scholarly journals High Conversion Hydrogen Peroxide Microchannel Reactors: Design and Two-phase Flow Instability Investigation

2021 ◽  
pp. 130080
Author(s):  
Xingchen Li ◽  
Yiyong Huang ◽  
Zan Wu ◽  
Huaduo Gu ◽  
Xiaoqian Chen
Keyword(s):  
Hydrogen Peroxide ◽  
Two Phase Flow ◽  
Flow Instability ◽  
High Conversion ◽  
Phase Flow ◽  
Two Phase ◽  
Microchannel Reactors

Research on Two-Phase Flow Instability in Parallel Multi-Channel Under Rolling Motion Condition

2008 ◽  
Author(s):  
Y. J. Zhang ◽  
G. H. Su ◽  
S. Z. Qiu ◽  
X. B. Yang
Keyword(s):  
Two Phase Flow ◽  
Flow Instability ◽  
Stability Boundary ◽  
Channel Number ◽  
Rolling Motion ◽  
Phase Flow ◽  
Two Phase ◽  
Channel System ◽  
Motion Condition ◽  
High Equilibrium

Two-phase flow instability of the parallel multi-channel system has been studied under rolling motion condition in this paper. Based on the homogeneous flow model with considering the rolling motion condition, the parallel multi-channel model is established by using the control volume integrating method. Gear method is used to solve the system equations. The influences of the inlet and upward sections and the heating power on the flow instability under rolling motion condition have been analyzed. The marginal stability boundary (MSB) under rolling motion condition is obtained and the unstable regions occur in both low and high equilibrium quality regions. The region with low inlet subcooling is also instable. In high equilibrium quality region, the multiplied period phenomenon is found and the chaotic phenomenon appears at the MSB. The oscillation part of mass flow rate (amplitude) may be averaged into other channels so that the influence of rolling motion is weakened. But the stability of multi-channel system is independent of the channel number and the increase of the channel number could only make the amplitude more uniformity in channels.

scholarly journals Numerical Study of Bubble Rising and Coalescence Characteristics under Flow Pulsation Based on Particle Method

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Ronghua Chen ◽  
Minghao Zhang ◽  
Kailun Guo ◽  
Dawei Zhao ◽  
Wenxi Tian ◽  
...  
Keyword(s):  
Flow Rate ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Numerical Study ◽  
Phase Flow ◽  
Flow Pulsation ◽  
Two Phase ◽  
Inlet Flow ◽  
Inlet Flow Rate ◽  
Bubble Rising

Two-phase flow instability may occur in nuclear reactor systems, which is often accompanied by periodic fluctuation in fluid flow rate. In this study, bubble rising and coalescence characteristics under inlet flow pulsation condition are analyzed based on the MPS-MAFL method. To begin with, the single bubble rising behavior under flow pulsation condition was simulated. The simulation results show that the bubble shape and rising velocity fluctuate periodically as same as the inlet flow rate. Additionally, the bubble pairs’ coalescence behavior under flow pulsation condition was simulated and compared with static condition results. It is found that the coalescence time of bubble pairs slightly increased under the pulsation condition, and then the bubbles will continue to pulsate with almost the same period as the inlet flow rate after coalescence. In view of these facts, this study could offer theory support and method basis to a better understanding of the two-phase flow configuration under flow pulsation condition.

The influence of non-uniform heating on two-phase flow instability in subchannel

2019 ◽  
Vol 345 ◽  
pp. 7-14
Author(s):  
Sipeng Wang ◽  
Bao-Wen Yang ◽  
Hu Mao ◽  
Yu-chen Lin ◽  
Guanyi Wang
Keyword(s):  
Two Phase Flow ◽  
Flow Instability ◽  
Phase Flow ◽  
Uniform Heating ◽  
Two Phase

scholarly journals A Unifying Numerical Framework for the “Small-Slope” Based Core-Annular Flow Instability Models

Mathematics ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1941
Author(s):  
Antonio Quevedo ◽  
Carlos Fuentes ◽  
Carlos Chávez ◽  
Enrique González-Sosa ◽  
Carlos Mota
Keyword(s):  
Evolution Equations ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Nonlinear Partial Differential Equations ◽  
Mass Conservation ◽  
Flow In Porous Media ◽  
Phase Flow ◽  
Two Phase ◽  
Theoretical Approaches ◽  
Highly Nonlinear

The snap-off is an instability phenomenon that takes place during the immiscible two-phase flow in porous media due to competing forces acting on the fluid phases and at the interface between them. Different theoretical approaches have been proposed for the development of mathematical models that describe the dynamics of a fluid/fluid interface in order to analyze the snap-off mechanism. The models studied here are based on the “small-slope” approach and were derived from the mass conservation and other governing equations of two-phase flow at pore scale in circular capillaries for pure and complex interfaces. The models consist of evolution equations; highly nonlinear partial differential equations of fourth order in space and first order in time. Although the structure of the models for each type of interface is similar, different numerical techniques have been employed to solve them. Here, we propose a unifying numerical framework to solve the group of such models. Such a framework is based on the Fourier pseudo-spectral differentiation method which uses the Fast Fourier Transform (FFT) and the inverse FFT (IFFT) algorithms. We compared the solutions obtained with this method to the results reported in the literature in order to validate our framework. In general, acceptable agreements were obtained in the dynamics of the snap-off.

Numerical investigation of the mechanism of two-phase flow instability in parallel narrow channels

2015 ◽  
Vol 287 ◽  
pp. 78-89 ◽  
Author(s):  
Lian Hu ◽  
Deqi Chen ◽  
Yanping Huang ◽  
Dewen Yuan ◽  
Yanling Wang ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Phase Flow ◽  
Two Phase ◽  
Narrow Channels

The Influence of Non-Uniform Heating on Two-Phase Flow Instability in Parallel Channels

2013 ◽  
Author(s):  
Xiaodong Lu ◽  
Linglan Zhou ◽  
Hong Zhang ◽  
Yingwei Wu ◽  
Guanghui Su ◽  
...  
Keyword(s):  
Heat Flux ◽  
Two Phase Flow ◽  
Flow Instability ◽  
System Stability ◽  
System Control ◽  
Phase Flow ◽  
Uniform Heating ◽  
Two Phase ◽  
System Pressure ◽  
Parallel Channels

The two-phase flow instability in parallel channels heated by uniform and non-uniform heat flux has been theoretically studied in this paper. Based on the homogeneous flow model in two-phase region, the system control equations of parallel channels were established. Semi-implicit finite-difference method and staggered mesh method were used to discretize the system control equations and the difference equations were solved with a chasing method. The cosine profile and uniform constant heat flux represent the non-uniform and uniform heating condition, respectively. The marginal stability boundaries (MSB) of parallel channels and the three-dimensional instability spaces (or instability reefs) of different heat flux models were obtained. For cosine profile heating, the stability of parallel channels increases with the increase of the system pressure and inlet resistant coefficient. In high inlet subcooling region, cosine heat flux can strengthen the system stability. However, in low inlet subcooling region, the negative effect to system stability will be caused by non-uniform heating. The increase of inlet resistant coefficient will move the turning point of the MSB to high inlet subcooling number.

Flow Boiling Heat Transfer and Two-Phase Flow Instability of Nanofluids in a Minichannel

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Leyuan Yu ◽  
Aritra Sur ◽  
Dong Liu
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Flow Instabilities ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Boiling Heat Transfer

Single-phase convective heat transfer of nanofluids has been studied extensively, and different degrees of enhancement were observed over the base fluids, whereas there is still debate on the improvement in overall thermal performance when both heat transfer and hydrodynamic characteristics are considered. Meanwhile, very few studies have been devoted to investigating two-phase heat transfer of nanofluids, and it remains inconclusive whether the same pessimistic outlook should be expected. In this work, an experimental study of forced convective flow boiling and two-phase flow was conducted for Al2O3–water nanofluids through a minichannel. General flow boiling heat transfer characteristics were measured, and the effects of nanofluids on the onset of nucleate boiling (ONB) were studied. Two-phase flow instabilities were also explored with an emphasis on the transition boundaries of onset of flow instabilities (OFI). It was found that the presence of nanoparticles delays ONB and suppresses OFI, and the extent is correlated to the nanoparticle volume concentration. These effects were attributed to the changes in available nucleation sites and surface wettability as well as thinning of thermal boundary layers in nanofluid flow. Additionally, it was observed that the pressure-drop type flow instability prevails in two-phase flow of nanofluids, but with reduced amplitude in pressure, temperature, and mass flux oscillations.

Sign in / Sign up

Export Citation Format

Share Document