Effect of Helical Surface Disc Turbulators on Heat Transfer and Friction Factor Characteristics in the Annuli of a Double‐Pipe Heat Exchanger

The heat transfer and pressure drop characteristics in annuli of a double‐pipe heat exchanger (DPHE) using helical surface disc turbulators (HSDTs) are experimentally investigated. The effect of a helical surface disc turbulator is studied for three pitch ratios, three diameter ratios, and varying Reynolds numbers. Water flows in the inner tube and air through the annulus. The tests are conducted for air with uniform wall temperature condition. The heat exchanger with the least pitch ratio and least diameter ratio was found to exhibit the highest Nusselt number and pressure drop. The thermal performance factor turned out to be greater than unity for all cases. Correlations were developed for Nusselt number, friction factor, and thermal performance. Turbulators are effective tools to enhance the heat transfer performance in heat exchangers. The heat transfer and pressure drop characteristics of a double‐pipe heat exchanger equipped with helical surface disc turbulators inside the annulus under counterflow conditions were experimentally evaluated. The impact of pitch ratios, diameter ratios, and Reynolds numbers was investigated and discussed.