. (2015). Numerical models to predict steady and unsteady thermalhydraulic behaviour of supercritical water flow in circular tubes. Nuclear Engineering and Design, 289, 155-165. DOI: 10.1016/j.nucengdes.2015.04.028 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. • The supercritical flows with the normal heat transfer and deteriorated heat transfer are simulated.• The numerical results are compared with the experimental data and the errors are reported.• The transient simulations are also carried out using the CFD and THRUST.• The transient results obtained using the CFD and THRUST are compared under different conditions. a r t i c l e i n f o t r a c tThe present paper is aimed at the development of numerical models to predict steady and unsteady thermal-hydraulic behaviour of supercritical water flow at various operating conditions. A simple onedimensional numerical thermal-hydraulic model based on a finite-difference scheme has been developed. A detailed CFD analysis based on two turbulence models, Reynolds Stress Model and k-ω SST model, has also been presented in this paper. Seven experimental cases of steady state and vertically up flowing supercritical water in circular tubes operated at various working regimes, such as normal and deteriorated heat transfer regions, are used to validate the numerical models. Comparisons for steady state flow show good agreement between the numerical and experimental results for all normal heat transfer cases and most of the deteriorated heat transfer cases. Next, the numerical models are used for transient simulations. Three case studies are undertaken with a purpose to quantify the time dependent responses from both the 1-D model and CFD model. The comparisons carried out for both the normal and deteriorated heat transfer conditions show a good agreement between the two numerical models.
The present work demonstrates the extension of a thermal-hydraulic model, THRUST, with an objective to simulate the fast transient flow dynamics in a supercritical water channel of circular cross section. THRUST is a 1-D model which solves the nonlinearly coupled mass, axial momentum and energy conservation equations in time domain based on a characteristics-dependent fully implicit finite difference scheme using an Eulerian approach. The model developed accounts for the compressibility of the supercritical flow by considering the finite value of acoustic speed in the solution algorithm and treats the boundary conditions naturally. A supercritical water channel of circular cross section, for which the experimental data is available at steady state operating conditions, is chosen for the transient simulations to start with. Two different case studies are undertaken with a purpose to assess the capability of the model to analyze the fast transient processes caused by the large reduction in system pressure. The first transient case study is where the initial exit pressure is reduced by 1MPaexponentially in a time span of 5s. In the second case study, the transient is initiated with a sudden step decrease in the exit pressure by the same amount. Results obtained for both the case studies show the desired performance from the model developed.
The present paper is aimed at the in-depth thermalhydraulic analysis of supercritical water flow at various operating conditions in vertical circular tubes. A onedimensional thermal-hydraulic solution algorithm has been used for the analysis in this paper. Nine experimental cases are studied thoroughly and out of these, four cases which are operated at various working regimes are chosen and presented for the detailed analysis of deteriorated heat transfer and normal heat transfer cases. The studies are carried out for the distributions of nondimensional acceleration and buoyancy parameters, and different types of pressure drops along the axial direction and its effect on the heat transfer.
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