| Abstract: | Increasing importance of heat transfer in chemical engineering science causes that investigation in the field of enhancement techniques is always one of the up-to-date topics for study. In the current comparative analysis, the thermal enhancement and friction penalty are explored numerically for curved tubes via twisted configuration. To accomplish this, three common geometries namely helical, serpentine, and Archimedes spiral, are considered at different coil-pitches and twist-pitches as well as five Reynolds numbers in the laminar flow regime. The results exhibit noticeable enhancements (up to 60%) in the thermal performance of the twisted cases as compared to the smooth cases. The highest increases are recorded for the serpentine case, followed by the helical and spiral cases. It is found that these enhancements vary via coil-pitch and twist-pitch. Increasing coil-pitch and twist-pitch augments both heat transfer coefficient and pressure drop in all curved-twisted tubes, however, the effects of twist-pitch are more pronounced. To predict Nusselt number and friction factor, new correlations are also proposed. The maximum deviations of the predicted results compared to the simulated data are within ±5%. |
