Study Advancement for Multiphase Flow and Heat and Mass Transfer Characteristics for Gas Hydrate Decomposition in South China Sea Offshore Sediment

2013 ◽  
Author(s):  
Xichong Yu ◽  
Jiafei Zhao ◽  
Weixin Pang ◽  
Gang Li ◽  
Yu Liu
Keyword(s):  
Mass Transfer ◽  
Multiphase Flow ◽  
Heat And Mass Transfer ◽  
Gas Hydrate ◽  
Flow Characteristics ◽  
Decomposition Process ◽  
Lattice Boltzmann Model ◽  
Experimental Simulation ◽  
Hydrate Decomposition ◽  
Multi Phase Flow

Gas hydrates are crystalline solids that consist of gas molecules, usually methane, surrounded by water molecules. According to the phase equilibrium characteristics of gas hydrate, there are three basic development methods, including heating, pressure decreasing and chemical injecting. The development process is actually the multi-phase flow process. Currently, there is no good commercial software used to simulate the multiphase flow, heat transmission and mass transfer in the gas hydrate decomposition process. The study is not mature, still in the development and trial stage. So in this paper, we will make a deeply study on the multi-phase flow simulation method of gas hydrate decomposition in the sediment. We try to make breakthrough in the theory and simulate method. According to the different scales, the simulation computation study of flow characteristics model has microcosmic, mesocosmic and macrocosmic scales. In this paper, mesocosmic scales is used to study for the multiphase flow, heat and mass transfer in the offshore gas hydrate decomposition process, and numerical simulation and experimental simulation are together used to study. Study advancements are shown as follows: firstly, conventional Lattice Boltzmann model is modified to new Lattice Boltzmann Model (LBM) based on sediment with gas hydrate and flow characteristics for gas hydrate decomposition, the interaction and density difference between the phases are considered, and Magnetic Resonance Imaging (MRI) visual technology is used to successfully verified to LBM methods. Secondly, contraction core reaction methods based on fractal theory is used to simulate heat and mass transfer in the offshore gas hydrate decomposition process and is successfully verified by experimental simulation for South China Sea offshore gas hydrate sediment.

Heat and Mass Transfer Mechanism of Gas Hydrate Development for South China Sea

2014 ◽  
Author(s):  
Xichong Yu ◽  
Li Gang ◽  
Weixin Pang ◽  
Wu Yaling
Keyword(s):  
Mass Transfer ◽  
South China Sea ◽  
Heat And Mass Transfer ◽  
South China ◽  
Gas Hydrate ◽  
Fractal Theory ◽  
China Sea ◽  
Hydrate Decomposition ◽  
Mass Transfer Mechanism ◽  
Development Methods

The decomposition process of gas hydrate in sediments is actually the dynamic phase transition process of solid hydrate in sediments after absorbing heat decomposition. According to the phase equilibrium characteristics of gas hydrate, there are three basic development methods, including heating, chemical injecting and depressurization. Currently, there is no good commercial software used to simulate heat transmission and mass transfer in the gas hydrate decomposition process. So in this paper, based on typical gas hydrate sediment in South China Sea, microcosmic, mesocosmic (fractal theory) and macrocosmic scales are respectively used to successfully reveal the heat and mass transfer mechanism of three basis development methods. Molecular dynamics simulation shows heat injection is the best method for heat and mass transferring, and chemical injecting is better than depressurization. Fractal theory is successfully used to describe the complex structure of the porous sediments with gas hydrate occurrence, and can realize the prediction of heat and mass transfer law of hydrate dissociation in porous media. Macrocosmic numerical simulation of depressurization for gas hydrate sediment in South China Sea shows gas hydrate reservoir geological model has a large influence on the gas hydrate decomposition, and permeability and hydrate saturation of the upper cover layer have great effect on gas hydrate decomposition. It is poor development efficiency for only depressurization development and the problem of water drainage should be paid attention during development process.

Study for Modification Lattice Boltzmann Model Application to Flow Characteristics for Gas Hydrate Decomposition in Sediment

2012 ◽  
Author(s):  
Xichong Yu ◽  
Yu Liu ◽  
Weixin Pang ◽  
Yuhu Bai ◽  
Jiafei Zhao
Keyword(s):  
Porous Media ◽  
Gas Hydrate ◽  
Lattice Boltzmann ◽  
Single Phase ◽  
Flow Characteristics ◽  
Lattice Boltzmann Model ◽  
Flow In Porous Media ◽  
Micro Channel ◽  
Hydrate Decomposition ◽  
Boltzmann Model

In this paper, based on sediment with gas hydrate and flow characteristics for gas hydrate decomposition, the interaction and density difference between the phases are considered, conventional lattice Boltzmann model is modified to new lattice Boltzmann model then is applied to study flow characteristics for gas hydrate decomposition in sediment. The method is the mesoscopic model between macro and micro methods between. Modification lattice Boltzmann model is applied to carry out a complex micro-channel single-phase, multiphase flow simulation analysis, single-phase flow in porous media for gas hydrate decomposition. The results show that complex micro-channel flow field depends on the micro-channel roughness, bending degree, surface wet ability, fluid properties and other media. Single-phase flow in porous media depends on the pore diameter (saturation) and permeability of the sediment and the hydrate formation in the sediment so greatly reduces the permeability of porous media.

scholarly journals Effect of Radiation and Hall Current on an MHD Transient Heat and Mass Transfer Flow in Presence of Rotation

2019 ◽  
Vol 9 (1) ◽  
pp. 2501-2504
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Laplace Transformation ◽  
Hall Current ◽  
Equations Of Motion ◽  
Porous Plate ◽  
Flow Characteristics ◽  
Heat Radiation ◽  
Viscous Drag ◽  
Transfer Flow

A parametric study to inspect the effect of heat and mass transfer characteristics with Hall current and radiation past a uniformly accelerated porous plate is prepared. The equations of motion are simplified by using the technique of Laplace transformation. The flow characteristics with viscous drag, Nusselt number and Sherwood number are conferred through different graphs by taking some subjective conditions given in the present paper and physical interpretations are described. It is highlited from graphical section that the rising of Prandtl number and heat radiation trim down the temperature profile gradually

Modeling Liquid Film Evaporation in a Wetted Wall Bioaerosol Sampling Cyclone

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
J. A. Hubbard ◽  
O. A. Ezekoye ◽  
J. S. Haglund
Keyword(s):  
Mass Transfer ◽  
Relative Humidity ◽  
Multiphase Flow ◽  
Heat And Mass Transfer ◽  
Nonlinear Dependence ◽  
Model Parameters ◽  
Empirical Correlations ◽  
Lab On Chip ◽  
Film Evaporation ◽  
Semi Empirical

The wetted wall bioaerosol sampling cyclone (WWC) is a complex multiphase flow device which collects and concentrates dilute bioaerosols into liquid samples for biological analysis (McFarland et al., 2009, “Wetted Wall Cyclones for Bioaerosol Sampling,” Aerosol Sci. Technol., 44(4), pp. 241–252). Understanding heat and mass transfer processes occurring inside the WWC is the key to enhancing its performance through an effective coupling to lab-on-chip analysis platforms which require small volumes of liquid output. There exists a critical liquid input rate below which there is no sample collection since all liquid is lost to evaporative effects. The purpose of this study was to model critical film evaporation based on first principles and develop semi-empirical WWC performance correlations as an improvement to existing empirical correlations. A one-dimensional, coupled heat and mass transfer model was developed approximating WWC multiphase flow as cocurrent air-film flow. Governing equations were simplified and approximate solutions were used to optimize model parameters like the heat transfer coefficient based on empirical data from previous works. Optimized model parameters were then used in the full numerical solution to calculate liquid evaporation rates within the WWC over the full range of relative humidity and air temperature. Semi-empirical correlations developed in this study were compared to existing empirical models and showed much improvement: proper physical behavior at the extreme limits of temperature and relative humidity was observed, and the nonlinear dependence of evaporative effects on environmental conditions was also captured.

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