Thermal performance enhancement in a heat exchanging tube via a four-lobe swirl generator: An experimental and numerical approach

Abstract

The effects of a new swirl generator on thermal and flow fields in a heat exchanging tube are investigated experimentally and numerically. The swirl generator is a tube with a four-lobe cross section helically twisted with four different angles (θ=90, 180, 270 and 360). In the experiments, the heat transfer rate and pressure drop are measured as the main outcomes to extract the role of swirl generator on the thermal performance of the test tube. The experimental study is performed for different Reynolds numbers in the range of 6000–30,000. The experimental results reveal that the swirl generator makes an enhancement up to 87% in the heat transfer rate and an increase up to 48% in the pressure drop. The experimental results are supported by Large Eddy Simulation (LES) of the generated swirling flow. The study applies open-source CFD code named OpenFOAM. It is proved that the swirl generator creates an intense swirling flow at the tube inlet. The numerical results show that the high tangential and axial velocity components, near the tube wall, are the main reason of the better convection rate for the tube equipped with the swirl generator.