Change In Pressure Drop Research Articles

Blood Pressure Monitoring: A noble method for stepwise decision making in percutaneous mitral valvuloplasty

Background : To find out if systolic blood pressure changes during percutaneous Mitral comissurotomy (PMC) could be a reliable guide to staged decision making and evaluate stop point. Method: 102 patients with moderate to severe mitral stenosis were chosen for PMC with Inue technique. Echocardiographic and homodynamic criteria were used as references for decision making during procedure .Systolic blood pressure changes were also evaluated by a fluid filled system at the end of each balloon inflation and deflation. To reach optimal results balloon inflation was done only once in one case (0.98%),twice in16.66% and three times in 82.35% of cases .in every stage of balloon inflation, trans-mitral gradient was compared with changes in systolic blood pressure. Results: correlation between systolic blood pressure drop and trans-mitral gradient changes were analyzed with Pearson method and via regression formula. Relation between final mitral orifice area and systolic blood pressure was also analyzed with T test. Significant relation was found in every stage:R;0.63 in stage 1,R:0.823 in stage 2, R:673in stage 3 in regression formula.

A preliminary approach to modeling gas hydrate/ice deposition from dissolved water in a liquid condensate system

AbstractGas hydrate/ice deposition from a dissolved water phase in a liquid condensate system was modeled using a mass and energy balance. The same modeling parameters were used to model three flow loop experiments (1.89 and 2.83 L/min flow rate deposition tests and a 1.89 L/min dissociation test) with acceptable accuracy. Relative changes in both temperature and pressure drop were modeled using an ice deposit with a 67% void fraction. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Patient triggered ventilation

Intermittent Mandatory Ventilation (IMV) in neonates leads to respiratory asynchrony and inefficient gas exchange. This can result in increased incidence of air leaks, fluctuation in blood pressure and cerebral blood flow irregularities leading to intraventricular haemorrhage (IVH). Efforts have been made to synchronize the ventilator breath with baby's inspiration, i.e. Patient Triggered Ventilation (PTV). A good trigger sensor is the most critical part for PTV success. Various trigger sensors have been devised based on their ability to detect changes in neonate's abdominal wall movement, thoracic impedance, airway pressure and air flow volume drop. Sensors which can detect minute changes in airway flow volume are the most recent ones. They are able to synchronize ventilator breath with neonate's inspiration as well as expiration. Simultaneously, they are also able to measure and calculate the complex dynamic respiratory volumes like compliance, resistance, tidal volume and minute volume. Various newer modes of ventilation have been devised using these calculations to make the mechanical breaths more close to physiological breaths. Patient triggered ventilation has been found to decrease the duration of ventilation but it does not decrease the death rate, incidence of Broncho pulmoary dysplasia (BPD) or intraventricular hemorrhage (IVH) as compared to IMV.

P-411 Blood Pressure Monitoring: A Novel Method for Stepwise Decision Making in Percutaneous Mitral Valvuloplasty

Background : To find out if systolic blood pressure changes during percutaneous Mitral comissurotomy (PMC) could be a reliable guide to staged decision making and evaluate stop point. Method: 102 patients with moderate to severe mitral stenosis were chosen for PMC with Inue technique. Echocardiographic and homodynamic criteria were used as references for decision making during procedure .Systolic blood pressure changes were also evaluated by a fluid filled system at the end of each balloon inflation and deflation. To reach optimal results balloon inflation was done only once in one case (0.98%),twice in16.66% and three times in 82.35% of cases .in every stage of balloon inflation, trans-mitral gradient was compared with changes in systolic blood pressure. Results: correlation between systolic blood pressure drop and trans-mitral gradient changes were analyzed with Pearson method and via regression formula. Relation between final mitral orifice area and systolic blood pressure was also analyzed with T test. Significant relation was found in every stage:R;0.63 in stage 1,R:0.823 in stage 2, R:673in stage 3 in regression formula.

Multi-objective optimization of rotary regenerator using genetic algorithm

The rotary regenerator (heat wheel) is an important heat recovery equipment, which rotates between two cold and hot streams. The pressure drop and effectiveness of rotary regenerator are important parameters in optimal design of this equipment for industrial applications. For optimal design of such a system, it was thermally modeled using ɛ-NTU method to estimate its pressure drop and effectiveness. Frontal area, ratio of hot to cold frontal heat transfer area, matrix thickness, matrix rotational speed, matrix rod diameter and porosity were considered as design parameters. Then fast and elitist non-dominated sorting genetic algorithm (NSGA-II) method was applied to find the optimum values of design parameters. In the presented optimal design approach, the effectiveness and the total pressure drop are two objective functions. The results of optimal designs were a set of multiple optimum solutions, called ‘Pareto optimal solutions’. The sensitivity analysis of change in optimum effectiveness and pressure drop with change in design parameters of the regenerator was also performed and the results are reported.

Pressure drop and heat transfer of catalyzed diesel particulate filters due to changes in soot loading and flow rate

When soot particles are loaded in a diesel particulate filter, it causes increase in back pressure of the exhaust system. To minimize this pressure drop due to DPF, the filter needs to be regenerated after a certain amount of soot has been accumulated. It is crucial to estimate the correct amount of soot that has been accumulated by measuring the differential pressure. It is also important to understand changes in pressure drop due to flow rate variations of the exhaust gas, since the pressure drop would be influenced by the exhaust flow rate as well as the amount of soot. Furthermore, the heat transfer characteristics of the catalyzed diesel particulate filter (CDPF) are another major issue, as the filter is occasionally exposed to high temperature gas. This study presents the characteristics of pressure drop according to the variation of soot loading and the mass flow rate in CDPF. In addition, heat transfer characteristics in the filter was investigated when a high temperature gas flows into the CDPF. Tests were performed in several CDPF samples having varying amounts of catalyst coating. Experimental results indicate that rig-based experiments are useful in understanding the characteristics of pressure drop in the CDPF. In the cake filtration region, a pressure drop has a proportional relationship according to soot loading and mass flow rate. It was found that an increased catalyst coating may lead to enhanced convective heat transfer.

Exergy analysis of gas turbine trigeneration system for combined production of power heat and refrigeration

A conceptual trigeneration system is proposed based on the conventional gas turbine cycle for the high temperature heat addition while adopting the heat recovery steam generator for process heat and vapor absorption refrigeration for the cold production. Combined first and second law approach is applied and computational analysis is performed to investigate the effects of overall pressure ratio, turbine inlet temperature, pressure drop in combustor and heat recovery steam generator, and evaporator temperature on the exergy destruction in each component, first law efficiency, electrical to thermal energy ratio, and second law efficiency of the system. Thermodynamic analysis indicates that exergy destruction in combustion chamber and HRSG is significantly affected by the pressure ratio and turbine inlet temperature, and not at all affected by pressure drop and evaporator temperature. The process heat pressure and evaporator temperature causes significant exergy destruction in various components of vapor absorption refrigeration cycle and HRSG. It also indicates that maximum exergy is destroyed during the combustion and steam generation process; which represents over 80% of the total exergy destruction in the overall system. The first law efficiency, electrical to thermal energy ratio and second law efficiency of the trigeneration, cogeneration, and gas turbine cycle significantly varies with the change in overall pressure ratio and turbine inlet temperature, but the change in pressure drop, process heat pressure, and evaporator temperature shows small variations in these parameters. Decision makers should find the methodology contained in this paper useful in the comparison and selection of advanced heat recovery systems.

Steady flow of ionic liquid through a cylindrical microfluidic contraction–expansion pipe: Electroviscous effects and pressure drop

Electroviscous effects in steady, pressure-driven flow of a symmetric 1:1 electrolyte in a cylindrical microfluidic 4:1:4 contraction–expansion at low Reynolds number are investigated numerically by solving the field equations using a finite volume method. Predicted profiles of electrical potential, charge distribution, pressure drop and apparent viscosity are qualitatively similar to those for the slit-like contraction–expansion studied previously by the authors. However, the changes in electrical potential and pressure drop along the channel are greater than those for a corresponding slit-like geometry. The apparent viscosity is lower in the cylindrical contraction–expansion than it is in the equivalent slit-like geometry, whereas the converse is found for uniform channels except when the electrical double layers (EDLs) overlap. As for the slit-like case, a simple model is developed to calculate the pressure drop, and hence the apparent viscosity, by adding the pressure drops over the inlet, outlet and contracted sections of the channel (based on the fully developed flow in a uniform pipe), and an extra pressure drop due to contraction–expansion using the low Reynolds number analytical solution for a circular orifice. For the parameter range considered, the predictions of the simple model overestimate the apparent viscosity by up to 5 – 12 % compared with that obtained by a finite volume numerical solution. The differences become smaller when the thickness of the EDL or the surface charge density are reduced.

A hybrid method of turbulent flow modelling in packings of complex geometry

In this work, experimental investigations and computational simulations were combined into a hybrid method of complex phenomena modelling. In particular, the thermo-anemometric technique and the multi-scale methodology of modelling were applied to investigate air turbulent flow within a rectangular container filled with spheres in cubic arrangement and different baffles alternatively inserted between the spheres. The model systems formed the complex geometric structures where three length scales were distinguished. Hence, the local fluctuations of air velocity were examined in the micro-scale determined by the size of the anemometric probe. The interstitial flow distributions, in turn, were investigated in the cell scale related to the sphere diameter. At last, the pressure drop changes caused by the superficial flow distributions were analysed in the apparatus scale. In each case, the particular experimental data were approximated by numerical modelling. However, when the information exchange between the complementary models was arranged, the significance of the flow mechanisms dominating in particular length scales could be confirmed in relation to all the experimental data determined in this work. In recapitulation, it was indicated how experimental and numerical investigations can be effectively combined in searching for a “profitable” anisotropy of the packing resistance to flow.

Pressure Drop EVOLution of a Medium-Performance Fibrous Filter during Loading of Mist Aerosol Particles

Collection characteristics of mist aerosol particles by a medium-performance fibrous filter was studied by analyzing the effect of filtration velocity, numbers of filter, types of liquid with different physical properties (palm oil and propylene glycol) during the initial filtration period and the saturation behavior. The results show that the pressure drop evolutions during clogging increases when the filtration velocity increases because at high filtration velocity, the aerosol particles deposit on the collecting surface rapidly. Furthermore, the change in pressure drop increases with increasing numbers of filter. Particle size, concentration, viscosity and surface tension of the liquids have an influence on clogging. The deposition of palm oil aerosol particles is only made up of droplets deposited around the fibers while in the case of propylene glycol the droplets deposited around the fiber join to form bridges and liquid films on the surface of the filter so that the fibrous filter that is exposed to propylene glycol aerosol has a higher pressure drop. The result of saturation behavior study shows that the saturation pressure drop from the lower initial velocity is greater than that from the higher initial velocity. The retained mass on the filter sheet saturated with palm oil after the pressure drop is constant is higher than in the case of propylene glycol. Palm oil is more viscous than propylene glycol so that palm oil cannot re-entrain easily.

The effect of mechanical vibration on gas fluidization of a fine aeratable powder

Fluidization behaviour of a fine aeratable FCC powder assisted by mechanical vibration was studied in a 85 mm i.d. transparent column. The investigated parameters of vibration were the peak acceleration value ( a/ g = 0.5, 1 and 2) and the frequency (between 7 and 200 Hz). The most significant variations obtained by changing these parameters regard the voidage of the fixed bed, the effects of aeration on bed expansion and fluidization, the maximum bed expansion and the onset of bubbling conditions. The typical fluidization curve in presence of mechanical vibration is characterized with the introduction of key fluidization velocities: a minimum bed expansion velocity, a minimum velocity for fluid dynamic suspension, the minimum bubbling velocity and a minimum velocity for stable bubbling. The possibility to apply the Ergun equation under gas fluidization assisted by vibration was also verified. Differential pressure drops at different heights inside the bed were used to investigate on the effects of vibrations on the gas fluidized bed. Changes of differential pressure drop along the bed were interpreted in the light of some internal bed structure.

Load-Wash Testing of Regenerable Sintered Metal and Ceramic Membrane Filter Media

Sintered metal and ceramic membrane filtration media have a broad range of applicability due to their mechanical strength, chemical resistance, and their ability to withstand conditions of excessive heat and moisture. Additionally, these media can be cleaned with back pulses of liquid or air. However, these filters are sufficiently more expensive than traditional media, and must last significantly longer in order to be cost effective. Thus, it is necessary to confirm that these filter media maintain efficiency after repeated cleaning. A series of tests has been conducted using ceramic membrane, sintered metal fiber, and powdered sintered metal filter media supplied from three manufacturers to evaluate their performance after repeated loading and washing cycles. The media were loaded to approximately twice their initial differential pressures with a water-insoluble, iron-rich aerosol challenge, and regenerated with a weak acid solution and water. Media were evaluated for pressure drop and filter efficiency changes from one cleaning cycle to the next. Microscopic examination of filter media was also conducted to determine the extent to which particle residues remain after cleaning. Filter efficiencies on the order of 90 to 98% were typical, and the most penetrating particle size was observed to be on the order of 100 nm. The media demonstrated the ability to be effectively cleaned with minimal performance degradation. Although filter efficiencies are reported, the reader should keep in mind that the focus of this study was to evaluate filter media performance after a series of load/wash cycles, and is not intended to be a filter efficiency study.

Innovation in sodium borohydride production process from borosilicate glass with sodium under hydrogen atmosphere: “high pressure process”

This paper presents a new process for producing sodium borohydride ( NaBH 4 ) , which can be used as a hydrogen storage medium. The process is based on the conversion reaction of borosilicate glass at temperatures between about 400 and 500 ∘ C under high hydrogen pressure of 22 atm . For this purpose, borax ( Na 2 B 4 O 7 ) is sintered with quartz powder ( SiO 2 ) to obtain borosilicate glass then heated with metallic sodium (Na) under high hydrogen pressure. Furthermore, a study of the hydrogenation characteristics of borosilicate glass has been made using change in hydrogen pressure drop as function of reaction time in the process. It is concluded that the required hydrogenation time is 70 min at 475 ∘ C under 22 atm of hydrogen pressure for production of NaBH 4 with excellent yield.

Streaming potential generated by two-phase flow in a capillary

The streaming potential generated by pressure-driven two-phase flow in a circular capillary differs from that generated by single-phase flow. Three model problems are considered, in which the dispersed phase consists of either (i) a rigid spherical particle (possibly charged), (ii) an uncharged spherical bubble, and (iii) a long, uncharged Bretherton bubble. In all three cases, the particle or bubble is assumed to lie on the center line of the capillary tube, so that the problem is axisymmetric, and is assumed to be of almost the same diameter as the internal diameter of the capillary, so that lubrication theory can be used. The electrical potentials on the surface of the particle and on the walls of the capillary are ζp and ζc, respectively, and the Debye length is assumed much smaller than the gap between the particle and the walls of the capillary. If the flow rate is held constant, the presence of the rigid particle increases the pressure drop between the ends of the capillary, and also changes the streaming potential by an amount proportional to ζc−ζp. This change in potential will in general be small compared to the total streaming potential developed between the two ends of a long capillary. However, if the capillary is filled with a large number of rigid particles, not only will the changes in pressure drop and streaming potential between the two ends of the capillary be large, but there will be a significant change in the coefficient of proportionality between pressure drop and streaming potential. The presence of an uncharged spherical bubble or Bretherton bubble changes the pressure drop between the ends of the capillary (for a given flow rate) but does not change the linear relation between pressure drop and streaming potential. However, the linear relation between flow rate and streaming potential is modified for the spherical bubble, and becomes nonlinear when a Bretherton bubble is present.

Data envelopment analysis for assessing optimal operation of an immersed membrane bioreactor equipped with a draft tube for domestic wastewater reclamation

Membrane fouling can be minimized by air lifting that plays a key role in cake removal from membrane surface. This study presents the results of tests that were carried out at Kiryat Sde-Boker, Israel, and focuses on the influence of hydrodynamic conditions on membrane fouling in a pilot-scale Immersed Membrane Bio-Reactor (IMBR) using a hollow fiber membrane module of ZW-10 (Zenon Environmental, Canada) under ambient conditions. In this system, the cross-flow velocities across the membrane surface were induced by a cylindrical draft-tube. The relationship between cross-flow velocity and aeration strength and the influence of the cross-flow on fouling rate (under various hydrodynamic conditions) were investigated using Data Envelopment Analysis (DEA). According to DEA, Technical Efficiency (TE) is defined as the ratio between outputs and inputs of the system [in this case the inputs are: feed temperature and trans-membrane pressure and the outputs are: normalized flux and fouling rate (change of membrane pressure drop with time)]. The developed DEA model for 2# draft tube, Ø = 235 mm allows further modification by changing the inputoutput variables and analyzing a broad pattern of possibilities. Data normalization of the field results and implementing the DEA approach with reference to the technical efficiency is for that reason useful to characterize performance changes for data classification and detecting deviations from expected behavior of the system.

Effect of the bottom-contracted and edge-sloped vent-pipe on the cyclone separator performance

Abstract The influence of the bottom-contracted and edge-sloped vent-pipe on the separation efficiency and pressure drop of a cyclone separator under different vent-pipe insert depth and different orientation of the sloped edge were studied in a visual cold circulating fluidized bed (CFB) experimental setup according to a commercial 100 MW CFB boiler with a scale of 20:1. And the correlative results were also compared with the traditional linear-pipe-shaped cyclone separator. Results indicate that the cyclone inlet stream velocity has a strong influence on the separation efficiency and pressure drop, and the results are similar to that of the conventional cyclone. Namely, both separation efficiency and pressure drop increase with increasing cyclone inlet stream velocity. The separation efficiency of the modified cyclone separator increases firstly and then decreases with the increasing of the vent-pipe insert depth. However, there is not a very clear rule of the effect of vent-pipe insert depth on the pressure drop for modified cyclone separator. Both the separating efficiency and the pressure drop change with the orientation of the sloped edge, and they have the same rule of change, the maximum at 90° and the minimum at 270°. Due to the configuration of the bottom-contracted and edge-sloped vent-pipe is suitable with the flow field inside cyclone separator, the separation efficiencies of the modified cyclone separator are usually higher than those of traditional cyclone separators.

Hydrodynamic modeling of a circulating fluidized bed

Hydrodynamics plays a crucial role in defining the performance of circulating fluidized beds (CFB). The numerical simulation of CFBs is very important in the prediction of its flow behavior. From this point of view, in the present study a dynamic two dimensional model is developed considering the hydrodynamic behavior of CFB. In the modeling, the CFB riser is analyzed in two regions: The bottom zone in turbulent fluidization regime is modeled in detail as two-phase flow which is subdivided into a solid-free bubble phase and a solid-laden emulsion phase. In the upper zone core–annulus solids flow structure is established. Simulation model takes into account the axial and radial distribution of voidage, velocity and pressure drop for gas and solid phase, and solids volume fraction and particle size distribution for solid phase. The model results are compared with and validated against atmospheric cold bed CFB units' experimental data given in the literature for axial and radial distribution of void fraction, solids volume fraction and particle velocity, total pressure drop along the bed height and radial solids flux. Ranges of experimental data used in comparisons are as follows: bed diameter from 0.05–0.418 m, bed height from 5–18 m, mean particle diameter from 67–520 μm, particle density from 1398 to 2620 kg/m 3, mass fluxes from 21.3 to 300 kg/m 2s and gas superficial velocities from 2.52–9.1 m/s. As a result of sensitivity analysis, the variation in mean particle diameter and superficial velocity, does affect the pressure especially in the core region and it does not affect considerably the pressure in the annulus region. Radial pressure profile is getting flatter in the core region as the mean particle diameter increases. Similar results can be obtained for lower superficial velocities. It has also been found that the contribution to the total pressure drop by gas and solids friction components is negligibly small when compared to the acceleration and solids hydrodynamic head components. At the bottom of the riser, in the core region the acceleration component of the pressure drop in total pressure drop changes from 0.65% to 0.28% from the riser center to the core–annulus interface, respectively; within the annulus region the acceleration component in total pressure drop changes from 0.22% to 0.11% radially from the core–annulus interface to the riser wall. On the other hand, the acceleration component weakens as it moves upwards in the riser decreasing to 1% in both regions at the top of the riser which is an important indicator of the fact that hydrodynamic head of solids is the most important factor in the total pressure drop.

Optimum design of reverse osmosis system under different feed concentration and product specification

The design of various multistage RO systems under different feed concentration and product specification is presented in this work. An optimization method using the process synthesis approach to design an RO system has been developed. First, a simplified superstructure that contains all the feasible design in present desalination process has been presented. It offers extensive flexibility towards optimizing various types of RO system and thus may be used for the selection of the optimal structural and operating schemes. A pressure vessel model that takes into account the pressure drop and concentration changes in the membrane channel has also been given to simulate multi-element performance in the pressure vessel. Then the cost equation relating the capital and operating cost to the design variables, as well as the structural variables of the designed system have been introduced in the objective function. Finally the optimum design problem can be formulated as a mixed-integer nonlinear programming (MINLP) problem, which minimizes the total annualized cost. The solution to the problem includes optimal arrangement of the RO modules, pumps, energy recovery devices, the optimal operating conditions, and the optimal selection of types and number of membrane elements. The effectiveness of this design methodology has been demonstrated by solving several seawater desalination cases. Some of the trends of the optimum RO system design have been presented.

Modeling the filtration process with a flat-type fabric filter

Abstract The fabric filtration process is divided into three stages, i.e. depth filtration, transition filtration and surface filtration. A new model is proposed to describe the three stages under both virgin and regeneration conditions. The concept of an interface dust layer is introduced to predict the transition from the depth filtration stage to the transition filtration stage. The transition filtration stage due to the non-uniform accumulation of residual dust on a filter is characterized by two parameters — the surface cleaning fraction, f, and the residual dust load on the uncleaned surface, W u0. It is found that f decreases and W u0 increases with the number of filtration cycles. This result suggests that both the fraction of uncleaned surface and the thickness of dust cake on the uncleaned surface increase with the number of filtration cycles. The present model successfully describes the change in pressure drop during the filtration cycles using the parameters.

Laboratory observations of altered porous fluid flow behavior in Berea sandstone induced by low-frequency dynamic stress stimulation

It has been observed repeatedly that low-frequency (1–500 Hz) seismic stress waves can enhance oil production from depleted reservoirs and contaminant extraction from groundwater aquifers. The physics coupling stress waves to fluid flow behavior in porous media is not understood, although numerous physical mechanisms have been proposed to explain the observations. To quantify the effects of low-frequency, dynamic-stress stimulation on multiphase fluid flow and in situ particle behavior in porous media, laboratory experiments were conducted with a core flow stimulation apparatus that allows for precise control and measurement of applied stress and strain, static confinement, and fluid flow parameters. Results are reported for experiments on stimulated single-phase and two-phase fluid flow behavior in 2.54-cm-diameter Berea sandstone cores. For all experiments, stimulation was applied to the cores in the form of sinusoidal, axial, mechanical stress coupled to the solid porous matrix at frequencies of 25 to 75 Hz. Applied stress RMS amplitudes ranged from 300 to 1200 kPa and, at these levels, produced coupled, pore-pressure fluctuations of much less than 1.2 to 4.8 kPa, respectively. During single-phase brine flow, stimulation increased the absolute permeability of the rock by 10–20%. This was caused by mobilizing in situ clay particles that were partially plugging the pore throats. During two-phase, steady-state, constant-rate flow of oil-brine and decane-brine mixtures, stimulation caused significant changes in the bulk fluid pressure drop across the core. The pressure changes showed a strong dependence on the viscosity of the nonwetting fluid phase (oil or decane) relative to the wetting phase (brine). This may indicate that relative changes in the mobility of wetting versus nonwetting fluid phases were induced by the dynamic stress. Under the specific experimental conditions used, pore-scale particle perturbation and altered wettability are possible physical mechanisms that can explain the results.