Experimental investigation of heat transfer enhancement of a heat exchanger tube equipped with double-cut twisted tapes

An Experimental study has been performed to investigate the heat transfer characteristics and friction factors of fluid flow through a heat exchanger tube equipped with double-cut twisted tapes (DCTT) with different cut ratios. The rectangular cuts have ratio values ranging from 0.25 to 0.90. This study is carried out under turbulent flow regime (5000 ≤ Re ≤ 15,000) and water is selected as the working fluid. Due to swirl flows, DCTTs lead to more fluid mixing between the tube wall and core regions, which has considerable effects on the heat transfer inside heat exchanger tubes. The results show that by increasing the cut ratio from 0.25 to 0.90, the Nusselt number (Nu) enhances up to 177.4%. The thermal performance varies from 1.63 to 1.44 for the cut ratio of 0.90. Three correlations based on the experimental data are developed to predict Nu, f and as functions of design parameters under turbulent flow regimes. These results provide evidence that the use of DCTTs is an effective technique to enhance heat transfer in a heat exchanger tube.