Vent Port Research Articles

Experimental investigation for the effect of bust pressure on hydrogen explosion venting

A series of experiments are carried out to investigate the effect of burst pressure on hydrogen explosion venting in a 20 L square vessel. Pressure buildup and flame evolution are recorded using piezoelectric pressure transducers, high speed camera, high speed infrared camera and schlieren system. The results show that both the maximum explosion pressure (Pmax) inside and outside the vessel increase with the increasing burst pressure, and the Pmax in the external space decreases rapidly with the increase of the distance from the vent port. Compared to the burst pressure of 0 kPa, the Pmax inside the vessel and at 1200 mm increased by 79.1 % and 153.6 %, respectively, when the burst pressure was 325 kPa. The venting flame surface during the propagation is smoother with the increasing burst pressure, the width and area of the flame also increases. There is little effect of burst pressure on the maximum flame propagation distance (Lmax), but with the increase of burst pressure, the flame propagation time is shortened and the average propagation velocity is increased. The venting flame propagation time is shortened from 5.0 ms to 3.5 ms with the burst pressure increases from 0 kPa to 325 kPa. The high temperature zone of venting flame is mainly distributed in the flame front, while the maximum flame temperature (Tmax) gradually increases with the increase of burst pressure. The increase in burst pressure results in an increase in the turbulence intensity inside the vessel and an advance in the time to stabilization inside the vessel. Furthermore, the moment at which flow backflow occurs at the vent port is advanced from 16.5 ms to 8.5 ms with the increase in burst pressure.

Active and passive methods for cooling load reduction in a tropical building: A case study

In the present study, energy saving potential and economical viability of implementing various active and passive cooling methods to a hostel building was accessed for tropical climate. The transmitted load for the building envelope was reduced by proposed Energy conservation measures (ECMs) including Gypsum-based cow dung plaster at the walls, double glazing glass for the windows and cool paint in conjunction with Photovoltaic panel for the roof. The experimentally calculated U-values for proposed plastered wall, double glazing window and cool painted with Photovoltaic shaded roof were 1.85 W/m2 K, 3.45 W/m2 K and 1.1 W/m2 K respectively. The ventilation load for the proposed centralized air conditioning system was reduced by connecting an Earth Air Heat Exchanger (EAHE) to the outlet vent port. The sizing of EAHE system was done using a MATLAB code validated with own experimental data. By parametric analysis, EAHE system of 16 pipe configuration with each of length 100 m and diameter 0.4 m was selected as a good compromise between effectiveness of heat transfer and pressure drops. Using eQuest simulation software, the total peak cooling load calculated for base and proposed case was 285 TR and 186 TR respectively. For the proposed case, the ventilation load was reduced by 18 TR and transmission load was reduced by 81 TR. The energy saving, payback time, and Greenhouse house gas mitigation for the proposed case with ECMs and EAHE was 344 MWh/year, 3.2 year, and 378 t CO2/year respectively.

ELSO Interim Guidelines for Venoarterial Extracorporeal Membrane Oxygenation in Adult Cardiac Patients.

ELSO Interim Guidelines for Venoarterial Extracorporeal Membrane Oxygenation in Adult Cardiac Patients.

Free vent boundary conditions for thermal buoyancy driven laminar flows inside open building enclosures

A comprehensive investigation and review about the free vent boundary conditions are conducted regarding of natural convections inside an open cavity with one side horizontal opening, aiming to abandon the extended computational domain through imposing suitable pressure and momentum boundary conditions on the free ventilated ports. The main differences among Type A, Type C and Type D BCs are the definitions and assumptions on the free port boundary pressures. The physical governing equations for the present investigation are solved numerically for a wide range of thermal Rayleigh number and enclosure aspect ratio to identify the applicability of the four categories of free port boundary conditions. The simulation results show that, with the flow intensity increasing in the region near free opening, Type D BCs, Type C BCs and Type A BCs would take turns being the most effective and suitable BCs to achieve the flow solutions approaching to the reference ones. Regarding of the computational stability, authors-proposed free vent port boundary conditions (Type D BCs) achieve the best performance. In addition, it is found that enclosure ventilation rate is a more suitable and convincing criterion than heat transfer rate to validate the accuracy of the numerical methods.

Effect of insulation thickness on pressure evolution and thermal stratification in a cryogenic tank

A transient analytical, multi-phase, thermodynamic model of foam insulated liquid hydrogen tank is developed to understand the effect of insulation thickness on the evolution of tank pressure and liquid thermal stratification. The model is validated with experimental data reported in literature. Analyses are carried out for pressurization considering two scenarios: first case with tank vent port closed after pressurization to study the pressure evolution and the second case for a constant tank pressure of 3.0bar to study the growth of liquid thermal stratification. Both cases are investigated for different tank insulation thicknesses of 10mm, 20mm, 30mm and 40mm and with a pressurization gas temperature of 50K. Effects of variations in ambient wind velocity and presence of solar flux on self-pressurization profile of the tank are also analysed. The study shows that the reduction in insulation thickness leads to increase in stratified mass. The study also brings out significant increase in pressure rise when tank is insulated with lower insulation thickness.

NEXT-GENERATION DUAL-BORE CANNULA FOR INJECTION OF VITAL DYES AND HEAVY LIQUIDS DURING PARS PLANA VITRECTOMY.

The objective of this study was to introduce and validate a next-generation dual bore cannula for microincisional vitrectomy surgery. The SideFlō cannula with a closed tip and four vent ports on the sides was designed and manufactured. The cannula is designed to inject vital dyes for macular staining and perfluorocarbon liquids. Injection and venting properties were assessed subjectively in vivo, and venting was quantified in a plastic eye model system; 23-, 25-, and 27-gauge SideFlō cannulas were assessed and compared with existing axial dual bore cannula designs. The SideFlō cannula created a broad fan-like egress of fluid that was perpendicular to the axial direction of the cannula and eliminated the possibility for retinal fluid jet damage. Enhanced outflow venting was clinically relevant in terms of smoother injection experience and less intraocular pressure rise when compared with previous dual bore designs. Testing in a model eye system confirmed marked improvement in passive outflow compared with the first-generation dual bore cannula single vent port design for all gauges. The SideFlō cannula represents a novel next-generation dual bore cannula design with significantly improved performance over first-generation dual bore cannulas. Axial jet damage from fluid injection is eliminated, and pressure equilibration by passive venting from the eye is significantly enhanced.

Mechanical Response and Microprocesses of Reconsolidating Crushed Salt at Elevated Temperature

Design, analysis and performance assessment of potential salt repositories for heat-generating nuclear waste require knowledge of thermal, mechanical, and fluid transport properties of reconsolidating granular salt. To inform salt repository evaluations, we have undertaken an experimental program to determine Bulk and Young’s moduli and Poisson’s ratio of reconsolidated granular salt as a function of porosity and temperature and to establish the deformational processes by which the salt reconsolidates. Tests were conducted at 100, 175, and 250 °C. In hydrostatic tests, confining pressure is increased to 20 MPa with periodic unload/reload loops to determine K. Volume strain increases with increasing temperature. In shear tests at 2.5 and 5 MPa confining pressure, after confining pressure is applied, the crushed salt is subjected to a differential stress, with periodic unload/reload loops to determine E and ν. At predetermined differential stress levels the stress is held constant and the salt consolidates. Displacement gages mounted on the samples show little lateral deformation until the samples reach a porosity of ~10 %. Interestingly, vapor is vented only for 250 °C tests and condenses at the vent port. It is hypothesized that the brine originates from fluid inclusions, which were made accessible by heating and intragranular deformational processes including decrepitation. Identification and documentation of consolidation processes are inferred from optical and scanning electron microstructural observations. Densification at low porosity is enhanced by water film on grain boundaries that enables solution-precipitation phenomena.

Influence of degassing on hot-melt extrusion process

The present study aimed to evaluate the effect of degassing on an extrusion process, with respect to extrudate quality and drug release properties. Processed formulations were extruded with and without a degassing vent port at various locations along the barrel. All the experiments were performed under constant processing temperature, feeding rate, and screw speed. During the extrusion process, torque and pressure were monitored and recorded. The degassing process was beneficial when used over a conveying section after a mixing section. This is attributed to the large surface area available on the conveying elements, which minimizes the internal volume of the processed material, thereby facilitating the escape of entrapped gases. Degassing enhanced the homogeneity, physical appearance, and drug release properties of all the formulations. Furthermore, the degassing process also enhanced the cross-sectional uniformity of the extruded material, which is beneficial for visual monitoring during processing. Degassing considerably reduced the post-extrusion moisture content of Formula D3, which contains the highly hygroscopic polymer Kollidon® 17 PF, suggesting that the greatest influence of this process is on hygroscopic materials. The reduction in post-extrusion moisture content resulting from the inclusion of a degassing vent port, reduced fluctuations in the values of in-line monitoring parameters such as pressure and torque. Employing a degassing unit during hot-melt extrusion processing could help increase process efficacy and product quality.

C33 気泡除去装置の高性能化(M-OS5-3 フルードパワーの応用,M-OS5 フルードパワーの基礎と応用,「海を越え,国を越え,世代を超えて!」)

Air bubbles in hydraulic oil lower the efficiency of hydraulic systems and contribute to instrument malfunctions. To mitigate these problems, it is possible to use an active "bubble eliminator" that uses swirl flow to remove air bubbles. The device shape affects the efficiency of bubble removal; hence, the selection of geometry is the most important parameter for optimizing the device performance. This study investigates the effect of the shape parameters of the device on bubble behavior in the oil, using experimental flow visualization and numerical simulations of the device. In this paper, we conducted the experimental flow visualization and numerical simulation involving various diameters of an outlet port and vent port. The simulation results are analyzed using considering the relationship between axial flow and swirl flow in the bubble eliminator. We conclude that the diameters of the outlet port and vent port, and the length of the tapered tube of the bubble eliminator can be determined.

Mechanism of Nanofibre Fabrication by Meltblowing

Fabrication of nanofibres has become a growing area of research because of their unique properties (i.e. smaller fibre diameter and higher surface area) and potential applications in various fields such as filtration, composites and biomedical applications. The mechanism of nanofibre fabrication by meltblowing process with the injection of different fluids (such as air and water) has been investigated in this paper. In the meltblowing equipment the fluids were injected at a vent port along the extrusion barrel, for the fabrication of nanofibres. The injection of water resulted in better fibre morphology compared to the injection of air. Nanofibres were fabricated by the drafting action of the high-velocity flow of the heated air and the steam in the extruder. The fibres collected were straight prior to the fluid injection and coiled fibres were collected with the injection of fluids. Three types of fibres such as ribbon shaped, fused and branched fibres were obtained in addition to the circular fibres.

Fabrication and characterisation of polypropylene nanofibres by meltblowing process using different fluids

In nonwoven industry, meltblowing has been widely used as an important technique for the production of nonwoven webs consisting of microfibres, suitable for various applications. Recently, great attention is being paid to fabricate nonwoven webs consisting of nanofibres, commonly known as nanowebs. In this paper, polypropylene has been successfully used for the fabrication of nanowebs by meltblowing process with the injection of different fluids (such as air and water) at the vent port of commercial meltblowing equipment. The lowest average fibre diameters achieved were 755 and 438 nm by the use of air and water, respectively. Differential scanning calorimetry results showed the presence of single melting peaks in the first heating cycle and double melting peaks in the second, due to the re-crystallisation and re-organisation by heating during the experiments. The results obtained from thermo gravimetric analysis and intrinsic viscosity studies showed thermal degradation of the nanofibres during meltblowing. X-ray diffraction studies showed that all the meltblown polypropylene fibres produced with the injection of the fluids contained low degrees of crystallinity and monoclinic α-form crystals. The crystallinity was increased with annealing. Similar Fourier transform infrared spectra of the polymer and the fibres indicated no change to the chemical functionality of the nanofibres by the application of the fluids and high temperature during meltblowing.

Optimization of Bubble Eliminator Through Numerical and Experimental Investigation

Air bubbles in working oil affect the stiffness and efficiency of hydraulic systems; thus it is important for technical issues that air bubbles be actively eliminated from the hydraulic oil. A bubble eliminator is a device that uses a swirl flow to remove air bubbles. The shape of the device affects bubble elimination performance, so the selection of shape is the most important parameter in increasing the performance of the device. The purpose of this study is to design a bubble eliminator with an optimal shape. This paper discusses the validity of numerical simulation by comparing, using various diameters of the vent port, the numerical results with the results of the experimental flow visualization. Moreover, we focus on the length of the inlet tube and tapered tube of the bubble eliminator and establish a method of selecting them.

Miniature Non-Directional Microphone

A miniature microphone comprising a diaphragm compliantly suspended over an enclosed air volume having a vent port is provided, wherein an effective stiffness of the diaphragm with respect to displacement by acoustic vibrations is controlled principally by the enclosed air volume and the port. The microphone may be formed using silicon microfabrication techniques and has sensitivity to sound pressure substantially unrelated to the size of the diaphragm over a broad range of realistic sizes. The diaphragm is rotatively suspend for movement through an arc in response to acoustic vibrations, for example by beams or tabs, and has a surrounding perimeter slit separating the diaphragm from its support structure. The air volume behind the diaphragm provides a restoring spring force for the diaphragm. The microphone's sensitivity is related to the air volume, perimeter slit, and stiffness of the diaphragm and its mechanical supports, and not the area of the diaphragm.

Dynamic control of split flow in packed column supercritical fluid chromatography using dual resistively heated restrictors

Remote control of the vent/detector split flow ratio in packed column supercritical fluid chromatography (pSFC) with flame ionization detector (FID) is demonstrated using a dual heated restrictor method. Restrictors stemming from a Tee at the separation column outlet were, respectively, fixed into an FID and a vent port, and their individual temperatures were controlled using resistively heated wires. Subsequently, both system pressure and split flow could be manipulated. For example, for applied restrictor temperatures examined up to 600 degrees C, corresponding vent/FID split flow ratios between 2 and 7 were observed depending on the port heated. As well, column pressures around 16-23 MPa were also achievable over the same range. Conversely, isobaric altering of the split flow ratio was possible when opposing positive and negative temperature gradients were applied at the two restrictors. Under these conditions, the system pressure varied less than 1% RSD over a 10 min period. As an application, the method was used to establish stable detector operation in the analysis of n-alkanes under pSFC-FID conditions that initiated flame instability. Results indicate that this technique could be a relatively simple and inexpensive means of controlling system pressure and detector split flow ratios in pSFC-FID.

밀폐공간에서의 VCE에 의한 충격파 고찰

In order to establish detailed plans for fire protection and reduce the possible fire accidents in the future, a study on the shock wave caused by VCE(Vapor Cloud Explosion) is very important. Destruction phenomena of structure by gas explosion is due to the explosion pressure and heat. Explosion pressure is a kind of energy converted from the gas mixture explosion. Therefore, the propagation progress of shock wave and flame is very important. This study investigated the shock wave caused by VCE in enclosure with opened vent port. From a result, the vent port of top at the straight line of ignition and leak location was opened most rapidly, and the vertical vent port not opened.

Can Vacuum Assisted Venous Drainage be Achieved using a Roller Pump in an Emergency? A Pilot Study using Neonatal Circuitry

There has been much advancement in perfusion technology over its 50 years of progression. One of these techniques is vacuum-assisted venous drainage (VAVD). Many perfusionists augment venous drainage using VAVD, typically from a wall vacuum source. This study explores alternates to providing VAVD if the wall vacuum fails. In two porcine laboratories, ∼36 in. of 3/16-in. tubing was connected to a sucker return port and placed into the roller head next to the arterial pump. The vacuum was monitored with a DLP pressure monitoring system (Medtronic). This system was connected to small-bore tubing and attached to a stopcock on top of the reservoir. The vacuum was regulated using another stopcock connected to a non-filtered luer lock port on top of the reservoir or by a segment of 3 × 0.25-in.-diameter tubing attached to the vent port with a c-clamp. Vacuum drainage was achieved, ranging from −18 mmHg to −71 mmHg by manipulating the stopcock or c-clamp. Changes in venous drainage were seen by volume fluctuations in the venous reservoir. The vacuum was adjusted to account for dramatic changes. Augmented venous drainage using a roller pump can be achieved successfully during cardiopulmonary bypass (CPB). This method of active drainage can be used in lieu of wall suction or during times of emergency if wall suction fails.

Transverse pressure distributions in a simple model ear canal occluded by a hearing aid test fixture

The sound field in a model ear canal with a hearing aid test fixture has been investigated experimentally and theoretically. Large transverse variations of sound pressure level, as much as 20 dB at 8 kHz, were found across the inner face of the hearing aid. Variations are greatest near the outlet port of the receiver and the vent port. Deeper into the canal, the transverse variations are less significant and, at depths greater than 4 mm, only a longitudinal variation remains. The model canal was cylindrical, 7.5 mm diameter, and terminated with a Zwislocki coupler to represent absorption by the human middle ear. The outer end of the canal was driven by the receiver in the hearing aid test fixture, with the acoustic output entering the canal through a 1 mm port. The hearing aid was provided with a 20-mm-long vent, either 1 or 2 mm in diameter. The sound field inside the canal was measured using a specially designed 0.2-mm-diam probe microphone [Daigle and Stinson, J. Acoust. Soc. Am. 116, 2618 (2004)]. In parallel, calculations of the interior sound field were performed using a boundary element technique and found to agree well with measurements.

Prediction of air/oil exit flows in a commercial aero-engine bearing chamber

An understanding and optimization of three-dimensional air/oil flows in aero-engine transmission systems forms an integral part of future designs. This especially applies to bearing chambers, which contain a complex two-phase flow formed by the interaction of sealing airflows and lubrication oil. A critical design quantity is the composition of the liquid (oil) and gas (air) phases in the exit flows. Using a previously validated numerical model, the air/oil flow in a commercial bearing chamber is computed with particular focus on the flow exiting the chamber. The division of oil exiting the chamber through the vent and scavenge ports is determined for three shaft speeds and two configurations of the vent port. Comparison with available experimental data shows that consistent trends are predicted, but further model development is necessary in the vicinity of the scavenge port.

756 気泡除去装置内の流れ解析 : 放気口モデルによる検討(流体パワーによる駆動と制御II)

756 気泡除去装置内の流れ解析 : 放気口モデルによる検討(流体パワーによる駆動と制御II)

Technical note: Minimal conditions for venturi aeration of water flows

Air vacuum processes with venturi, simple in design and easy to operate, have been used in a wide variety of industrial and water/waste water treatment applications in environmental engineering. The air vacuum process occurs when a minimal amount of differential pressure exists between the inlet and outlet regions of a venturi device. This paper introduces an air vacuum process within a venturi device and its relationship with the Reynolds number. In this case study, air vacuum characteristics such as volumetric air flowrate were studied, depending on water flowrate. An empirical correlation for air vacuum with a venturi device is presented to predict the volumetric air flowrate (Qa) as a function of water flowrate (Qw), diameter of throat (d2), diameter of air vent or suction port (dh) and Reynolds number (Re). A minimal Reynolds number for absorption of air is observed in the transition flow region for the inlet of a venturi device (Re ≥ 1900) and in the turbulent flow region for the throat of a venturi (Re ≥ 3900).