Numerical Investigation of Heat Transfer Performance in Cylindrical Pipes using Wall Grooves and Nanofluids

Gunti, Ajay (2025) Numerical Investigation of Heat Transfer Performance in Cylindrical Pipes using Wall Grooves and Nanofluids. Doctoral thesis, Birmingham City University.

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Abstract

Optimising heat exchangers by enhancing heat transfer, reducing heat transfer time, and improving fluid thermal properties is essential for maximising energy efficiency. While grooves and nanofluids are promising solutions, their combined effects introduce challenges, such as increased pumping power requirements and inconsistent numerical modelling results. This study addresses these issues by numerically analysing a single-tube heat exchanger under turbulent forced convection by incorporating grooves and nanofluids. This numerical investigation uses single and multiphase models alongside the Realizable k-ε and SST k-ω turbulence models to capture the thermal and hydrodynamic behaviour of the single-tube heat exchanger. Initial validation with experimental data for a smooth tube and a smooth tube with circular grooves using water at Re = 10,000 to 60,000 with an average error of less than 8% confirmed the reliability of the models.

This study assessed different groove shapes such as circular, triangular, rectangular, trapezoidal, and hybrid combinations to enhance heat transfer in corrugated tubes. The trapezoidal grooves achieved the highest Nusselt number, with a 37.92% improvement compared to a smooth tube, for Reynolds numbers ranging from 10 × 10³ to 60 × 10³ . However, triangular grooves exhibited the maximum thermal performance factor (PEC) due to the lower pressure drop compared to other groove shapes and hybrid combinations. Additionally, optimising rectangular grooves by adding curvature reduced pressure drop by 10.76% and improved the heat transfer coefficient of the single-tube heat exchanger by 13.4%, although triangular grooves remained superior.

This study evaluated the impact of turbulent models on nanofluid simulations, revealing significant variations in the Nusselt number, friction factor, turbulent kinetic energy, and wall shear stress. The single-phase model with the Realizable k-ε turbulence model showed an average error under 5% in predicting the Nusselt number and was closer to experimental data, outperforming the two-phase models (Eulerian and Mixture). In addition, the Al₂O₃-based hybrid nanofluids demonstrated up to 83.8% enhancement in heat transfer compared to pure water in a smooth tube at Re = 60,000. Finally, the combination of efficient triangular grooves with a 1% Al₂O₃-CuO/Water-EG hybrid nanofluid enhanced heat transfer rates by a factor of 2.14 in PEC values.

Item Type: Thesis (Doctoral)
Dates:
Date
Event
2 January 2025
Accepted
Uncontrolled Keywords: Forced Convection, Heat Transfer Enhancement, Surface Corrugation, Shear Stress Transport k – ω turbulence model, Realizable k – ε turbulence model, Design Optimisation, Turbulence, convection heat transfer, Single phase model, Eulerian model, Mixture model, nanofluid.
Subjects: CAH10 - engineering and technology > CAH10-01 - engineering > CAH10-01-09 - chemical, process and energy engineering
Divisions: Doctoral Research College > Doctoral Theses Collection
Faculty of Computing, Engineering and the Built Environment
Depositing User: Louise Muldowney
Date Deposited: 16 Jan 2025 13:10
Last Modified: 16 Jan 2025 13:10
URI: https://www.open-access.bcu.ac.uk/id/eprint/16082

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