Natural circulation flow through water-in-glass evacuated tube solar collectors

Experimental and numerical investigations were undertaken to develop a correlation for natural circulation flow rate through single-ended water-in-glass evacuated tubes mounted over a diffuse reflector. The circulation flow rate was correlated in terms of solar input, tank temperature, collector inclination and tube aspect ratio. The sensitivity of the flow rate correlation to the variation in circumferential heat flux distribution was also investigated. (c) 2007 Elsevier Ltd. All rights reserved.