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Experimental study of thermal characteristics of alternatively twisted swirl generator tape in a heat exchanger tube

ABSTRACT The heat transfer capacity of a convectional heat exchanger needs to be increased to minimize size and cost. Inserts are a promising way to enhance heat transfer at a bearable penalty in pressure drop. The objective of this study is to evaluate experimentally the thermal-hydraulic characteristics of a heat exchanger tube inserted with a novel alternatively twisted swirl generator (ATSG) tape. The experimental data has been collected for nine distinct combinations of ATSG tapes, includes the tapes with three twist angles (45°, 60°, and 90°) and three twist ratios (3, 4 and 5) for Reynolds numbers of 4,000 to 20,000. The use of ATSG tapes resulted in a considerable improvement in heat transfer rate compared to simple twisted tapes (TT). Over the range evaluated, heat transfer coefficient, pressure drop and thermal performance factor (TPF) with ATSG tapes in a tube are, respectively, 1.57–1.82, 1.58–2.54, and 1.22–1.46 times to that of simple TT in a tube. The maximum TPF achieved is 1.52 for ATSG tape with twist ratio of 3 and twist angle of 90°. The TPF for any combination of ATSG tapes is greater than one, which signifies that it is an efficient approach.