1. Field of the Invention
This invention relates to devices for converting solar energy into process heat in which heat exchanger elements are positioned in a heat exchanger chamber and subjected to sunlight radiation.
2. Description of the Prior Art
In known devices for converting solar energy into process heat, e.g. open, volumetric receivers, a network of ceramic fibers is positioned in a heat exchanger chamber. The ceramic fibers absorb radiated sunlight energy and emit the absorbed energy to a gas stream fed through the heat exchanger chamber and around the ceramic fibers. However, the efficiency of this type of device for converting solar energy into process heat is limited.
Pipe receivers are also known, wherein heat exchanger pipes are closely positioned in a plane. The total gas stream to be heated flows through the heat exchanger pipes, and is heated by sunlight radiation absorbed by the heat exchanger pipes. This type of heat exchanger is expensive to manufacture, because the heat exchanger pipes must be impermeable. This type of heat exchanger has the further drawback in that the heat exchanger pipes are exposed to a high temperature drop between the outside surfaces of the pipes and the inside surfaces of the pipes. The high temperature drop tends to impair the useful service life of the pipes.