Stability of Single-Phase Natural Circulation With Inverted U-Tube Steam Generators

1988 ◽  
Vol 110 (3) ◽  
pp. 735-742 ◽  
Author(s):  
J. Sanders
Keyword(s):  
Mathematical Model ◽  
Single Phase ◽  
Flow Direction ◽  
Natural Circulation ◽  
Boussinesq Equations ◽  
Test Facility ◽  
Normal Flow ◽  
Steam Generators ◽  
One Dimensional ◽  
Water Flows

For natural circulation it is shown that parallel flow in the tubes of an inverted U-tube steam generator can be, at certain power levels, unstable. A mathematical model, based on one-dimensional Oberbeck-Boussinesq equations, shows that stability can be attained if in some tubes the water flows backward, opposite to the normal flow direction. The results are compared to measurements obtained from the natural circulation test A2-77A in the LOBI-MOD2 integral system test facility.

scholarly journals CATHARE Assessment of Natural Circulation in the PKL Test Facility during Asymmetric Cooldown Transients

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Anis Bousbia Salah ◽  
Jacques Vlassenbroeck
Keyword(s):  
Natural Circulation ◽  
Test Facility ◽  
Steam Generators ◽  
Calculation Results ◽  
The Impact

Results of the CATHARE code calculations related to asymmetric cooldown tests in the PKL facility are presented. The test under consideration is the G2.1 experiment performed within the OECD/NEA PKL-2 project. It consists of carrying out a cooldown under natural circulation conditions in presence of two (out of four) emptied Steam Generators (SGs) and isolated on their secondary sides. The main goal of the current study is to assess the impact of a chosen cooldown strategy upon the occurrence of a Natural Circulation Interruption (NCI) in the inactive (i.e., noncooling) loops. For this purpose, three G2.1 test runs were investigated. The calculation results emphasize, mainly, the effect of the cooldown strategy, and the conditions that could lead to the occurrence of the NCI phenomenon.

Stability Analysis on Single-Phase Natural Circulation in Argonne Lead Loop Facility

2002 ◽  
Author(s):  
Qiao Wu ◽  
James J. Sienicki
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Single Phase ◽  
Natural Circulation ◽  
Stability Boundary ◽  
One Dimensional ◽  
Cooling Conditions ◽  
Characteristic Wavelength ◽  
Nyquist Criterion ◽  
High Reynolds

One-dimensional linear stability analysis was performed for single-phase lead-bismuth eutectic natural circulation. The Nyquist criterion and a root search method were employed to find the linear stability boundary of both forward and backward circulations. It was found that the natural circulations could be linearly unstable in a high Reynolds number region. Increasing loop friction makes a forward circulation more stable, but destabilizes the corresponding backward circulation under the same heating/cooling conditions. The characteristic wavelength of an unstable disturbance is roughly equal to the entire loop length.

Mixing of Two Streams, Steam and Water, in a Converging Nozzle

2000 ◽  
Author(s):  
Hikmet S. Aybar
Keyword(s):  
Single Phase ◽  
Cold Water ◽  
Chemical Processing ◽  
Contact Heat ◽  
Velocity Difference ◽  
One Dimensional ◽  
Water Flows ◽  
Contact Heat Transfer ◽  
Energy Equations ◽  
Two Fluid

Abstract Mixing of two fluid streams can be seen in many applications in chemical processing and energy generation industries. The supersonic steam blows into the cold water in the mixing nozzle. When the steam condenses, steam transfers to water heat and mass (because of the temperature difference and condensation) and momentum (because of the velocity difference). The condensation should be fully completed before the end of mixing nozzle. Thus, the length of the mixing nozzle is important parameter. After the condensation is completed, the flow is single phase, that is, liquid water, and the subsonic water flows in the converging nozzle. In this study, the mixing of the supersonic steam and subsonic water in a converging nozzle is investigated. The problem is modeled using one-dimensional continuity, momentum and energy equations, and solved numerically. For the calculation of the rate of condensation, a correlation for the contact heat transfer coefficient is used.

scholarly journals Steam Generator Water-Level Control

1966 ◽  
Vol 88 (2) ◽  
pp. 343-354 ◽  
Author(s):  
Amir N. Nahavandi ◽  
Abram Batenburg
Keyword(s):  
Mathematical Model ◽  
Control System ◽  
Water Level ◽  
Steam Generator ◽  
Natural Circulation ◽  
Level Control ◽  
Steam Generators ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
The Difference

A combined digital-analog mathematical model for the dynamic analysis of vertical U-tube natural-circulation steam generators is presented. The application of this model to the optimal design of a water-level controller for a steam generating unit is demonstrated. It is shown that a control system consisting of standard proportional and reset controls on water-level deviation from a desired set point and the difference between the steam and feedwater mass flow rates can be successfully employed for the control of water level in such a plant. The optimum values, as well as the range of the controller parameter sellings for which the steam generator exhibits a desired stable response, are determined.

scholarly journals Flow Stagnation under Single and Two-Phase Natural Circulation Conditions in the APEX-CE Test Facility

2008 ◽  
Vol 2008 ◽  
pp. 1-5
Author(s):  
José N. Reyes
Keyword(s):  
Single Phase ◽  
Natural Circulation ◽  
Supply System ◽  
Test Facility ◽  
State University ◽  
Circulation Flow ◽  
Two Phase ◽  
Flow Stagnation ◽  
Plant Experiment ◽  
Oregon State University

Natural circulation experiments were conducted at Oregon State University using the advanced plant experiment (APEX-CE) integral system test facility as configured to simulate a typical2×4Combustion Engineering nuclear steam supply system. This paper describes the mechanisms by which natural circulation flow was interrupted under single-phase and two-phase natural circulation conditions in APEX-CE.

scholarly journals Effect of Heaving Movement on Flow Instability in U-Tubes of Marine Steam Generator under Natural Circulation

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Jianli Hao ◽  
Wenzhen Chen ◽  
De Zhang
Keyword(s):  
Steam Generator ◽  
Single Phase ◽  
Flow Instability ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Critical Mass ◽  
Space Distribution ◽  
Tube Length ◽  
One Dimensional ◽  
Acceleration Amplitude

Under heaving movement conditions, the single phase flow instability in U-tubes is affected by the additional force, which will influence the marine reactor operation. In the present work, one-dimensional thermal-hydraulic model in U-tubes under heaving movement conditions is established, and the critical pressure drop (CPD) and critical mass flow rate (CMFR) which relate to the occurrence of reverse flow in U-tubes are proposed and analyzed. The effects of the heaving period and heaving acceleration amplitude on the flow instability in U-tubes with the different length are discussed. It is shown that (1) the CPD and CMFR are obviously affected by the heaving movement, which means that the reverse flow characteristic in U-tubes will be changed; (2) the fluctuation periods of the CPD and CMFR are the same as the heaving period, but the fluctuation magnitude of them is little affected by the heaving period; (3) the relative changes of CPD and CMFR are the linear function of heaving acceleration amplitude; and (4) the U-tube length has little influence on the relative changes of CPD and CMFR compared with the heaving acceleration amplitude, which means that the heaving movement has little influence on the space distribution of reverse flow in the U-tubes of marine steam generator.

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