Preliminary Experiments With an Underexpanded Gas Jet Into Water

2009 ◽  
Author(s):  
Mitsunori Uchida ◽  
Satoshi Someya ◽  
Koji Okamoto ◽  
Hiroyuki Ohshima
Keyword(s):  
Heat Exchanger ◽  
Critical Pressure ◽  
Two Phase Flow ◽  
Ambient Pressure ◽  
Hydrogen Gas ◽  
Gas Jet ◽  
Liquid Sodium ◽  
Phase Flow ◽  
Two Phase ◽  
Pressurized Water

When a heat exchanger in a Fast Breeder Reactor cracks, highly pressurized water or steam escapes into the surrounding liquid sodium. A sodium-water reaction then occurs, forming disodium oxide (and hydrogen gas). It can cause secondary damages to the heat exchangers by the reaction heat and erosion corrosion. The released flow of steam from the cracks of the heat exchanger is an underexpanded jet because the ambient pressure outside the tubes is lower than the critical pressure. When the pressure of a jet released at high pressure cannot be reduced to the low pressure of the ambient fluid, the flow is said to be underexpanded. Because this expansion causes a reduction of pressure and the pressure is lower than the critical pressure, the velocity of the flow can reach supersonic speed. Several studies have examined the underexpansion of the gas-gas phase. However, there have been few studies on the underexpansion of gas-liquid two-phase flows. The flow characteristics of the gas-liquid two-phase flow differ from the gas-gas flow because breakups of the bubbles appear in the gas-liquid two-phase flow. Therefore, in this study qualitative measurement was carried out for the purpose of revealing the flow with the underexpanded gas jet injected into water. The gas jet distance L and the expansion angle θ were then obtained from averaged image of a high-speed camera. L and θ increased approximately linearly with increasing pressure. The entrainment velocity and the velocity of entrained water droplets into the gas jet were obtained by PIV. Images of unstable expansion near the jet nozzle were captured for the first time.

Efficiency of a Combined Desalination and Power System Utilizing a Two-Phase Flow Multistream Heat Exchanger

2016 ◽  
Vol 38 (11-12) ◽  
pp. 1000-1007 ◽  
Author(s):  
Alireza Hosseini Araghi ◽  
Mehdi Khiadani ◽  
Kamel Hooman ◽  
Gordon Lucas
Keyword(s):  
Heat Exchanger ◽  
Power System ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase

An Analytical Model for Prediction of Two-Phase (Noncondensable) Flow Pump Performance

1985 ◽  
Vol 107 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Okitsugu Furuya
Keyword(s):  
Analytical Method ◽  
Single Phase ◽  
Two Phase Flow ◽  
Control Volume ◽  
Model Development ◽  
Oil Well ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Pressurized Water

During operational transients or a hypothetical LOCA (loss of coolant accident) condition, the recirculating coolant of PWR (pressurized water reactor) may flash into steam due to a loss of line pressure. Under such two-phase flow conditions, it is well known that the recirculation pump becomes unable to generate the same head as that of the single-phase flow case. Similar situations also exist in oil well submersible pumps where a fair amount of gas is contained in oil. Based on the one dimensional control volume method, an analytical method has been developed to determine the performance of pumps operating under two-phase flow conditions. The analytical method has incorporated pump geometry, void fraction, flow slippage and flow regime into the basic formula, but neglected the compressibility and condensation effects. During the course of model development, it has been found that the head degradation is mainly caused by higher acceleration on liquid phase and deceleration on gas phase than in the case of single-phase flows. The numerical results for head degradations and torques obtained with the model favorably compared with the air/water two-phase flow test data of Babcock and Wilcox (1/3 scale) and Creare (1/20 scale) pumps.

Damping of Heat Exchanger Tubes in Two-Phase Flow: Review and Design Guidelines

2004 ◽  
Vol 126 (4) ◽  
pp. 523-533 ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor
Keyword(s):  
Heat Exchanger ◽  
Two Phase Flow ◽  
Cross Flow ◽  
Design Guidelines ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Design Guideline ◽  
Fluid Properties ◽  
Semi Empirical

Two-phase flow exists in many shell-and-tube heat exchangers such as condensers, evaporators, and nuclear steam generators. Some knowledge on tube damping mechanisms is required to avoid flow-induced vibration problems. This paper outlines the development of a semi-empirical model to formulate damping of heat exchanger tube bundles in two-phase cross flow. The formulation is based on information available in the literature and on the results of recently completed experiments. The compilation of a database and the formulation of a design guideline are outlined in this paper. The effects of several parameters such as flow velocity, void fraction, confinement, flow regime and fluid properties are discussed. These parameters are taken into consideration in the formulation of a practical design guideline.

Numerical Simulation of Subcooled Flow Boiling Heat Transfer in Helical Tubes

2006 ◽  
Author(s):  
Jong Chull Jo ◽  
Woong Sik Kim ◽  
Chang-Yong Choi ◽  
Yong Kab Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Steam Generator ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Heat Transfer Analysis ◽  
Normal Operation ◽  
Phase Flow ◽  
Two Phase ◽  
Pressurized Water

This paper addresses the numerical simulation of two phase flow heat transfer in the helically coiled tubes of an integral type pressurized water reactor steam generator under normal operation using a CFD code. The single phase flow which flow downward direction in the shell side is also calculated together. For the calculation of tube side two-phase flow the inhomogeneous two-fluid model is used. Both the RPI (Rensselaer Polytechnic Institute) wall boiling model and the bulk boiling model are implemented for the numerical simulation and the computed results are compared with the available measured data. The conjugate heat transfer analysis method is employed to calculate the conduction in the tube wall with finite thickness and the convections in the internal and external fluids simultaneously so as to match the fluid-wall-fluid interface conditions properly. Both the internal and external turbulent flows are simulated using the standard k-ε model From the results of present numerical simulation, it is shown that the bulk boiling model can be applied to the simulation of two-phase flow in the helically coiled steam generator tubes. The results also show that the present simulation method is considered to be physically plausible when the computed results are compared with available previous experimental and numerical studies.

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