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.

Asymmetry Investigation on Single Phase Flow in Inverted U-Tubes of Steam Generator Under the Condition of Natural Circulation

2010 ◽  
Author(s):  
Chuan Wang ◽  
Lei Yu
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Steam Generator ◽  
Mass Flux ◽  
Single Phase ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Outlet Temperature

In order to study the reverse flow characteristics in U-tubes of steam generator in the natural circulation case, the code RELAP5/MOD3.3 is used to model and calculate single-phase water flow for PWR under some typical operating conditions in the natural circulation case. The U-tubes of steam generator are classified according to their length and then are divided into different nodes and flow lines. The calculated results show that reverse flow exists in some inverted U-tubes of the steam generator, the natural circulation capacity of the primary coolant circuit system declines and the calculated net mass flux of the natural circulation accords with the experimental data. The traditional lumped parameter method can not simulate the reverse flow characteristics in inverted U-tubes and its result is much greater than the experimental data. When the steam generator outlet pressure is higher than inlet pressure, and gravitational pressure drop is lower than the total of frictional pressure drop and area change pressure drop, the reverse flow will occur. As to the nuclear power plant described in this paper, the mass flux of the shorter U-tubes drops more quickly and at last reverse flow will occur. The temperature distribution is uniform in inverted U-tubes, and it is almost identical with that of SG in secondary side. The occurrence of reverse flow can be judged by that whether the steam generator inlet temperature is lower than reactor outlet temperature obviously. It is indicated that reverse flow occurred in the U-tubes of the steam generator reduces the mass flux in the natural circulation system.

Stability of single-phase natural-circulation flows in steam generator U tubes

2013 ◽  
Vol 60 ◽  
pp. 344-349 ◽  
Author(s):  
Tadashi Watanabe ◽  
Yoshinari Anoda ◽  
Masahito Takano
Keyword(s):  
Steam Generator ◽  
Single Phase ◽  
Natural Circulation

Flow Reversal in a Horizontal Type Natural Circulation Heat Recovery Steam Generator

2006 ◽  
Author(s):  
Heimo Walter ◽  
Wladimir Linzer
Keyword(s):  
Steam Generator ◽  
Heat Recovery ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Heating Surface ◽  
Heat Absorption ◽  
System Pressure ◽  
Horizontal Type ◽  
The Stability ◽  
The Individual

Natural circulation heat recovery steam generators (HRSG) are used in many applications for the thermal recycling of the waste flue gas. Many of these boilers are designed as a horizontal type HRSG (see fig. 1). The evaporator of such a steam generator is characterized by an array of parallel tubes with different heat input. The paper presents the results of a theoretical stability analysis for a HRSG with a vertical tube bank. For the horizontal type HRSG the static instability, namely the reverse flow was analysed. The study was done at low system pressures and under hot start-up conditions for the boiler. The investigations show the influence of the geometry, the system pressure and the heat absorption of the individual tubes in the evaporator on the stability of the boiler. The aim of the study was to find design criteria to avoid reverse flow in the tubes of the evaporator. Addition of flow resistance at certain locations of the evaporator can improve the stability. A higher stability will be also achieved by the homogenization of the heat absorption in the individual layers of the bundle heating surface.

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.

Flow Stability of Heat Recovery Steam Generators

2004 ◽  
Author(s):  
Heimo Walter ◽  
Wladimir Linzer
Keyword(s):  
Heat Recovery ◽  
Flow Instability ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Density Wave ◽  
Horizontal Tube ◽  
Steam Generators ◽  
Tube Bank ◽  
First Results ◽  
The Stability

In this paper the results of a theoretical stability analysis are presented. The investigation was done for two different types of natural circulation Heat Recovery Steam Generators (HRSG) — a two-drum steam generator and a HRSG with a horizontal tube bank. The investigation shows the influence of the boiler geometry on the stability of the steam generators. For the two-drum boiler the static instability, namely the reverse flow is analysed. First results of the investigations for the HRSG with a horizontal tube bank are also presented. In this case the dynamic flow instability of density wave oscillations is analysed.

Aperiodic Instability of a Once-Through Steam Generator with a Feedwater Line

2006 ◽  
Author(s):  
Jae-Kwang Seo ◽  
Han-Ok Kang ◽  
Juhyeon Yoon ◽  
Keung-Koo Kim
Keyword(s):  
Experimental Data ◽  
Steam Generator ◽  
Pressure Difference ◽  
Flow Instability ◽  
Reverse Flow ◽  
Flow Direction ◽  
Minimum Pressure ◽  
Multiple Flows ◽  
Static Flow ◽  
Aperiodic Instability

Aperiodic (static) flow instability is an instability related to the change of a flow direction in individual steam generating U-shaped channels operating at given pressure difference. The nature of an aperiodic instability is close to a Ledinegg instability [1] related to the presence of multiple flows at the full hydraulic curve of a U-shaped channel. In this paper, the conditions for a reverse flow for a once-through steam generator (OTSG) with U-shaped modular feedwater line (MFL) are studied. From the results of the studies, it is revealed that the change of a flow direction in the MFL is due to the boiling of the feedwater in the downcomer branch of the U-shaped MFL and that multiple flows start in an area of the extremes corresponding to the minimum pressure difference of the hydraulic curves. Calculation models for predicting a threshold of an aperiodic instability for the OTSG of interest is proposed and the analysis results are compared with the experimental data.

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.

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