Proposing a New Egg-Shaped Profile to Further Enhance the Hydrothermal Performance of Extended Dimple Tubes in Turbulent Flows

Tube dimpling is known as an innovative approach, which has greatly helped to enhance the thermal performance of ordinary tubes. Although dimples mostly increase the thermal performance of ordinary tubes, they likely increase the fluid flow pressure drop and cause a reduction in its hydraulic performance. The primary goal of the present work is to introduce a new egg-shaped profile, which can considerably improve the hydrothermal efficiencies compared with the hydrothermal performances of the past extended dimple tubes, e.g., the spherical, conical, and elliptical ones. The present research is carried out using the numerical simulation approach; however, the experimental data is used to validate the numerical results. After demonstrating the accuracy of the employed numerical method, the performance evaluation criterion (PEC) parameter is used to evaluate the hydrothermal performance of the present dimpled-tubes equipped with the new egg-shaped dimple profiles. The present calculated PEC values are then compared with those of similar dimpled-tubes; however, equipped with the previously developed dimple profiles. The data conclusion is that the dimpled-tube with the present egg-shaped profile will provide at least 12.5% greater thermal performance than that of the previously developed dimpled-tube with the best practicing dimple profile. One of the key findings of this study is that the PEC value of the egg-shaped dimpled tube is double that of the corresponding smooth tube. This improvement is largely attributed to a higher turbulence mixing phenomenon caused by the egg-shaped dimples.