Changes In Mass Flow Research Articles

Heat transfer characterizations of water flow through a single fracture with integrating water dissolution effects for the Enhanced Geothermal Systems

The Enhanced Geothermal Systems (EGS) is the technology that generates connected fracture networks in the Hot Dry Rock (HDR) reservoir with the application of water as the working fluid for hydraulic fracturing and geothermal energy production. A good understanding of water flow behaviors in the single fracture is critically important because connected fracture networks are composed of individual fractures. It should be noticed that the dissolution reaction between the reservoir rock and the working fluid (water) will change the fracture surface directly and consequently affect the mass and heat transfer process of water through the rock fracture in the HDR reservoir. In this study, the heat transfer process of water flow in the single fracture by considering dissolution reactions between water and fracture surfaces of reservoir rock have been investigated under high pressure and temperature conditions. The experiments of dissolution reaction and convective heat transfer have been performed separately for different temperature conditions with the rock sample of 0.2 mm fracture aperture. The influences of reaction duration, mass flow rates and initial temperature have been presented and analyzed. It is found that mass flow rates and temperature have significant effects on measured temperature of fracture surfaces. The effects of dissolution reaction on fracture surface morphology exists but it is extremely small for heat transfer. Based on experimental and simulation data, a modified correlation that integrates reaction duration, mass flow rates and changes of thermophysical properties has been proposed and its maximum error that compares with experimental results is less than 7%. The results of this study provided an accurate correlation for simulations and characterizations of the Hot Dry Rock reservoirs, which is of great importance for geothermal energy production and optimization.

Design of a Parabolic Trough Collector Solar Field for a Pilot CO2 Capture Plant from Natural Gas Combined Cycle Power Plant Flue Gas.

A parabolic trough collector solar field was designed to supply the heat needed to regenerate the CO2-rich monoethanolamine in a solar-assisted carbon capture system. Process design modeling was performed for 90% of the CO2 removal from 1% of the flue gas produced by a 255 MWe natural gas combined cycle power plant. Calculations with and without 24 h of thermal energy storage by increasing the solar collector size needed and providing a buffer vessel to store hot heat transfer fluid were performed. A dynamic analysis of the solar field using the hourly solar forecast was performed to investigate how heat transfer fluid mass flow changes during January and June to maintain the desired parabolic solar field outlet temperature needed for CO2 reboiler operation. The calculations provided here present an explicit method to calculate relevant solar field design parameters that can be scaled up and used in solar energy-assisted gas capture processes.

Characteristics of Shock-Induced Boundary-Layer Separation on Nacelles Under Windmilling Diversion Conditions

The boundary layer on the external cowl of an aeroengine nacelle under windmilling diversion conditions is subjected to a notable adverse pressure gradient due to the interaction with a near-normal shock wave. Within the context of computational fluid dynamics (CFD) methods, the correct representation of the characteristics of the boundary layer is a major challenge in capturing the onset of the separation. This is important for the aerodynamic design of the nacelle, as it may assist in the characterization of candidate designs. This work uses experimental data obtained from a quasi-2D rig configuration to provide an assessment of the CFD methods typically used within an industrial context. A range of operating conditions are investigated to assess the sensitivity of the boundary layer to changes in inlet Mach number and mass flow through a notional windmilling engine. Fully turbulent and transitional boundary-layer computations are used to determine the characteristics of the boundary layer and the interaction with the shock on the nacelle cowl. The correlation between the onset of shock-induced boundary-layer separation and the preshock Mach number is assessed, and it was found that the CFD is able to discern the onset of boundary-layer separation.

An experimental investigation of shear-driven rivulets on a flat plate by using a two-perspective view

Shear-driven liquid rivulet flow on a horizontal plate is experimentally investigated. In contrast to publications found in the literature, a two-side view on the rivulet is used to simultaneously capture the side and top view. This enables more accurate measurements of the rivulet dimensions and the subsequent calculation of derived quantities. Throughout the experimental test campaign, the ambient gas velocity and the liquid mass flux are altered. In a first qualitative analysis, the occurring rivulet flow regimes are classified and mapped depending on the gas Reynolds number ReG and the rivulet Weber number We. Furthermore, the goal is to quantify the correlation between characteristic rivulet dimensions and the ambient conditions, with a focus on straight and surging rivulets. The quantitative analysis results in an implicit correlation for the rivulet width and height depending solely on the ambient gas velocity and the rivulet mass flow. The investigation of the rivulet wavelength reveals an analogous dependence on the ambient gas velocity. However, the dependence on the rivulet mass flow changes depending on the rivulet flow regimes.

The role of volume effect on the transient behavior of a transonic compressor

Abstract The significance of the volume effect on the compressor performance during acceleration and deceleration has received limited attention, despite its demonstrated importance in compressor flow instabilities. To better understand this effect, the in-house simulation program CAM (a modular transient simulator) is used to investigate the volume effect on the compressor transient performance. The modeling procedure is derived from Greziter’s lumped parameter approach and the accuracy of the simulation model is verified by experimental data. This study presents a comprehensive comparison and explanation of variations in compressor transient behavior observed under different conditions, including different shaft speed change rates, compressor volume sizes, and operating speeds. The relative difference between the compressor inlet and outlet mass flow is identified as the key factor contributing to these discrepancies. In addition, a simplified analytical model is developed to provide a basic description of the compressor operating line during acceleration and deceleration, which also provides additional support for the validity of the numerical results. This study systematically establishes the dynamic dependencies between shaft speed change, pressure and mass flow change, offering critical information for ensuring the safety of compressors during transient operation.

The British Steam Generating Heavy Water Reactor: A reassessment with thermal hydraulic-neutronic coupling

The Steam Generating Heavy Water Reactor (SGHWR) was of significant interest in the UK in the late 1960s and early 1970s but failed to be developed into a commercial programme. This paper reassesses the reactor physics of the SGHWR with modern day modelling tools: neutronics and thermal hydraulics are coupled using Serpent and THERMO. Such a coupling is required since the boiling coolant along the SGHWR pressure tube height will have a significant influence on the neutronics of the system. Results show that the coolant void coefficient is negative at nominal conditions. This is achieved by the important contribution of the coolant towards moderation. Plutonium build-up throughout burnup also has a beneficial effect on the void coefficient. Quasi-static analyses of mass flow changes, pressure changes, and overpower events are examined. Most importantly, the power coefficient is negative. Superheated steam coolant conditions are also simulated for a SGHWR pressure tube. Although the steam temperature coefficient is slightly positive, the power coefficient is also negative.

About geological theory

The author’s advection-polymorphic hypothesis of deep processes in the tectonosphere is based on V.V. Belousov’s system of endogenous regimes, a certain source of energy (radioactive decay in crustal and upper mantle rocks), and the method of energy transfer (advection). Elementary volumes of transported material have been termed «quanta of tectonic action» (QTA) with the diameter of about 50―70 km. The physical reality of such objects is proved. The choice of endogenous regime is related to the type of the preceding thermal model.
 The mechanism of the tectonosphere’s «heat machine», which relies firmly established facts and quantitatively explains the main events of geological history within the energy conservation law, has been substantiated.
 For any period, from the Early Archaean to our time, it is possible to numerically justify the pattern of heat and mass transfer, to select the endogenous regimes, and construct a non-stationary heat model and variation in time of the distribution of physical properties of rocks. By using the findings and solving only direct problems, one can determine the geological manifestations of the process and the anomalies of the physical fields. The results are compared with the observed ones (without fitting), and the discrepancies do not exceed the values due to the observation and calculation errors.
 Pursuant to the advection-polymorphic hypothesis, it became possible for the first time to predict: 1. The emergence of quanta of tectonic action. 2. Stability of parameters (depth and temperature) of magma chambers in the mantle in the history of the Earth. 3. Existence of the global asthenosphere (depth about 700―1000 km). 4. Velocity distribution of longitudinal seismic waves in the upper mantle of regions with all types of endogenous regimes. 5. The difference in the nature of earthquakes at various depths in the focal zones. Successful verification of predictions transfers the hypothesis into the rank of theory.
 The theory is used to explain the following at the quantitative level: dating of active processes on all platforms of the Earth, temperature distribution in the crust and upper mantle of platforms and active regions, sediment thickness in geosynclines and post-rift depressions, changes in mass flow in geological history, heat flow and gravitational field anomalies.
 Several applications of the theory to studies of seismicity and UHP-blocks problems and prospecting for mineral deposits (hydrocarbons, hydrothermal sulfide ores, diamonds, and geothermal energy resources) have been considered.

Design and analysis of 5 kW helium turbine for EAST cryoplant

The helium turbine is an important core component in the refrigerator, which provides support and guarantee for the stable operation of the cryogenic system. This paper refers to the parameters of one of the four helium turbines in EAST, designs a 5 kW helium turbine. The overall structure of the turbine has been described, and the design and analysis of the impeller and bearing have been carried out. Through CFD analysis, the internal pressure and temperature change law of the flow is analyzed. The variable-condition operating characteristics of the turbine are predicted, and it is found that the turbine can maintain efficient operation within a wide range of mass flow changes. The bearing performance is calculated by solving the Reynolds equation. After determining the optimal bearing clearance 28 μm based on the principle of maximum stiffness, bearing performance parameters of load capacity and stiffness can be further calculated.

Numerical study on the influence of mist-air mixtures on axial compressor performance

To study the influence of mist-air mixtures on the performance of an axial-flow compressor, based on the Euler-Lagrange multiphase flow model coupled with compressor aerodynamic calculation, droplet motion, and wall film model, we establish a numerical method for compressor multiphase flow, which is used to study the performance change law of a low-pressure axial compressor with mist-air injection. The results indicate that the compressor inlet fogging will produce a wall film on the blade surface and the casing wall, resulting in a decrease in the total pressure coefficient and mechanical efficiency of the compressor under full operating conditions, and this decrease is more significant with the increase of spray water-air ratio and spray particle size. With the change of compressor mass flow, the wall film on the blade surface presents the following migration law: the thickness of wall film on the pressure surface and on the suction surface decreases and increases respectively with the increase of mass flow, and the specific distribution law of wall film on the blade surface does not change obviously. Meanwhile, a compressor inlet fogging test is carried out in this study to verify the accuracy of the multiphase flow numerical method for compressor performance prediction. The experimental results show that the numerical method can effectively and quantitatively analyze the effect of mist-air mixture injection on compressor performance, and can be further improved by more detailed experimental research to achieve a more accurate numerical method for compressor multiphase flow.

Development of an analytical constituent split method to analyze a semi-closed supercritical carbon dioxide power cycle

Semi-closed S-CO2 cycle (SC) has attracted much attention for its compactness and high power generation efficiency. For the purpose of deepening the understanding of the cycle and clarifying its construction process, this paper proposes a constituent split method suitable for the analysis of SC. This method can equivalently split the SC into two parts based on the constituent of the working fluid, and one part is an open cycle of fuel and oxidant, and the other part is a closed S-CO2 cycle. The method is described based on single-compression semi-closed S-CO2 cycle (SSC) and recompression semi-closed S-CO2 cycle (RSC), respectively. The principle of split method is explained through the analysis of the cycle process, and it is found that the two sub-cycles after splitting not only have independent processes, but there are also thermal integration connections in the combustor and the regenerators, respectively. In addition, the effect of split method is expressed through the calculation model of each equipment and the equations derivation of the cycle efficiency. The constituent split method is evaluated by the analysis of three performance results: the sensitivity of main vapor temperature and pressure to cycle performance, the improvement of thermal efficiency from 59.9% for SSC to 66.1% for RSC, and the change of mass flow of working fluid from SSC to RSC. It is found that the above performance changes can be directly and visually explained by the proposed method, which proves the applicability and superiority of constituent split method for SC.

Ecosystem services (ES) provided by ditches in a desert agricultural valley

Agricultural ditches can be an efficient method for removing nutrients in wetlands and rivers. In this paper, we document that additionally, ditches offer other ecosystem services (ES) such as providing bird habitat and sediment retention. A typical ditch reach of 6 km with variable width between 3 and 80 m and water depth from 0.06 and 0.5 m, was selected as a monitoring site among 1492 km of a drain network in the agricultural Mexicali Valley located in the Colorado River Delta. Nitrogen and phosphorus concentration and discharge flow rate determinations were obtained monthly during a year, at three stations along the ditch, dividing the reach into two segments. Total nutrient removal efficiency of 39%, along the monitoring year was observed. Additionally, nutrient mass flow had a significant winter-spring seasonal increment associated with crop irrigation, up four times for total nitrogen, nearly 2.5 times for nitrogen-based nutrients, and five times for PO4. Monthly estimations of normalized difference vegetation index (NDVI) from Sentinel images were obtained to evaluate the response of riparian vegetation to high flow discharge seasonal fluctuations, from 0.072 to 1.219 m3 s−1, and nutrient mass flow changes. No correlation among them was found, as riparian species are tolerant to high water levels and nutrient concentration fluctuation. Downstream changes in water electrical conductivity from 6.06 to 8.45 mS cm−1 along the resulted in the shift from Typha domingensis to Phragmatis australis which has a higher salinity tolerance. An intensive bird census showed ditch vegetation provided suitable habitat and refuge to 29 different bird species, including five common birds of the flooded remnant areas of the Colorado River Delta, as well as migratory birds. By using slope criteria of drainage network, 47% of it has a high and moderated potential of sediment retention. These ES are fundamental in semiarid regions because of the intense land-use changes from riparian and desert ecosystems to irrigation lands, as well as water being diverted from natural streams to irrigation channels. This study highlights the importance of considering agricultural ditches as helpful, not only as a natural water treatment of agricultural pollutants, but also as providers of resident and migratory bird habitat and vegetation diversity and erosion regulation by sediment retention on desert agricultural valleys.

The Analysis of Network Models for the Design of Industrial and Fire Safety Systems for Oil Refineries

Tensor network models represent the processes and structure of complex systems, including dangerous technological objects of oil refineries. Complex systems tensor method research based on duality invariance. It is the sum constancy of the metric tensors dual networks whenever there is a change in structure. Dual subspaces closed and unclosed paths are responses to external and internal influences, which do not depend on each other. As an example of a network model is considered the atmospheric column oil-refining plant, which is used to organize the work of training stand. Thermal energy flows are presented in a mesh network, and massive flows of mechanical energy - in a junction network. The amount of mechanical and thermal energy flows allows you to determine the load on the nodes of the unit. The results are applied to predict dangerous situations on refining facilities to assess changes in restructuring processes and the risk of accidents. Calculations, such as heat and mass flow change if you change the control actions, disable installation elements and assess change critical settings.

A Transient Response Comparison of a Conventional and a Meso Heat Exchanger under Mass Flow and Temperature Step Changes

A Transient Response Comparison of a Conventional and a Meso Heat Exchanger under Mass Flow and Temperature Step Changes

Removal and formation of perfluoroalkyl substances in Canadian sludge treatment systems – A mass balance approach

Poly- and per-fluoroalkyl substances (PFAS) are an emerging class of anthropogenic contaminants whose occurrence has raised concerns with the beneficial reuse of biosolids from wastewater treatment. This study evaluated the behavior of thirteen PFAS in nine Canadian sludge treatment systems including pelletization, alkaline stabilization, aerobic and anaerobic digestion processes. The composition of the overall PFAS-fluorine (ΣPFAS-F) loading in a system fed with only primary sludge was dominated by perfluorodecanoate (PFDA), whereas systems with blended primary and waste activated sludge feeds had a mix of short and long chain PFAS in raw sludges and treated biosolids. An increase in average ΣPFAS-F mass flow was observed through pelletization (19% formation) and alkaline stabilization (99% formation) processes indicating negative removal or contaminant formation. One of the two aerobic digestion systems and three of the five anaerobic digestion systems showed modest reductions (< 40% removal) in ΣPFAS-F loading. Long chain PFAS such as perfluorodecanoate (PFDA) and perfluorooctane sulfonate (PFOS) exhibited a wide variation in behavior ranging from substantial formation (> 75% formation) to modest removal (42% removal) in the surveyed systems while short chain perfluoropentanoate (PFPeA) mass flows increased through the three systems where they occurred. Overall, the contaminant mass balances revealed that there were significant changes in mass flows of the target PFAS through all kinds of sludge treatment systems. The results of this study on PFAS fate through sludge processing can inform future global PFAS risk management activities as well as sludge treatment considerations.

Axial Turbine Performance Estimation During Dynamic Operations

During service, a turbine engine undergoes frequently dynamic operations. Because of the changes in mass flow, temperature, pressure, as well as the different reaction of the components of turbine to these changes, the turbine performances may vary significantly. It is critical to understand and quantify these variations to design and integrate the turbine to the engine. This paper presents a study of the performances and the variation of the performances for an axial gas turbine across its operating envelope. Numerical simulations are used to describe the flow across the turbine and to estimate the turbine maps. Using theoretical charts for typical turbine thermal expansion, the variation of tip clearance across the working line is approximated. Because of the changes of the tip clearance, using a single geometry may not supply relevant information during real dynamic operations. In order to eliminate these additional errors in the numerical study, a number of turbines maps are recalculated for different tip clearances, respectively to engine regimes. With the resulting data, the working line is recalculated across multiple maps. The comparison between the two working lines is presented as well as the study of performance variation of the turbine across the operation envelope and the influence of tip clearance at different regimes.

Three Dimensional Simulation and Experimental Study of a Loop Thermosyphon for High Temperature Oil Cooling

The loop thermosiphon for high temperature oil cooling is a high-performance cooling heat exchanger capable of rapidly cooling high-temperature oil by transferring a large amount of thermal energy through boiling and condensation of the working fluid even with a small temperature difference. The loop thermosyphon for high-temperature oil cooling consists of an evaporation unit, an insulation unit, and a condensing section. A 3D simulation and experimental studiss were conducted simultaneously. In this study, the size of the loop thermosyphon for oil cooling is 500mm wide, 70mm long, and 1,100mm high. In addition, the size of the heat transfer tubes of the heat exchanger is 15 mm in diameter and 1,000 mm in length, and 98 heat transfer tubes were installed. The inside of the condensing unit was constructed with heat transfer tubes equipped with high-efficiency insert devices to increase the heat transfer surface area of the heating medium in the heat transfer tubes and low fin shapes were enchased on the outside of the heat transfer tubes with form rolling to increase the heat transfer surface area in contact the fluid inside the cylinder. R134a refrigerant was used as the working fluid of the loop thermosyphon to experiment changes in the temperature of the cooling air outside the condensing unit and the temperature of the refrigerant, and heat transfer performance in relation to mass flow changes and the experimental results were compared with the results of the 3D simulation. According to the results of this study, the rate of transfer of the thermal energy supplied by the evaporation unit of the loop thermosyphon heat exchanger for high-temperature oil cooling and the rate of transfer of the thermal energy absorbed by the air in the condensing unit matched well within the range of ±5%. Therefore, the reliability of the experimental results of this study was verified. In addition, thanks to the heat transfer tubes equipped with high-efficiency insert fins installed inside the condensing unit of the loop thermosiphon for high temperature oil cooling, the condensation heat transfer performance of the condensing unit increased significantly compared to that of condensing units made with flat plates.

ESTIMATION OF WALL SHEAR STRESS OF COMPLIANT THORACIC AORTA WITH ANEURYSM

In this paper, a numerical estimation of wall shear stress (WSS) in a compliant Thoracic Aorta (TA) with aneurysm is modeled and the hemodynamic pattern is studied using Computational Fluid Dynamics (CFD). Thoracic Aortic Aneurysm (TAA) is an excessively localized enlargement of TA caused by weakness in the arterial wall and it can rupture the inner wall intima and continue on to the outer wall adventitia. WSS is a tangential force exerted by blood flow on the vessel wall, and its estimation is clinically very important because any change in WSS is considered as a vital cue in the onset of aneurysm. In this work, a three-dimensional (3D) model of a TAA reconstructed from computed tomography (CT) images comprising of 600 slices with 1-mm resolution from neck to hip is considered and patient-specific simulations have been carried out in compliant TA under rest and exercise conditions. The findings show that the change in wall geometry was marginal due to variation in pressure forces inside and is not the primary source for expansion of an aneurysm. It was inferred that expansion was rather due to thinning of the wall, owing to damage caused to the inner lining of the tissues, at regions of high WSS. It was found that the geometry extraction is important as any change in length causes a corresponding variation in mass flow through it. Although mass conservation is maintained irrespective of the length, it does affect the rate of flow due to shifting in the pressure boundary conditions with the length as it varies the pressure inside the system. Modeling of the geometry is very important as the change in mass flow will affect the outlet velocity and strength of vortices. Surprisingly, the split-up of flow is consistent but the geometric change in the model has no effect on WSS values and flow pattern. The results of this study provide important information such as blood flow pattern and pressure drops in the compliant TA on WSS estimations with TAA diseases.

The Effect of Cordierite-Platinum SCR Catalyst on the NOx Removal Efficiency in an Engine Fueled with Diesel-Ethanol-Biodiesel Blends

Today, vehicles especially diesel engines emitted a large amount of NOx in the urban areas. So, it is required to find ways such as SCR catalysts to reduce this hazard pollutant emission. In this work, a 3D model of cordierite/Pt SCR catalyst has been developed by using AVL FIRE software to analyze the NOx conversion efficiency. The simulation was performed based on experimental tests conducted on a single-cylinder engine. The exhaust gas from the engine that appears at the inlet of the catalyst was measured for E20B50D30 (20% ethanol, 50% biodiesel, 30% diesel) D100, E10D90, E20D80, B25D75 and B50D50 fuel blends at the engine speeds of 1800, 2150 and 2500 rpm under full load. The results showed that an increase in the engine’s rotational speed resulted in a reduction of NOx conversion, and the conversion rate reaches its minimum value at speed of 2500 RPM for all fuel mixtures. Moreover, increasing the ammonia mass flow rate resulted in higher NOx conversion for all fuel mixtures. However, the effect of increasing ammonia flow rate from 0.2 to 0.3 kg/h on the NOx conversion is lower than that when the ammonia mass flow changes from 0.1 to 0.2 kg/h. The maximum NOx conversion rate was observed for the mixture containing 20% ethanol and 80% diesel at the rotational speed of 1800 RPM while the lowest conversion rate is observed for pure diesel fuel. According to the results, it was seen that the SCR catalytic process for fuel blends contained ethanol have a better performance to reduce the NOx pollutant compared to the mixtures containing biodiesel at lower engine speeds; but at higher rotational speeds ethanol and biodiesel has not a positive effect on the NOx conversion.

Study on Safety Characteristics of Gate Valve Transient Operation in High Temperature Molten Salt Thermal Energy Storage System

At present, the new energy industry in the world is thriving, but there are obvious intermittent and random characteristics of various power generation methods such as solar energy and wind power. The molten salt energy storage power generation system can effectively reduce the peak fluctuations of the power grid and greatly improve the overall economic advantage. As an important component of the pipe system, the gate valve is widely used in power generation systems. Because molten salt systems may face faster power changes so during certain transient process, the main gate valve may have to withstand rapid changes in mass flow and temperature, which may cause rapid changes in the temperature field of the valve body, resulting in additional thermal stress. In this paper, the CFD method is used to analysis the flow and temperature fields of the main gate valve during the transient process. The key to success is to describe the geometry as accurately as possible and to build a reasonable grid because of larger calculation quality for transient. Then based on the temperature field of valve body the thermal stress and change law can be obtained, which can provide guidance for the design of the gate valve.

Research on Fluid Flow and Permeability in Low Porous Rock Sample Using Laboratory and Computational Techniques

The paper presents results of fluid flow simulation in tight rock being potentially gas-bearing formation. Core samples are under careful investigation because of the high cost of production from the well. Numerical simulations allow determining absolute permeability based on computed X-ray tomography images of the rock sample. Computational fluid dynamics (CFD) give the opportunity to use the partial slip Maxwell model for permeability calculations. A detailed 3D geometrical model of the pore space was the input data. These 3D models of the pore space were extracted from the rock sample using highly specialized software poROSE (poROus materials examination SoftwarE, AGH University of Science and Technology, Kraków, Poland), which is the product of close cooperation of petroleum science and industry. The changes in mass flow depended on the pressure difference, and the tangential momentum accommodation coefficient was delivered and used in further quantitative analysis. The results of fluid flow simulations were combined with laboratory measurement results using a gas permeameter. It appeared that for the established parameters and proper fluid flow model (partial slip model, Tangential Momentum Accommodation Coefficient (TMAC), volumetric flow rate values), the obtained absolute permeability was similar to the permeability from the core test analysis.