New Designs of Molten-salt Tubular-receiver for Solar Power Tower.

Abstract: One of the main problems of solar power tower plants with molten salt as heat transfer fluid is the reliability and lifetime estimation of central receivers. The receivers must withstand high working temperatures, molten salt corrosion and important solar flux transients that lead to thermal stresses and fatigue. Therefore, it is necessary optimize the design of these receivers. The aim of this work is to study the thermal behavior of a new design of central receiver. This new external receiver is composed by several vertical panels formed by bayonet tubes. Each bayonet tube presents an inner tube and an outer tube concentric to the internal one. Both are joined in one side by a bayonet end-cap. The heat transfer fluid flows through the inner tube and the annular gap between the two tubes. In addition, the outer tube will be coated in its external surface by a material of high absorptivity of the solar radiation. In absence of experimental data of the receivers both concepts of external receiver, traditional and bayonet, have been characterized using simplified numerical simulations. The results obtained have been the salt, the film and the wall temperature evolutions and the thermal efficiencies. The advantages of the bayonet receiver over the traditional tubular receiver are: soften wall and film temperatures, lower thermal stresses due to a more homogeneous wall temperature, and lower corrosion rate, that allows use more economical materials to built the receiver tubes or even reduce the receiver surface increasing the thermal efficiency. [Copyright &y& Elsevier]