Vent Holes Research Articles

Influence of Aerosol Mask Design on Fugitive Aerosol Concentrations During Nebulization.

Secondhand exposure to fugitive aerosols may cause airway diseases in health providers. We hypothesized that redesigning aerosol masks to be closed-featured would reduce the fugitive aerosol concentrations during nebulization. This study aimed to evaluate the influence of a mask designed for a jet nebulizer on the concentration of fugitive aerosols and delivered doses. An adult intubation manikin was attached to a lung simulator to mimic normal and distressed adult breathing patterns. The jet nebulizer delivered salbutamol as an aerosol tracer. The nebulizer was attached to 3 aerosol face masks: an aerosol mask, a modified non-rebreathing mask (NRM, with no vent holes), and an AerosoLess mask. An aerosol particle sizer measured aerosol concentrations at parallel distances of 0.8 m and 2.2 m and a frontal distance of 1.8 m from the manikin. The drug dose delivered distal to the manikin's airway was collected, eluted, and analyzed using a spectrophotometer at a 276 nm wavelength. With a normal breathing pattern, the trends of aerosol concentrations were higher with an NRM followed by an aerosol mask and AerosoLess mask (P < .001) at 0.8 m; however, the concentrations were higher with an aerosol mask followed by NRM and AerosoLess mask at 1.8 m (P < .001) and 2.2 m (P < .001). With a distressed breathing pattern, the aerosol concentrations were higher with an aerosol mask followed by an NRM and AerosoLess mask at 0.8 m, 1.8 m (P < .001), and 2.2 m (P = .005). The delivered drug dose was significantly higher with AerosoLess mask with a normal breathing pattern and with an aerosol mask with a distressed breathing pattern. Mask design influences fugitive aerosol concentrations in the environment, and a filtered mask reduces the concentration of aerosols at 3 different distances and with 2 breathing patterns.

Study on the influence of barrel venting on the overload waveform of projectile in bore

In order to evaluate the anti shock overload ability of electronic components and parts in explosive device launcher, half sine wave generator with certain amplitude and pulse width is often used to verify it. In this paper, gun launcher is used as the shock wave generator. Different charge structures are studied for the interior ballistics process of barrel with or without venting according to certain requirements of mechanical overload. The influence of different charge structure, chamber volume and vent hole size on the overload waveform of projectile in the process of interior ballistic is studied by numerical simulation. The simulation results show that the larger the vent diameter is, the closer it is to the standard waveform. The research results can provide references for the matching design of projectile and artillery, the research and development of intelligent ammunition and the assessment. The research results can provide for the matching design of new artillery projectile and artillery and the research and development of intelligent ammunition.

Designing vent holes for thermoforming tooling produced via fused deposition modeling

Vent holes in thermoforming tooling are traditionally round and run perpendicular to the tool surface, as this is easy to produce via drilling and minimizes surface imperfections. This geometry should be reevaluated when producing tooling via fused deposition modeling (FDM). FDM offers thermoformers the possibility of lower tool cost and reduced lead-time compared to traditional aluminum molds. With FDM it is easier to create vent holes, even very small ones, in difficult-to-access locations. This is especially true if the holes have a rectangular cross section and lie parallel to the build plane. This alternative geometry requires modified rules to estimate the required number of holes and the size of dimple on the final part created by the vent hole during forming. In addition, FDM will produce holes with a very rough surface finish, potentially impeding flow. Computational fluid dynamics was used to show that this concern is unwarranted in practice. Finally, the Markforged Mark 2 printer was used to produce test holes, and their suitability for thermoforming is discussed.

Improvement of a soundproofing vent hole

In tropical climate countries, the house structure with a vent hole is widely used. The vent hole has a structure that penetrates the house's outer wall, allowing fresh air from outside to enter the room. However, external traffic noise also enters the living spaces through the vents. A novel type of soundproof vent hole unit with both soundproofing and ventilation functions was proposed in previous work. An elliptical cavity was used for this unit, but it is difficult to manufacture an elliptical cavity with a high eccentricity; also, the installation and adjustment work are expected to be difficult. A rectangular cavity with an inlet and outlet in orthogonal planes fitted to the house walls is used in this study to provide soundproofing functionality to the vent hole. First, the generation mechanism of sound pressure components propagating inside the unit was theoretically elucidated using the three-dimensional wave equation. Second, to maximize soundproofing ability, methods for reducing the number of resonances and reducing the effect of higher-order sound pressure components are described.

Comprehensive investigation of corrugated fiberboard boxes with edge vents for ambient loading of Chinese cabbage: Part Ⅱ – Quality changes in cellulose paper- and LLDPE film-wrapped Chinese cabbage stored in ventilated corrugated fiberboard boxes

Consumption of fresh produce has increased in recent years, as have the post-harvest losses during produce distribution. This has generated a need for optimum post-harvest treatment to increase the longevity of the produce. In this study, the temperature and relative humidity for the storage test were set as the refrigerated container conditions (ambient loading) and the quality change in Chinese cabbage wrapped with a cellulose paper sheet or linear low-density polyethylene (LLDPE) film in ventilated corrugated fiberboard boxes was evaluated. Weight loss, trimming loss, total soluble solid, pH, firmness, and color were measured every 10 d from 0 to 30 d. The weight loss values of Chinese cabbage wrapped with cellulose paper and LLDPE film at 30 d were approximately 3.7–4.4% and less than 1%, respectively. The trimming loss and firmness of Chinese cabbage wrapped with an LLDPE film were significantly better than those wrapped with a cellulose paper sheet at 30 d. However, the outer leaf surface measured by color meter was more damaged in Chinese cabbage wrapped with the LLDPE film than in those wrapped with the cellulose paper sheet because the wrapping of the former was tighter than that of the latter. In addition, the reduction in the mechanical properties of the boxes with 0%, 2%, and 3% of vent hole area against the horizontal cross section containing Chinese cabbage was measured at 0 and 30 d by performing not only mechanical property tests, such as edge crush test, bursting strength test, and box compression strength test, but also data logging of relative humidity in the headspace of each box. The relative humidity in the headspace of each box was constant at 75 ± 5% after the first increase during 0–24 h. Further, we evaluated the results of the box compression strength test at 30 d, comparing them with the required box compression strengths calculated by the equations provided in the criteria of the Fibre Box Association and American Society for Testing and Materials D4619. Thus, our findings can explain the changes in the quality of Chinese cabbage and the mechanical properties of corrugated fiberboard boxes prepared using two different internal package treatments.

A HiLo interior ballistic model based on the hypothesis of gases adiabatic transformation in the high pressure chamber

Weapons built on high-low pressure (HiLo) principle involve the existence of two chambers between which a gas flow occurs. The usual approach in the mathematical models developed for such systems is to consider that the gas flow is accompanied by an isothermal transformation of gas in the high pressure chamber. The present paper deals with the development of a lumped interior ballistic model built on more realistic assumptions like an adiabatic transformation of the gases in the high pressure chamber, an isentropic flow of real gases through the nozzles, a variable burning surface of the propellant grains and the occurrence of heat losses at the level of vent holes lateral surfaces. The experimental results obtained with a modified closed vessel were used in order to validate the proposed model. The pressure time variations in both chambers were accurately predicted by the proposed lumped model. The lumped model application on a 40 mm grenade launcher gives results consistent to the experimental measurements regarding the grenade muzzle velocity.

Optimal design of gas distributor in fluidized bed for synthesis of silicone monomer

The structure of the gas distributor is closely related to the production efficiency of organosilicon monomers. To improve the production efficiency of organosilicon monomers, this study uses Eulerian-Eulerian two fluid model and proposes a design formula for the gas distributor to optimize the gas distributor. It is proposed that the pressure drop of the gas distributor, the velocity nonuniformity coefficient, the relative standard deviation of the solid holdup, and the solid particle dispersion coefficient are used to evaluate the performance of the gas distributor. The results show that the performance of the gas distributor is significantly improved when the opening ratio Φ = 0.53% is optimized to Φ = 0.18%, in which the relative standard deviation of the solid holdup is reduced by 22%, and the solid particle dispersion coefficient is reduced by 40%. On this basis, this article studies the influence of different arrangements of vent holes on gas-solid fluidization characteristics. The results show that the circular arrangement of vent holes is helpful to the mixing of gas and solid.

Base heating and stage separation of launch vehicles

AbstractThis paper presents the results of the experimental study carried out to address the issues of base heating and smooth separation of the stage of launch vehicles. The pressure at the base of a convergent-divergent circular nozzle, from which Mach 1.8 jet emanates, attached to an annular shroud of larger area is controlled by providing air vents on the shroud. On the shroud, vent holes were made at different azimuthal locations, to entrain the surrounding air mass at a higher pressure, pa, to increase the low-pressure, pb, at the base region, caused by the suction creating large-scale vortices formed owing to the sudden expansion of the jet emerging from the nozzle into the shroud. For different number and size of the vents on the shroud, the base pressure was measured. This measurement was done at five levels of overexpansion of the nozzle in the range from –64% to –58%. It is found that increase in vent area results in increase of base pressure, up to some limiting level of the area. Also, the increase of base pressure for the case of vents closer to the nozzle exit is found to be marginally more than the increase caused by vents at distances away from the nozzle exit. Increase of base pressure can be regarded as an advantage not only from base heating point of view but also from the point of view of deflection of the plume to the shroud wall for uniform melting of the pyro layer bonding the stages of the launch vehicle, leading to a smooth separation of the launch vehicle stages.

Visual detection of Cronobacter sakazakii on a microfluidic chip fabricated by a 3D molding method.

Cronobacter sakazakii (C. sakazakii) is a pathogenic bacterium associated with life-threatening neonatal infections that have been linked to contaminated powdered infant formula (PIF). Most C. sakazakii testing is still limited in microbiology laboratories due to the need for sophisticated equipment and professional technicians. Microfluidic chips combined with isothermal amplification analysis are shown to be one of the most attractive microbiological on-site detection platforms. In this study, PDMS microfluidic chips were fabricated by a simple 3D molding method and sealed with "PDMS glue". The chip consisted of an inlet, a microchannel, six reaction wells, and six vent holes. And based on the 16S rRNA and ITS genes of C. sakazakii, we have successfully proposed a multiplex competitive annealing mediated isothermal amplification (mCAMP) assay on the microfluidic chip for the visual detection of C. sakazakii in PIF samples. The primers were fixed in the reaction wells of the chip before detection, which can be preserved for 60 days at 4 °C. The results showed that the established mCAMP assay had high specificity, and the limit of detection was 2.2 × 103 CFU g-1. With enrichment culture, even if the initial inoculation level is 1 CFU g-1, the mCAMP assay can still detect the presence of C. sakazakii in spiked PIF samples. The test results are visible to the naked eye, which is suitable for rapid analysis in resource-limited settings.

Determination of the design velocity of the gas flow in coarse and fine filters with varying degrees of contamination in the paint booths

OBJECT. Determination of the design velocity of the gas flow in coarse and fine filters with varying degrees of contamination. METHODS. We carried experimental studies out to solve the problem. To exclude errors during the studies caused by marriage or other reasons, 3 samples of each of the coarse and fine filters (clean and used) were used. To determine the design speed, an experimental installation was assembled, presented in the work, which included an air duct, an air injection fan, a nozzle for measuring excess pressure in front of the filter under study, an air vent hole, filter samples, a ventilation grate and measuring instruments – a differential pressure gauge testo 510i and an anemometer testo 405i. RESULTS. The article describes the relevance of the topic, analyzes the change in the pressure drop in the duct when using spent and clean coarse and fine filters. They showed that an increase in their operational life is possible with the use of a multi-vortex separator, which can be installed as a preliminary stage of purification. CONCLUSION. The estimated gas flow velocity when using coarse filters is only 2 m/s. The estimated gas flow velocity when using fine filters is only 0.5 m/s. A comparison of the difference in the pressure drop in the duct when using coarse and fine (spent and clean) filters shows that coarse filters are more susceptible to dusty flow, i.e. the bulk of particles in the dusty flow at an enterprise with paint chambers are relatively large particles. Hydraulic resistance increases by 1.58 times.

Should the vent hole of posterior implant crowns be placed on the lateral surface? An in vitro study of the hydrodynamic feature of cement extrusion and retention ability.

Although placing a vent hole on the occlusal surface of the implant crown can reduce cervical marginal cement extrusion, it has disadvantages. Transferring the hole to the buccal or lingual surface of the posterior implant crown could therefore be an alternative solution. This study investigated the effect of transferring the vent hole to the lateral side of the implant posterior crown on the hydrodynamics of excess cement extrusion and the crown’s retention ability. Specially fabricated posterior implant crowns were divided into five groups: crowns with an occlusal hole (OH), occlusal lateral hole (OLH), middle lateral hole (MLH), cervical lateral hole (CLH), and no hole (NH). Each set of implant analog-abutment-crown specimens was wrapped in a polymethylacrylate base. The base of the implant crown was divided into four 90-degree quadrants along the diagonal of the square base with a pen mark. Cement was used to bond the crowns and the abutments, and the weight of cement extrusions at the vent holes and the abutment cervical margins were calculated. The distribution of cement extrusion at the margin was photographed in each quadrant, and the areas of surface coverage of cement extrusion were compared with ImageJ software. Retentive strength was measured as the dislocation force using a universal testing machine. One-way analysis of variance was used for result analysis. The cervical marginal cement extrusions of crowns with lateral holes (OLH, MLH, and CLH) were significantly less than that of NH crowns (P<0.05), but more than that of OH crowns (P<0.05). Subgroup analysis among the lateral hole groups indicated that the higher the position of the lateral hole, the lower the weight of the cement extrusion, and the smaller the total distribution area of cement extrusion. The cement extrusion distribution area was larger in the quadrant with the hole than in those opposite and next to the hole. Retention strength comparison indicated no significant difference between crowns with NH, OH, or lateral holes. Transferring the vent hole of the posterior implant crown to the lateral side could reduce cement extrusion at the cervical margin while reducing retention strength deterioration and the esthetic drawbacks caused by occlusal hole opening.

Enhance the anti-scaling performance of conductive heating vacuum membrane distillation by carbon nanotube-based electroactive membrane

Membrane distillation (MD) is an emerging technology for the brine desalination. Directly heating feed liquid at the membrane-water interface for improving the performance of MD has been demonstrated, while the problem of membrane scaling remained. Herein, carbon nanotube-based electroactive membranes were prepared and characterized by a variety of methods. It was then used in a conductive heating vacuum membrane distillation system. We firstly increased the flux by optimizing system configuration, placing a spacer in the feed channel, and setting vent holes on the thermal conducting layer. Then, aiming at silicates and sulfates scaling in MD, the electroactive membranes and titanium were used as working electrodes and the counter electrode, respectively, to discuss the electrochemical anti-scaling performance and mechanism. Results showed that the silicate scale on the membrane surface can be effectively cleaned by using the electroactive membrane as the cathode and applying a potential of − 5 V to destroy the structure of the silicate through an electrochemical reaction. With the electroactive membrane as the anode, the scaling of calcium sulfate can be mitigated by providing a continuous potential through electrostatic repulsion. This paper may provide further insights into inorganic scaling control in conductive heating vacuum membrane distillation process.

Thermal Runaway Propagation in Li-ion Battery Packs Due to Combustion of Vent Gases

Accurate understanding of propagation of thermal runaway is of much importance for developing safe battery pack designs. Combustion of vent gases emerging from a trigger cell undergoing thermal runaway has not been studied in sufficient detail, even though the additional heat generated during combustion likely plays an important role in thermal runaway propagation. This work presents comprehensive numerical modeling and simulations of thermal runaway propagation in a pack of cylindrical cells. The model accounts for multiple coupled non-linear phenomena, including vent gas flow and combustion, radiation and thermal runaway. Non-premixed combustion of venting gas is modeled using k-ε turbulence model and finite rate chemical kinetics. Simulation results are shown to be in good agreement with experimental data for a benchmark turbulent non-premixed jet flame. Simulations show that hot combustion products are rapidly transported in gaps between cells, potentially leading to self-sustained thermal runaway propagation to adjacent cells. Results demonstrate the critical importance of combustion in determining the nature of propagation of thermal runaway. The vent hole location is identified as an important parameter that influences whether and the extent to which thermal runaway propagation occurs. This work contributes towards the practical understanding of thermal runaway safety of Li-ion battery packs.

Effect of Vent Hole and Cement Type on Fracture Resistance of CAD-CAM Monolithic Zirconia Crowns.

To assess the fracture resistance of monolithic zirconia crowns cemented with different types of cement on cement-retained implant abutments. Forty implant analogs were positioned in acrylic resin blocks, and cement-retained straight implant abutments were fastened to the analogs. Crowns were designed with/without occlusal vent holes and produced from monolithic zirconia blocks by the CAD-CAM technique. The two crown types were divided into two groups and cemented with resin and zinc-polycarboxylate cement under 5 kg weight. A universal testing machine applied compressive forces to the crowns until fracture. Fracture resistance values were analyzed using two-way ANOVA and the independent samples t-test with statistical significance set at p < 0.05. According to the two-way ANOVA results, although the crown design did not have a significant effect on fracture resistance (1417.65 ± 337.39 N, 1565.16 ± 517.12 N; crowns with and without vent holes, respectively), the main effect of the cement variable on the fracture resistance was significant. Zinc-polycarboxylate cement (1680.1 ± 375.23 N) showed higher fracture resistance than resin cement (1302.71 ± 420.64 N) in the crowns designed with vent holes (p < 0.005). The use of cement-retained implant-supported monolithic zirconia crowns with an occlusal vent hole is safe, and zinc-polycarboxylate cement use may be an appropriate choice for cementation of these crowns.

Experimental and Theoretical Study of Internal Pressure Loads on Boundary Walls under Gusty Wind Conditions

This work contains an acceptable solution to the most practical interest to reduce the internal pressure load variations acting on closed envelops (i.e., inner building walls, fairing of rocket, and missile payloads) under gusty wind conditions. To simulate the gusty wind conditions (i.e., tangential unsteady flow condition), an experimental setup of a wind tunnel with a sinusoidal gust generating mechanism has been established in IDR of the Universidad Politécnica de Madrid (IDR/UPM), Spain. The wind tunnel has been equipped with an air reservoir with vent holes. The pressure jumps shown across the vent holes are studied as a function of sinusoidal gust frequency, volume of the air reservoir, and vent hole size. A theoretical model (based on the mass conservation equation and polytropic law gas evolution) has been proposed to predict the pressure jumps and variations under gusty wind conditions. At the end of the work, theoretical and experimental results have been studied and compared. The relationship between pressure loss coefficient ξ and flow coefficient α under unsteady flow conditions has been evaluated.

Active structural acoustic control for radiated sound power reduction of enclosure with vent holes based on radiation modes

Active structural acoustic control for radiated sound power reduction of enclosure with vent holes based on radiation modes

Exploring novel carton footprints for improved refrigerated containers usage and a more efficient supply chain

Large quantities of fresh produce are exported every year to international markets across the world using refrigerated freight containers (RFCs). However, many packaging systems are legacy designs for older shipping technologies. For fruit, more than 10% of the RFC floor area is unused by current packaging systems, and designs often do not facilitate adequate cooling conditions. This study showed that novel packaging designs could improve packing density by up to 19%. Two new packaging systems were investigated using CFD to emulate conditions similar to forced-air cooling (FAC) and a RFC, respectively. The proposed packaging increased floor area utilisation to about 98%. The FAC energy efficiency was improved by 29%. An analysis of the results indicates considerable cooling improvements are possible by modifying vent hole designs and using taller cartons. The study thus demonstrated substantial merits to implementing new fruit packaging systems.

Stress Optimization of Vent Holes with Different Shapes Using Efficient Switching Delayed PSO Algorithm

An effective integrated design optimization method is developed to reduce the maximum von Mises stress around vent holes of a high-pressure turbine sealing disk. It mainly includes four different shape designs (circular, elliptical, race-track, and four-arc) for holes, an updated self-developed modelling and meshing tool, an APDL-based strength analysis, and a self-proposed efficient switching delayed particle swarm optimization (SDPSO) algorithm. The main idea of SDPSO is: (1) by evaluating an evolutionary factor and utilizing a probability transition matrix, a non-homogeneous Markov chain is determined and auto-updated in each generation; (2) the evolutionary factor and the Markov chain are used to adaptively select the inertia weight, acceleration coefficients, and delayed information to adjust the particle’s velocity. The performance of SDPSO is evaluated through two benchmark optimization problems with constraints. The results show that SDPSO is superior to two well-known PSO algorithms in optimization capability, numerical robustness, and convergence speed. Furthermore, SDPSO is used for the stress optimization of vent holes with four different shapes. The results show that: (1) SDPSO is suitable and valuable for practical engineering optimization problems with constraints; (2) the developed integrated design optimization method is effective and advanced for reducing the maximum von Mises stress around the vent holes; and (3) the four-arc hole has more tremendous advantages in reducing the maximum von Mises stress, followed by the elliptical hole, the race-track hole, and the circular hole.

Numerical and Experimental Investigation of the Conjugate Heat Transfer for a High-Pressure Pneumatic Control Valve Assembly.

This paper uses heat transfer experiments and computational fluid dynamics (CFD) simulations to investigate the conjugate heat transfer (CHT) in a high-pressure pneumatic control valve assembly. A heat transfer test rig was constructed, and time–temperature histories of five test points placed on the valve assembly’s outer surface were recorded for study validation. The Unsteady Reynolds-Averaged Navier–Stokes (URANS) CFD methods with the standard k-ε turbulence closure equations were adopted in the numerical computations. Polyhedral grids were used; time step and mesh convergence studies were conducted. Simulated and measured temperatures profile comparisons revealed a good agreement. The CHT results obtained from CFD showed huge velocity fields downstream of the valve throat and the vent hole. The airflow through the valve was icy, mainly in the supersonic flow areas. Low temperatures below 273.15 K were recorded on the internal and external walls of the valve assembly. The consistency of the measured data with the numerical results demonstrates the effectiveness of polyhedral grids in exploring the CHT using CFD methods. The local entropy production rate analysis revealed that irreversibility is mainly due to viscous dissipation. The current CHT investigation provides a potential basis for thermostress analysis and optimization.

Angularly Independent Frequency Selective Surface With Good Ventilation for Millimeter Wave EM Shielding

A distinctive frequency selective surface (FSS) to effectively enhance the electromagnetic shielding performance of high-speed electronic systems while preserving good mechanical ventilation is proposed in this article. The FSS consists of periodic segmented circular patterns in two-dimensional view and hollow vent holes in spatial, which exhibits a wide 2 GHz stopband at the interested frequency of 28 GHz. The new design also demonstrates stability to wave oblique incidence and polarization. The FSS shielding panel is prototyped and measured for validation. A satisfactory agreement between simulation and physical experiment is achieved.