Parabolic reflector

The microfabricated version of parabolic reflector is used in solar energy concentration [130]. 

Contrary to the CPC, a parabolic concentrator is a high-concentrating device, but is more sensitive to scattering of incident radiation than the CPC. A problem with parabolic concentrators is that their total transmission is much smaller than that of CPC and reaches about 0.60. 

A 2D implementation of the full paraboloid geometry is the parabolic trough [131], Fig. 2.9. Although a fuU three-dimensional paraboloid is more energy efficient than a trough, 2D implementation is less complex and can be useful in sim-ations where there is a linear array of photodetectors. 

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Trough systems currently account for more than 90 percent of the world s solar electric capacity. They nse parabolic reflectors in long trough configurations to focus and concentrate sunlight (up to one hundred times) on oil-filled glass tubes placed along the... 

A dish-engine system uses a dish-shaped parabolic reflector, or a collection of smaller mirrors in the shape of a dish, to focus the sun s rays onto a rccciv-... 

Within the general concept of the ESVE models, Alfano et al. conceived a model for the radiant power profile of a tubular light source located in the focal axis of a parabolic reflector in order to analyze the design of a cylindrical photochemical reactor irradiated from the bottom [118]. Differences between experimental and calculated (ESVE) results were always less than 15%. 

Parabolic reflector concentrates sun s rays onto target area... 

Fig. 12 Large parabolic reflector and focal building in foreground. Concentrated energy is directed at the solar furnace located within the focal building. Installation is at Odeillo, Font Romeu, France. Photo by Glenn D. Considine)...

The solar energy incident on an area of about 2.000 square meters is concentrated by the parabolic reflector onto an area of less than 0.3 square meters. Sixty percent of the total thermal energy (about 600 kilowatts) is concentrated in an area of less than 0.08 square meter at the center of the focal plane of the parabola. 

Unlike the Odeillo installation, previously described, where a held of heliostats finally focus their energy to a small aperture by way of a huge parabolic reflector, in the solar tower approach, the energy from each mirror is directed to a central receiving tower, located high above the field, as... 

For symmetrical cylindrical parabolic reflector concentration ratio is even higher ... 

Many of these difficulties can be overcome by choosing an appropriate configuration of the photoreactor system. One such a system is the mechanically agitated cylindrical reactor with parabolic reflector. In this type of reactor, the reaction system is isolated from the radiation source (which could also simplify the solution of the well-known problem of wall deposits, generally more severe at the radiation entrance wall). The reactor system uses a cylindrical reactor irradiated from the bottom by a tubular source located at the focal axis of a cylindrical reflector of parabolic cross-section (Fig. 40). Since the cylindrical reactor may be a perfectly stirred tank reactor, this device is especially required. This type of reactor is applicable for both laboratory-and commercial-scale work and can be used in batch, semibatch, or continuous operations. Problems of corrosion and sealing can be easily handled in this system. 

Fig. 40. Cylindrical photoreactor with parabolic reflector. (After Cassano et al., 1986, by permission of Gordon and Breach, Science publishers S.A.)...

It has been shown that under some geometric restrictions that involve conditions in distances and dimensions of the complete experimental device that is, lamps, reflectors, and reactors, the radiation field produced by the tubular lamp, and the parabolic reflector can be modeled by a onedimensional representation (Alfano et al., 1986). These limitations were imposed on the equipment design of this work. Since is a function of the radiation-absorption species concentration, in this case. Equation (34) is coupled with Equation (32). 

Flaf plafe wifh recycle. Irradiafed from one wall wifh two tubular lamps and parabolic reflectors Photoreactor Vr = 734.4 cm ... 

Figures 22a, b provides a schematic representation of the pilot scale reactor. Essentially it is a rectangular parallelepiped limited by two parallel windows made of borosilicate glass and operated as a slurry reactor inside the loop of a batch recycling system. Irradiation of one of the reactor faces is obtained using two tubular lamps that were placed along the focal axis of two parabolic reflectors made of specularly finished aluminum (Brandi et al., 1996, 1999, 2002). The specific information concerning the experimental device is presented in Table 9, and more details can be found in Satuf et al. (2007b).

Typically, large-scale solar concentrators utilize parabolic reflectors in the form of trough, tower, or dish systems. These solar concentrators are characterized in terms of their mean flux concentration ratio Cr over an area Sa at the receiving focal plane as follows ... 

Figure 2 Set-up of the photostability testing equipment Suntest CPS. (1) Xenon burner, (2) UV light mirror, (3) visible light mirror, (4) quartz dish, (5) optional light filter for special purposes, (6) parabolic reflector, (7) sample level. Source From Ref. 6.

Parabolic reflectors are used in other devices as well. Radar antennas, the dishes used to pick up satellite television signals, and the reflectors used to concentrate sound from distant sources are all parabolic. 

A solar collector, see Fig. 3.58, consists of a parabolic reflector and an absorber pipe whose axis is located at the focusing point of the reflector. The reflector concentrates the solar radiation received onto the absorber pipe which has water running through it at a velocity of 0.03 m/s which is heated up. How long do the reflector and pipe have to be if the water is to be heated from = 20 °C to e = 80 °C and the solar radiation amounts to ijs = 800 W/m2 How high is the internal temperature of the pipe wall at the outlet ... 

MAGIC incorporates many technological innovations in order to fulfill the requirements imposed by the physics goals. The telescope is installed at 2200 m above see level on the Canary island La Palma (Spain). The 17 m diameter tessellated reflector dish consists of 964 0.5 x 0.5 m2 diamond milled aluminum mirrors. The parabolic reflector shape conserves the time structure of the Cherenkov pulses to increase the signal-to-noise ratio with respect to the night sky background. 

Figure 1. Photoreactivity set-up. (a) Air cylinder, (b) control valves, (c) bottle with water, (d) bottle with toluene, (e) switch valves, (f) thermostatted chamber, (g) parabolic reflector, (h) cylindrical photoreactor, (i) lamp, (1) power supply, (m) water filter, (n) gas chromatograph, (o) bubbling bottle containing acetonitrile. Thick line was electrically warmed in order to avoid product condensation.

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