Thermal-frictional behavior of solid magnetic strip turbulator and helical coiled wire turbulator inside a double tube heat exchanger

In recent years, the magnetic turbulator, which employs an electromagnetic vibration (EMV) technique, has gained popularity for its effectiveness in enhancing heat transfer within heat exchangers. This study introduces a novel approach by using solid strips instead of traditional flexible strips to construct solid magnetic strip turbulators (SMST) for the first time. Additionally, a helical coiled wire turbulator (HCWT) was combined with the SMST to investigate the synergistic effects of active and passive methods. Tests were conducted on SMST with various strip widths ranging from 5 to 7 mm and at different flow rates ranging 0.5 to 4 l/min, extensively analyzing the thermal-frictional parameters. The results revealed that the oscillating motion of the SMST induced higher turbulence near the tube wall compared to traditional turbulators. Moreover, an increase in strip width led to higher heat transfer coefficient and friction factor levels. When SMST and HCWT were used independently, heat transfer increased by up to 311 % and 201 %, respectively. When used together, heat transfer coefficient and friction factor increased by up to 6.55 and 3.85 times those of a plain tube, respectively. In an optimal scenario, the thermal efficiency factor increased to 4.18.