Values Of Pressure Difference Research Articles

Differential manometer with reflective optical sensor

For the purpose of the identification and quantification of the plasma effect on gas flow rate in atmospheric pressure discharges there was a strong need for differential manometer for fine and precise measurements which is indifferent on the influence of the charged particles. Therefore, a differential manometer with a completely free membrane has been constructed. Manometer is based on the use of reflective sensor CNY70. The basic request, undisturbed measurement of small value of differential pressure, up to 10 Pa, is realized with satisfying sensitivity and accuracy. Furthermore, different ranges of differential pressures measurable with the constructed instrument have been achieved by use of membranes made of different materials and with different thicknesses. The best linearity showed membranes made of copper and rubber. By means of five different membranes, the complete range of pressures from 1 Pa to 100 kPa is covered with substantial overlap.

Prediction of internal carotid artery aneurysm recurrence by pressure difference at the coil mass surface

PurposeA previous study on computational fluid dynamics reported that a high pressure difference (PD) at the surface of a coil mass is a strong predictor of aneurysm recurrence after coil embolization. PD was calculated using a virtual post-coiling model (VM), created by manually cutting the aneurysm by the flat plane from an anatomic model created with pre-coil embolization data; however, its credibility has not been fully evaluated. This study aims to clarify whether PD values calculated using the post-coiling model, which reflects the actual coil plane, are a strong predictor of aneurysm recurrence.MethodsFifty internal carotid artery aneurysms treated with endovascular coil embolization were analyzed (7 recanalized, 43 stable). We created and subjected two post-coiling models, namely, VM and the real post-coiling model (RM), constructed from the post-coil embolization data. The relationship between PD and aneurysm recurrence was examined using these models. PD and its constituent three parameters were compared between VM and RM.ResultsPD values calculated using RM showed significantly higher aneurysm recurrence in recurrence group than stable group (p < 0.001), and multivariate analysis showed that PD in RM (p = 0.02; odds ratio, 36.24) was significantly associated with aneurysm recurrence. The receiver operating characteristic analysis revealed that PD values accurately predicted aneurysm recurrence (area under the curve, 0.977; cutoff value, 3.08; sensitivity, 100%; specificity, 97.7%). All four parameters showed a significant correlation with VM and RM (p < 0.001).ConclusionUse of PD to predict recurrence after coil embolization can be clinically relevant.

Performance of surfactant blend formulations for controlling gas mobility and foam propagation under reservoir conditions

The use of surfactant is one of the possible solutions to minimize the mobility of gases and improve the sweep efficiency, but the main problem with this process is its stability in the presence of injection water and crude oil under reservoir conditions. In this study, the three types of surfactant anionic, nonionic and amphoteric are examined in the presence of brine salinity at 96 °C and 1400 psia. To access the potential blended surfactant solutions as gas mobility control, laboratory test including aqueous stability, interfacial tension (IFT) and mobility reduction factor (MRF) were performed. The purpose of MRF is to evaluate the blocking effect of selected optimum surfactant solutions. Based on experimental results, no precipitation was observed by testing the surfactant solutions at reservoir temperature of 96 °C. The tested surfactant solutions reduced the IFT between crude oil and brine. The effectiveness and strength of surfactant solutions without crude oil under reservoir conditions were evaluated. A high value of differential pressure demonstrates that the strong foam was generated inside a core that resulted in delay in breakthrough time and reduction in the gas mobility. High mobility reduction factor result was measured by the solution of blended surfactant 0.6%AOS + 0.6%CA406H. Mobility reduction factor of other tested surfactant solutions was found low due to less generated foam by using CO2 under reservoir conditions. The result of these tested surfactant solutions can provide the better understanding of the mechanisms behind generated foam stability and guideline for their implementation as gas mobility control during the process of surfactant alternating gas injection.

Use of pressure signal analysis to characterise counter-current two-phase flow regimes in annuli

We characterised different flow regimes and their transition through an objective and quantitative assessment of flow behaviour by applying four signal process techniques (autocorrelation, power spectral density (PSD), Shannon entropy, and permutation entropy) onto pressure signals of counter-current two-phase flows in a 170mm×70mm concentric vertical annulus. Differential pressure values were measured using a 100Hz sampling rate with 30 second sample sizes in 147 experiments at superficial gas velocities within 0.043–5.387m/s and superficial liquid velocities within 0.016–0.093m/s. Video images were also captured during all flow experiments. Using the signal analysis techniques, we could overcome the difficulties and uncertainties that accompany subjective visual observations in the characterisation and classification of flow regimes. Also, the signal analyses of the pressure signals allowed us to provide insights into the mechanisms responsible for formation of each flow regimes and their transitions.

Reynolds number effect on compressible cylindrical cavity flow

Presence of a cavity changes the mean and fluctuating pressure distributions inside and near the cavity. For cylindrical cavity flow, the diameter-to-depth ratio is the dominant factor. In this study, flow is naturally developed along a flat plate with two different lengths, resulting in different incoming boundary layer thicknesses ahead of the cavity. The effect of Reynolds number based on incoming boundary layer thickness on characteristics of mean and fluctuating pressure distributions is addressed. Pressure sensitive paint was also used to visualize the mean surface pressure patterns. The effect of Reynolds number on the classification of compressible cylindrical cavity flow and self-sustained oscillating frequency is not significant. An increase in Reynolds number results in a reduction in the value of differential pressure or momentum flux near the rear edge.

Influence of Pipeline Operating Pressure on Value Setting of Automatic Control Valves at Different Pressure Drop Rates

When a natural gas pipeline ruptures, the adjacent upstream and downstream automatic control valves (ACV) should close quickly to prevent leakage or explosion. The differential pressure set point (DPS) at each valve location is the main criteria for value setting in ACV actions. If the DPS is not properly adjusted, the ACV may mistakenly close or it may not take any actions at a proper time. In this study, the effect of characteristic parameters such as pipeline operational pressure (POP) and pipeline pressure drop rate (ROD) due to rupture or a major leak was experimentally investigated on DPS. 25 different conditions with the double set of the mentioned typical characteristic parameters were chosen. In each condition, the differential pressure (DP) was measured over a period of 180 s by statistically analyzing the experimental results, so 25 maximum DP values (DPSs) were obtained. The DPS rises by an increase in ROD or a decrease in POP. Because of using nitrogen gas instead of natural gas for safety reasons and the uncertainties, the DPS results can be practically applied by adding a safety factor of 15%. Finally, the diagram of DPS with respect to ROD and that of non-dimensional DPS (DOP) versus non-dimensional ROD (RTP) were provided for different POP’s.

Heat Transfer Improvements in a Solid Fueled Boiler and Modeling of Pressure Differences by Artificial Neural Network

Bu çalışmada, duman borularının çapı 42 mm, baca çapı 230 mm ve su giriş ve çıkış çapları 65 mm olan 125.000 kcal/h ısı kapasiteli katı yakıtlı kazanda, 4 farklı tipte şerit türbülatör kullanılarak ısı transferinin iyileştirilmesi incelenmiştir. Kazandaki duman borularının tümüne yerleştirilen türbülatörlerle deneyler yapılmıştır. İlk olarak içerisine türbülatör yerleştirmeden deneyler yapılmıştır. İkinci adımda ise duman boruları içerisine türbülatörler yerleştirerek her tip için ayrı ayrı deneyler yapılmış ve ısı transferi hesaplanmıştır. Deneylerde fan debisi damper yardımıyla değiştirilerek Reynolds sayısı 1800 ile 2800 arasındaki değerlerde hesaplamalar yapılmıştır. Isı transferi iyileştirmesi için yapılan türbülatörlü deneyler, türbülatörsüz deneylere göre ısı transferinde en az % 44, en fazla % 82 oranında artış sağlanmıştır. Hesaplamalar sonucu elde edilen basınç farkı değerleri için yapay sinir ağı (YSA) kullanılarak tahminsel bir model elde edilmiştir. Elde edilen modelin hata analizleri yapılmış ve basınç değerlerini başarılı bir şekilde tahmin ettiği gösterilmiştir.

The Impact of Air Pressure Conditions on the Performance of Single Room Ventilation Units in Multi-Story Buildings

Single room ventilation units with heat recovery is one of the ventilation solutions that have been used in renovated residential buildings in Estonia. In multi-story buildings, especially in a cold climate, the performance of units is affected by the stack effect and wind-induced pressure differences between the indoor and the outdoor air. Renovation of the building envelope improves air tightness and the impact of the pressure conditions is amplified. The aim of this study was to predict the air pressure conditions in typical renovated multi-story apartment buildings and to analyze the performance of room-based ventilation units. The field measurements of air pressure differences in a renovated 5-story apartment building during the winter season were conducted and the results were used to simulate whole-year pressure conditions with IDA-ICE software. Performance of two types of single room ventilation units were measured in the laboratory and their suitability as ventilation renovation solutions was assessed with simulations. The results show that one unit stopped its operation as a heat recovery ventilator. In order to ensure satisfactory indoor climate and heat recovery using wall mounted units the pressure difference values were determined and proposed for correct design.

Investigation of Heat Transfer Surfaces for Space Power Systems

Heat exchangers used in the composition of large-capacity energy conversion systems for space applications must be able to operate at high temperatures (above 1000 K) and at high (several MPa) values of pressure difference between the “hot” and “cold” heat carrier/coolant channels. This is why especially demanding strength and stiffness requirements are posed to the heat-transfer matrix of these devices, a circumstance that precludes almost completely the use of well-known compact and light plate-and-fin devices with 50–100-μm-thick foil fins. The article presents the results from experimental investigations into the thermal and hydraulic characteristics of alternative versions of heat-transfer elements involving the use of different heat transfer enhancement methods. Experimental investigations of heat transfer and hydrodynamics were carried out for three types of heat-transfer surfaces: a tubular one composed of small-diameter (3 mm) thin-walled tubes deformed over the cross-section perimeter and length (twisted tubes), a plate one finned with pins having a diamond-shaped cross section (2 × 2 mm in cross section and 4 mm in height), and a plate one composed of thin-walled 0.2-mm-thick plates with the surface formed by oppositely directed truncated cones with saddle-like bridges (a biconvex stamped plate). After processing and analyzing the experimental data obtained for these heat-transfer surfaces, dimensionless dependences for the Nusselt number and the pressure-drop coefficient on the Reynolds number were constructed. The dimensionless formulas obtained for twisted tubes and for the pin-finned surface are compared with the well-known correlations. It is shown that the use of twisted tubes instead of round ones results in improving the heat transfer intensity by more than 20% with the hydrodynamic indicators worsened by 50%. The use of the pin-finned plate surface improves the heat transfer intensity by more than a factor of two as compared with using a staggered tube bundle.

Experimental values for adjusting an automatic control valve in gas pipeline transportation

When a natural gas pipeline ruptures, the adjacent automatic line control valves (ALCVs) should close quickly to prevent leakage or explosion. The differential pressure set point (DPS) at each valve location is the main criteria for value setting in ALCV action. If the DPS is not properly adjusted, the ALCV may mistakenly close or it may not take any action at proper time. This study focused on the DPS values prediction for setting ALCV installed on a gas pipeline with 1mm orifice diameter. The effect of characteristic parameters such as pipeline operational pressure (POP) and pipeline pressure drop rate (ROD) due to rupture or major leak was experimentally investigated on DPS. Twenty-five different conditions with double set of typical mentioned characteristic parameters were chosen. For each condition, the differential pressure (DP) was measured over 180 seconds by analyzing the experimental values. Therefore, 25 maximum DP values (DPSs) were obtained. The DPS increases by increase in ROD or decreasing POP parameters. Because of using nitrogen gas instead of natural gas due to safety reasons, the DPS results can be practically applied by adding a safety factor of 15%. The diagram of DPS with respect to ROD and non-dimensional DPS (DOP) versus non-dimensional ROD (RTP) was provided for different POPs.

An experimental study of the effective parameters on automatic line-break control valves action in natural gas pipelines

The automatic line-break control valve (LBV) is a robust self-contained pipeline monitoring system which is widely used to prevent gas releasing upon rupture or large leakage event in the oil and gas pipelines. The differential pressure set point (DPS) at each valve location is the main criteria for value setting in LBV action. If the DPS is not properly adjusted, the LBV may mistakenly close or it may not take any action at proper time. In this study, the effect of characteristic parameters such as orifice diameter (OD), pipeline operational pressure (POP) and pipeline pressure drop rate (ROD) due to rupture or major leak was experimentally investigated on DPS. 100 different conditions with triple set of typical mentioned characteristic parameters were chosen. For each condition, the differential pressure (DP) was measured over 180 s by statistically analyzing the experimental results. Therefore, 100 maximum DP values (DPSs) were obtained. The attainable time to DPS depends only on OD and is independent of the POP and ROD and decreases by increasing the OD. The DPS increases by increase in ROD or decreasing OD or POP parameters. Because of using nitrogen gas instead of natural gas due to safety reasons and the uncertainties, the DPS results can be practically applied by adding a safety factor of 10%–15%. Finally, the diagram of DPS with respect to ROD was provided for different POPs and ODs. The diagram can be used as a basis for designing and regulating of LBVs installed on gas transportation pipelines.

The Development of the Drilling Fluid Rheological Meter

A set of on-line test equipment for drilling fluid rheological parameters is developed, which can realize real-time on-line monitoring. Design method: first of all let the drilling fluid to flow through the same shape and dimension of the section, in turn, change, will produce different velocity of different section, between all the pipe sections using pressure sensor real-time acquisition of differential pressure value, and the differential pressure and flow rate signals to the data acquisition system for transformation, such as display and processing, and then according to the rheology model to calculate the rheological parameters of drilling fluid to be measured. The final measurement results will be compared with the results of rotary viscometer measurement, shows the practicability and feasibility of the device have zero since the calibration function, measuring range is 5-150 mpa’s, measurement accuracy can satisfy the requirement of 5%.

Determining the Presence of Thin-Walled Regions at High-Pressure Areas in Unruptured Cerebral Aneurysms by Using Computational Fluid Dynamics.

Thin-walled regions (TWRs) of cerebral aneurysms are at high risk of rupture, and careful attention should be paid during surgical procedures. Despite this, an optimal imaging technique to estimate TWRs has not been established. Previously, pressure elevation at TWRs was reported with computational fluid dynamics (CFD) but not fully evaluated. To investigate the possibility of predicting aneurysmal TWRs at high-pressure areas with CFD. Fifty unruptured middle cerebral artery aneurysms were analyzed. Spatial and temporal maximum pressure (Pmax) areas were determined with a fluid-flow formula under pulsatile blood flow conditions. Intraoperatively, TWRs of aneurysm domes were identified as reddish areas relative to the healthy normal middle cerebral arteries; 5 neurosurgeons evaluated and divided these regions according to Pmax area and TWR correspondence. Pressure difference (PD) was defined as the degree of pressure elevation on the aneurysmal wall at Pmax and was calculated by subtracting the average pressure from the Pmax and dividing by the dynamic pressure at the aneurysm inlet side for normalization. In 41 of the 50 cases (82.0%), the Pmax areas and TWRs corresponded. PD values were significantly higher in the correspondence group than in the noncorrespondence group (P = .008). A receiver-operating characteristic curve demonstrated that PD accurately predicted TWRs at Pmax areas (area under the curve, 0.764; 95% confidence interval, 0.574-0.955; cutoff value, 0.607; sensitivity, 66.7%; specificity, 82.9%). A high PD may be a key parameter for predicting TWRs in unruptured cerebral aneurysms. CFD, computational fluid dynamicsMCA, middle cerebral arteryPave, average pressurePD, pressure differencePmax, maximum pressureTWR, thin-walled regionWSS, wall shear stress.

Thermal behavior of supercritical fluids near the critical point

ABSTRACTIn this paper, a numerical study focusing on the thermal behavior of carbon dioxide within the supercritical thermodynamic region is performed. For that, the well-known Graetz problem, which considers the fluid flow between two parallel plates with a uniformly distributed heat flux on both walls and a specified pressure difference across the channel, is studied. The numerical solution is obtained by discretizing the energy equation within a two-dimensional rectangular domain using a finite-volume formulation and enforcing spatially variable thermophysical properties throughout the channel. The boundary conditions are selected such that the pressure and temperature of the working fluid are slightly above the critical point (Tc = 304.13 K and Pc = 7.34 MPa for carbon dioxide). The figure of merit used, the Nusselt number, is shown to be highly sensitive to changes in key thermodynamic properties, such as the specific heat. However, the results revealed that the specific heat could not be simply determined as a function of the local temperature and pressure. Instead, the specific heat must be corrected with an additional term, which depends on thermodynamic properties and the flow field – the modified specific heat is referred to as c*. The results obtained show that the agreement between the traditionally defined specific heat and c* is satisfactory up to pressure drops across the channel of roughly 10 kPa. For larger values of pressure difference, the Nusselt number is severely underestimated if the specific heat is not properly corrected.

Optimization of suspensions filtration with compressible cake

In this paper there is described filtering process for separating reaction mixture after enzymatic hydrolysis to process the chromium tanning waste. Filtration of this mixture is very complicated because it is case of mixture filtration with compressible cake. Successful process strongly depends on mathematical describing of filtration, calculating optimal values of pressure difference, specific resistant of filtration cake and temperature maintenance which is connected with viscosity change. The mathematic model of filtration with compressible cake we verified in laboratory conditions on special filtration device developed on our department.

Air Pressure Difference between Indoor and Outdoor or Staircase in Multi-family Buildings with Exhaust Ventilation System in Finland

Pressure differences between outdoors and indoors influence indoor environmental quality (IEQ) and building physics of the building envelope. This paper focuses on measurements of pressure difference values of about 152 apartments from 26 multi- family buildings in Finland. Measured data include pressure differences between indoor spaces and both outdoors and staircases before and after renovation. In buildings equipped with mechanical exhaust, the pressure differences between indoors and outdoors before renovation varied from +10,1 to -95,0Pa (average -7,8Pa), and between indoors and staircases from -3,5 to -6,0Pa (average -18,6Pa), being lower than -5Pa in 36% of the buildings. In naturally ventilated buildings, the pressure differences between indoors and outdoors were lower than -5Pa in 44% of the buildings. The average pressure differences after renovation in nine buildings equipped with mechanical exhaust were slightly higher (-19,1Pa against outdoor and -9,0Pa against staircase). A possible reason for higher negative pressure could be that the airtightness of building was improved by renovation, but the ventilation system was not balanced accordingly. Improving energy efficiency (EE) could effect on pressure difference either positively or negatively. Measured pressure difference between indoors and outdoors or staircase before and after renovation could be a possible indicator when assessing the impacts of improving EE on IEQ and occupant satisfaction.

Preparation and characterization of low temperature PTFE-Nafion composite membranes for hydrogen production

A simple method produces PTFE-Nafion membrane with ceramic tube as a support was used to study the separation of hydrogen gas. The membrane was made using the method of coating, wherein the liquid polymer, Nafion and PTFE material were alternately injected into the surface of the ceramic tube. This step was performed in order to form the membrane layers. Two layers of PTFE were used to sandwich the Nafion layer, providing the Nafion with stability up to 300 °C. In contrast to the palladium membranes which have to be carried out at a high temperature, the resulted membrane can be operated at a low temperature (below 100 °C) and is still stable in temperature up to 300 °C. Moreover, the PTFE-Nafion membrane can also be employed in a membrane reactor to produce hydrogen. The highest hydrogen permeation flux obtained from this membrane was 13.6 cm3 cm−2 s−1 at permselectivity of 3.2. Result showed that the hydrogen separation factor increased align with temperature rising. On the other hand, the hydrogen separation decreased in line with increasing value of pressure difference between permeate and retentate. This hydrogen separation phenomena revealed that the gas permeation in the membrane was dominated by Knudsen diffusion. The occurrence of Knudsen diffusion in the membrane concluded that the PTFE-Nafion membrane has an ability to separate H2 from N2, CO and CO2.

Free Surface of the Liquid-Gas Phase Separation as a Measuring Membrane of a Device for Measuring Small Hydrostatic Pressure Difference Values / Powierzchnia Swobodna Rozdziału Faz Ciecz-Gaz Jako Membrana Pomiarowa Urządzenia Do Pomiaru Małych Wartości Różnicy Ciśnienia Hydrostatycznego

Abstract To obtain a correct reading of fluid flow through a porous medium, it is necessary to know the pressure distribution. While in the case of large Reynolds numbers (turbulent flows) finding pressure measurement devices on the market is not a major problem, there are currently no available devices with sufficient accuracy for measurement of laminar flows (i.e. for Re numbers (Bear, 1988; Duckworth, 1983; Troskolański, 1957) in the range from 0.01 to 3). The reasons of this situation has been discussed in a previous articles (Broda &amp; Filipek, 2012, 2013). Therefore, most of the work on this issue relates to testing velocity distribution of the filter medium (Bear, 1988) or pressure distribution at high hydraulic gradient levels (Trzaska &amp; Broda, 1991, 2000; Trzaska et al., 2005). The so-called measurements of the lower limit of the applicability of Darcy’s law for liquid, as well as determining a threshold hydraulic gradient J0 (Bear, 1988) tend to cause especially great difficulty. Such measurements would be particularly important application in determining the infiltration of water into the mine workings, filtering through the foundations of buildings, etc. For several years, the authors (Broda &amp; Filipek, 2012, 2013) have been engaged in the development of methods and measuring instruments (patent applications: P.407 380 and P.407 381), which would allow for measurement of hydrostatic pressure (differences) below 1 Pa. In the course of research, a new concept of methodology for measuring low values of hydrostatic pressure differences was developed, which is the subject of this article. This article seeks to introduce a new concept of using the free surface of liquid-gas separation as the measuring membrane of a device used in measurement of small values of hydrostatic pressure. The focus is mainly on the possibility of building such a device - describing the technical difficulties that occurred during the execution of the idea. Consequently, less attention was paid to the broader considerations related to uncertainty of the proposed method’s measurements, due to the authors’ awareness that this is the first prototype of such a device and, on the basis of this experience, another one will be built and tested. The observations and numerical analysis of the image formed on the screen by the passage of a laser beam through the free surface of the liquid-gas separation show that at low values of pressure difference, the bubble acts as a membrane shifting in the direction of lower pressure, in such way that the displacement is proportional to the pressure difference at both ends of the bubble. The proprietary method of numerical data processing presented in this article, based on analysis of the intensity of color change in a frame moving along a selected line outside of visual changes in the image of the laser beam after passing through the test structure, provided a tool to create first mathematical models to describe the observed changes (2),(3). Presented in this article method of measuring the difference between the free surface levels in two containers, and hence the measurement of hydrostatic pressure difference provides a new tool for laboratory measurements in the fields of science, which were previously unattainable.

Improvement of a Gas Intake Device and a Gas Mixing Study in a Large‐Scale Vessel

AbstractGas mixing is a common process in chemical engineering. For actual industrial manufacturing of chemicals, most reactions commonly run in reactors or reaction vessels with large volumes (over 10 m3). In order to simulate a gas mixing process in a sealed reactor, and finally to improve the mixing effect between the gases, here the mixing process between methane and air in a reaction vessel with a volume of 10 m3 was studied via several approaches. Several specific evaluation indexes, including the mixing degree, the maximum concentration difference, and the mixing time, were obtained and recorded to evaluate the mixing effect on the gases. After a series of experiments targeting the determination of the size and pressure difference values of the gas intake device, the mixing effect between methane and air was finally optimized. The mixing degree was found to reach 0.97 within 1 h of monitoring, and the mixing time was decreased by 1700 % from the original situation.

The emissions of gases from abandoned mines: role of atmospheric pressure changes and air temperature on the surface

Intrinsic parameters influence abandoned mine gas emissions. Independent of the presence or not of noxious gas in mine voids, meteorological factors influenced directly the gas outflow or inflow. Measurement stations were installed in the exits located in abandoned mines of the iron Lorraine basin, the Lorraine and the north east France coal basins to enhance the gas flow behaviour. Closure methods of the mines and exits from the abandoned mines are quite different. For the first, shafts are associated with adits. Some of them are closed with bars to avoid people entrance into abandoned mine workings, but gas flow is enabled. For the second, there are essentially shafts which are secured. Some of them are equipped with a vent to enable outflow of the mine gas in specific conditions. Mine gas parameters were measured. Besides, external parameters like temperature and atmospheric pressure were monitored. Gas flow can be influenced mainly by the temperature difference between external atmosphere and mine workings (in iron mines, which can be considered as an open system) while atmospheric pressure influences gas flow in the coal mines, which can be considered as closed systems. Modelling has confirmed the differential pressure value measured that exceeds friction losses.