Study on the heat transfer improvement of double pipe concentric heat exchanger enhancement using twisted tape and nanofluids

Abstract

Heat exchanger is a device that used to transfer heat between two fluids. Heat exchanger performance depends on the fluid’s Nusselt number. The greater the fluid’s nusselt number, the greater heat transfer will be. There are several ways to enhance Nusselt number such as adding twisted tape in tube and using nanofluids as working fluids. But by using the method mentioned before it can also increase the pressure drop along the pipes. So it must to be examined is it worth the enhance in heat transfer compared to increase of pressure drop that happen. This article try to modeling parallel heat exchanger that use twisted tape with twist ratio 7.35, 5.25, 4.72 and nanofluids with volume fraction 0 %(base fluid) 0.1% and 0.3% from the experiment that had done. Nanofluid assumed as homogenic fluid and have characteristic as studied in previous research. From simulation using ANSYS Fluent showed that the usage of twisted tapes with twist ratio 7.35, 5.25, 4.72 increase the Nusselt number by 131.88 %, 142.271 %, 145.82 % and increase the pressure drop by 232.52 %, 280.23%, 304.50 % respectively compared to usage of plain tube with base fluid, furthermore the usage of nanofluids with fraction volume 0.1 % and 0.3% increase the Nusselt Number by 6.72 %, 13.85 % and pressure drop by 14.01 %, 37.09 % respectively compared to usage of plain tube with base fluid. From simulation also showed that twisted tape with twist ratio 7.35 and using base fluid as working fluid give the highest thermal performance compared to the others.