What is it about?
This study uses 3D CFD simulations to evaluate how non-circular inner tube cross sections—specifically Koch snowflake fractal, Koch-Cesaro fractal, and star shaped corrugated geometries—enhance heat exchanger performance across Reynolds numbers from 5,000 to 35,000. Results show that all non-circular shapes significantly improve heat transfer due to an increased wetted perimeter and localized flow acceleration, with the Koch-Cesaro fractal achieving the highest gains at up to 1.85 times the heat transfer rate of a standard circular duct. Despite the higher pressure drops and hydraulic losses associated with these complex geometries, the Koch-Cesaro design maintains the best overall thermal-hydraulic efficiency, yielding a 15% to 21% net improvement in Performance Evaluation Criterion (PEC) over the circular baseline.
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Why is it important?
With energy restrictions becoming increasingly stringent, it is no surprise that industries are requiring more advanced equipment with better energy efficiency. This situation leads to the demand for more efficient components. Therefore, as fundamental parts of certain systems, this push for modernization has resulted in numerous research efforts aimed at improving the performance and efficiency of heat exchangers.
Perspectives
In this work, the thermal and hydraulic performance of counter flow concentric tubes heat exchangers with non-circular cross-sections inner ducts were numerically evaluated. Then, their performance was compared to a conventional heat exchanger with circular tubes under the same operating conditions.
Dr. Lorenzo Martínez-Suástegui
Instituto Politecnico Nacional
Read the Original
This page is a summary of: Thermal and hydraulic performance of concentric counter flow tube heat exchangers using inner tubes with fractal cross sections, International Communications in Heat and Mass Transfer, November 2026, Elsevier,
DOI: 10.1016/j.icheatmasstransfer.2026.112569.
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