Heat transfer improvement of tubular heat exchangers with twisted nail wire inserts
Year: 2025
Type: article
Abstract: Meeting the challenge of designing compact, energy-efficient, and sustainable heat exchangers requires innovative yet practical passive heat transfer improvement techniques. This study introduces a new passive technique using innovative twisted nail wire inserts (TNWIs) in double-tube heat exchangers (DTHXs). Experiments are conducted under turbulent flow conditions (Reynolds number of 5000–21,250) with constant inlet temperatures of hot- and cold-water streams. Three distinct TNWI configurations − aligned, cross, and alternating nail arrangements − were tested at fixed nail spacing ( P ) to evaluate thermal-hydraulic performance and entropy generation, using a plain-tube DTHX as the baseline. Among these, the alternating configuration yields the best performance, achieving a 1.78-times higher Nusselt number ( Nu ), a maximum thermal performance factor ( TPF ) of 1.75, and the lowest entropy generation ratio ( EGR ), while requiring minimal material and maintaining low friction losses. Further evaluation with varying nail density ratios ( L / P = 60, 30, and 20; L is the insert length) reveals that increased nail density enhances heat transfer (up to 2.29 times Nu enhancement) and reduces EGR (down to 2.15). New empirical correlations are developed for Nu , friction factor, and TPF , with prediction errors within ± 10 %. Compared to conventional inserts, TNWIs offer a simpler and energy-efficient alternative for advanced thermal system applications.
Authors: Fahmid Zaman Adnan, Saiadul Morsalin, Md Siyam Ahmed, Sadman Hassan Labib, Abu Hamja, Anjan Goswami
Language: English
Topic: Heat Transfer Mechanisms
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,560
OpenAlex ID: W4416432776