scholarly journals Study on Flow Instability in Natural Cycle Parallel Channel Based on RELAP5

2021 ◽  
Vol 770 (1) ◽  
pp. 012038
Author(s):  
Haibo Meng ◽  
Haoqiang Zhu ◽  
Tianyao Wang
Keyword(s):  
Flow Instability ◽  
Natural Cycle ◽  
Parallel Channel

Flow Instability Investigation at Supercritical Pressures in Parallel Channels by Computational Fluid Dynamics Adopting Low- and High-Power Boundaries

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Edward Shitsi ◽  
Seth Kofi Debrah ◽  
Vincent Yao Agbodemegbe ◽  
Emmanuel Ampomah-Amoako
Keyword(s):  
Flow Instability ◽  
Oscillation Amplitude ◽  
Lower Threshold ◽  
Inlet Temperature ◽  
Parallel Channel ◽  
Flow Oscillation ◽  
Channel System ◽  
Numerical Studies ◽  
Mass Flowrate ◽  
Parallel Channels

Abstract Supercritical water-cooled reactor (SCWR), which is considered as the logical extension of existing light water reactors (LWRs) (pressurized water reactor and boiling water reactor (BWR)), has the potential of increasing the efficiency of power generation to 45% compared to 33% of that of LWRs. But without the challenges of heat transfer and hydrodynamics, and reactor core design materials due to supercritical flow instability which is associated with sharp variation in fluid properties near the vicinity of the pseudo-critical temperature. Supercritical flow instability therefore needs to be addressed ahead of the deployment and operation of SCWR in the near future. The main purpose of this study is to carry out flow instability analysis in parallel channels with supercritical water. The study also aims at examining the capability of using three-dimensional (3D) simulation of turbulent flow in arbitrary regions computational continuum mechanics C++ based code (3D STAR-CCM+ CFD code) to predict flow oscillation amplitude and periods, and instability power boundaries at low-power boundary (LPB) and at high-power boundary (HPB). Parameters considered in the investigation include mass flowrate, system pressure, and gravity. Two different threshold power instability boundaries were obtained from the study. These instability power boundaries include lower threshold where stability of the parallel channel system decreases with increasing coolant inlet temperature, and upper threshold where stability of the parallel channel system increases with increasing coolant inlet temperature. From the results of the investigation, it can be found that: (1) for LPB at 23 MPa, only lower threshold was obtained as flow instability power boundary; and for HPB at 23 MPa, both lower and upper thresholds were obtained as flow instability power boundaries. The numerical findings quite well agree with the experimental findings at 23 MPa for both LPB and HPB; (2) only lower threshold was obtained as flow instability power boundary at both 23 MPa and 25 MPa for LPB. For HPB, both lower and upper thresholds were obtained as flow instability power boundaries at both 23 MPa and 25 MPa; (3) only lower threshold was obtained as flow instability power boundary for the parallel channel system with or without gravity influence for LPB. For HPB, both lower and upper threshold flow instability power boundaries were obtained for the parallel channel system with gravity influence, but only lower threshold flow instability power boundary was obtained for system without gravity influence; (4) only lower threshold was obtained as flow instability power boundary at system mass flowrates of 125 kg/h and 145 kg/h for LPB. For HPB, both lower and upper threshold flow instability power boundaries were obtained for system mass flowrate of 125 kg/h, but only lower threshold flow instability power boundary was obtained for system mass flowrate of 145 kg/h. For both LPB and HPB, the numerical findings agree quite well with the experimental results for a system operated at 125 kg/h and 145 kg/h; (5) the investigated parameters such as mass flowrate, pressure, and gravity have significant effects on amplitude of mass flow oscillation, but have little effects on the period of mass flow oscillation for both LPB and HPB. Results from the numerical simulation were compared with the results from the experiment for both LPB and HPB. The numerical amplitude results obtained were far less than the amplitude results obtained from the experiment. But there was no significant difference between the oscillation periods obtained from both the numerical simulation and experiment. (6) Flow instability studies including predicting flow oscillation amplitude and periods, and instability power boundaries could be carried out using 3D STAR-CCM+ CFD code. The effects of heating structures on flow instability results have not been considered in this study. Previous studies have shown that including heating structures in geometrical models for numerical studies may have effects on flow instability results. More experimental studies are needed for validation of similar numerical studies carried out at supercritical pressures using various numerical tools.

Analysis of Two-Phase Flow Instability in Multi-Channel System

2014 ◽  
Author(s):  
Genglei Xia ◽  
Minjun Peng ◽  
Du Xue
Keyword(s):  
Two Phase Flow ◽  
Flow Instability ◽  
Saturation Pressure ◽  
Computer Code ◽  
Phase Flow ◽  
Parallel Channel ◽  
Multichannel System ◽  
Two Phase ◽  
Forced Circulation ◽  
Channel System

Ledinegg instability is one of the most important static instabilities for two phase flow system, especially in microchannel systems. In this paper, the force circulation two phase flow instability in vertical multi-channel system is performed by the best estimate system computer code RELAP5. The process and inherent reason of flow instability between multichannel system (FIBM) and flow excursion in forced circulation parallel channel system are analyzed. The effects of main operating parameters related to static onset of flow instability are investigated. Inlet subcooling, inlet restrictor, and saturation pressure are sensitive to the stability of parallel channel system.

Experimental Investigation of Flow Instability Between Two Vertical Parallel Channels Using Supercritical CO2

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Anantvir Singh Saini ◽  
Vijay Chatoorgoon ◽  
Dhanashree S. Ghadge
Keyword(s):  
Flow Instability ◽  
Working Fluid ◽  
Parallel Channel ◽  
Outlet Channel ◽  
Supercritical Flow ◽  
University Of Manitoba ◽  
Parallel Channels ◽  
Channel Assembly ◽  
Flow Experiments ◽  
Insight Into

Abstract Supercritical flow experiments were conducted at University of Manitoba using supercritical flow facility-vertical (SFF-V), which is a two vertical parallel channel assembly. The working fluid was CO2 at supercritical pressure and was driven by natural convective forces rather than a pump. Different system pressures (7.4 MPa–9.1 MPa), inlet temperatures (7 °C–30.1 °C) and various outlet-channel k-factors were used. A total of eleven parallel channel out-of-phase instability boundary points were obtained and the details of those cases are reported herein. These results can be used for code validation, to enrich the limited database of supercritical parallel-channel instability and to lend further insight into supercritical flow instability in heated parallel channels.

Study of flow instability in parallel channel system for water cooled blanket

2019 ◽  
Vol 148 ◽  
pp. 111291 ◽  
Author(s):  
Qiang Lian ◽  
Wenxi Tian ◽  
Xinli Gao ◽  
Suizheng Qiu ◽  
G.H. Su
Keyword(s):  
Flow Instability ◽  
Parallel Channel ◽  
Channel System

Flow instability in parallel-channel systems with ultra-supercritical water

2020 ◽  
Vol 119 ◽  
pp. 104907
Author(s):  
Shijie Ouyang ◽  
Tiantian Niu ◽  
Le Dong ◽  
Xihong Zhou ◽  
Dong Yang
Keyword(s):  
Supercritical Water ◽  
Flow Instability ◽  
Parallel Channel ◽  
Channel Systems

The Basic Thermal Hydraulic Issues of Applying Supercritical Fluid to Nuclear Reactors

2021 ◽  
pp. 682-716
Author(s):  
Jinguang Zang ◽  
Xiao Yan ◽  
Yanping Huang
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Flow Instability ◽  
Nuclear Reactors ◽  
Natural Circulation ◽  
Parallel Channel ◽  
Validation Data ◽  
Channel System ◽  
Stability Issues ◽  
The Heat Transfer Coefficient

This chapter is mainly focused on illustrating some introductory progress on thermal hydraulic issues of supercritical water, including heat transfer characteristics, pressure loss characteristics, flow stability issues, and numerical method. These works are mainly to give a basic idea of elementary but important topics in this area. An analytical method was proposed up to predict the heat transfer coefficient and friction coefficient based on the two-layer wall function. Flow instability experiments have been carried out in a two-parallel-channel system with supercritical water, aiming to provide an up-to-date knowledge of supercritical flow instability phenomena and initial validation data for numerical analysis. The natural circulation instability of supercritical water was also investigated in the experiments.

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