Abstract
Boosting heat transfer rates inside an absorber tube is of significant attention to optimize solar collectors' performance. Generally, the absorber tube comes in the forms of straight and smooth geometries, which besides the poor thermal performance, in some cases, it is subjected to tube deformation due to thermal stress. To overcome such problems, different twisted structures for the absorber tube are considered in this study, and the obtained results are discussed through a synergy analysis. First, a straight tube equipped with a twisted insert is examined compared to the twisted tube. Then, to further fulfill the desired goals, two combinations of the twisted tube with the twisted insert are considered, in which the twisted inserts are placed on the minor and major axes of the twisted tube cross-section. Results show that replacing the smooth tube with twisted structures brings about better thermal performance (between 1.08 and 3.72 times). Flow resistance augmentation reported for the enhanced models is between 1.21 and 2.93 times higher than that of the smooth tube. Likewise, the combined techniques result in great enhancements in performance index and energy efficiency, thus, at N = 12, these parameters increase up to 2.63 and 90%, respectively.
Published Version
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