Investigate the Impact of Employing Dimples in Circular Tubes on Fluid Flow and Thermal Performance

ABSTRACT This paper conducts a numerical investigation on how the degree of dimple pitch around the tube circumference, the distance between dimples along the tube, and the dimple diameter affect the hydrothermal performance under turbulent flow conditions. Dimple tubes provide increased surface area compared to conventional tubes, resulting in improved heat transfer. Furthermore, the overall coefficient of performance of dimple tubes is enhanced by the decreasing Re number and increasing dimple quantity. The dimple tubes' thermal performance and friction coefficients were assessed over the Re number range (2300–10,000). The outcomes indicate improved rates of heat transfer in dimple tubes at the expense of increased pressure loss. The configuration with a 45° dimple angle, 1 mm axial distance along the tube, and 1 mm dimple diameter showed a superior average overall performance factor (OPF) compared to the other configurations, reaching a value of 1.27. Pumping losses increase significantly with increasing dimple diameter. Two equations derived from multiple regression analysis are explored. These equations link the Nu number, and friction factor to parameters including Re number, Pr number, tube dimensions, and dimple properties. This simplifies the prediction of the thermal performance and enhances the study of these systems.