Large eddy simulation on the heat transfer of supercritical pressure water in a circular pipe

2021 ◽  
Vol 377 ◽  
pp. 111146
Author(s):  
Han Wang ◽  
Shunqi Wang ◽  
Daogang Lu
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Supercritical Pressure ◽  
Circular Pipe ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Pressure Water ◽  
Supercritical Pressure Water

scholarly journals Large Eddy Simulation Study on Forced Convection Heat Transfer to Water at Supercritical Pressure in a Trapezoid Annulus

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Muhsin Mohd Amin ◽  
Yu Duan ◽  
Shuisheng He
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Forced Convection ◽  
Supercritical Water ◽  
Supercritical Pressure ◽  
Working Fluid ◽  
Flow Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Large Flow

It is now well known that heat transfer to fluid at supercritical pressure in a confined channel shows complex behaviors. This is due to the strong variations of the thermal–physical properties resulting from the changes of pressure and temperature. To improve the reliability and efficiency of the supercritical water-cooled reactors (SCWRs) to be designed, the understanding of supercritical fluid flow in the fuel assemblies is very important. The study reported here reconsiders a simplified geometry made of a trapezoid channel enclosing an inner rod to simulate the triangular arrangement of a fuel assembly. Large eddy simulation (LES) with the wall adapting local eddy viscosity (WALE) model is used to simulate the forced convection flow in the channel. Supercritical water at 25 MPa is used as the working fluid. The Reynolds number of flow based on the hydraulic diameter and the bulk velocity is 10,540, while the heat flux from the inner rod wall has been varied from 10 kW/m2 to 75 kW/m2. Large unsteady flow structures are observed to be present due to the nonuniformity of the cross section of the flow channel. The characteristics of the flow structures and their effect on the local heat transfer are analyzed using instantaneous velocities, spectrum analysis, and correlation analysis. The swinging flow structures in the wide gap are much weaker than those in the narrow gap. The behaviors of such large flow structures are influenced by the strong spatial and temporal variations of the properties. When the temperature distribution follows Tb < Tpc < Tw, the mixing parameters due to the large flow structures, including mixing coefficient and effective mixing velocity in the gap, are also significantly influenced.

scholarly journals Assessing IDDES-Based Wall-Modeled Large-Eddy Simulation (WMLES) for Separated Flows with Heat Transfer

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 246
Author(s):  
Rozie Zangeneh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Skin Friction ◽  
Heat Fluxes ◽  
Separated Flows ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Wall

The Wall-modeled Large-eddy Simulation (WMLES) methods are commonly accompanied with an underprediction of the skin friction and a deviation of the velocity profile. The widely-used Improved Delayed Detached Eddy Simulation (IDDES) method is suggested to improve the prediction of the mean skin friction when it acts as WMLES, as claimed by the original authors. However, the model tested only on flow configurations with no heat transfer. This study takes a systematic approach to assess the performance of the IDDES model for separated flows with heat transfer. Separated flows on an isothermal wall and walls with mild and intense heat fluxes are considered. For the case of the wall with heat flux, the skin friction and Stanton number are underpredicted by the IDDES model however, the underprediction is less significant for the isothermal wall case. The simulations of the cases with intense wall heat transfer reveal an interesting dependence on the heat flux level supplied; as the heat flux increases, the IDDES model declines to predict the accurate skin friction.

scholarly journals Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

2021 ◽  
Vol 11 (15) ◽  
pp. 7167
Author(s):  
Liang Xu ◽  
Xu Zhao ◽  
Lei Xi ◽  
Yonghao Ma ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Wall Temperature ◽  
Target Surface ◽  
Impinging Jets ◽  
Small Scale ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Swirling impinging jet (SIJ) is considered as an effective means to achieve uniform cooling at high heat transfer rates, and the complex flow structure and its mechanism of enhancing heat transfer have attracted much attention in recent years. The large eddy simulation (LES) technique is employed to analyze the flow fields of swirling and non-swirling impinging jet emanating from a hole with four spiral and straight grooves, respectively, at a relatively high Reynolds number (Re) of 16,000 and a small jet spacing of H/D = 2 on a concave surface with uniform heat flux. Firstly, this work analyzes two different sub-grid stress models, and LES with the wall-adapting local eddy-viscosity model (WALEM) is established for accurately predicting flow and heat transfer performance of SIJ on a flat surface. The complex flow field structures, spectral characteristics, time-averaged flow characteristics and heat transfer on the target surface for the swirling and non-swirling impinging jets are compared in detail using the established method. The results show that small-scale recirculation vortices near the wall change the nearby flow into an unstable microwave state, resulting in small-scale fluctuation of the local Nusselt number (Nu) of the wall. There is a stable recirculation vortex at the stagnation point of the target surface, and the axial and radial fluctuating speeds are consistent with the fluctuating wall temperature. With the increase in the radial radius away from the stagnation point, the main frequency of the fluctuation of wall temperature coincides with the main frequency of the fluctuation of radial fluctuating velocity at x/D = 0.5. Compared with 0° straight hole, 45° spiral hole has a larger fluctuating speed because of speed deflection, resulting in a larger turbulence intensity and a stronger air transport capacity. The heat transfer intensity of the 45° spiral hole on the target surface is slightly improved within 5–10%.

Towards High-Order Large Eddy Simulation of Aero-Thermal Flows for Turbomachinery Applications

2017 ◽  
Author(s):  
R. Bhaskaran ◽  
Feilin Jia ◽  
Gregory M. Laskowski ◽  
Z. J. Wang ◽  
Umesh Paliath
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Numerical Algorithms ◽  
High Order ◽  
Sixth Order ◽  
Computational Grids ◽  
Variable Order ◽  
Free Stream Turbulence ◽  
Eddy Simulation ◽  
Large Eddy

The solution accuracy and computational efficiency of high order Large Eddy Simulation (LES) solvers are evaluated on two benchmark open literature blade cascade problems. The first problem concerns wake development in the T106A low pressure turbine cascade [1]. The second problem examines the effect of free-stream turbulence on heat transfer from the VKI first stage high pressure turbine vane [2]. The calculations are performed with two independently developed high order LES solvers using completely different numerical algorithms. The first solver FDL3Di [3] was originally developed at the Airforce Research Laboratory (AFRL) and employs structured overset grids. It uses a sixth order compact finite difference scheme in space along with an implicit Beam-Warming scheme for time marching. The second solver, hpMusic, is developed at the University of Kansas [4]. This is a variable order (up to sixth order) unstructured grid solver employing a discontinuous formulation known as flux reconstruction (FR) / correction procedure via reconstruction (CPR) [5]. The computational grids used are independently tuned for each application. The solvers are benchmarked against experimental data for wake development and blade heat transfer coefficient. Further physical insights in to the test cases are also obtained, filling gaps in experimental results, especially for the VKI problem.

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