Experimental investigation of transparent parabolic trough collector based on gas-phase nanofluid

An experimental study on new high temperature parabolic trough collector (PTC), with transparent receiver tube, based on gas-phase nanofluid, has been carried out for the first time in this work. Two-axes solar tracking PTC, with 4 m2 reflecting surface has been realized. Besides, two coaxial quartz tubes, with vacuum in the inner space were used as receiver pipe, with air-dispersed CuO nano-powders as working fluid. The aim of this work was to investigate the technological issues related to the use of gas-based nanofluid coupled with transparent quartz receiver and to evaluate the performance of the first prototype, comparing numerical and experimental results. The experimental campaign highlighted a critical issue related to nanopowder deposition within the receiver pipe, due to humidity. Moreover, in a day of measurement, the fluid temperature higher than 145 °C has been maintained for about 10 h, reaching a maximum value of 180 °C, with a mean efficiency of about 65%.