Values Of Pressure Difference Research Articles

Ventilation improvement for effective protection of healthcare workers in negative pressure airborne infectious isolation room from viral aerosols

A negative pressure airborne infectious isolation room (AIIR) is the primary healthcare air contamination control system used for the treatment of severe respiratory infectious patients. Effects of the ventilation system configuration and conditions on airflow pattern, aerosol distribution and ventilation performance were investigated using computational fluid dynamics (CFD). The field measurement by SARS-CoV-2 environmental surface test was also conducted. The cycle threshold values from transcription polymerase chain reaction (RT-PCR) method showed inverse relation to the simulated number of particles trapped on the surfaces indicating a good agreement. Modification of the present AIIR to have alignment between air inlet and outlet where the aspect ratio of the air outlet, Width (W): Height (H) = 1:1 (Improved case: IC#1) showed a 78 % reduction of aerosol concentration in healthcare workers (HCWs) zones. Aerosol concentrations were increased when the openings of the air outlet were enlarged. Addition of air outlet led to large swirling air, resulting in more aerosols being trapped and suspended in the air. Results suggested that AIIR with alignment air inlet on the ceiling and air outlet at the wall over the patient's head with W:H = 1:1 be the most suitable configuration to maximize the ventilation performance and minimize exposure risk to aerosolized viral infection for HCWs. Air change rate plays a more important role than the differential pressure on the removal efficiency. The differential pressure value should be at least −2.5 Pa and the air supply rate 12 ACH for effective protection of HCWs in the negative pressure AIIR.

Research on the Error Calibration Method of Rheological Parameters of Rectangular Tubular Viscometer

In order to solve the problem of high error in the process of measuring the rheology of drilling fluids by the common pipe flow method, an online measurement device for the rheology of drilling fluids with rectangular tubular drilling fluids was fabricated, and a calibration method for the measurement error of rheological parameters was proposed and corresponding experiments were carried out. By measuring the differential pressure value and flow, flow rate and other parameters when the drilling fluid flows through the measuring tube, upload them to the host computer for processing, use VMD to decompose the measured differential pressure data, remove the residual term, and then perform Hibert transform on each modal component to obtain its analytical signal, modulate the amplitude and phase of each analytical signal, and then reconstruct the signal to obtain the optimized differential data, and finally bring it into the constructed calibration model of the rheological parameter measurement error of drilling fluid to obtain the rheological parameters. The experimental results show that the proposed method can obtain more accurate rheological parameters of drilling fluid, improve the measurement accuracy of drilling fluid rheology parameters, so as to judge the downhole situation more accurately and ensure the personal safety of on-site staff.

Performance Qualification of Automatic System for Antineoplastic Preparation

The preparation of antiblastic and parental drugs should be carried out by ensuring an aseptic condition and minimizing exposure to toxic drugs. The aim of this study is to evaluate the quality and qualification of these features of an automated dispensing system, called PHARMODUCT®, built by Bioduct s.r.l, part of the Dedalus group. Three antiblastic drugs (cyclophosphamide (powder), 5-fluorouracil and paclitaxel) were used and three preparation and dispensing sessions were carried out for each drug, using PHARMODUCT®. Some of the infusion bags, prepared for each type of antiblastic, were sent to an external laboratory to perform the quantitative dosage analysis and compare it with the quantitative concentration, set on the automatic dispensing equipment, which was found to meet the acceptance criteria of 10%. In addition, to assess the safety of the process for operator exposure to toxic drugs, the differential pressure value between the main chamber and the clean room was measured to be ˂0 Pa, with an hourly leakage rate of ˂2.5 × 10−3 h−1. Media fill tests showed no microbiological growth after a 14-day incubation period. The PHARMODUCT® system meets the requirements of safety and repeatability for the dispensation of parenteral antiblastic drugs.

Semi-empirical modeling of CO2 and particles in moving buses

Two semi-empirical time-series mathematical models were developed to describe mass CO2 and PM2.5 concentrations in metropolitan buses under realistic conditions. A CFD (Computational Fluid Dynamics) approach was utilized to ascertain the pressure distribution on a specific bus surface traveling at different speeds. The simulation results indicated that the differential pressure of the front door and the rear door gaps varied from −0.652 Pa to −98.687 Pa and − 0.083 to −13.19 Pa, respectively, under driving speeds ranging from 5 to 60 km/h. To improve accuracy, several modifications were made to the mathematical models using field measurement data. Thus, this study quantified the pressure difference values at different locations and provided an accurate prediction model for typical pollutants by comprehensively considering the influence of multiple factors, thereby allowing for a better understanding of the dispersion and exposure levels of pollutants in buses over time.

Simplified model for estimating the neutral pressure level in the elevator shaft of a building

This paper presents a simplified model for estimating the locations of the neutral pressure levels (NPLs) in elevator shafts. The proposed model considers the mass balance of airflow based on the vertical zoning of the elevator shafts. To verify this model, the heights of the NPLs and pressure distributions as estimated by the model for three high-rise buildings with different shaft zoning plans were compared with field measurement data. The NPLs in multi-zone elevator shafts exist at different locations, and each set of measured results is consistent with the proposed model with the error within approximately 8% of the building height. Then, infiltration results from the proposed model were evaluated by comparison with simulations, to further validate the feasibility of this model. The proposed model can present a plot curve similar in shape to that provided by a simulation, such as in regard to making calculations separately for sections in which infiltration and exfiltration occur. The results show that this model can quickly estimate the NPLs with satisfactory results for both the architectural designer and the HVAC engineer. Therefore, the proposed NPL estimation model can be used to evaluate pressure difference values and airflow patterns in high-rise buildings in the planning stage.

A study on transport and plugging of sodium aerosol in leak paths of concrete blocks

In the event of a severe accident in Sodium Cooled Fast Reactors (SFR), the sodium combustion aerosols along with fission product aerosols would migrate to the environment through leak paths of the Reactor Containment Building (RCB) concrete wall under positive pressure. Understanding the characteristics of sodium aerosol transport through concrete leak paths is important as it governs the environmental source term. In this context, experiments are conducted to study the influence of various parameters like pressure, initial mass concentration, leak path diameter, humidity etc., on the transport and deposition of sodium aerosols in straight leak paths of concrete. The leak paths in concrete specimens are prepared by casting and the diameter of the leak path is measured using thermography technique. Aerosol transport experiments are conducted to measure the transported and plugged aerosol mass in the leak paths and corresponding plugging times. The values of differential pressure, aerosol concentration and relative humidity taken for the study are in the ranges 10–15 kPa, 0.65–3.04 g/m3 and 30–90% respectively. These observations are numerically simulated using 1-Dimensional transport equation. The simulated values are compared with the experimental results and reasonable agreement among them is observed. From the safety assessment view of reactor, the approach presented here is conservative as it is with straight leak paths.

A dual-parameter measuring method for wet steam based on the characteristics of differential pressure under phase-isolation state

To achieve accurate measurement of steam injection volume in the process of steam-driving heavy oil, a low-cost online metering device for wet steam flows is urgently needed. Primarily, the traditional Venturi device has a relative error due to the wet steam flow patterns. Therefore, a new physical model for wet steam measurement composed of a swirler and a Venturi was designed, based on the phase-isolation technology for multi-phase flow measurement. A theoretical explanation of the differential pressures was then proposed. Numerical simulations were conducted to investigate wet steam measurement, specifically under the condition of 10∼20 MPa. A new correlation for the steam quality and mass flow rate with the pressure drop was developed by the multiphase flow model via Eulerian. A novel wet steam dual-differential pressure measurement model was established by considering the effects of temperature and pressure, which predicts the wet steam overall mass flow rate and steam quality of the measurement device. Block P601 and Block P6 of the oilfield located in eastern China were selected as the development test area, and the differential pressure prediction was carried out for 68 different working conditions of two Wells based on the dual-parameter measurement model, which was then calibrated. The experimental fieldwork on Block P601 demonstrated that the feasibility of the dual-parameter measuring method was verified, with relative deviations of ±7% between the predicted and experimental values of differential pressure. After calibration of the measurement model, the predicted values were compared with the experimental values, yielding relative deviations of ±3.5% and ±5% for mass flow rate and steam mass measured online for wet steam, with Mean Absolute Percentage Errors (MAPE) of 1.73% and 2.21%. Thus, the dual-parameter measuring method has a certain engineering significance for the steam injection technology of heavy oil in oilfields.

Experimental and Numerical Simulations of Climatic Loads in Insulating Glass Units by Controlled Change of Pressure in the Gap

Insulating glass units (IGUs) are building components that show a particular structural behavior. Although such structures have many advantages from the point of view of thermal protection of buildings, they show particular structural behavior under climatic loads. The inability to equalize the pressure with the surrounding atmospheric air causes over- or under-pressure inside the gap. The phenomenon may result in the deformation of the panes under the influence of temporary or cyclical changes in weather conditions. This article presents the results of an experimental campaign with a representative IGU sample. The sample had dimensions of 500 mm × 500 mm and was composed of two 6 mm glass panes and a 16 mm wide spacer. The experiments were carried out using a rarely used methodology by inducing a controlled pressure change in the gap. Subsequently, analytical and numerical models were developed, and the results were compared with the experimental findings. The study found that the rapid injection/withdrawal of gas into/from the gap causes a sudden change in the pressure inside the gap, which decreases in absolute value and stabilizes after a few seconds. The decrease, on average, of 7% is due to adiabatic effects resulting from the high rate of gas exchange. The results from the numerical and analytical studies underestimate the pressure difference values obtained in the tests by an average of 8%. In terms of deflections and stresses, the results overestimate the experiments by 16% and 32%, respectively. This finding indicates the presence of a partial rotational restrain of the panes’ edges, which some researchers have also reported. This effect is usually ignored in engineering practice.

Modelling fluid flow in carbon fibre porous media based on X-ray microtomography and lattice Boltzmann method

Carbon fibre media possess complex internal porous structures; the microstructures are vital and can impact the efficiency of fluid flow and mass transfer. In this study, X-ray microtomography (XMT) and the lattice Boltzmann method (LBM) was employed to reconstruct the authentic three-dimensional (3D) pore structures of carbon fibre media and simulate its fluid flow. The effects of fluid properties and boundary conditions were elucidated. Results demonstrated that the flow velocity increased as the displacement differential pressure increased, but decreased as the fluid kinematic viscosity increased. The critical values of differential pressure and viscosity were 4.0106 Pa and 0.0101 m2/s, respectively. The simulation results of the average volume velocity revealed that three boundary conditions had extremely small relative errors of 0.0037 % depending on the carbon fibre material. When the Kozeny–Carman constant (KC, k) was 3.5, the relative error of permeability between the predicted values and the simulated values decreased with increasing porosity. When the porosity was 54.069 %, the relative error decreased to 4.18 %. The fractal model revealed worse results for the permeability prediction of carbon fibre porous media, and the relative error between the simulated and predicted values was 50.40 % when the porosity was 45.585 %.

A Universal Calibration Device for an Air Flow Sensor of the VAV Terminal Unit.

In this paper, a new calibration device for an air flow sensor of the VAV terminal unit is designed. Multi-aperture air outlets are designed to meet the calibration requirements of the air flow sensor in a variety of measurement range. The device can calibrate the air flow sensors of different types of VAV terminal unit by a movable flow rectifier without repeating the design of a different calibration pipeline. The Raspberry PI is used to design the high-performance GUI interface and controlling algorithm to achieve a one-button intelligent calibration. The air flow sensors in three different types of VAV terminal units are used to calibrate the experiment. After testing, the differential pressure value measured by the air flow sensor can accurately measure the air flow within the accuracy of 5% after the formula conversion. The conversion from differential pressure values to air flow values requires precise calibration in order to establish an accurate air flow equation, and here the calibration device plays a key role. The negative effect caused by the distance between the flow rectifiers and the VAV terminal unit is discovered. In other words, the distance between the inlet flow rectifier and the air inlet of VAV terminal unit should be kept as close as possible, or within a range of 2~3 cm. Moreover, the distance between the air outlet of VAV terminal unit and the middle-flow rectifier should be kept as close as possible; otherwise, any slight gap will cause a huge error in the calibration result. The research contributes to the further study of airflow sensing technology through the conversion and calibration of differential pressure measurements to accurate air flow values.

Characterization of internal thermohydraulic flow and heat transfer improvement in a three‐dimensional circular corrugated tube surfaces based on numerical simulation and design of experiment

AbstractTo meet the requirements of development in heat exchangers design, the effect of different tubes geometrical parameters on its flow field analysis and thermal heat transfer performance are investigated in the current research work. The hydraulic thermal fluid coupling with computational simulations is applied. The numerical results are solving used flow transport and heat transfer equations, then these results are validated with available experimental data. The behavior of hydraulic and thermal flow in the corrugated tube is discussed with different geometrical parameters' position and shape. Turbulent flow in the tube is calculated in three‐dimensional numerical simulations with optimization of a multiobjective algorithm are analyzed. The influences of various design parameters, for instance, the number of corrugated rings around the tube, distance between each corrugated ring, the diameter of the ring, and pitch of ring are investigated firstly in the flow field and then optimized by using the design of experiment (DOE). The influence of flow structural modifications such as static pressure, dynamic pressure, and pressure drop is taken into consideration as analyzed performance parameters. The DOE method is investigated based on implements and variances the L16 orthogonal arrays are chosen as the experimental strategy. Furthermore, the optimization results found that the maximum value of pressure difference was for corrugated diameter. The numerical method using DOE has enhanced heat transfer rate as compared to the smooth pipe. Moreover, the minimum Tout is for Case 11 (296.49°C) and the maximum Tout is for (303.10°C) hence the value of Nu number for both cases is 32.9 and 42, respectively. That means using this type of passive device can improve the heat transfer in the pipe. The outcomes illustrate that the performance evaluation factor (PEF) ratio of the corrugated pipe with different geometrical configurations is changed and increased as the corrugated pipe geometrically changed and the value of PEF is more than 1.3.

Postoperative Curative Effect of Cardiac Surgery Diagnosed by Compressed Sensing Algorithm-Based E-Health CT Image Information and Effect of Baduanjin Exercise on Cardiac Autonomic Nerve Function of Patients.

This research was aimed at exploring the effect of CT images reconstructed by optimized compressed sensing algorithm on postoperative diagnosis of patients with hypertensive heart disease and the influence of Baduanjin on cardiac autonomic nerve function. Based on the compressed sensing algorithm, the maximum likelihood expectation maximization algorithm was introduced to optimize it, and the optimization algorithm was established. The optimized algorithm and filtered back projection algorithm (FBP) were compared regarding the root mean squared error (RMSE), peak signal-to-noise ratio (PSNR), and structural similar image metric (SSIM). A total of 126 patients with hypertensive heart disease who underwent CT examination in the hospital were selected as study subjects. According to whether Baduanjin intervention was adopted, patients were divided into observation group (conventional treatment +Baduanjin) and control group (conventional treatment), with 63 patients in each group. The effect of CT examination on postoperative diagnosis was analyzed. Systolic blood pressure (SBP), diastolic blood pressure (DBP), differential pressure (DP), respiratory rate and heart rate (HR), very low-frequency (VLF) power, low-frequency (LF) power, high-frequency (HF) power, total power (TP) of HR variability, and changes in LF/HF of patients before and after treatment were compared. The RMSE of the compressed sensing optimization algorithm (3.28 ± 0.36) was significantly lower than that of the FBP algorithm (9.25 ± 1.03) (P < 0.05). The SSIM and PNSR of the compressed sensing optimization algorithm were (0.87 ± 0.10) and (21.22 ± 1.60) dB, respectively. The SSIM was significantly higher than the FBP algorithm (P < 0.01), and the PNSR was also higher than the FBP algorithm (P < 0.05). The detection rate of CT for pleural effusion was 16 cases (25.40%) higher than 5 cases (7.94%) with TTE (P < 0.01). After treatment, SBP, DBP, HR, LF, VLF, LF/HF, and DP values in the observation group were lower than those in the control group (P < 0.05), and TP and HF were higher than those in the control group (P < 0.05). It suggested that a novel algorithm was established based on compressed sensing algorithm to improve image quality. CT image had important guiding significance for postoperative diagnosis of heart. Baduanjin intervention could improve the integrated function of patient's autonomic nervous system and the regulation ability of the vagus nerve.

Comparison of the performance properties of spunlaid non-woven fabrics used as face mask

Face masks have an effect of preventing the spread of infectious diseases such as coronavirus disease 2019 (COVID-19). With these masks, it is primarily aimed to prevent the environment from being contaminated by the user. However, in the COVID-19 outbreak, many countries made it mandatory to use masks in areas with high human circulation such as marketplaces, shopping malls and hospitals, and then in all areas outside the home. Some tests such as filtration efficiency, microbial load, resistance to body fluids, flammability and breathability are performed to determine the protection potential and wearing comfort of face masks. In this study, we investigated the bacterial filtration efficiency (%), microbial load (cfu/g), breathability (Pa/cm2) and air permeability values of five different face masks obtained by combining polypropylene (PP) nonwoven layers in different weights (accordance with EN 14683:2019 + AC:2019, EN ISO 11737-1:2018 and TS 391 EN ISO 9237 Standards). The surface morphologies of the nonwoven fabrics were characterized by scanning electron microscope (SEM). It was observed that the weight change in spunbond masks (1–4) was directly proportional to bacterial filtration efficiency and differential pressure, and inversely proportional to air permeability. In addition, SEM analysis showed that the average fiber diameter of the meltblown layer was at least 5.80 times smaller than the spunbond layers, and as a result, dramatic differences were also observed in the air permeability and differential pressure values of the Spunbond-Meltblown-Spunbond (SMS) mask (5) compared to spunbond masks.

A Resonant Differential Pressure Microsensor With Temperature and Static Pressure Compensations

This paper presents a resonant differential-pressure (DP) microsensor with temperature (T) and static-pressure (SP) compensations. In this microsensor, three resonators were positioned on and beside the pressure-sensitive diaphragm and the corresponding intrinsic frequencies were translated into differential pressure under the interferences of temperature and static pressure. Finite element simulation was conducted for device modeling, locating the relationship between the intrinsic resonant frequencies of three resonators and values of differential pressure, temperature and static pressure. Microfabrication (e.g., photolithography, deep reactive-ion etching and anodic bonding) was employed to manufacture the microsensor with key fabrication results displayed in this study. Experimental characterizations were conducted, which indicated that the maximum fitting error of the fabricated microsensor was deceased from 2145.7 Pa (before compensation) to 98.2 Pa (after compensation) under a differential-pressure range from 0 kPa to 100 kPa, a temperature range from 10 °C to 60 °C and a static-pressure range from 110 kPa to 200 kPa.

Structural optimization and characteristics of a novel single-ended pressure vessel with inside and outside tubes

A new type of inside and outside tubes differential pressure flowmeter was designed. The throat structure and single-end pressure tapping method is proposed. Three-dimensional numerical simulation is used for structural optimization. The experimental prototype is processed and calibrated in real-time. It was found that the differential pressure values of the new flowmeter was 3.4 times higher and pressure loss ratio only 20% of the original flowmeter in forward flow, while 2.6 times higher and pressure loss ratio only 25% in reverse flow. The sensitivity and energy efficiency of the novel flowmeter is shown to be significantly improved.

Experimental investigation on sphere pig movement in multiple thickness pipe

In the petroleum industry, using pipelines is the safest and most reliable method for crude oil or product transportation. Pipeline pigging is crucial for safe and reliable pipeline operation. The driver pressure of a pig is an important parameter of this operation. Thus, it should be known in advance. In the present survey, an experimental setup has been built to investigate the driver pressure for sphere pig motion for various material hardness as well as oversize ratios. Three spheres have been produced from 55, 65, and 75 Shore-A hardness polyurethane and they have been launched into a six-inch test spool, containing four pipes with different wall thicknesses, equipped with a reciprocating pump as well as a digital pressure measurement system. Then the driver pressures have been measured for all test cases. The uniaxial tension test results of each material along with the test spool and sphere geometries were imported into the simulation software, ABAQUS. The predicted pressure difference values by the simulation had no similar manner to the experimental results when a fixed friction coefficient has been employed. A modification of the simulation scheme is presented here, which is the use of contact pressure dependent frictional behavior in finite element simulations, as the main novelty of the work. This correction leads to close matching of the experimental and numerical results with less than 10% deviation which is an acceptable estimation in the pigging operation. Thus, the pressure-dependent coefficient of friction along with the proper hyperelastic material model can successfully evaluate the differential pressure needed for ball pig motion in a pipe. As the experimental tests are time consuming and expensive for larger pipeline pigs, this method provides a fast and economic tool for driver pressure prediction in larger pipes, based on FEM simulation.

Practical Design of Flow Meter for Mechanical Ventilation Equipment

This paper introduces a practical technique for the design of an instrument used in air flow measurement or flowmeter. This instrument is an essential component in the hospital medical ventilation equipment functioning, therefore, the parameters design presented in this article focus on this purpose. However, this instrument can be employed to any measurement scale. The technique is based on indirect flow measurement, using a sensor that converts the flow parameter into a differential pressure measurement. An electronic transducer allows the differential pressure values to be obtained as an electrical signal, which is then digitized and analyzed to obtain the original parameter. The experimental procedure presented in this paper utilizes a computational algorithm to perform the signal analysis; however, given the simplicity of the procedure, this could be adapted to any digital processing card or platform, to show the measurement obtained immediately. Preliminary analyses demonstrated instrument efficiency with sensitivity of 0.0681 L/s. Accuracy evaluation showed an average measurement error lesser than 1.4%, with a standard deviation of 0.0612 and normal distribution over the set of test measurements.

A Correction Method for Wet Gas Flow Metering Using a Standard Orifice and Slotted Orifices.

Flow measurements that utilize differential pressure meters are commonly applied in industry. In such conditions, gas flow is often accompanied by liquid condensation. For this reason, errors occur in the metering process that can be attributed to the fluctuations in continuous phase parameters in the flow. Furthermore, the occurrence of a dispersed phase results in flow disturbance and dynamic pressure pulsations. For the above reasons, new methods and tools are sought with the purpose of performing measurements of gas-liquid flows providing measurement results that can be considered as fairly accurate in the cases when flow involves a liquid phase form. The paper reports the results of a study involving measurement of wet gas flow using differential pressure flowmeters. The experiments were conducted for three constant mass air flow rates equal to 0.06, 0.078 and 0.086 kg/s. After stabilization of the air flow rates, water was fed into the pipe with flow rates in the range from 0.01 to 0.16 kg/s. The research involved a standard orifice and three types of slotted orifices with various slot arrangements and geometries. The analysis focused on the effect of orifice geometry on the flow metering results. On the basis of the results, it was found that the slotted orifice generates smaller differential pressure values compared to the standard orifice. The water mass fraction in the gas leads to overestimated results of measurements across the flowmeter. Regardless of the type of the orifice, is necessary to undertake a correction of the results. The paper proposes a method of gas mass flow correction. The results were compared with the common over-reading correction models available in the literature.

The effect of low Reynolds number on coefficient of S-type pitot tube with the variation in port to port distance

In this research work the S-type pitot tube is used to determine the velocity of air in dusty environment and slurry flow. Whenever any dusty or slurry air passes through the pitot static tube, then air gets obstructed by the 900 bend of L-type pitot tube resulting in the choking of the flow of measurement device. Therefore S-type pitot tube is used to avoid this type of obstruction in dusty environment or slurry flow and enhances the coefficient of S-type pitot tube. In the present work three S-type pitot tube of different port to port distance are manufactured used to control the accuracy of S-type pitot tube co-efficient. An experimental work has been carried out in a simulated environment of wind tunnel and observed the effect of variation in port to port distances of tube on the tube coefficient. The results of the present work showed that the coefficient value is more scattered at low velocity range 3 to14 m/s than larger one. We observed that the effect of pressure of the forward facing port to that of the rearward facing port is showing optimal pressure difference values at different port to port distance. The findings of the present work are discussed in the light of previous researches and eventually conclusions and scope for future work are highlighted.

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.