Enhancing the Heat Transfer of the Airflow in a Circular Tube

This study investigates the impact of using new twisted tape (TT) inserts with rings on the Nusselt number (Nu) and friction factor (f) for heat exchangers and air intercoolers. The analysis compares the effects of air and water as cooling fluids. The experimental setup is used to obtain experimental data needed for Computational Fluid Dynamics (CFD) validation. Then, the CFD model is utilized to predict the impact of using the new TT insert with rings compared to the conventional TT without rings under various conditions, which cannot be attained by the experimental facilities at the laboratory scale. The results show that the proposed TT insert with rings significantly enhances heat transfer efficiency while maintaining acceptable pressure drops. The findings suggest that incorporating TT with rings can optimize heat transfer performance in various heating and cooling applications. The experimental results show that adding the rings to the TT improves the heat transfer characteristics compared with the TT without rings, especially at larger TT pitch distances. Further, the experimental results demonstrate that the Nu values when using the TT inserts with rings significantly increase by up to 25% more than smooth pipes at low air velocities with larger pitch distances and by about 43 % at higher velocities with smaller pitch distances. However, this increase in heat transfer also leads to a rise in the friction factor, which increases by up to four times at low velocities and larger pitch distances and up to seven times higher at greater velocities and smaller pitch distances.