A comprehensive review of methods of heat transfer enhancement in shell and tube heat exchangers

A wide range of studies was conducted to increase the heat transfer rate and reduce the size and cost of shell and tube heat exchangers (STHE). The paper's contributions lie in its ability to provide a comprehensive, up-to-date, and systematic overview of the various methods available for heat transfer enhancement in STHEs, making it an essential resource for researchers, engineers, and practitioners in the field of heat transfer. The studies that researched the overall heat transfer coefficient (U), number of transfer units, exergy efficiency, pressure drop, and thermal-hydraulic performance were reviewed. There are some advantages of the passive method such as no external needed power and lower operating cost compared to the active methods. The studies broadly support the view that heat transfer enhancement in STHE is heading toward considerable progress. A total of 47.8% of studies have focused on the passive approach, the air injection method, enhancing heat transfer utilizing nanofluids, and compound methods have percentages of studies 20.2, 22.3, and 9.7%, respectively. The air bubble injection causes the rise of the U ratio where the maximum value was indicated at 452% compared to only water flow. Swirl vane, corrugated tube, and wire coil insert have U ratio values of 130, 161, and 264%, respectively. Nanofluid results in a growth in the heat transfer where the TiO2 has the maximum U ratio (175.9%) compared to traditional fluid. The combination of air injection and passive heat augmentation methods, which was shown to be a substantial solution to several issues, needs to be the focus of more work in the future. Geometrical changes in tube surfaces in STHE are too required in the future with the use of materials coating to enhance heat transfer. The theoretical analysis of heat transfer techniques still needs to be improved, especially for pertinent empirical formulations. Also, since there aren't many relevant numerical simulations, more attention is required.