scholarly journals Considering the Diffusive Effects of Cavitation in a Homogeneous Mixture Model

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 662
Author(s):  
Yanghui Ye ◽  
Cong Dong ◽  
Zhiguo Zhang ◽  
Yangyang Liang
Keyword(s):  
Transfer Coefficient ◽  
Pressure Pulse ◽  
Good Accuracy ◽  
Homogeneous Model ◽  
Mass Diffusion ◽  
Homogeneous Mixture ◽  
Hydrodynamic Cavitation ◽  
Rectangular Tube ◽  
Diffusive Effects ◽  
Homogeneous Mixture Model

Homogeneous mixture models are widely used to predict the hydrodynamic cavitation. In this study, the constant-transfer coefficient model is implemented into a homogeneous cavitation model to predict the heat and mass diffusion. Modifications are made to the average bubble temperature and the Peclet number for thermal diffusivity in the constant-transfer coefficient model. The evolutions of a spherical bubble triggered by negative pressure pulse are simulated to evaluate the prediction of heat and mass diffusion by the homogeneous model. The evolutions of three bubbles inside a rectangular tube are simulated, which show good accuracy of the homogeneous model for multibubbles in stationary liquid.

Experimental Investigation of Large Particle Slurry Transport in Vertically Oscillating Pipe for Subsea Mining

2021 ◽  
Author(s):  
Sotaro Masanobu ◽  
Satoru Takano ◽  
Shigeo Kanada ◽  
Masao Ono
Keyword(s):  
Mixture Model ◽  
Pressure Loss ◽  
Prediction Method ◽  
Axial Direction ◽  
Hydraulic Gradient ◽  
Solid Particles ◽  
Homogeneous Mixture ◽  
Pipe Model ◽  
Slurry Transport ◽  
Homogeneous Mixture Model

Abstract For subsea mining, it is important to predict the pressure loss in oscillating pipes for the safe and reliable operation of ore lifting as well as the design of lifting system. In the present paper, the authors focused on the internal flow in vertical lifting pipe oscillating in the axial direction and carried out slurry transport experiment to investigate the effects of pipe oscillation on the pressure loss. The spherical alumina beads and glass beads were used as the solid particles in the experiment, and the oscillating periods and amplitudes of pipe model as well as the solid concentrations and the mean slurry velocities were varied. The time-averaged components of hydraulic gradient calculated by the prediction method for the steady flow proposed in the past by the authors agreed well with the experimental ones. As for the fluctuating components of hydraulic gradient, the calculation results using a homogeneous mixture model were compared with the experimental data. The comparison result indicated that the homogeneous mixture model would be applicable to the prediction of pressure loss in the vertical pipe oscillating in the axial direction.

scholarly journals Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

2017 ◽  
Vol 473 (2199) ◽  
pp. 20160345 ◽  
Author(s):  
A. Ferrari
Keyword(s):  
Power Systems ◽  
Acoustic Cavitation ◽  
Vapour Phase ◽  
Cavitation Number ◽  
Homogeneous Mixture ◽  
Hydrodynamic Cavitation ◽  
Hydraulic Power ◽  
Two Phase ◽  
Advantages And Disadvantages ◽  
Propagation Of Waves

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh–Plesset equation are examined.

scholarly journals Pressure Pulse Propagation in Two-Component Slug Flow

1979 ◽  
Vol 101 (1) ◽  
pp. 44-52 ◽  
Author(s):  
C. Samuel Martin ◽  
M. Padmanabhan
Keyword(s):  
Simple Model ◽  
Slug Flow ◽  
Pulse Propagation ◽  
Pressure Pulse ◽  
Center Of Mass ◽  
Homogeneous Model ◽  
Propagation Speed ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Flux Model

The simple model of pressure pulse propagation in slug flow proposed by Henry, Grolmes, and Fauske has been extended by considering wave reflection and wave transmission at gas-liquid interfaces. A frequency-response model applied to a series of idealized gas and liquid slugs yields a pulse propagation speed that approaches the homogeneous model value as the number of slugs is increased for a given void fraction. All characteristic roots from the solution to a three-equation drift-flux model are related to the velocity of the center of mass of the mixture. The pulse propagation speed relative to this velocity is exactly equal to the homogeneous model value, however. Measured pulse propagation speeds in vertically downward slug flow are, as anticipated, much less than those predicted by the simple model of Henry, Grolmes, and Fauske, but slightly greater than the homogeneous model value. Measured pressure surges produced by the rapid closure of a downstream valve in a pipeline are reasonably well predicted by the drift-flux model. For the range of void fractions, pressures, and velocities encountered in this study, it is concluded that pressure pulse speeds and the magnitude of pressure surges in slug flow can be adequately predicted by a homogeneous model.

Numerical Modeling of Aerated Cavitation Using a Penalization Approach for Air Bubble Modeling Coupled to Homogeneous Equilibrium Model

2014 ◽  
Author(s):  
Petar Tomov ◽  
Sofiane Khelladi ◽  
Christophe Sarraf ◽  
Farid Bakir
Keyword(s):  
Fluid Flow ◽  
Mixture Model ◽  
Stokes Equations ◽  
Saturation Pressure ◽  
Homogeneous Mixture ◽  
Navier Stokes ◽  
Strain Rate Tensor ◽  
Computational Domain ◽  
Time Step ◽  
Homogeneous Mixture Model

Cavitation is a well-known physical phenomena occurring in various technical applications. It appears when the pressure of the liquid drops below the saturation pressure. Coupling aeration in a cavitating flow is a recent technique to control the overall effect of the cavitation. It is achieved by introducing air bubbles into the flow. In order to reveal and explore the behaviour of air gas in the vicinity of the cavitation region, the paper is oriented towards the physics of the colliding vapor phase bubbles and cavitating regions. The re-entrant jet may influence the dynamics of the bubbles as well as the frequency of cavitation separation. Therefore, a two-way coupling between the fluid flow and the introduced vapor is of capital importance. By penalizing the strain rate tensor in the Homogeneous Mixture Model, the two-way coupling has been achieved. The contact-handling algorithm is based on the projections of the velocity fields of the injected particles over the velocity field of the fluid flow. At each time step the gradient of the distance between the bubbles, is kept non-negative as a guarantee of the physical non overlapping. The bubbles’ collisions are considered as inelastic. The differential equations system is composed of the Navier-Stokes equations, implemented with the Homogeneous Mixture Model. A high-order Finite Volume (FV) solver based on Moving Least Squares (MLS) approximations is used. The code uses a SLAU-type Riemann solver for the accurate calculation of the low Mach numbers. The computational domain is a symmetrical 2D venturi duct with an 18°–8° convergent/divergent angles respectively.

scholarly journals Comparison of Nannochloropsis sp. cells disruption between hydrodynamic cavitation and conventional extraction

2018 ◽  
Vol 154 ◽  
pp. 01023 ◽  
Author(s):  
Martomo Setyawan ◽  
Panut Mulyono ◽  
Sutijan ◽  
Arief Budiman
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Distribution Coefficient ◽  
Mass Transfer Coefficient ◽  
Lipid Extraction ◽  
Cell Disruption ◽  
Hydrodynamic Cavitation ◽  
Biodiesel Production ◽  
Experimental Result ◽  
Conventional Extraction

Biodiesel production from microalgae is one of the solution of the future energy problem, but its production cost is still high. One of the costly stages of this process is the lipid extraction process. It can be reduced by microalgae cell disruption. One of the mechanical method to cell disruption with the lowest energy requirement is hydrodynamic cavitation. This aim of this study is to evaluate the distribution coefficient and the mass transfer coefficient value of lipid extraction of Nannochloropsis sp. assisted by hydrodynamic cavitation and compare with conventional extraction. The hydrodynamic cavitation extraction was done at 34 °C, 1 atm. The conventional extraction was done at 34 °C, 1 atm with stirring speed 260 and 1000 rpm. The experimental result shows that the distribution coefficient dependent on the temperature with the values for 50, 44, 38 and 34 °C were 0.502, 0.394, 0.349, and 0.314 respectively. And it was according to Van’ Hoff equation with the values of ΔH° was 20.718 kJ/mol and ΔS° was 58.05 J/mol/K. The hydrodynamic cavitation extraction was faster than conventional. The mass transfer coefficient values for hydrodynamic cavitation, conventional 260 rpm and 1000 rpm were 7.373, 0.534 and 0.121 1/s respectively.

Advanced Capillary Structures for High Performance Heat Pipes

2003 ◽  
Author(s):  
P. Stephan ◽  
C. Brandt
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Performance ◽  
Good Accuracy ◽  
Electronic Devices ◽  
Heat Pipes ◽  
Thermal Control ◽  
Axial Pressure ◽  
The Heat Transfer Coefficient

High performance heat pipes are widely used for thermal control of electronic devices. Concerning heat transport limitations typical wick or capillary structures show advantages in some aspects and disadvantages in others. An advanced capillary structure was developed with high thermal effectiveness, low axial pressure drop, high capillary pressure, and a high boiling limit. It combines open minichannels with open microchannels that are manufactured perpendicular on top of the minichannels. The heat transfer coefficient in the evaporator zone which is a characteristic value for the thermal effectiveness was up to 3.3 times higher compared to a similar structure without microchannels. A model that combines micro- and macroscopic phenomena was developed. It predicts the heat transfer coefficient with quite good accuracy as long as the microchannels are not smaller than about 300μm.

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