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Tests of pressurized solar radiation absorbers require suitable pressure vessels and window structures for the penetrating light in order to heat up pressurized gases or gases other than air [1]. A test setup for such investigations has been developed at the Solar-Institut Jülich and is presented below. Air and Helium are the fluids used in the experiments. Helium has more favorable heat transfer properties. Computations have shown that helium has a higher volumetric heat transfer coefficient than air. Therefore, helium is a more suitable fluid to achieve the volumetric effect. [ABSTRACT FROM AUTHOR]

Volumetric absorbers are used to transfer solar radiation energy to a crossing fluid. The absorbers considered are made of parallel wire meshes. The incident radiation is modelled as a heat source with an exponential decay inside the absorber. Heat transfer depends on crossing fluid properties and flow parameters. The absorber shows a so called “volumetric effect” if the highest temperatures are found at the exit of the absorber. In case of high heat transfer coefficients and larger radiation penetration depth such a situation is found. It is interesting that the volumetric effect will not depend on the heat conductivity inside the absorber for the model considered here. [ABSTRACT FROM AUTHOR]