Investigation of Thermal Performance of Evacuated Tube with Parabolic Trough Collector with and without Porous Media

Abstract

In this paper a new model has demonstrated that it operates in a moderate performance scale to generate hot water. In its early stage, the preliminary model, which built with double pass water tube inside evacuated tube, was investigated experimentally. The model was tested inside room under different operation conditions in terms of solar radiation 300, 400, 500 and 600 W/m2 and water mass flow rates 0.00305 and 0.0083kg/s. In the first case, there was a problem because of the air gap inside the tube and surrounding the double pass water tube, so In the second stage, two different filling medium inside the evacuated tube was proposed to modify the preliminary model. The mediums cases include porous media (stainless steel wire mesh and Aluminum fiber metallic). The results show that maximum efficiency without porous media was 62.4% at 0.0083 kg/s and heat flux 600 W/m2, but after porous media applied, the efficiency reached 79.4% at 99.997% porosity of Aluminum fiber metallic and heat flux 600 W/m2 with same water mass flow.