Power density, 310

Mean length of routine shutdown for refuelling (excluding long maintenance periods) 

Plant Power density (kW/litre of fuel) [fiiel volume defined by space within eladdingl Mean length of reactor run (days) Mean length of routine shutdown for refuelling (exeluding long maintenance periods) (days) 

Mean residence time for subassemblies (full power days) 

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Optical second-harmonic generation (SHG) has recently emerged as a powerful surface probe [95, 96]. Second harmonic generation has long been used to produce frequency doublers from noncentrosymmetric crystals. As a surface probe, SHG can be caused by the break in symmetry at the interface between two centrosymmetric media. A high-powered pulsed laser is focused at an angle of incidence from 30 to 70° onto the sample at a power density of 10 to 10 W/cm. The harmonic is observed in reflection or transmission at twice the incident frequency with a photomultiplier tube. 

Luminance is the luminous intensity divided by the area of emission of light (Iumens/steradian/m2). This is the power density emitted per unit area. 

The integral of the temperature gradient of the spectral power density from wavelength Xl to X2, is readily calculable using the Planck radiation law (5). Constant emissivity is assumed for equation 3. 

Spectral discrimination (9) and specific gas detection can be modeled if one assumes the gas absorbs photons of a specific wavelength exponentially with distance into the gas (Beet s law). When the absorption distance is x (cm), the incident it power density at the detector in the spectral band pass is J (W/cm ) and the power density incident on the gas is the gas concentration, C (ppm) is given by ... 

The Japanese Government initiated a program in 1992 to promote the development of PFFCs for both portable and stationary appHcations. The goal is to demonstrate a 1-kW module having a power density of 0.3 W/cm at a cell voltage greater than 0.75 V by 1995. A few research projects are under way in Japan. 

A unique capability of induction heating is apparent in its abdity to heat the surface of a part to a high temperature whde the interior remains at room temperature. Proper selection of material, high frequency, and high power density can produce a thin surface hardness with a heat unaffected core (3). Figure 4 shows the cross section of a typical automotive shaft heated with 10 kH2 at various power densities. The required hardness depth is selected to... 

Fig. 4. Automotive shaft cross sections showing the effect of power density vs hardened depth.

Induction heating using low frequency and low power density when apphed to a stationary or moving bar can produce a uniformly heated part suitable for introduction to a rolling mill (4). A cod line capable of producing 32 t/h of 17.8 cm (7 in.) diameter alloy steel bars heated to 1177°C is shown in Figure 5. 

The extremely high peak power densities available ia particle beams and lasers can heat the small amounts of matter ia the fuel capsules to the temperatures required for fusion. In order to attain such temperatures, however, the mass of the fuel capsules must be kept quite low. As a result, the capsules are quite small. Typical dimensions are less than 1 mm. Fuel capsules ia reactors could be larger (up to 1 cm) because of the iacreased driver energies available. 

A second property, closely related to the first, is the abiHty of the heat pipe to effect heat-flux transformation. As long as the total heat flow is ia equiHbrium, the fluid streams connecting the evaporatiag and condensing regions essentially are unaffected by the local power densities ia these two... 

Ozone Generator Design. A better understanding of discharge physics and the chemistry of ozone formation has led to improvements in power density, efficiency, and ozone concentration, initiating a trend toward downsizing. 

Blackbody Emittance. Representative blackbody emittance (9,10), calculated as a power spectral density, is shown in Figure 2. The wavelength, X, of peak power density for a blackbody at temperature, T, is given by Wien s displacement law ... 

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