New Simulator for Gas–Hydrate Slurry Stratified Flow Based on the Hydrate Kinetic Growth Model

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Bohui Shi ◽  
Yang Liu ◽  
Lin Ding ◽  
Xiaofang Lv ◽  
Jing Gong
Keyword(s):  
Heat Transfer ◽  
Shell Model ◽  
Gas Hydrate ◽  
Hydrodynamic Model ◽  
Formation Rate ◽  
Hydrate Formation ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Two Phase ◽  
Mass And Heat Transfer

A new simulator for gas–hydrate slurry stratified flow is presented, which can simulate the flow characteristics, including gas/liquid velocity, liquid holdup, and pressure drop. The simulator includes an inward and outward hydrate growth shell model and two-phase flow hydrodynamic model. The hydrate growth model systematically considers the kinetics and limitations of hydrate formation, namely, the mass– and heat–transfer. The two-phase flow hydrodynamic model is composed of mass and momentum equations for each phase as well as energy balance equations considering the heat generation related to hydrate formation. Thereafter, an inclined pipeline case is simulated using the simulator. The results demonstrate that, once the kinetic requirements for hydrate crystallization are satisfied, hydrates form rapidly during the initial stage and the hydrate formation rate then decreases owing to the limitation of the mass– and heat–transfer. Meanwhile, the hydrate states (formation onset time, formation rate, and volume fraction) as well as flow characteristics of a multiphase system are obtained, providing acceptable results for engineers in the field. Sensitivity analyses of the key hydrate growth shell model parameters are implemented, and the results indicate that the influences of diffusivity and initial water droplet size on the hydrate formation rate are greater than the of the porous parameter.

Simulation of Gas-Hydrate Slurry Stratified Flow With Inward and Outward Hydrate Growth Model

2016 ◽  
Author(s):  
Bohui Shi ◽  
Yang Liu ◽  
Lin Ding ◽  
Xiaofang Lv ◽  
Jing Gong
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Shell Model ◽  
Gas Hydrate ◽  
Hydrodynamic Model ◽  
Formation Rate ◽  
Hydrate Formation ◽  
Phase Flow ◽  
Two Phase

The topic of hydrate formation and blocking in offshore petroleum industry has attracted more and more attentions, which is known as one of the flow assurance issues. A new technology has been proposed to avoid the occurrence of hydrate blockage in multiphase transportation system, which is hydrate slurry flow technology, also named as cold flow technology. The low dosage hydrate inhibitor of anti-agglomerate was added into the flow systems to allow hydrate formation in the liquid phase while it prevented the aggregation of hydrate particles. Thus these particles were evacuated with the liquid phase as pseudo-fluid like slurry. In this work, an inward and outward hydrate growth shell model coupled with two phase flow hydrodynamic model was applied to investigate the characteristics of gas-hydrate slurry stratified flow. The inward and outward hydrate growth shell model considered the kinetics, mass transfer and heat transfer process of hydrate formation, which could predict the hydrate formation rate and the released heat. The two phase flow hydrodynamic model included mass, momentum and energy equations. A case for an inclined pipeline was simulated using the combined models. The results showed that once the kinetic requirements for hydrate crystallization was satisfied, hydrates would form quickly at the initial stage and then hydrate formation rate would decrease obviously due to the limitation of mass transfer and heat transfer. Meanwhile, the flow characteristics, such as the liquid holdup and pressure drop, were predicted by the model, which also provided an acceptable results about the state of hydrates (onset time of formation, formation rate, volume fraction, etc.) in multiphase system for the operation engineers in the field. The key parameters of the inward and outward hydrate growth shell model were determined by referring to the literatures. To investigate the reliability and influence of these set values on the results, a sensitivity analysis of the key parameters of the shell model was implemented. Further works should be done, such as the flow mechanism in other flow regimes as well as the influence of particle aggregation.

An Experimental Investigation of Gas-Liquid Heat Transfer in Rectangular Micro-Channels

2013 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises ◽  
Piyawat Kuaseng ◽  
Chompunut Nuibutr ◽  
Wattana Chanphan
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Camera System ◽  
Micro Channels ◽  
Flow Mechanisms

The investigations of heat transfer and fluid flow characteristics of non-boiling air-water flow in micro-channels are experimentally studied. The gas-liquid mixture from y-shape mixer is forced to flow in the 21 parallel rectangular microchannels with 40 mm long in the flow direction. Each channel has a width and a depth of 0.45 and 0.41 mm, respectively. Flow visualization is feasible by incorporating the stereozoom microscope into the camera system and different flow patterns are recorded. The experiments are performed under low superficial velocities. Two-phase heat transfer gives better results when compared with the single-phase flow. It is found from the experiment that heat transfer enhancement up to 53% is obtained over the single-phase flow. Also, the change in the configuration of the inlet plenum can result in the different two-phase flow mechanisms.

Flow and Heat Transfer of Mist/Steam Two-Phase Flow in Two-Pass Rectangular Channels With Paralleled and V-Shaped Rib Turbulators

2018 ◽  
Author(s):  
Guangwen Jiang ◽  
Jianmin Gao ◽  
Xiaojun Shi ◽  
Wang Zhao ◽  
Yunlong Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Internal Cooling ◽  
Phase Flow ◽  
Transfer Performance ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Cooling Passage

The heat and flow characteristics of mist/steam two-phase flow in U-shaped internal cooling passage of gas turbine blade are studid numerically in this paper. The standard k-ε model was used as the turbulence model combined with the DPM model to calculate the influence of mist/steam mass ratio and mist diameter on flow and heat transfer of U-passage with different shaped ribs. The result indicates that under the same working condition, the U-shaped channel with 45 deg. V-shaped ribs has better heat transfer performance than other channels and heat transfer non-uniformity of the U-shaped channel with 75 deg. ribs is the worst among all channels studied in this paper. The heat transfer performance of the U-shaped channel with V-shaped ribs is higher than that of the channel with paralleled ribs. As for the mist/steam cooling in U-shaped passage with same ribs structure, heat transfer non-uniformity increases with the increasing of heat transfer performance. When mists diameter increases from 5μm to 15μm, the heat transfer performance of the Second-Flow-Passage increases obviously and the heat transfer non-uniformity increases at the same time. The heat transfer performance has not been further enhanced when the mists diameter continuously increases after mist diameter are larger than 10μm.

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