Operating Pressure Level Research Articles

Effectiveness of Copper Minerals Liberation from the Gangue through Application of HRC Press in Copper Ore Processing Circuits

The article concerns investigations over benefits of application of HRC devices into sulphide copper ore processing plant. High pressure comminution appears to be very effective technology in hard ore processing circuits, especially in terms of energy consumption. This can be particularly observed in downstream grinding and beneficiation operations. A series of pilot-scale crushing tests in HRC roller press for various levels of operating pressure, were performed. HRC crushing effectiveness along with downstream grinding process course for each crushing product were also under analysis. The investigations were supplemented by analysis of flotation process effectiveness and impact of the process of high-pressure comminution on environment (dust emission). The results of investigation show that operating pressure level influences the obtained comminution results (comminution degree, yield of finest particle size fractions). The grinding effectiveness, measured through production of the finest particle size fractions was significantly influenced by the operating pressure. The results show that higher values of operating pressure (4.0 and 4.5 N/mm 2 ) are not as efficient within this scope as the pressure 3.5 N/mm2. Dust emission is also correlated with the operating pressure value.

Development and Application of Silicone Outer Shell-Type Pneumatic Soft Actuators

Pneumatic soft actuators exhibit both passive flexibility from the casing and active flexibility from pressurizing and depressurizing. These actuators are expected to be human-friendly and are often used in nursing and medical situations because they allow access to soft systems through control of the internal air pressure. The current design of pneumatic soft actuators has two technical points of interest: the control method for the drive direction and the operating pressure level. An actuator that addresses these points is required. In this study, a pneumatic soft actuator with a silicone rubber casing – called a sponge core soft rubber actuator (SCSRA) – is developed to solve these problems. SCSRAs can perform various functions by changing the bonding state of the silicon film. Thus, a large stroke can be achieved in a low-pressure area of ≤ 30 Pa, and the driving system can be controlled by peeling off and bonding the silicon film. We clarified the expansion and stiffness characteristics of the “bonded SCSRA” and “peeled SCSRA” when unpressurized and pressurized and measured the grip strength when walking in shoes with protrusions on the insole and single-tooth sandals with protrusions on the sole as example applications of the sensing ability.

Parametric Thermo-Economic Analysis of a Power-to-Gas Energy System with Renewable Input, High Temperature Co-Electrolysis and Methanation

A complete thermo-economic analysis on a cutting-edge Power-to-Gas system that comprises innovative technologies (a Solid Oxide Electrolyte Cell co-electrolyzer and an experimental methanator) and coupled with a renewable generator is provided in this study. The conducted economic analysis (which has never been applied to this typology of system) is aimed at the estimation of the synthetic natural gas cost of a product through a cash flow analysis. Various plant configurations—with different operating temperatures and pressure levels of the key components (electrolyzer: 600–850 °C; 1–8 bar)—are compared to identify possible thermal synergies. Parametric investigations are performed, to assess both the effect of the thermodynamic arrangements and of the economic boundary conditions. Results show that the combination of a system at ambient pressure and with a thermal synergy between the co-electrolyzer and the high-temperature methanator presents the best economic performance (up to 8% lower synthetic natural gas value). The production cost of the synthetic natural gas obtained by the Power-to-Gas solutions in study (up to 80% lower than the natural gas price) could become competitive in the natural gas market, if some techno-economic driving factors (proper size ratio of the storage system and the renewable generation, electrolytic cell cost developments and introduction of a carbon tax) are considered.

WITHDRAWN: Experimental evaluation of Mechatronics based cushioning performance in hydraulic cylinder

Many of the rigid structures are moved one place another place the hydraulic drives are used; the hydraulic actuators are elaborately used in the industries and the most of the mechanical movements. In this research concentrated to study the cushioning effect of retraction stroke and analysis the pressure build up in the cylinder effectively. The different shape of the cushioning arrangements is considering to analysis the pressure level; the shapes are taken as conical, cylindrical, dome and point. Mechatronices based analysis was implemented to this work that is two pressure sensors are fixed in the both end of the cylinder. The pressure sensors sending the signals to A/D converters the pressure levels are measured in the cylinder chamber by applying of two different operating pressure levels are 50 bar and 80 bars. From the all-cushioning shapes the conical and cylindrical shapes are reduced the pressure in the chamber, further the profiles of the cushioning are analyzed and optimized.

Quantitative assessment of leakage orifices within gas pipelines using a Bayesian network

Leakage is a significant threat to gas pipeline reliability, causing serious safety incidents such as fire and explosion, which is determined by the leakage rate. Leakage rate estimation are critical to predict leakage level and take effective control measures for a response strategy. Many experimental and numerical studies have been conducted focusing on leakage estimation, with theoretical and empirical equations being determined. However, the dependency of leakage rate on the leakage orifice diameter, which is unknown in most situations, makes it difficult to apply established models in the field. To solve the problem, this paper presents a probabilistic simulation of leakage orifice diameters of gas pipelines based on a Bayesian network model, with experimental verification of the results. According to the established Bayesian network model the leakage orifice diameter can be assessed precisely, which is verified using a range of gas pipeline leakage experiments. Four different diameters of leakage orifice were studied under five different operating pressure levels. The results indicated that the proposed Bayesian network can assess leakage orifice diameters, which can be further applied to the leakage rate estimation in the actual situations.

Flow boiling heat transfer characteristics of low global warming potential refrigerants in a vertical mini-channel

Flow boiling heat transfer characteristics in narrow channels have been investigated extensively by researchers due to its wide range of applications in micro-electromechanical systems, however, being a complex transport process the controlling mechanisms still lack clarity in understanding. Refrigerants related environmental hazards also urged to look for alternative environment friendly refrigerants. It has been noticed that relatively less information is available in the literature specifically for environmentally benign mediums. This study is focused on experimental findings for flow boiling heat transfer performance of low global warming potential refrigerants (R152a, R600a, and R1234yf). The test object was a vertical stainless steel tube (1.60 mm inner diameter and heated surface length 245 mm), experiments were done under upward fluid-flow conditions. The tested conditions were: heat flux 5-245 kW/m2, 50-500 kg/m2s mass velocities while saturation temperatures were 27 ?C and 32 ?C. The effects of operating parameters like heat and mass fluxes, saturation temperature, and vapor quality on heat transfer were analyzed in detail. It was noticed that heat transfer coefficients were significantly influenced by heat flux and operating pressure level whereas the same were not significantly affected by mass flux and vapor quality. The experimental data of heat transfer was compared with the prediction from various macro and micro scale correlations from the literature.

EXPERIMENTAL EVALUATION OF PERFORMANCE AND MECHANICAL RELIABILITY FOR HIGH PRESSURE CO2 INTEGRALLY GEARED COMPRESSOR

Energy saving has become a trend as well as a countermeasure for global environmental issues. It can be one of the efficient solutions for reducing energy consumptions by adopting integrally geared compressors instead of inline compressors for industrial plants. The development of key technologies for the design centrifugal compressor such as CFD, FEM, Rotor dynamic Analysis has enabled integrally geared centrifugal compressors for higher pressure applications than ever. A commercial size, 5 stages integrally geared CO2 centrifugal compressor of 20MPaG discharge pressure level was designed, manufactured and evaluated the fluid dynamic performances and rotor stability. It was installed in OEM’s factory and the full load and full pressure test was carried out using real CO2 gas. The actual compressor fluid dynamic performance has shown superior results even at high pressure supercritical gas conditions at the high pressure stages of the compressor. The mechanical performances such as rotor vibration and bearing temperature were also measured and observed that the vibration was substantially low and within safe limits even at high pressure operating conditions above 20MPaG. Also the authors established a novel on Direct Rotor Excitation Method to experimentally investigate the rotor stability even at a high operating pressure level of 20MPaG. With this technique the measurements of the actual rotor natural frequencies and the damping ratios (log decrement) during high pressure operating conditions provided more precise results rather than conventional casing excitation method. The open impeller blade vibration was measured during running condition by using a non-contact blade vibration measurement technique. This measurement results revealed that impeller blades stress against the centrifugal force and the external excitation force was very low compared to the allowable stress value of the impeller material. The fluid dynamic characteristics and mechanical reliability are assessed as acceptable including super critical gas condition of CO2 gas.

Progress with development of foil and slot thermal transfer technology

Foil And Slot Thermal Transfer (FASTT) devices have a unique set of characteristics and the technology may have an important role in future thermal engineering. The absence of freezing and boiling issues, together with the potential for very wide operating temperature range from below 100 K to above 1000 K, as well as their use of low cost, environmentally friendly materials are among those features which have already been mentioned in literature. The geometry of FASTT devices is currently limited to planar or extrudable sections, however, such formats are found in a number of important applications, such as high power, high flux cooling of semiconductors.The core of any FASTT device is the slotted region within a thermally conductive material through which solid foils move and, in a similar fashion to fluids, carries heat away to a larger, lower flux zone where the heat may be dissipated by convection. This allows very high input cooling flux levels to be achieved. There are a number of differences between FASTT and pumped fluid heat transfer. “Equivalent” heat transfer coefficients comparable to those in pumped liquid systems can be obtained but at much lower media velocities (0.05 cf 3.00 ms−1). Narrow channel flow for liquids can be limited by viscosity and allowable operating pressure level. The thin solid foils used in FASTT can run with very low friction at foil to slot gaps below 10 µm, and with channel widths below 100 µm. This ensures low circuit parasitic losses and low pressure operation. The foils can provide both primary heat transfer as well as acting as the extended output surfaces in unsealed variants of these devices. This can remove the need for fluid channels/pipework and thus, potentially, reduce system mass.Limiting flux levels for simple air blast cooled finned arrays are considered, as are theoretical flux limits for FASTT devices, using a selection of foil material and gap media. Results from an unsealed prototype device are given which show that flux values of over 250 Wcm−2 at 70C temperature differences are possible with this type of device operating at room temperature, even in prototype form. Future proposals include sealed devices operating at cryogenic temperatures where the technology is predicted to show significant advantages over existing cooling systems.

Analiza stabilnosti sagorevanja kompozitnih raketnih goriva sa oktogenom

Research of operating pressure levels with irregular combustion and the effect on combustion instability of composite solid propellants with different quantity of octogen (HMX) are presented in this paper. The content of HMX increased in relation to the oxidant, ammonium perchlorate (AP). Combustion stability of the propellants was improved by adding titanium (IV) oxide powder and through the optimal projected ratio of two oxidizer fractions. Parameters of burning rate laws were determined and p-t diagrams were observed and compared.

Influence of operating pressure on emitter anti-clogging performance of drip irrigation system with high-sediment water

Reducing emitters operating pressure has been widely acknowledged as one of the most effective approach to reduce drip irrigation system maintenance and operation costs. However, utilization of low-quality water, such as high-sediment water, reclaimed water, and brackish water, inevitably increases the emitters clogging risks. To examine the influence of different pressure levels on emitter clogging behavior and regulation path, an in-situ accelerated experiment of emitter clogging with high-sediment water was conducted with five operating pressure levels. The experiment was conducted from July 15, 2016, to October 15, 2016 with a total running time of 720 h. The results showed that emitter anti-clogging capability was gradually decreased as the operating pressure decreased below 100 to 60 kPa and was significant decreased as the operating pressure decreased below 60 to 40 kPa or lower. Therefore, the operating pressure should be kept above 60 kPa to maintain the favorable emitter anti-clogging performance. The change of the operating pressure directly and indirectly influenced the formation of clogging substance in the emitters. In addition, at different operating pressures, the anti-clogging performance parameters discharge ratio variation (Dra), coefficient of uniformity (CU), statistical uniformity coefficient (Us), emitter discharge variation (qvar), clogging substance within emitters (CSE) and clogging substance within laterals (CSL) were linearly correlated with anti-clogging performance parameters (Dra, CU, Us, qvar, CSE, CSL) of 100 kPa. Therefore, basing the Dra, CU, Us, qvar, CSE and CSL at 100 kPa, a simple linear model was established to predict anti-clogging performance parameters at the different pressures e.g. 20, 40, 60 and 80 kPa. This study could provide technical support for the application and promotion of the drip irrigation system with high-sediment water.

ОПТИМАЛЬНЫЙ СИНТЕЗ ПРИВОДНЫХ ШАРНИРНЫХ СОЕДИНЕНИЙ ГИДРАВЛИЧЕСКИХ МАНИПУЛЯЦИОННЫХ СИСТЕМ МОБИЛЬНЫХ КРАНОВ

Рассмотрены конструкция, особенности работы и методика оптимального проектирования приводного шарнирного соединения, предложенного в качестве альтернативного конструктивного варианта шарнирного соединения смежных звеньев гидравлических манипуляционных систем мобильных стреловых кранов-манипуляторов. Конструкция устройства позволяет совместить две функции: обеспечить постоянную неразрывную кинематическую связь между смежными звеньями манипуляционной системы путем создания цилиндрического шарнира для выполнения возвратно-поворотного относительного движения смежных звеньев и сформировать встроенный поворотный гидродвигатель шиберного типа. Разработана математическая модель, сформулирована и решена задача оптимального синтеза приводного шарнирного соединения на основе минимизации массы устройства при соблюдении нелинейной системы конструкторских, монтажных, силовых, прочностных и кинематических ограничений. Анализ результатов выполненных оптимизационных расчетов показал, что масса оптимального варианта устройства возрастает с ростом преодолеваемого момента от перемещаемого груза и снижается с увеличением числа камер шарнирного соединения. Рабочее давление гидросистемы не оказывает практического влияния на оптимальную массу, что позволяет использовать для обеспечения движения звеньев манипуляционной системы насосный агрегат меньшей мощности. Оптимальные значения основных конструктивных размеров приводного шарнирного соединения определяются как величиной эксплуатационной нагрузки, так и условиями монтажа устройства с учетом размеров поперечных сечений смежных звеньев манипуляционной системы. При проектировании манипуляционных систем приводные шарнирные соединения позволяют отказаться от выносных силовых гидродвигателей, исключить эксплуатационные отказы вследствие изнашивания и усталостного разрушения элементов шарниров, а также повысить энергоэффективность кранов-манипуляторов путем перевода гидросистемы на более низкие уровни рабочего давления при сохранении требуемых грузо-высотных характеристик.

Hybrid Fickian–Darcian flow model for high pressure impregnation of fluids into porous biomaterials

Pressure-driven fluid flow is an inevitable consequence which occurs during the high pressure processing of porous biological materials confined in a fluid phase. A hybrid numerical model was adopted to simulate the mass flow of fluids into an enclosed biological porous matrix under constant high hydrostatic pressure treatments. The numerical model was based on the finite element simulation of time-dependent Fickian mass transfer represented as saturation rate of fluid flow in the unsaturated media. The Kozeny–Carman model was used for correction of relative permeability because of the pressure-induced textural changes. As a case study, the proposed methodology was applied to simulate the high pressure impregnation of apple cubes by ascorbic acid solution (1% by mass). The proposed model demonstrated the existence of a low-pressure zone in the geometrical centre of the computational domain associated with the operating pressure level which provides a sufficient driving force for liquid migration. The numerical results were corroborated through implementing gravimetric and image processing experiments. Finally, a linear flow front rate of 0.03 cm s−1 was estimated along the porous matrix, and the analytical solutions to the Darcian model were used to determine the lumped permeability as a function of pressure difference at the impregnation flow front.

Characterization of Mechanical Properties and Residual Stress in API 5L X80 Steel Welded Joints

The use of high-strength and low-alloy steels, high design factors and increasingly stringent safety requirements have increased the operating pressure levels and, consequently, the need for further studies to avoid and prevent premature pipe failure. To evaluate the possibility of improving productivity in manual arc welding of this type of steel, this work characterizes the mechanical properties and residual stresses in API 5L X80 steel welded joints using the SMAW and FCAW processes. The residual stresses were analyzed using x-ray diffraction with the sin2 ψ method at the top and root of the welded joints in the longitudinal and transverse directions of the weld bead. The mechanical properties of the welded joints by both processes were characterized in terms of tensile strength, impact toughness and Vickers microhardness in the welded and shot peening conditions. A predominantly compressive residual stress was found, and shot peening increased the tensile strength and impact toughness in both welded joints.

Alternatives of integrated processes for coproduction of LNG and NGLs recovery

In this paper, integrated schemes for production of LNG and NGLs recovery are presented and DMR liquefaction cycle serves as a base process to which separation process of NGLs is integrated at. Main highlight of integration is a split of demethanizer into rectifying and stripping sections whereby light components of liquid stream from natural gas flashed throughout phase separator are stripped via stripping column while vapor stream is rectified into rectifier. To reach operating pressure of demethanizer requires to reduce pressure of flashed natural gas which gives an option of reusing the released power to recompress lean methane from NGLs recovery process. As for heat integration, rectifier is operated at low temperature and direct heat integration between both sections of demethanizer is not likely; thus heat of the final products in NGLs recovery train is retrieved by interreboiling stripping section. After all integration, mixed refrigerant cycle is optimized for compression energy requirement by varying the refrigerant composition and operating pressure levels through knowledge-based optimization methodology. The integrated schemes minimize the overall energy requirements.

Design, construction, and preliminary results of a 250-kW organic Rankine cycle system

This study involved designing and constructing a 250-kW organic Rankine cycle system, consisting of a pump, preheater, evaporator, turbine, generator, condenser, as well as hot and cooling water circulation systems. Refrigerant R245fa was used as a working fluid. The design operating pressure levels of the preheater/evaporator and condenser was 1.265 MPa and 0.242 MPa, respectively. Under design conditions, the net power output was 243 kW and the system thermal efficiency was 9.5%. The preliminary experimental results under off-design conditions showed that the average net power output was 219.5 kW with a fluctuation of ±5.5 kW during prolonged operation. The maximal net power output and system thermal efficiency were 225 kW and 7.94%, respectively. Under this condition, the isentropic efficiency of the turbine was 63.7% with a rotational speed of 12 386 rpm, and the back-work ratio was 6.7%. In addition, the results of the dynamic testing demonstrated that the present system responded very rapidly as the heat source temperature changed. The experimental results also demonstrated that the system thermal efficiency and net power output increased linearly with an increasing heat source temperature. However, the effect of the heat source temperature on the turbine efficiency was not obvious.

PERFORMANCE OF FILTERS USED IN MODERN IRRIGATION NETWORK

Dual Irrigation Filter, as new integral filter, was developed, it has the ability to filter water regardless the particles specific gravity and without fear of screen clogging. The new filter is locally manufactured with combination between the sand separator and screen filter. The dual irrigation filter was developed to have dual of application; as irrigation filters with a closed sedimentation tank, and as an alternative for the sedimentation pool with opened underflow to the atmosphere. With opened and closed underflow apex, the dual irrigation filter was tested to estimate and evaluate the filtration efficiency and outflow rate under different operation parameters. Three levels of feed suspension concentration (600, 1500 and 2400 ppm) prepared by using a coarse sandy loam soil sample, two levels of different operating pressure (2.5 and 4.0 psi) and three levels of the screen filtration degree (100, 150 and 200 mesh), were selected for the test. With opened underflow apex, the highest mean of the filtration efficiency for the feed suspension of 600, 1500, 2400 ppm were 0.46205, 0.42126 and 0.38719, respectively, for the different operating pressure of 4.0 and 2.5 psi were 0.46205 and 0.44135, respectively, and for the screen filtration degree of 100, 150 and 200 mesh were 0.42855, 0.45515 and 0.46205, respectively, whereas, with closed underflow apex, the highest value of the filtration efficiency for the feed suspension of 600, 1500, 2400 ppm were 0.4479, 0.3985 and 0.3601, respectively, for the different operating pressure of 4.0 and 2.5 psi were 0.4479 and 0.4258, respectively, and for the screen filtration degree of 100, 150 and 200 mesh were 0.4100, 0.4367 and 0.4479 respectively. The outflow rate was just statistically correlated to the different operating pressure; and in the case of opened apex, the highest mean of the outflow rate for the different operating pressure of 4.0 and 2.5 psi were 8.678 and 4.977 m3/h, respectively, whereas, in the case of closed apex, they were 9.345and 5.613m3/h, respectively.

Energy saving opportunities in integrated NGL/LNG schemes exploiting: Thermal-coupling common-utilities and process knowledge

Novel integrated and optimization schemes for natural gas (NG) liquid recovery and liquefaction step are presented. The liquefaction of NG was carried out using the newly developed KSMR liquefaction cycle while the separation of NG liquids was performed using energy efficient thermally coupled distillation schemes. The main highlight of integration are, (i) feed splitting to provide reboiler duty in the methane scrubber, (ii) common refrigeration utilities required all over the plant; and (iii) flexibility of integrated plant for easy transition between ethane recovery or ethane rejection. These integration steps minimize the overall plant-specific power requirements and the duplication of processing equipment. After successful integration, the MR cycle was optimized for the compression energy requirement by varying the refrigerant composition and operating pressure levels with the aid of an in-house established knowledge-based optimization (KBO) methodology. The KBO approach is robust in application and gives consistent results. Compared to the base case, 9% improvement in plant compression energy requirement was obtained.

Optimum number of stages and intermediate pressure level for highest exergy efficiency in large helium liquefiers

In this paper, an attempt has been made to study the influence of different design and operating parameters on the performance of large scale helium liquefiers through the concept of pre-cooling stages. Through exergy analysis and simulation with Aspen HYSYS® 7.0, it has been demonstrated that four refrigeration stages is the best option for large helium liquefiers when all expanders operate between the entire available pressure differences. However, when some of the expanders are operated at intermediate pressure, a more number of stages gives a higher thermodynamic efficiency. Relationship between the number of stages, effective heat exchanger area and operating pressure levels of expanders, which could optimally be employed for least specific power consumption has been established through exergy analysis. Optimum number of stages, intermediate pressure and corresponding plant efficiency are, however to a large extent, dictated by the prevailing compressor efficiency. The intermediate pressure that gives the maximum exergy efficiency for the plant increases from 0.2 MPa with constant compressor efficiency to 0.35 MPa when considering two-staged compressor where pressure ratio influences compressor efficiency. Results presented may be useful in designing energy-efficient helium liquefiers of large capacity.

Time series analysis of hydrologic data obtained from a man-made undersea LPG cavern

Characteristics of hydrologic time series data obtained from an undersea LPG (butane and propane) storage cavern were analyzed in time and frequency domains. The analyzed data included cavern seepage rates, cavern operating pressures (gas pressures), water levels of monitoring boreholes in and around the cavern, surrounding tidal levels and site precipitations of long and short periods. The seepage rates showed annual periodic behaviors, which were related to seasonal LPG use pattern. The gas operating pressures were the most dominant controlling factor for the seepage rates. The tidal level revealed an apparent negative cross-correlation with the seepage rate. However, the long-term close correlation between the tidal level and the seepage rate might be attributed to coincident concurrence of the seasonal LPG use and the tidal level variation. The water levels of the monitoring boreholes showed significantly different auto-correlations and spectral densities with locations. The water levels near the butane cavern exhibited high memory effects and low cross-correlations with the tidal level while those of the propane cavern exhibited short memory effects and relatively higher cross-correlations with the tidal level. The difference in all the hydrologic responses (seepage and water level) of the two caverns to the outer stresses such as precipitation, gas operating pressure and tidal level, can be mostly related to the hydrogeologic stratification surrounding the caverns. The low permeable silty clay layer is very thick above the butane cavern while it is very thin about the propane, such that greater hydraulic connection to the overlying sea could be expected.

Comparison of low temperature mixed refrigerant cycles for separation systems

Numerous mixed refrigerant cycles (MRCs) were developed in the past several decades in different applications. In this paper, two sets of low temperature MRCs are developed and simulated for a typical olefin plant utilizing a mixture of methane, ethane, propane and nitrogen as cycle working fluid to replace the pure ethylene refrigeration cycle that is used in conjunction with propylene refrigeration cycle in conventional plants. The key parameters of the cycles including mixture compositions and operating pressure levels are optimized to meet the objective of minimum shaftwork in compressor. The results show that different cycle configuration has different optimal mixture composition and low and high operating pressures. The results of exergy analysis reveal that the main location of the exergy loss in the cycles is the heat exchanger system. Also, the Carnot factor versus heat flow diagram is provided to identify the distribution of inefficiencies in the heat exchangers for each cycle. The simulation results show that MRCs can improve the thermodynamic performance of refrigeration system using the optimal working fluid mixture composition, optimal high and low operating pressures and optimal arrangement of the cycle components. Copyright © 2008 John Wiley & Sons, Ltd.