scholarly journals Laboratory experimental investigation of heat transport in fractured media

2016 ◽  
Author(s):  
Claudia Cherubini ◽  
Nicola Pastore ◽  
Concetta I. Giasi ◽  
Nicoletta Maria Allegretti
Keyword(s):  
Heat Transport ◽  
Power Plants ◽  
Time Moment ◽  
Experimental Studies ◽  
Renewable Resource ◽  
Fractured Media ◽  
Single Fracture ◽  
Tracer Transport ◽  
Transport Dynamics ◽  
Experimental Apparatus

Abstract. Low enthalpy geothermal energy is a renewable resource that is still underexploited nowadays, in relation to its potential for development in the society worldwide. Most of its applicabilities have already been investigated, such as: heating and cooling of private and public buildings, roads defrost, cooling of industrial processes, food drying systems, desalination. One of the major limitations related to the choice of installing low enthalpy geothermal power plants regards the initial investment costs. In order to increase the optimal efficiency of installations which use groundwater as geothermal resource, flow and heat transport dynamics in aquifers need to be well characterized. Especially in fractured rock aquifers these processes represent critical elements that are not well known. Therefore there is a tendency to oversize geothermal plants. In literature there are very few studies on heat transport especially in fractured media. This study is aimed to deepen the understanding of this topic through heat transport experiments in fractured network and their interpretation. The heat transfer tests have been carried out on the experimental apparatus previously employed to perform flow and tracer transport experiments, which has been modified in order to analyze heat transport dynamics in a network of fractures. In order to model the obtained thermal breakthrough curves, the Explicit Network Model (ENM) has been used, which is based on an adaptation of a Tang's solution for the transport of the solutes in a semi-infinite single fracture embedded in a porous matrix. Parameter estimation, time moment analysis, tailing character and other dimensionless parameters have permitted to better understand the dynamics of heat transport and the efficiency of heat exchange between the fractures and matrix. The results have been compared with the previous experimental studies on solute transport.

scholarly journals Laboratory experimental investigation of heat transport in fractured media

2017 ◽  
Vol 24 (1) ◽  
pp. 23-42 ◽  
Author(s):  
Claudia Cherubini ◽  
Nicola Pastore ◽  
Concetta I. Giasi ◽  
Nicoletta Maria Allegretti
Keyword(s):  
Heat Transport ◽  
Time Moment ◽  
Fractured Media ◽  
Single Fracture ◽  
Tracer Transport ◽  
Initial Development ◽  
Capital Costs ◽  
Transport Dynamics ◽  
Experimental Apparatus ◽  
Geothermal Power

Abstract. Low enthalpy geothermal energy is a renewable resource that is still underexploited nowadays in relation to its potential for development in society worldwide. Most of its applications have already been investigated, such as heating and cooling of private and public buildings, road defrosting, cooling of industrial processes, food drying systems or desalination. Geothermal power development is a long, risky and expensive process. It basically consists of successive development stages aimed at locating the resources (exploration), confirming the power generating capacity of the reservoir (confirmation) and building the power plant and associated structures (site development). Different factors intervene in influencing the length, difficulty and materials required for these phases, thereby affecting their cost. One of the major limitations related to the installation of low enthalpy geothermal power plants regards the initial development steps that are risky and the upfront capital costs that are huge. Most of the total cost of geothermal power is related to the reimbursement of invested capital and associated returns. In order to increase the optimal efficiency of installations which use groundwater as a geothermal resource, flow and heat transport dynamics in aquifers need to be well characterized. Especially in fractured rock aquifers these processes represent critical elements that are not well known. Therefore there is a tendency to oversize geothermal plants. In the literature there are very few studies on heat transport, especially on fractured media. This study is aimed at deepening the understanding of this topic through heat transport experiments in fractured networks and their interpretation. Heat transfer tests have been carried out on the experimental apparatus previously employed to perform flow and tracer transport experiments, which has been modified in order to analyze heat transport dynamics in a network of fractures. In order to model the obtained thermal breakthrough curves, the Explicit Network Model (ENM) has been used, which is based on an adaptation of Tang's solution for the transport of the solutes in a semi-infinite single fracture embedded in a porous matrix. Parameter estimation, time moment analysis, tailing character and other dimensionless parameters have permitted a better understanding of the dynamics of heat transport and the efficiency of heat exchange between the fractures and the matrix. The results have been compared with the previous experimental studies on solute transport.

scholarly journals Evidence of non-Darcy flow and non-Fickian transport in fractured media at laboratory scale

2013 ◽  
Vol 10 (1) ◽  
pp. 221-254 ◽  
Author(s):  
C. Cherubini ◽  
C. I. Giasi ◽  
N. Pastore
Keyword(s):  
Solute Transport ◽  
Rock Sample ◽  
Breakthrough Curves ◽  
Fractured Media ◽  
Hydraulic Loss ◽  
Assessment Procedure ◽  
Tracer Transport ◽  
Flow And Transport ◽  
Experimental Apparatus ◽  
Study Laboratory

Abstract. Accurate predictions of solute propagation in fractured rocks are of particular importance when assessing exposure pathways through which contaminants reach receptors during a risk assessment procedure, as well as when dealing with cleanup and monitoring strategies. The difficulty in modeling fractured media leads to the application of simplified analytical solutions that fail to reproduce flow and transport patterns in such complex geological formations. A way for understanding and quantifying the migration of contaminants in groundwater systems is that of analyzing tracer transport. Experimental data obtained under controlled conditions such as in a laboratory allow to increase the understanding of the fundamental physics of fluid flow and solute transport in fractures. In this study laboratory hydraulic and tracer tests have been carried out on an artificially created fractured rock sample. The tests regard the analysis of the hydraulic loss and the measurement of breakthrough curves for saline tracer pulse inside a rock sample of parallelepiped (0.60 × 0.40 × 0.8 m) shape. The effect of the experimental apparatus on flow and transport tests has been estimated. In particular the convolution theory has been applied in order to remove the effect of acquisition apparatus on tracer experiment. The experimental results have shown evidence of a non-Darcy relationship between flow rate and hydraulic loss that is best described by Forchheimer's law. The observed experimental breakthrough curves of solute transport have been modeled by the classical one-dimensional analytical solution for advection–dispersion equation (ADE) and the single rate mobile–immobile model (MIM). The former model does not fit properly the first arrival and the tail while the latter provides a very decent fit.

АКУСТИЧНА ПОМІТНІСТЬ БЕЗПІЛОТНИХ ЛІТАЛЬНИХ АПАРАТІВ З СИЛОВИМИ УСТАНОВКАМИ НА БАЗІ ПОРШНЕВИХ ДВИГУНІВ

2020 ◽  
pp. 62-80
Author(s):  
В. В. Руденко ◽  
И. В. Калужинов ◽  
Н. А. Андрущенко
Keyword(s):  
Control System ◽  
Internal Combustion Engine ◽  
Power Plants ◽  
Combustion Engine ◽  
Spectral Characteristics ◽  
Experimental Studies ◽  
Internal Combustion ◽  
Detection Range ◽  
Acoustic Signature ◽  
Static Conditions

The presence in operation of many prototypes of UAVs with propeller propellers, the use of such devices at relatively low altitudes and flight speeds makes the problem of noise reduction from UAVs urgent both from the point of view of acoustic imperceptibility and ecology.The aim of the work is to determine a set of methods that help to reduce the visibility of UAVs in the acoustic range. It is shown that the main source of noise from the UAV on the ground is the power plant, which includes the engine and the propeller. The parameters of the power plants influencing the processes that determine the acoustic signature of the UAV were investigated. A comprehensive analysis of the factors affecting visibility was carried out. The power plants include two-stroke and four-stroke engines, internal combustion and two-blade propellers. The use of silencers on the exhaust of the internal combustion engine was considered. The spectral characteristics of the acoustic fields of the propeller-driven power plants for the operating sample of the UAV "Eco" were obtained. The measurements were carried out in one-third octave and 1/48 octave frequency bands under static conditions. The venue is the KhAI airfield. Note that the propellers that were part of the power plants operated at Reynolds numbers (Re0,75<2*105), which can significantly affect its aerodynamic and acoustic characteristics. It is shown that when choosing a UAV control system, one should take into account the fact that two-stroke piston engines are the dominant source in the noise of propeller-driven control systems in the absence of a hood and mufflers in the intake and exhaust tracts. The use of a four-stroke internal combustion engine significantly reduces the noise of the control system. In the general case, the position of the boundaries of the zone of acoustic visibility of a UAV at the location of the observer is determined by the ratio between the intensity of acoustic radiation perceived by the observer from the UAV and the intensity of sound corresponding to the natural acoustic background and depends on the degree of manifestation of acoustic effects accompanying the propagation of sound in a turbulent atmosphere - the refraction of sound waves. Absorption and dissipation of acoustic energy. The calculation and comparison of the UAV detection range was carried out taking into account the existing natural maskers.The results of experimental studies are presented that allow assessing the degree of acoustic signature of the UAV. A set of measures aimed at reducing the intensity of the acoustic signature of the UAV in various regions of the radiation spectrum has been determined.

Channeling Flow and Solute Transport in a Single Fracture

2013 ◽  
Vol 316-317 ◽  
pp. 632-635
Author(s):  
Ye Fei Tan ◽  
Zhi Fang Zhou ◽  
Shi Qiang Wu ◽  
Xing Hua Xie ◽  
Bo Ning
Keyword(s):  
Finite Element Method ◽  
Drinking Water ◽  
Breakthrough Curve ◽  
Laboratory Experiments ◽  
Fractured Media ◽  
Single Fracture ◽  
The Finite Element Method ◽  
Dispersive Equation ◽  
One Dimensional ◽  
Channeling Flow

Groundwater in fractured media plays an important role in drinking water supply, and the understanding of its principle mechanisms is essential for securing the groundwater exploring and utilization. In this paper, a novel conceptual fracture model was presented on the basis of the reality of channeling flow in natural fractures and laboratory experiments were conducted for the purpose of getting a better understanding of the step-like breakthrough curve (BTC). Experimental results were fitted with convective dispersive equation (CDE) and compared with those of the finite element method (FEM) models. Results showed that the traditional one-dimensional CDE was invalid in the fitting of a step-like BTC and needed to be improved.

Experimental Study on Various Mineral Admixtures in Fibre Reinforced Concrete

2019 ◽  
pp. 309-317
Author(s):  
Kavitha E ◽  
Karthik S ◽  
Eithya B ◽  
Seenirajan M
Keyword(s):  
Fly Ash ◽  
Rice Husk ◽  
Power Plants ◽  
Rice Husk Ash ◽  
Thermal Power ◽  
Experimental Studies ◽  
Mineral Admixtures ◽  
Hardened Concrete ◽  
Polypropylene Fibres ◽  
Concrete Production

The quantity of fly ash produced from thermal power plants in India is approximately 80 million tons each year, and its percentage utilization is less than 10%. An attempt has been made to utilize these cheaper materials in concrete production. This thesis aims at investigating the characteristics of fresh concrete and various strengths of hardened concrete made with various mineral admixtures such as fly ash. GGBFS, silica fume. Rice husk ash along with polypropylene fibres in various proportions.  M20 grade concrete is considered for experimental studies with 53grade Ordinary Portland Cement blended with varying percentages of mineral admixtures. The maximum size of coarse aggregate used is 20mm.  Various mineral admixtures such as fly ash. GGBFS.Silica fume. Rice Husk Ash were added concrete in various percentages by partially replacing cement and the optimum percentage of the mineral admixtures will be found.  Based on the obtained values, the admixture with maximum mechanical strength is determined and to this polypropylene fibre is added by varying 0 to 0.5 % by weight of cement to the mix.  The test results obtained were compared and discussed with conventional concrete.

scholarly journals STUDY OF THE EFFECTIVENESS OF VIBRATION ISOLATION OF UNCONVENTIONAL TOROIDAL ROPE VIBRATION ISOLATORS IN DIESEL UNITS VIBRATION ISOLATION SYSTEM

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 110-114
Author(s):  
Minas Minasyan ◽  
Armen Minasyan ◽  
Aung Thant
Keyword(s):  
Power Plants ◽  
Vibration Isolation ◽  
Steel Wire ◽  
Experimental Studies ◽  
Wire Rope ◽  
Diesel Generator ◽  
Isolation System ◽  
Vibration Isolators ◽  
Before And After ◽  
Materials Used

The paper notes that the structure of the wire rope is one of the most suitable materials used as a fire-resistant elastic element of vibration-insulating structures and fasteners (vibration isolators). To solve the problems of vibration isolation of marine diesel power plants in the framework of development and improvement of the shock absorption system, the original patented elastic supports with elastic elements made of steel wire rope in the form of a torus are presented. When commercially available vibration isolators do not meet the relevant requirements of vibration protection of a particular object, the solution to the existing problem can be achieved by using the proposed wire rope vibration isolators. The technical results of the original patented inventions are: - equal stiffness in the horizontal plane - ensuring the reliability and high vibration efficiency of protection against impacts and shocks. The proposed designs of vibration isolators are easy (technological in manufacturing) to manufacture and assemble, reliable and durable - the service life is 10 years or more. Vibration efficiency is confirmed by the vibration acceleration spectra before and after the vibration isolator of the damping system of the ship diesel-generator DGA-500 and the diesel unit with a 2H 8.5/11 engine and water brake on a common sub-frame. The three-year trial life of the DGA-500 and experimental studies on a diesel unit with a 2H 8.5/11 engine and water brake on a common sub-frame confirms their efficiency and effectiveness.

scholarly journals EXPERIMENTAL FACILITY FOR THE STUDY OF THE PROCESSES IN MIXING LOW-PRESSURE HEATERS OF K-1000-60/3000 TURBINES

2020 ◽  
Vol 2 (61) ◽  
pp. 42-50
Author(s):  
A. Smychok ◽  
◽  
V. Gerliga ◽  
V. Zaporozhan ◽  
M. Panchenko ◽  
...  
Keyword(s):  
Power Plants ◽  
Thermal Power ◽  
Experimental Studies ◽  
Operating Experience ◽  
Low Pressure ◽  
Main Task ◽  
Experimental Facility ◽  
Design Features ◽  
Technical Problems ◽  
Hydraulic Processes

Nowadays, the development of nuclear energy is determined by solving the set of scientific and technical problems that provides reliable, safe and sustainable work of the operated and designed NPPs. At the same time different accident conditions and likelihood (probability) of variant equipment operating failures are analyzed. Obtained operating experience of the mixing low-pressure heaters (LPH) at thermal power plants (TPP) and NPPs shows that pulsations occur in some operation regimes of LPH turbine which lead to inner element destructions of LPH and pipeline malfunctions. These circumstances negatively affect operation of equipment that locates after LPH in condensate-supply tract. Consequently, unit capacity factor and economic indicators descend since troubleshooting for LPH mechanisms require some time and material resources. This work presents the experimental facility design and description of main design features of the facility components. The stand was designed to study the processes that lead to the vibration appearance in mixing LPH in condensate-supply tract of K-1000-60/3000 turbines. The main task of scale modeling is the need to observe equivalent conditions of the thermal-hydraulic processes behavior in the model in relation to full-scale equipment. To solve this problem using ANSYS code a preliminary simulation of hydraulic processes occurring in the experimental facility was performed. This allowed to determine in advance certain design features in the design of given facility. The results of experimental studies of the developed facility should allow to develop measures for reduction or complete elimination of vibrations in mixing LPH, as well as to validate computer programs for design analysis of stationary and non-stationary thermal-hydraulic processes in the specified equipment and designed measures testing.

A SINGULAR PERTURBATION PROBLEM IN FRACTURED MEDIA WITH PARALLEL DIFFUSION

1998 ◽  
Vol 08 (04) ◽  
pp. 645-655 ◽  
Author(s):  
J. DAVID LOGAN ◽  
GLENN LEDDER ◽  
MICHELLE REEB HOMP
Keyword(s):  
Boundary Condition ◽  
Singular Perturbation ◽  
Porous Matrix ◽  
Fractured Media ◽  
Singular Perturbation Problem ◽  
Single Fracture ◽  
Direction Parallel ◽  
Flux Boundary Condition ◽  
Perturbation Problem ◽  
Parallel Diffusion

We study differential equations that model contaminant flow in a semi-infinite, fractured, porous medium consisting of a single fracture channel bounded by a porous matrix. Models in the literature usually do not incorporate diffusion in the porous matrix in the direction parallel to the fracture, and therefore they must omit a no-flux boundary condition at the edge, which, in some problems, may be unphysical. Herein we show that the problem usually treated in the literature is the outer problem for a correctly posed singular perturbation problem which includes diffusion in both directions as well as the no-flux boundary condition.

Methods for calculating thermal processes under conditions of natural convection of gaseous methane under the influence of electrostatic fields

2021 ◽  
Author(s):  
V.A. Altunin ◽  
K.V. Altunin ◽  
M.R. Abdullin ◽  
M.R. Chigarev ◽  
I.N. Aliev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Power Plants ◽  
Experimental Studies ◽  
Thermal Processes ◽  
Technical Literature ◽  
New Methods ◽  
Electric Wind ◽  
Electrostatic Fields ◽  
General Method

Relying on the review and analysis of scientific and technical literature, as well as the results of experimental studies, we developed new methods for calculating thermal processes occurring in gaseous methane during its natural convection, under the influence of electrostatic fields. In this study we show methods for calculating and determining the coefficients of heat transfer to gaseous methane under the influence of electric wind, as well as methods for calculating and determining the effect of electrostatic fields on the negative process of sedimentation on a heated experimental working plate in the volume of gaseous methane. A general method has been developed for the effective and safe application of electrostatic fields in gaseous methane, which must be carried out in the calculations, design, creation, and operation of new engines, power plants, and techno systems for single and reusable ground, air, aerospace and space-based aircraft.

Sign in / Sign up

Export Citation Format

Share Document