Enhancing heat exchanger performance with combined twisted tubes and twisted Tapes: Design and retrofit strategies

This study investigates the application of twisted tubes and twisted tapes as heat transfer enhancement tools in both new designs and revamping of shell-and-tube heat exchangers. This research introduces a new design approach based on published data of thermohydraulic performance of combined twisted tubes and twisted tapes. This work discusses general design considerations and proposes methodologies for the sizing of new heat exchangers and the incorporation of twisted tubes and twisted tapes into existing units. In design, surfaces with the best trade-off between heat transfer enhancement and pressure drop are simple twisted tubes and twisted tubes with triple-channel twisted tape (TT-3C) with a PEC of 3.06 and 2.59 respectively. It is found that for new designs, reductions in area relative to the original units are observed. With twisted tubes alone, the reduction is 19.11 %, while with the incorporation of TT-3C, it reaches 29.70%. In revamping of existing heat exchangers, the replacement of smooth tubes by twisted tubes and TT-3C results in average thermal load increases of 26.32 % and 27.50 %, equivalent to 19,526 kW and 20,442 kW, respectively. The results reveal significant improvements in heat transfer efficiency without substantial pressure drop increments, making twisted tubes and twisted tapes valuable options for enhancing heat transfer.