Compound enhanced heat transfer inside tubes by combined use of spirally corrugated tubes and inlet axial vane swirlers

This paper describes an experimental study of single-phase air flow and hea t transfer inside a spirally corrugated tube with an inlet axial vane swirl er. Three spirally corrugated tubes and six inlet axial vane swirlers are u sed with different geometry parameters and spiral directions. Results show that the combined use of spirally corrugated tube and inlet axial vane swir ler can enhance the convective heat transfer inside a tube, but with the di sadvantage of friction factor increase. The compound angle formed by the sp irally corrugated tube and the inlet axial vane swirler has a marked influe nce on the compound enhancement effect. For same conditions, the combinatio n of the spirally corrugated tube with the inlet axial vane swirler in the opposite spiral direction has a higher heat transfer coefficient, a higher friction factor and a higher thermodynamical performance than that in the s ame spiral direction. The compound thermodynamical performance curves are a lso presented. It is showed that with the same pump power and same heat tra nsfer area, the heat flux transferred by the spirally corrugated tube with an inlet axial vane swirler can be increased up to 1.9 times, compared to t he smooth-tube values. Finally, a new method is proposed for correlating th e compound friction and heat transfer experimental data.