Experimental study of radiation absorption by minichannels of varying geometry

Increasing energy demands and decreasing fossil fuel reserves require that reliable and innovative technological advancements in renewable energy collection are made. Enhancement of net radiative heat transfer into the heat collection elements of parabolic solar thermal collection systems is imperative to the advancement of this renewable energy technology. The addition of small scale features to the normally smooth surface of a heat collection element results in a directionally selective surface with enhanced radiative heat transfer. Experimental results for the change in enthalpy and efficiency of three aluminum test pieces machined with channels of differing geometries and one smooth control piece subjected to incoming radiation of incidence angles between 0 degrees and 20 degrees are presented. The structured surfaces showed a minimum increase in efficiency over the smooth control of 14% and a maximum of 68%, with a circular channeled test piece performing the best. (C) 2012 Elsevier Inc. All rights reserved.