An Investigation Into the Effect of Subcooled Liquid Inertia on Flow-Change-Induced Transient Flow Surges in Horizontal Condensing Flow Systems

2005 ◽  
Vol 127 (11) ◽  
pp. 1280-1284 ◽  
Author(s):  
C. J. Kobus
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Transient Flow ◽  
Phase Region ◽  
Complex Nature ◽  
Vapor Flow ◽  
Two Phase ◽  
Subcooled Liquid ◽  
Flow Systems ◽  
Final Steady State

The objective of this research is to investigate large-scale transient flow surges of the condensate leaving in-tube condensing flow systems because of perturbations in the inlet vapor flow rate, and the influence of the subcooled liquid inertia of the condensate on these transient responses. Small changes in the inlet vapor flow rate momentarily cause large transient flow surges in the outlet liquid flow rate. Condensate inertia is seen to destabilize the system into an underdamped behavior where the flow rate can overshoot the final steady-state position several times. A one-dimensional, two-fluid, distributed parameter system mean void fraction (SMVF) model of the time-dependent distribution of liquid and vapor within the two-phase region is developed for predicting these transient characteristics, which it is seen to do quite well, especially when consideration is given to the complex nature of the problem.

Onset of Water Hammer Phenomenon Following Flow Surge Characteristics in Tube-Type Condensing Flows

2003 ◽  
Author(s):  
B. L. Bhatt
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Density Ratio ◽  
Water Hammer ◽  
Phase Region ◽  
Bubble Collapse ◽  
Vapor Flow ◽  
Two Phase ◽  
Condensing Flows

Two-Phase region, in condensing flow undergoing complete condensation inside a tube, acts as an amplifier of any small internal or external disturbances. A small, externally imposed change in the inlet vapor flow rate, or heat flux, leads to substantial surges in the outlet liquid flow rate, including the possibility of flow reversals. Also, if the conditions are right, slight internal disturbances as a result of vapor/liquid interaction, can lead to sustained oscillations of large amplitude, such as in the outlet liquid flow rate. Such surging characteristics coupled with rapid bubble collapse may lead to water hammer phenomenon. This paper will summarize both experimental observations and theoretical models as a result of externally imposed, or internally induced, flow changes in condensing flows. The physics of the processes, including liquid/vapor density ratio, vapor compressibility, bubble collapse, and liquid inertia will be highlighted. The condensing flow stability criterion will be used to provide a possible physical and an analytical basis for the catastrophic piping failure due to a condensation induced water hammer.

An Experimental and Theoretical Investigation Into Thermally Governed Transient Flow Surges in Two-Phase Condensing Flow

1977 ◽  
Vol 99 (4) ◽  
pp. 561-567 ◽  
Author(s):  
G. L. Wedekind ◽  
B. L. Bhatt
Keyword(s):  
Experimental Data ◽  
Transient Flow ◽  
Vapor Flow ◽  
Transient Phenomenon ◽  
Two Phase ◽  
Subcooled Liquid ◽  
Measured Flow ◽  
Tube Type ◽  
Complete Condensation ◽  
Small Change

The specific transient phenomenon under consideration is the outlet flowrate of subcooled liquid from a tube-type condenser where complete condensation takes place. Experimental data are presented which indicates that a small change in the inlet vapor flow-rate will momentarily cause a very large transient surge in the outlet flowrate of subcooled liquid. These experimentally measured flow transients are predicted quite accurately using a system mean void fraction model. Also, some preliminary results are presented which indicate the influence of throttling at the condenser outlet as a means of attenuating the transient overshoot characteristics.

Modeling the Characteristics of Thermally Governed Transient Flow Surges in Multitube Two-Phase Condensing Flow Systems With Compressibility and Thermal and Flow Distribution Asymmetry

1997 ◽  
Vol 119 (3) ◽  
pp. 534-543 ◽  
Author(s):  
G. L. Wedekind ◽  
C. J. Kobus ◽  
B. L Bhatt
Keyword(s):  
Flow Rate ◽  
Transient Flow ◽  
Flow Distribution ◽  
Vapor Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Physical Mechanisms ◽  
Tube Type ◽  
Design Perspective ◽  
Spreadsheet Software

In a tube-type condenser involving complete condensation, small changes in the inlet vapor flow rate momentarily cause very large transient surges in the outlet mass flow rate. An Equivalent Single-Tube Model (ESTM), based on the System Mean Void Fraction Model, is developed that predicts these transient flow surges for a multitube system; including the effects of compressibility as well as thermal and flow distribution asymmetry. The model is verified theoretical and experimentally. From a design perspective, the significant value of the ESTM is that it includes the primary physical mechanisms involved in such complex flow transients, yet is simple enough to be solved on typical “spreadsheet” software.

An Investigation Into the Effect of Subcooled Liquid Inertia on Flowrate Induced Transient Flow Surges in Horizontal Condensing Flow Systems

2003 ◽  
Author(s):  
Chris J. Kobus
Keyword(s):  
Experimental Data ◽  
Large Scale ◽  
Transient Flow ◽  
Salient Feature ◽  
Analytical Tool ◽  
Predictive Capability ◽  
Subcooled Liquid ◽  
Flow Systems ◽  
Tube Type ◽  
Complete Condensation

The objective of this research is to investigate large-scale transient flow surges of condensate leaving horizontal in-tube condensing flow systems, due to perturbations in the inlet vapor flowrate, and the influence of the subcooled condensate inertia on these surges. In a tube-type condenser involving complete condensation, it has been seen that small changes in the inlet vapor flowrate momentarily cause large transient flow surges in the outlet liquid flowrate. A System Mean Void Fraction (SMVF) Model is developed for predicting these flow surge characteristics. Experimental data are also presented, showing both the influence of subcooled liquid inertia, and the very good predictive capability of the SMVF Model. The salient feature of the SMVF Model is its simplicity that, with an experimentally verified predictive capability, enhances the models’ utility as an analytical tool as well as a tool for educational purposes.

scholarly journals Maximum Flow Rate of a Single Component, Two-Phase Mixture

1965 ◽  
Vol 87 (1) ◽  
pp. 134-141 ◽  
Author(s):  
F. J. Moody
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Maximum Flow ◽  
Single Component ◽  
Maximum Flow Rate ◽  
Vapor Flow ◽  
Two Phase ◽  
Slip Ratio ◽  
Phase Mixture ◽  
Local Slip

A theoretical model is developed for predicting the maximum flow rate of a single component, two-phase mixture. It is based upon annular flow, uniform linear velocities of each phase, and equilibrium between liquid and vapor. Flow rate is maximized with respect to local slip ratio and static pressure for known stagnation conditions. Graphs are presented giving maximum steam/water flow rates for: local static pressures between 25 and 3,000 psia, with local qualities from 0.01 to 1.00; local stagnation pressures and enthalpies which cover the range of saturation states.

Modeling the Thermally Governed Transient Flow Surges in Multitube Condensing Flow Systems With Thermal and Flow Distribution Asymmetry

1989 ◽  
Vol 111 (3) ◽  
pp. 786-791 ◽  
Author(s):  
G. L. Wedekind ◽  
B. L. Bhatt
Keyword(s):  
Flow Rate ◽  
Transient Flow ◽  
Liquid Flow Rate ◽  
Flow Distribution ◽  
Vapor Flow ◽  
Tube Model ◽  
Condenser Tube ◽  
Tube System ◽  
Tube Type ◽  
Complete Condensation

In a tube-type condenser involving complete condensation, small changes in the inlet vapor flow rate momentarily cause very large transient surges in the outlet liquid flow rate. An equivalent single-tube model is proposed that predicts these transient flow surges for a multitube system. The model, based upon a system mean void fraction model developed earlier, includes the effects of thermal and flow distribution asymmetry associated with each individual condenser tube in the multitube system. Theoretical and experimental verification for a two-tube system is presented.

An Investigation of the Liquid Distribution in Annular-Mist Flow

1970 ◽  
Vol 92 (4) ◽  
pp. 651-658 ◽  
Author(s):  
J. T. Pogson ◽  
J. H. Roberts ◽  
P. J. Waibler
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Liquid Film ◽  
Flow Rate ◽  
Droplet Size Distribution ◽  
Correlation Equation ◽  
Vapor Flow ◽  
Two Phase ◽  
Liquid Distribution ◽  
Liquid Film Flow

The results of an experimental investigation of the average liquid film thickness are presented for vertical upward annular-mist two-phase flow, with and without heat transfer. The effects on the film thickness for variations in vapor flow rate, liquid flow rate, vapor density, and heat transfer are described. A correlation equation is presented for the local time-averaged thickness and for the droplet size distribution. In addition, an equation is given for the liquid film flow rate as a function of the average film thickness.

A Comparative Study of Single-Phase, Two-Phase, and Supercritical Natural Circulation in a Rectangular Loop

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
P. K. Vijayan ◽  
M. Sharma ◽  
D. S. Pilkhwal ◽  
D. Saha ◽  
R. K. Sinha
Keyword(s):  
Steady State ◽  
Flow Rate ◽  
Significant Influence ◽  
Single Phase ◽  
Natural Circulation ◽  
Phase Region ◽  
Inlet Temperature ◽  
Two Phase ◽  
Supercritical Region ◽  
Stability Performance

A one-dimensional theoretical model has been used to analyze the steady state and stability performance of a single-phase, two-phase, and supercritical natural circulation in a uniform diameter rectangular loop. Parametric influences of diameter, inlet temperature, and system pressure on the steady state and stability performance have been studied. In the single-phase liquid filled region, the flow rate is found to increase monotonically with power. On the other hand, the flow rate in two-phase natural circulation systems is found to initially increase, reach a peak, and then decrease with power. For the supercritical region also, the steady state behavior is found to be similar to that of the two-phase region. However, if the heater inlet temperature is beyond the pseudo critical value, then the performance is similar to single-phase loops. Also, the supercritical natural circulation flow rate decreases drastically during this condition. With an increase in loop diameter, the flow rate is found to enhance for all the three regions of operation. Pressure has a significant influence on the flow rate in the two-phase region, marginal effect in the supercritical region, and practically no effect in the single-phase region. With the increase in loop diameter, operation in the single-phase and supercritical regions is found to destabilize, whereas the two-phase loops are found to stabilize. Again, pressure has a significant influence on stability in the two-phase region.

Simple Nonlinear Methods for Predicting Two-Phase Instabilities in a Helically Coiled Steam Generator

2007 ◽  
Author(s):  
Seok-Ki Choi ◽  
Seong-O Kim ◽  
Han-Ok Kang
Keyword(s):  
Pressure Drop ◽  
Steam Generator ◽  
Flow Rate ◽  
Density Wave ◽  
Vertical Direction ◽  
Temporal Variations ◽  
Phase Region ◽  
Two Phase ◽  
Energy Agency ◽  
Proposed Model

A simple model to analyze the non-linear density-wave instability in a sodium cooled, helically coiled steam generator is developed. The model is formulated with three regions with moving boundaries. The homogeneous equilibrium flow model is used for the two-phase region and the shell-side energy conservation is also considered for the heat flux variation in each region. The proposed model is applied to the analysis of two-phase instability in a JAEA (Japan Atomic Energy Agency) 50MWt No.2 steam generator. The steady state results show that the proposed model accurately predicts the six cases of the operating temperatures in the primary and secondary sides. The sizes of the three regions and the secondary side pressure drop according to the flow rate, and the temperature variation in the vertical direction are also predicted well. The temporal variations of the inlet flow rate according to the throttling coefficient, the boiling and superheating boundaries and the pressure drop in the two-phase and superheating regions are obtained from the unsteady analysis.

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