Numerical study of heat transfer and flow characteristic of twisted tube with different cross section shapes

In the present work, three dimensional numerical study is conducted to investigate the heat transfer and flow characteristics of twisted tubes of different cross section shapes with the Reynolds number ranging from 50 to 2000. The constant wall temperature condition is used in the simulation analysis. The numerical results of twisted square tube are compared with the available previous experimental data. The results indicate that the heat transfer performance of twisted tube is enhanced compared with the smooth tube, while the pressure drop increases as well. One of the key findings is that the transition point of twisted square tube from laminar flow to turbulent flow is identified and located at Re = 500. It is also found that the cross section shape has little effect on the heat transfer of twisted tubes, while it has great influence on the flow pattern. The results also reveal that the twist pitch has remarkable effects on the heat transfer performance of twisted tubes. In addition, the maximum value of PEC of 2.69 is obtained in twisted pentagon tube with twist pitch ratio of 0.17, and the Reynolds number of 350. These results are significant because it will contribute to the development of compact twisted tube heat exchangers.