3

Figure 16.7 Characteristics of a typical selective (black chrome) collector surface.

Figure 16.6 Comparison of collector efficiencies for various liquid type collectors.

Air systems may require large expenditures of fan power if the distances involved are large or if the delivery ducts are too small. Heat-transfer rates to air are typically lower than those to liquids, so care must be taken in air collectors and in air heat exchangers to provide sufficient heat-transfer surface. This very often involves the use of extended surfaces or fins on the sides of the surface, where air is to be heated or cooled. Typical air collector designs are shown in Figure 16.9.

Flat-plate collectors usually come in modules

Freezing is not a concern.

Leaks, although undesirable, are not as detrimental as in liquid systems. Corrosion is less likely to occur.

Figure 16.8 Comparison of the efficiencies of selective and nonselective collectors.

Figure 16.7 Characteristics of a typical selective (black chrome) collector surface.

Figure 16.8 Comparison of the efficiencies of selective and nonselective collectors.

Air flow normal to paper

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