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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

DIRECT NUMERICAL SIMULATION OF CONVECTIVE HEAT TRASFNER IN A VERTICAL PIPE FOR SUPERCRITICAL PRESSURE CO2

Junjie Yan
Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory of CO2 Utilization and Reduction Technology, Department of Energy and Power Engineering, Tsinghua University, China

Wei Wang
Department of Mechanical Engineering, University of Sheffield, Sheffield, UK, S1 4DE

Pei-Xue Jiang
Beijing Key Laboratory for CO2 Utilization and Reduction Technology; Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

Shuisheng He
School of Engineering The Robert Gordon University Schoolhill, Aberdeen, AB10 1FR, UK; Department of Mechanical Engineering University of Sheffield Sheffield, UK, S1 3JD

DOI: 10.1615/IHTC16.cms.023324
pages 1753-1760


KEY WORDS: Numerical simulation and super-computing, Convection, supercritical pressure fluids, direct numerical simulation, heat transfer deterioration, laminarisation

Abstract

Supercritical pressure fluids are widely used in heat transfer and energy systems, e.g. thermal and nuclear power plants, solar thermal power generation, and aerospace engines. The benefit of high heat transfer performance and the successful avoidance of phase change from the use of supercritical pressure fluids are well-known, but the complex behaviors of such fluids due to the dramatic thermal property variations pose strong challenges which may limit the applications of such systems and they should be carefully studied. The flow of supercritical pressure CO2 in a vertical, heated, pipe has been studied using an in-house Direct Numerical Simulation (DNS) package, CHAPSim. Both upward and downward flows with an inlet Reynolds number 3600 and pressure 7.6 MPa have been simulated and the results are compared with corresponding experimental data. Heat transfer deteriorations have been observed in upward flows. The distortion of streamwise velocity due to buoyancy near the heating wall has been observed, which shows a flat or an M-shaped profile in high-heat-flux cases. The turbulent production first reduces and then recovers along the pipe which is associated with the developing trends of the streamwise velocity. The heat transfer effectiveness has been found to be fairly well correlated with turbulence - the peak wall temperature occurs at a location where turbulent kinetic energy is the lowest. Instantaneous fields are presented to provide visualization of the flow structures, especially the laminarisation. The wall temperature obtained from DNS shows a general trend agreeing with experiment, yet quantitatively discrepancies are clearly in existence. It is postulated that this may be due to the (relatively small) differences in the boundary conditions between the DNS and experiments and further investigations are underway.

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