Twisted Tape Inserts and Vortex Generators in a Heat Exchanger

Twisted Tape Inserts and Vortex Generators in Heat Exchanger — ANSYS Fluent CFD Simulation

Description

This project investigates heat-transfer enhancement in a tubular heat exchanger using CFD, with nanofluid flow as the central modeling theme. The working medium in the inner tube is a hot alumina (Al₂O₃) nanofluid — a base liquid carrying suspended nanoparticles that raise its effective thermal conductivity and alter its flow and heat-transfer behavior relative to a conventional fluid. Treating this medium correctly is the core of the study, and it is combined with two passive enhancement devices — twisted-tape inserts and vortex generators — to examine how geometry and nanofluid properties together govern thermal performance. Enhancing heat transfer in tubular exchangers matters across many industrial processes, where higher thermal efficiency translates directly into energy and cost savings. Within the Nanofluid: Beginner CFD Training Package, this project combines nanofluid with passive turbulence-promoting geometry, building on the finned heat-exchanger case toward more complex enhancement techniques.

Methodology

The configuration has two sections: an inner passage carrying the hot alumina nanofluid and an outer passage carrying ambient air. As the nanofluid flows through the inner tube while the cooler air passes through the outer section, heat is transferred from the nanofluid to the air, and the simulation captures this cooling process and its effect on overall efficiency — with the specific aim of assessing how the twisted-tape inserts and vortex generators reshape the flow patterns, heat-transfer characteristics, and pressure drop. The geometry was created in ANSYS Design Modeler and meshed in ANSYS Meshing with 4,427,809 elements. The simulation uses a pressure-based solver, appropriate for the incompressible flow typical of heat-exchanger applications, with a steady-state approach representing continuous operation under constant flow conditions. The RNG k-ε turbulence model is applied to capture the complex swirling and recirculating flow created by the inserts, and the energy equation is enabled to resolve the temperature field and heat transfer throughout the system.

Analysis

The results give a detailed picture of the coupled flow and thermal behavior. The pressure field shows high pressure near the vortex generators and low pressure in the core flow, ranging from about −544.64 Pa to 1960.45 Pa, with an area-weighted average static pressure of 1953.92 Pa at the gas inlet and 206.98 Pa at the nanofluid inlet and both outlets at atmospheric pressure. The temperature field clearly shows the cooling of the nanofluid as it traverses the tube, falling from 353.15 K at the inlet to 352.50 K at the outlet, while the air rises from 298.15 K to 323.31 K as it absorbs the transferred heat. The velocity pathlines and contours reveal the complex flow induced by the geometry: the flow accelerates through the twisted-tape and vortex-generator regions, reaching velocities up to 0.5 m/s, and the twisted tape imposes a swirling motion that intensifies mixing and heat transfer. The turbulent kinetic energy peaks near the vortex generators and in their wakes, reaching up to 72.69 m²/s², driving the enhanced mixing in those regions. Taken together, the results demonstrate the strong interplay between fluid flow and heat transfer: the inserts and vortex generators create regions of high velocity and turbulence that directly enhance the cooling of the nanofluid. By the end of this project, you'll be able to represent a nanofluid working medium combined with passive turbulence-promoting geometry, apply the RNG k-ε model to capture insert-induced swirl, and evaluate thermal performance from the temperature, velocity, pressure, and turbulence fields.