On the correlations between collector efficiency factor and material content of parallel flow flat-plate solar collectors

The collector efficiency factor F 0, besides the collector heat loss coefficient UL, characterizes the thermal quality of a solar collector. As F 0 is strongly influenced by the tube distance w and the absorber plate thickness d, F 0 is also correlated with the material content of absorber plus tubing. Due to the future mass production of collectors and to the restricted copper resources (in the literature, a range until 2026 is given), the role of material savings can be expected to become more and more important. This paper focuses on the correlations between F 0 and the material content of absorber and tubing for flat-plate collectors with the fin-and-tube geometry. The correlations between w, d, F 0 and material content are presented in a new type of nomograph. This nomograph indicates the values of w and d that minimize the material content (for a given F 0). For a typical absorber with F 0 ¼ 0:90, material savings of 25% can theoretically be achieved without any deterioration of F 0, by reducing the absorber plate thickness and the tube distance. The resulting plate thickness is below 0.1 mm; the respective tube distance will be about 7 cm. Practical restrictions are discussed. In a sensitivity analysis, the influence of different parameters on F 0 is investigated. The most important parameters are w, UL; d and the Reynolds number. The technique chosen for contacting tube and absorber has only a minor influence on F 0. 2003 Elsevier Ltd. All rights reserved.