Heat Transfer Enhancement of Concentric Double-Pipe Heat Exchanger Utilizing Helical Wire Turbulator

Abstract

The present study involves fabrication and steady state experimental testing of double-pipe heat exchanger (DPHE) with turbulator. A helical wire has been inserted inside the inner tube of DPHE for creating extra turbulence to the flow through it. The effect of turbulator on heat transfer performance is studied. The working fluid used in the inner pipe and outer pipe is hot water and cold water, respectively. The test runs are performed at mass flow rates of hot and cold water ranging between 0.01 and 0.09 kg/s and between 0.01 and 0.04 kg/s, respectively. And the test is carried out in two separate modes, without using turbulator and with turbulator. Correlations and equations for flow properties and heat transfer characteristics were collected from various literature works involving flow through DPHE. The Nusselt number calculated from experiment values of the heat exchanger without turbulator is validated with the Dittus-Boelters equation for the pipe flow. A significant increase in the overall heat transfer coefficient is observed by using the turbulator in the inner pipe of the heat exchanger. Obviously, the increase in the performance comes with the cost of extra pressure drop. The reasons behind the enhancement of overall heat transfer coefficient and pressure drop of the DPHE using helical wire as turbulator were discussed. Dimensionless exergy analysis is carried out to study the changes by using the turbulator. In conclusion, for enhancing heat transfer performance, the helical wire turbulator can be employed in the heat exchanger.