Investigation of single-phase flow patterns in a model flash evaporation chamber using PIV measurement and numerical simulation

Desalination ◽  
2002 ◽  
Vol 150 (1) ◽  
pp. 51-63 ◽  
Author(s):  
W.X. Jin ◽  
S.C. Low
Keyword(s):  
Numerical Simulation ◽  
Single Phase ◽  
Flow Patterns ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Flash Evaporation ◽  
Evaporation Chamber ◽  
Piv Measurement

Flow Patterns During Flow Boiling Instability in Silicon-Based Pin-Fin Microchannels

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Fayao Xu ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Single Phase ◽  
Flow Instability ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Pin Fin ◽  
Short Period ◽  
Pin Fins ◽  
Amplitude Mode

In this paper, the flow patterns during water flow boiling instability in pin-fin microchannels were experimentally studied. Three types of pin-fin arrays (in-line/circular pin-fins, staggered/circular pin-fins, and staggered/square pin-fins) were used in the study. The flow instability started to occur as the outlet water reached the saturation temperature. Before the unstable boiling, a wider range of stable boiling existed in the pin-fin microchannels compared to that in the plain microchannels. Two flow instability modes for the temperature and pressure oscillations, which were long-period/large-amplitude mode and short-period/small-amplitude mode, were identified. The temperature variation during the oscillation period of the long-period/large-amplitude mode can be divided into two stages: increasing stage and decreasing stage. In the increasing stage, bubbly flow, vapor-slug flow, stratified flow, and wispy flow occurred sequentially with time for the in-line pin-fin microchannels; liquid single-phase flow, aforementioned four kinds of two-phase flow patterns, and vapor single-phase flow occurred sequentially with time for the staggered pin-fin microchannel. The flow pattern transitions in the decreasing stage were the inverse of those in the increasing stage for both in-line and staggered pin-fin microchannels. For the short-period/small-amplitude oscillation mode, only the wispy flow occurred. With the increase of heat flux, the wispy flow and the vapor single-phase flow occupied more and more time ratio during an oscillation period in the in-line and staggered pin-fin microchannels.

Numerical Simulation of the Transient Flow in a Pump-Turbine During the Load Rejection Process With Special Emphasis on the Cavitation Effect

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Xiaolong Fu ◽  
Deyou Li ◽  
Hongjie Wang ◽  
Guanghui Zhang ◽  
Zhenggui Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Single Phase ◽  
Pressure Pulsation ◽  
Phase Flow ◽  
Cavitation Flow ◽  
Single Phase Flow ◽  
Pump Turbine ◽  
Cavitation Effect ◽  
Simulation Results ◽  
Load Rejection Process

Abstract At present, pumped-storage power technology is the only available and effective way for the load balancing and energy storage in the grid network scale. During the frequent switch back and forth conditions, there are severe pressure pulsation and cavitation in pump-turbines. However, their generation mechanism has not been determined yet. This work contributes to the numerical simulation of the transient behaviors in a prototype pump-turbine during the load rejection process with special emphasis on cavitation effect. In this study, the two-dimensional dynamic remesh and variable speed slide mesh methodologies were employed to perform the simulation of the transient single-phase flow and cavitation flow in a pump-turbine. The simulation results of single-phase flow and cavitation flow were both consistent with the experimental data except in local regions based on the experimental validation of prototype tests. However, the numerical results considering cavitation effects have a better behavior than those of single-phase flow in the predictions of pressure pulsation and rotational speed. Then, the cavitation flow simulation results were analyzed deeply, especially in pressure pulsation and cavitation flow field. Analysis revealed that three typical complex frequency components of pressure were captured in the cavitation flow, which significantly affect the axial hydraulic thrust on the runner. And it is validated that they are primarily induced by the cavity collapse near the trailing edges of the runner blades in reverse pump mode and the interaction between cavitation and vortex rope in draft-tube in turbine mode.

Numerical Analysis of the Flow Field in the Nozzle of Hot Water Rocket Motor

2014 ◽  
Vol 1016 ◽  
pp. 635-639 ◽  
Author(s):  
Wei Wei Sun ◽  
Zhi Jun Wei
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Flow Field ◽  
Single Phase ◽  
Rocket Motor ◽  
Hot Water ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Working Process ◽  
Flow Process

Flashing is an important factor in the working process of hot water rocket motor. In order to deeply understand the performance characteristic of hot water rocket motor, a numerical simulation model of the flow field in the nozzle was established in this paper. According to the study of flow field in the nozzle of the motor,it is found that the phase change occurs at the position of the throat,and the flow reaches to supersonic after the throat because of the changing sound speed.The flow in the nozzle can be divided into three processes in this paper: single-phase flow process, flash process and expand-accelerating process.

scholarly journals Numerical Simulation of a Single-Phase Flow Through Fractures with Permeable, Porous and Non-Ductile Walls

2017 ◽  
Vol 7 (5) ◽  
pp. 2041-2046
Author(s):  
N. Pour Mahmoud ◽  
A. Zabihi
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Single Phase ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Surrounding Area ◽  
Fracture Geometry ◽  
Pressure Drops ◽  
Permeable Walls ◽  
Flow Through

This paper attempts to study flows within fractures through a set of numerical simulations. In addition, a special care is given to hydraulic features and characteristics of fractures. The research is performed through the application of calculative fluid dynamics and a finite volume discrete schema. The investigated flows are laminar, single-phase and stable flows of water and air through fractures with penetrable walls. The selected fracture geometry is inspired from the tomographic scan of a stone fracture. Water and air are modeled in fractures with permeable walls and different permeability levels. It has been observed that in case of permeable matrixes, the friction coefficient is lower compared to impermeable matrixes. In fact permeability reduced friction. In addition, highest pressure drops were observed in areas with smaller fracture diaphragms. Nonetheless, the surrounding area of the fracture is analyzed with the consideration of Darcy's rule.

Numerical simulation of single-phase flow in a single square tube with blockage

2021 ◽  
Vol 44 ◽  
pp. 101053
Author(s):  
Daheng Li ◽  
Yun Guo ◽  
Hui Bao ◽  
Jun Xiao ◽  
Changhong Peng
Keyword(s):  
Numerical Simulation ◽  
Single Phase ◽  
Phase Flow ◽  
Single Phase Flow
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