Evacuated tube collectors

Evacuated Tube Collector - A solar collector in which the absorber is contained in a seaied glass tube, thereby providing for relatively high temperature heat gain. 

The aim of the solar thermal collector development is to improve and optimize them for the temperature level from 80 °C to 250 °C. There are different approaches like double-glazed flat plate collectors with anti-reflection coated glazing, stationary compound parabolic concentrator (CPC) collectors, evacuated tube collectors, vacuum flat plate collectors, small parabolic trough collectors, linear concentrating Fresnel collectors and a concentrating collector with a stationary reflector. 

Evacuated tube collectors (ECTs) can be classified into two main groups ... 

Evacuated tube collectors have reduced conduction losses based on the insulation properties of the vacuum. With this collector technology, it is possible to reach good performances at relatively high temperatures (up to 120 °C). 

A historical introduction into the uses of solar energy was attempted followed by a description of the various types of collectors including flat-plate, compound parabolic, evacuated tube, parabolic trough, Fresnel lens, parabolic dish and heliostat field collectors (Kalogirou, 2004a, 2004b). Solar thermal electricity systems utilize... 

The structurally strongest shape is the tube this led to the development of a variety of evacuated tubular collectors (ETCs), as shown in Fig. 4. These can produce temperatures in excess of 200° C and can provide good efflciencies up to about 150°C. 

The analyzer tube is an evacuated (10-7 - 10-8 torr), curved, metal tube through which the ion beam passes from the ion source to the collector. The magnetic field is imposed perpendicular to the plane of the diagram (Fig. 2.2). The main requirement is a uniform magnetic field that can be smoothly varied in strength. 

Microwave-assisted distiller Microwave energy has also been used to facilitate the distillation of various compounds from solid samples [11,63-65]. Figure 5.12A depicts a typical microwave-assisted distillation apparatus. It consists of a laboratory-made poly-tetrafluoroethylene (PTFE) vessel of 120 ml inner volume and 10 mm wall thickness, and a 60 ml collector flask. The screw cap of the vessel includes a drilled PTFE disc located on its upper part that avoids sample ejection during distillation. A hole made in the vessel cap provides a means for evacuating volatile compounds via a PTFE tube that is passed through the vent holes of the microwave cavity and is then adapted to a glass line finished by a bubbler which is inserted in the collector flask. A domestic microwave oven equipped with a 2450 MHz magnetron is normally used for this purpose, altered only as required to connect the sample vessel with the collector flask. 

A photomultiplier consists of an evacuated glass tube with a photocathode at its entrance and several dynodes in the interior (Fig. 6.13). The anode, located at the end of a series of dynodes serves as the collector of electrons. The photons produced in the scintillator enter the phototube and hit the photocath-ode, which is made of a material that emits electrons when light strikes it. The electrons emitted by the photocathode are guided, with the help of an electric field, toward the first dynode, which is coated with a substance that emits secondary electrons, if electrons impinge upon it. The secondary electrons from the first dynode move toward the second, from there toward the third, and so on. Typical commercial phototubes may have up to 15 dynodes. The production of secondary electrons by the successive dynodes results in a final amplification of the number of electrons as shown in the next section. 

FIGURE 12 (a) Details of the actual profile shape and collector design for the integrated stationary evacuated concentrator (ISEC) tube, which has achieved a thermal efficiency of 50% at 200°C. (b) Ray trace diagram showing how essentially all the solar energy incident within 35° is directed onto the absorber tube. Because the reflector cannot physically touch the absorber, as required for an ideal concentrator, a small fraction is lost in the gap between the reflectors and the absorber. 

Gas Collector— i uncondensed gas is to be measured, a gas meter can be connected to the outlet of the cold trap but with a calcium chloride drying tube between them to keep moisture from collecting in the traps. When analysis of the gas sample is required, the gas can be collected in an empty plastic balloon of suitable size either in place of the meter or following it. The volume of its contents can be determined by calculation from the rise in pressure after expanding the sample into an evacuated vessel of known volume. 

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