Thermal performance assessment of self-rotating twisted tapes and Al₂O₃ nanoparticle in a circular pipe

In view of the practical importance of the heat transfer devices in various thermal engineering fields including chemical and nuclear engineering, this study aims at developing an effective method of heat transfer enhancement by using self-rotating twisted tapes (SRTTs) and Al₂O₃ nanoparticles. The effect of the self-rotating twisted tapes and Al₂O₃ nanoparticles on the thermal performance was comprehensively investigated in a circular pipe. The experimental results indicated the heat transfer rate was effectively improved by SRTTs in comparison of plain tube. In addition, the heat transfer multiplier with SRTTs decreased from 1.38 to 1.08 with the Reynolds number increasing from 19,322 to 64,407, while the friction factor multiplier decreased from 1.61 to 1.32. Besides, the results indicated that the employment of Al₂O₃ nanoparticles and SRTTs demonstrated superior thermal performance to the single SRTTs. As Reynolds number increases from 19,322 to 64,407, the heat transfer multiplier decreased from 2.08 to 1.18 in the mass concentration of 3.0% and from 1.38 to 1.08 in mass concentration of 0.0%. Finally, the new heat transfer and friction factor correlations considering the combined effect of Al₂O₃ nanoparticle and SRTTs were developed within 10% deviation of experimental values.