How does the flow affect the evolution of solution pipes ?

2020 ◽  
Author(s):  
Silvana Magni ◽  
Max Cooper ◽  
Piotr Szymczak
Keyword(s):  
Flow Rate ◽  
Pore Space ◽  
Petroleum Industry ◽  
High Porosity ◽  
Solubility In Water ◽  
Annual Variations ◽  
Formation And Evolution ◽  
Karst Systems ◽  
Natural Settings ◽  
Large Flow

<p>Dissolution by a reactive flow is a complex phenomenon influenced by a number of different parameters, including flow rate, diffusion rate of the reactant, reaction rate and the pore space characteristics of the host rock. Depending on the values of these parameters, the dissolution patterns will have different morphological features. In particular, there is range of parameters where the dissolution front becomes unstable, which is accompanied by a formation of pronounced dissolution channels, which are called solution pipes in geological literature and wormholes in the petroleum industry, where they are produced to stimulate the flow from oil reservoirs. In the natural settings, these features are formed in rocks with a very high porosity and then with a rather large flow rate. Their shapes are strongly related to their characteristic sizes. At the macroscale (1-10metres) they are usually almost cylindrical with a diameter from a few cm up to a meter, while at microscale they show a highly ramified, fractal-like shape. To investigate this variability and to understand their formation and evolution, we are conducting microfluidic experiments using a self-constructed microfluidic cell. We are using a system consisting of two polycarbonate chips in which it is possible to have a control on flow rate and on the aperture. The lower plate has an indentation that can be filled with gypsum, while on the upper chip there is a reservoir that allows water to be supplied to the system in a controlled way. We are using powder gypsum during these experiments because it has a very simple chemistry, high solubility in water and therefore allows a greater speed of dissolution The two chips are joined together with an ultrathin, double coated tape of variable thickness that allows us to control the aperture of the system, which can thus be regarded as an analog fracture. As the gypsum chip is dissolved, we observe the appearance of fingers of different shapes, depending on the flow rate and the aperture. We report the results of these experiments and relate the observed features with the natural shapes found in the karst systems. We also investigate how the shapes of the pipes change as we vary the flow rate periodically, which reflects annual variations in the flow in the natural karst systems.</p><p><strong>Key words: dissolution, solution pipes, microfluidics</strong></p><p> </p><p> </p>

Permeability-porosity transforms from small sandstone fragments

Geophysics ◽  
2006 ◽  
Vol 71 (1) ◽  
pp. N11-N19 ◽  
Author(s):  
Ayako Kameda ◽  
Jack Dvorkin ◽  
Youngseuk Keehm ◽  
Amos Nur ◽  
William Bosl
Keyword(s):  
Pore Space ◽  
Petroleum Industry ◽  
Rock Physics ◽  
Three Dimensions ◽  
Absolute Permeability ◽  
High Porosity ◽  
Drill Cuttings ◽  
Thin Sections ◽  
Numerical Experimentation ◽  
The Absolute

Numerical simulation of laboratory experiments on rocks, or digital rock physics, is an emerging field that may eventually benefit the petroleum industry. For numerical experimentation to find its way into the mainstream, it must be practical and easily repeatable — i.e., implemented on standard hardware and in real time. This condition reduces the size of a digital sample to just a few grains across. Also, small physical fragments of rock, such as cuttings, may be the only material available to produce digital images. Will the results be meaningful for a larger rock volume? To address this question, we use a number of natural and artificial medium- to high-porosity, well-sorted sandstones. The 3D microtomography volumes are obtained from each physical sample. Then, analogous to making thin sections of drill cuttings, we select a large number of small 2D slices from a 3D scan. As a result, a single physical sample produces hundreds of 2D virtual-drill-cuttings images. Corresponding 3D pore-space realizations are generated statistically from these 2D images; fluid flow is simulated in three dimensions, and the absolute permeability is computed. The results show that small fragments of medium– to high-porosity sandstones that are statistically subrepresentative of a larger sample will not yield the exact porosity and permeability of the sample. However, a significant number of small fragments will yield a site-specific permeability-porosity trend that can then be used to estimate the absolute permeability from independent porosity data obtained in the well or inferred from seismic techniques.

scholarly journals Thermal Efficiency and Economics of a Boil-Off Hydrogen Re-Liquefaction System Considering the Energy Efficiency Design Index for Liquid Hydrogen Carriers

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4566
Author(s):  
Minsoo Choi ◽  
Wongwan Jung ◽  
Sanghyuk Lee ◽  
Taehwan Joung ◽  
Daejun Chang
Keyword(s):  
Flow Rate ◽  
Life Cycle Cost ◽  
Specific Energy Consumption ◽  
Liquid Hydrogen ◽  
Efficient Design ◽  
Fuel Cell Stack ◽  
Energy Efficiency Design Index ◽  
The Cost ◽  
Large Flow

This study analyzes the thermodynamic, economic, and regulatory aspects of boil-off hydrogen (BOH) in liquid hydrogen (LH2) carriers that can be re-liquefied using a proposed re-liquefaction system or used as fuel in a fuel cell stack. Five LH2 carriers sailing between two designated ports are considered in a case study. The specific energy consumption of the proposed re-liquefaction system varies from 8.22 to 10.80 kWh/kg as the re-liquefaction-to-generation fraction (R/G fraction) is varied. The economic evaluation results show that the cost of re-liquefaction decreases as the re-liquefied flow rate increases and converges to 1.5 $/kg at an adequately large flow rate. Three energy efficient design index (EEDI) candidates are proposed to determine feasible R/G fractions: an EEDI equivalent to that of LNG carriers, an EEDI that considers the energy density of LH2, and no EEDI restrictions. The first EEDI candidate is so strict that the majority of the BOH should be used as fuel. In the case of the second EEDI candidate, the permittable R/G fraction is between 25% and 33%. If the EEDI is not applied for LH2 carriers, as in the third candidate, the specific life-cycle cost decreases to 67% compared with the first EEDI regulation.

Optimization of Inlet Ring Groove Arrangement for Suppression of Unstable Flow in a Centrifugal Impeller

2005 ◽  
Author(s):  
Masahiro Ishida ◽  
Daisaku Sakaguchi ◽  
Hironobu Ueki
Keyword(s):  
Flow Rate ◽  
The Other ◽  
Centrifugal Impeller ◽  
Shape Parameters ◽  
Unstable Flow ◽  
Ring Groove ◽  
Flow Rates ◽  
Small Flow ◽  
Specific Speed ◽  
Large Flow

An optimization of the inlet ring groove arrangement has been pursued in the present study for obtaining better impeller characteristics and a wider operation range at both small and large flow rates in a high specific speed type centrifugal impeller with inducer. The effects of the shape parameters with respect to the inlet ring groove on the impeller characteristic and the flow incidence were analyzed mainly based on numerical simulations, but also compared to the experimental results. At small flow rates, a significant improvement in the impeller characteristic is achieved due to reduction in the excessive-positive flow incidence by optimizing both location and width of the rear groove near the inducer tip throat. On the other hand, the impeller characteristic is improved at large flow rates by implementing the corner radius at the rear groove edge and by placing another front ring groove in the suction pipe. As a result, by the optimized configuration of the front and rear ring grooves, the unstable flow range of the test impeller can be reduced by about 50% without deterioration of the impeller characteristic even at the 125% flow rate.

Principle and structure of a multi-chamber piezoelectric pump with large flow rate integrated into printed circuit board

2022 ◽  
pp. 1045389X2110721
Author(s):  
Yun-Hao Peng ◽  
Dai-Hua Wang ◽  
Lian-Kai Tang
Keyword(s):  
Flow Rate ◽  
Compression Ratio ◽  
Layer Structure ◽  
Experimental Results ◽  
Processing Technology ◽  
Rate Model ◽  
Piezoelectric Pump ◽  
Central Deflection ◽  
Maximum Value ◽  
Large Flow

Parametric simulation of multi-chamber piezoelectric pump proposed by authors shows that its flow rate is positively correlated with chamber compression ratio when height of chamber wall is not less than central deflection of circular piezoelectric unimorph actuator (CPUA). Therefore, in this paper, principle and structure of multi-chamber piezoelectric pump with novel CPUAs with three-layer structure are proposed and realized, so as to improve its chamber compression ratio, and then improve its flow rate. Its processing technology compatible with PCB processing technology is studied and its flow rate model is established. Central deflection of CPUA with three-layer structure and the flow rate characteristics are tested. Experimental results show that when the central deflection of CPUA with three-layer structure reaches the maximum value of 106.8 μm, the chamber compression ratio and flow rate of multi-chamber piezoelectric pump reach the maximum value of 50% and 3.11 mL/min, respectively. The maximum flow rate is increased by 622% compared to unimproved pump. By comparing experimental results with numerical and finite element simulation results, the realized multi-chamber piezoelectric pump has large flow rate and the established flow rate model can predict its flow rate.

scholarly journals Investigation of Speed Matching Affecting Contrarotating Fan’s Performance Using Wireless Sensor Network including Big Data and Numerical Simulation

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Hengxuan Luan ◽  
Liyuan Weng ◽  
Ranhui Liu ◽  
Yuanzhong Luan ◽  
Dongmin Li
Keyword(s):  
Big Data ◽  
Numerical Method ◽  
Flow Rate ◽  
Rate Condition ◽  
Small Flow Rate ◽  
Large Flow Rate ◽  
Small Flow ◽  
Power Capability ◽  
Two Stages ◽  
Large Flow

This paper describes the investigations performed to better understand two-stage rotor speed matching in a contrarotating fan. In addition, this study develops a comprehensive measuring and communication system for a contrarotating fan using ZigBee network. The investigation method is based on three-dimensional RANS simulations; the RANS equations are solved by the numerical method in conjunction with a SST turbulence model. A wireless measurement system using big data method is first designed, and then a comparison is done with experimental measurements to outline the capacity of the numerical method. The results show that when contrarotating fan worked under designed speed, performance of two-stages rotors could not be matched as the designed working condition was deviated. Rotor 1 had huge influences on flow rate characteristics of a contrarotating fan. Rotor 2 was influenced by flow rates significantly. Under large flow rate condition, the power capability of rotor 2 became very weak; under working small flow rate condition, overloading would take place to class II motor. In order to solve the performance mismatch between two stages of CRF under nondesigned working conditions, under small flow rate condition, the priority shall be given to increase of the speed of rotor 1, while the speed of rotor 2 shall be reduced appropriately; under large flow rate condition, the speed of rotor 1 shall be reduced and the speed of rotor 2 shall be increased at the same time.

Predicted Liquid Water Saturation in Unstructured Pore Networks Based on PEMFC GDL Porosity Profiles

2010 ◽  
Author(s):  
J. Hinebaugh ◽  
Z. Fishman ◽  
A. Bazylak
Keyword(s):  
Liquid Water ◽  
Water Saturation ◽  
Pore Space ◽  
Polymer Electrolyte Membrane ◽  
Gas Diffusion ◽  
Pore Network Model ◽  
High Porosity ◽  
Pore Networks ◽  
Electrolyte Membrane ◽  
Capillary Pressures

An unstructured, two-dimensional pore network model is employed to describe the effect of through-plane porosity profiles on liquid water saturation within the gas diffusion layer (GDL) of the polymer electrolyte membrane fuel cell. Random fibre placements are based on the porosity profiles of six commercially available GDL materials recently obtained through x-ray computed tomography experiments. The pore space is characterized with a Voronoi diagram, and invasion percolation-based simulations are performed. It is shown that water tends to accumulate in regions of relatively high porosity due to the lower associated capillary pressures. It is predicted that GDLs tailored to have smooth porosity profiles will have fewer pockets of high saturation levels within the bulk of the material.

scholarly journals The surface CO2 gradient and pore-space storage flux in a high-porosity litter layer

Tellus B ◽  
2004 ◽  
Vol 56 (4) ◽  
pp. 312-321 ◽  
Author(s):  
Adam I. Hirsch ◽  
Susan E.: Trumbore ◽  
Michael L. Goulden
Keyword(s):  
Pore Space ◽  
High Porosity ◽  
Litter Layer ◽  
Storage Flux

scholarly journals Study on the Formation Law of the Freezing Temperature Field of Freezing Shaft Sinking under the Action of Large-Flow-Rate Groundwater

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Bin Wang ◽  
Chuan-xin Rong ◽  
Jian Lin ◽  
Hua Cheng ◽  
Hai-bing Cai
Keyword(s):  
Temperature Field ◽  
Groundwater Flow ◽  
Flow Velocity ◽  
Flow Rate ◽  
Freezing Temperature ◽  
Freezing Process ◽  
Flow Rates ◽  
Porosity Reduction ◽  
Shaft Sinking ◽  
Large Flow

Taking into account moisture migration and heat change during the soil freezing process, as well as the influence of absolute porosity reduction on seepage during the freezing process, we construct a numerical model of hydrothermal coupling using laws of conservation of energy and mass. The model is verified by the results of large-scale laboratory tests. By applying the numerical calculation model to the formation of artificial shaft freezing temperature fields under the action of large-flow groundwater, we conclude that groundwater with flow rates of less than 5 m/d will not have a significant impact on the artificial freezing temperature field. The maximum flow rates that can be handled by single-row freezing pipes and double-row freezing pipes are 10 m/d and 20 m/d, respectively, during the process of freezing shaft sinking. By analyzing the variation of groundwater flow rate during freezing process, we find that the groundwater flow velocity can reach 5–7 times the initial flow velocity near the closure moment of the frozen wall. Finally, in light of the action characteristics of groundwater on the freezing temperature field, we make suggestions for optimal pipe and row spacing in freezing pipe arrangement.

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