particles. The temperature at which it accounts for roughly half of the total heat loss from a surface in air depends on such factors as surface emissivity and the convection coefficient. For pipes in free convection, this is room temperature for fine wires of low emissivity it is above red heat. Gases at combustion-chamber temperatures lose more than 90 percent of their energy by radiation from the carbon dioxide, water vapor, and particulate matter. 

Radiation arrives at a grey surface of emissivity 0.75 al a constant temperature of 400 K, at the rate of 3 kW/m2. What is the radiosity and the net rate of radiation transfer to the surface What coefficient of heat transfer is required to maintain the surface temperature at 300 K if the rear of the surface is perfectly insulated and the front surface is cooled by convective heat transfer to air at 295 K ... 

Effects of Primary Beam Species Prediction of FABMS source sputtering yields can be generally supported by available data on secondary ion emission coefficients. For secondary ions detected at zero angle with respect to the surface normal, the secondary ion emission yield generally increases with the mass of the primary ions because of the... 

The insulation effect of the PTFE element is obvious if the temperature course is given as a function of the element position (see Figure 4.41). For this reason, the surface temperature of the six horizontal spacer bars was recorded. The surface temperatures of the spacer bars depend on the emissivity coefficient of the materials and on the surface characteristics. To eliminate these effects, the spacer bars were painted. 

This example illustrates how nonlinear equations with combined convection and radiation can be solved with a straightforward iterative procedure. Recognizing the uncertainties in knowledge of surface emissivity and convection coefficient, only a few iterations are necessary to achieve an acceptable solution. 

A thermocouple is constructed by welding two wires together so that a spherical bead is formed with a diameter of 1.0 mm. The bead is exposed to a high-velocity airstream at M = 6, p = 10 atm, and 7 = - 70°C. Estimate the temperature of the thermocouple bead assuming a surface emissivity of 0.7. Assume that the bead has an accommodation coefficient equal to that of cast iron. 

Another secondary electron emission mechanism is related to surface bombardment by excited metastable atoms with an excitation energy exceeding the surface work functiom This so-called potential electron emission indnced by metastable atoms can have a quite high secondary emission coefficient y. Some of them are presented in Table 2-14. 

While evaluating the dependence of the signal/noise function (Fig. 7) created with natural and artificial optical emission source (halogen tube), we observed the different surfaces weight coefficients combinations in (Table 1.)... 

From the graphics analysis at the Fig. 7, it follows that for all natural surfaces weight coefficients sets there is the dependence of the signal/ noise function maximum value from the electromagnetic emission selective source altitude above the Earth surface. Signal/noise fimction reaches its maximum at the altitude = 4i, than it has a steady decreasing character. Also for all vision types there is a vivid dependence from the random set of the natural surfaces weight coefficients. 

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