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.

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.

scholarly journals MODEL OF HEAT SIMULATOR FOR DATA CENTERS

2016 ◽  
Vol 56 (4) ◽  
pp. 301-305
Author(s):  
Jan Novotný ◽  
Jiří Nožička
Keyword(s):  
Temperature Field ◽  
Heat Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Data Centers ◽  
Heat Output ◽  
Heat Flow Rate ◽  
Flow Rates ◽  
Piv Method ◽  
Mass Flow Rates

The aim of this paper is to present a design and a development of a heat simulator, which will be used for a flow research in data centers. The designed heat simulator is based on an ideological basis of four-processor 1U Supermicro server. The designed heat simulator enables to control the flow and heat output within the range of 10–100 %. The paper covers also the results of testing measurements of mass flow rates and heat flow rates in the simulator. The flow field at the outlet of the server was measured by the stereo PIV method. The heat flow rate was determined, based on measuring the temperature field at the inlet and outlet of the simulator and known mass flow rate.

Development of Robust Microvavles for Compact Robust Pumps/Hydraulic Actuators

2007 ◽  
Vol 121-123 ◽  
pp. 1207-1210
Author(s):  
B. Li ◽  
Q. Chen
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Pressure Support ◽  
Test Results ◽  
Valve Design ◽  
Standard Process ◽  
Flow Rates ◽  
Forward Flow ◽  
Large Flow

In situ UV-LIGA assembled robust micro check valves with large flow rates (>10 ml/s, displacement related), high-pressure support ability (>10 MPa) and high operational frequencies (>10 kHz) made of nano-structured nickel were presented in this paper. The microvalve consists of an array of 80 single micro valves to achieve the required flow rates. Test results show that the forward flow rate is about 19 ml/s under pressure of 90Psi. The backward flow rate is negligible. The reliability of the valve is ensured by the valve design and nanostructured nickel realized. The tested tensile strength of a nano structured nickel is about 1GPa. The strength of SU-8 is 50MPa, which is more than 50% higher that fabricated with a standard process.

Numerical Simulations of Three Dimensional Turbulent Flows in a Shrouded Backswept Impeller at Design and Off-Design Flow Rates Using Unstructured Grid Method

2000 ◽  
Author(s):  
Chuhua Zhang ◽  
Yongmiao Miao ◽  
Chuangang Gu
Keyword(s):  
Flow Velocity ◽  
Flow Rate ◽  
Unstructured Grid ◽  
Three Dimensional ◽  
Grid Method ◽  
Main Flow ◽  
Design Flow ◽  
Radial Velocity Component ◽  
Flow Rates ◽  
Design Flow Rate

The three-dimensional turbulent flow fields in a shrouded fan impeller with backswept discharge at three operating flow rates are numerically calculated with an unstructured grid method recently developed by the authors. Reynolds-averaged Navier-Stokes (N-S) equations and k-ε equations are solved through finite volume method with pressure correction algorithm. Numerical results are presented for detailed main and secondary flow velocity. The agreements of radial velocity component at different sections at design flow rate between computations and measurements are generally good. It can be observed that different flow rates have distinctive effects on flow patterns. At design flow rate, the flow is behaved as attached flow pattern and has a relatively smooth distribution for the main flow velocity. Above the design flow rate, a sudden drop and non-smooth distribution for the main flow velocity appear at the pressure-hub corner near the impeller inlet, however, the distribution of main flow velocity becomes smooth gradually downstream. Under the design flow rate, the jet-wake structure appears obviously within the impeller passage.

Electroosmotic Pumps Fabricated From Porous Silicon Membranes

2004 ◽  
Author(s):  
Shuhuai Yao ◽  
Alan M. Myers ◽  
Jonathan D. Posner ◽  
Juan G. Santiago
Keyword(s):  
Porous Silicon ◽  
Flow Rate ◽  
Maximum Flow ◽  
Applied Potential ◽  
Flow Rates ◽  
Pump Performance ◽  
Silicon Membranes ◽  
Electroosmotic Pumps ◽  
The Impact ◽  
Large Flow

Large flow rates per applied potential are obtained from electroosmotic (EO) pumps fabricated from n-type porous silicon. Porous silicon membranes have ideal geometries for EO pumping. These membranes have hexagonally packed, uniform pores with near-unity tortuosity and are well suited to maximize flow rate for a given applied voltage. The 350 μm thick membranes were passivated with a SiO2 layer and exhibit a maximum flow rate of 1.2 ml/min/cm2/V. This is 4.4 times higher than previously demonstrated silica-based frit EO pumps. LPCVD polysilicon deposition followed by wet oxidation was used to control the pore size. The impact of these coatings on the pump performance has also been characterized.

scholarly journals Evolution Laws for Frozen Wall Formation under Conditions of Sudden Seepage

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Song Zhang ◽  
Zurun Yue ◽  
Tiecheng Sun ◽  
Yufu Han ◽  
Wei Gao ◽  
...  
Keyword(s):  
Temperature Field ◽  
Flow Velocity ◽  
Freezing Temperature ◽  
Model Tests ◽  
Seepage Velocity ◽  
Distribution Law ◽  
Average Temperature ◽  
Ground Freezing ◽  
Artificial Ground Freezing ◽  
Frozen Wall

Sudden seepage is a special working condition affecting artificial ground freezing (AGF) in many projects which results in significant differences within the temperature field. In order to study the characteristics of frozen walls influenced by water flow, a series of model tests were carried out at different seepage velocities. The model test results show that a frozen wall will change from symmetrical to eccentric as the cooling energy absorption of the soil and the brine return temperature increase. In model tests, when the seepage velocity was 0∼30 m/d, the frozen wall was partially destroyed. When the seepage velocity exceeded 30 m/d, the frozen wall was completely destroyed. This study examines the expansion rate of the upstream and downstream freezing fronts, and the distribution law of the freezing temperature field, the average temperature change under different seepage speeds, and the bearing capacity of the freezing wall are analyzed. Research on these factors suggests that a frozen wall has a certain level of resistance to sudden seepage. When the flow velocity is small, the freezing effect will be strengthened. With an increase in the flow velocity, the freezing effect will gradually weaken. Based on these conclusions, the current study points out targeted solutions that should be adopted in cases of sudden seepage in a project.

Hydraulic model of a water cooling system in a chemical plant

1988 ◽  
Vol 53 (4) ◽  
pp. 788-806
Author(s):  
Miloslav Hošťálek ◽  
Jiří Výborný ◽  
František Madron
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Cooling Water ◽  
Graph Algorithm ◽  
Automatic Generation ◽  
Hydraulic Calculation ◽  
Return Flow ◽  
Flow Rates ◽  
Pressure Losses ◽  
Controlled Flow

Steady state hydraulic calculation has been described of an extensive pipeline network based on a new graph algorithm for setting up and decomposition of balance equations of the model. The parameters of the model are characteristics of individual sections of the network (pumps, pipes, and heat exchangers with armatures). In case of sections with controlled flow rate (variable characteristic), or sections with measured flow rate, the flow rates are direct inputs. The interactions of the network with the surroundings are accounted for by appropriate sources and sinks of individual nodes. The result of the calculation is the knowledge of all flow rates and pressure losses in the network. Automatic generation of the model equations utilizes an efficient (vector) fixing of the network topology and predominantly logical, not numerical operations based on the graph theory. The calculation proper utilizes a modification of the model by the method of linearization of characteristics, while the properties of the modified set of equations permit further decrease of the requirements on the computer. The described approach is suitable for the solution of practical problems even on lower category personal computers. The calculations are illustrated on an example of a simple network with uncontrolled and controlled flow rates of cooling water while one of the sections of the network is also a gravitational return flow of the cooling water.

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.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

On-Line Monitoring System for Monitoring SO2 in Fumes (1) — Monitoring Subsystem for SO2 Mass Concentration

2011 ◽  
Vol 422 ◽  
pp. 296-299
Author(s):  
Shi Long Wang ◽  
Li Na Wang ◽  
Hong Bo Wang ◽  
Yong Hui Cai
Keyword(s):  
Flow Velocity ◽  
Monitoring System ◽  
Flow Rate ◽  
Mass Concentration ◽  
National Monitoring ◽  
Monitoring Result ◽  
Short Period ◽  
On Line ◽  
Working Principle

In order to achieve the target of controlling SO2 emissions in fumes in a short period of time in China, a SO2 on-line monitoring system (CEMS) has been developed by the authorased on the principle of electrochemistry. This system consists of two subsystems: (1) SO2 mass concentration monitoring and (2) SO2 flow velocity and flow rate monitoring. In the paper, the procedure of system and working principle and method of SO2 mass concentration monitoring subsystem are described in detail (SO2 flow velocity and flow rate monitoring subsystem is described by another paper).Two subsystems work synchronously to monitor and calculate the SO2 emissions, then the on-line monitoring of SO2 emissions is achieved. Through experiment and testing, monitoring result of the system is stable and reliable, which has reached the national monitoring standards and passed the appraisal.

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