Numerical study on the heat transfer enhancement and pressure drop inside deep dimpled tubes

Abstract

Heat transfer enhancement is important from the industry point of view. In this study, a new configuration of enhanced tubes has been investigated numerically. The geometry of this new type of tube was provided by exerting deep dimples on the conventional plain tube. Flow-field and heat transfer characteristics of deep dimpled tubes have been studied, and the effects of the various configuration of dimples comprising three different pitches, diameters, and depths of dimples resulting in twenty-seven configurations have been investigated. Performance Evaluation Criteria (PEC), which is commonly used in heat transfer enhancement subjects, has been studied for all geometries. Local temperature, velocity, streamline, and Nusselt number of the deep dimpled tube have been depicted in comparison to the plain tube to study thermo-fluid characteristics. The investigation for each configuration has been done in three different Reynolds numbers: Re = 500, 1000 and 2000, and k-ɛ turbulent model has been utilized in numerical studies. The higher heat transfer rate of deep dimpled tubes has been seen in higher depth and diameter and lower pitch up to 600%, while this lead to the intense growth of friction factor. It has been observed that PEC of the deep dimpled tubes generally varies from PEC = 1.15–3.3 in different cases. Furthermore, increase in the diameter, pitch and Reynolds number, and decrease in the depth, lead to augmentation of PEC of deep dimpled tubes which escalates up to PEC = 3.3 at Re = 2000 when Diameter = 18 mm, depth = 2 mm, and pitch = 4D.