The depletion of conventional energy resources highlights the growing need for efficient utilization of available energy sources. Heat exchangers play a vital role in transferring heat between two or more fluids, and enhancing their performance is crucial for improving energy efficiency. Various techniques, categorized as active, passive, or hybrid methods, can be employed to augment heat transfer in heat exchangers. This experimental study investigates the use of innovative sporadic flow divider inserts as a passive method for heat transfer enhancement. The experiments were conducted using inserts with different twist angles of 90°, 60°, 45°, and 30°, over a range of Reynolds numbers from 7000 to 21000. The effect of spacing between the inserts was also analyzed using different space ratios (0.19, 0.39, 0.59, 0.78) in combination with the various twist angles.
The results indicated that higher Reynolds numbers led to increased Nusselt numbers, a decrease in the Thermal Enhancement Factor (ψ), and a reduction in the Friction Factor (f). Among the tested configurations, the 45° twist angle insert exhibited the highest Thermal Enhancement Factor (ψ) and Overall Performance Criteria (η) across most conditions. Conversely, the 30° twist angle resulted in a significantly higher friction factor, impeding fluid flow. The optimal performance was achieved with a 45° twist angle and a space ratio of 0.59, yielding a 23% improvement in Thermal Enhancement Factor (ψ) and a 55% increase in Overall Performance Criteria (η) compared to a plain tube. These findings demonstrate that sporadic flow divider inserts can effectively enhance convective heat transfer with a moderate increase in friction, ultimately improving the Overall Performance Criteria (η).