Numerical investigation of parabolic trough receiver performance with outer vacuum shell

The useful heat gain of a parabolic collector system is directly dependent on the heat loss from the absorber at its operating temperature. Selective coatings with evacuated/non evacuated glass tubes are employed to control radiative and convective heat losses. A concentric glass shell under vacuum is investigated for its thermal performance as this method circumvents the need for direct sealing between the glass envelope and the metal receiver to maintain vacuum and its related technical challenges. The performance is compared against a non evacuated receiver and its influence under different wind velocities; emissivities are calculated by a one dimensional theoretical model and solved by an iterative method. (C) 2011 Elsevier Ltd. All rights reserved.