Differential Pressure Measurements Research Articles

Blood pressure measurement and nocturnal dipping patterns are heavily affected by body posture through changes in hydrostatic pressure between the arm and the heart.

Nocturnal blood pressure (BP) shows the highest predictive power for cardiovascular events. However, there is a poor reproducibility of personalized dipping patterns in single individuals. We hypothesize that changes in body position during sleep cause variations in hydrostatic pressure,leading to incorrect BP values and dipping classifications. 26 subjects aged 18-30 years, as well as 25 participants aged 50 years and older underwent ambulatory BP measurements on the left arm, as well as determination of the hydrostatic pressure difference between the cuff and heart level during BP measurement. We observed that the BP measurement cuff was above the heart level (negative hydrostatic pressure) mostly through the night. Laying on the right side revealed the largest hydrostatic pressure difference and maximum incorrect BP measurement, with a mean of -9.61 mmHg during sleep. Correcting for hydrostatic pressure led to reclassification of nocturnal hypertension in 14 subjects (27.5%). Dipping patterns changed in 19 participants (37.3%). In total, 25 subjects (49.0%) changed either their nocturnal hypertension and/or their dipping classification. Our findings underscore the importance of accounting for hydrostatic pressure in ambulatory BP monitoring. Changes in body posture during sleep provide a plausible reason for the variability seen in nocturnal dipping patterns. Further research should focus on incorporating hydrostatic pressure compensation mechanisms in 24-h BP measurement. Limiting the noticeable effect of hydrostatic pressure differences could greatly improve hypertension diagnosis, classification, and treatment monitoring.

Development of new gas analytical technique for infrared spectroscopy combined with differential pressure measurements.

A new gas analytical technique for infrared laser spectroscopy combined with differential pressure measurement (IR-DP) is developed. The basic idea of this technique is that the absorption process of molecules by laser irradiation is monitored as the pressure enhancement in a gas cell by use of a differential pressure gauge. The system is composed of a tunable IR laser system, sample cell, differential pressure gauge, and data accumulation system. Using this system, the measurements of the IR absorption spectra for cyclohexane (50 ppm) and ammonia (100 ppm) are demonstrated. By comparison of the current IR-DP spectra with conventional Fourier-transform infrared spectra, the spectral resolution is found to be about 3cm-1, reflecting the laser resolution. Furthermore, the estimated pressure enhancement based on a simple model is consistent with the experimental results. These results suggest that the newly developed IR-DP technique is one of a powerful tool for trace gas detection.

Numerical Simulation Study on Predicting the Critical Icing Conditions of Aircraft Pitot Tubes.

Aircraft pitot tubes are sophisticated instruments designed to detect airflow pressure and relay this information to onboard computers and flight instruments, enabling the calculation of airspeed through the measurement of total-static pressure differences. The formation of ice on aircraft pitot tubes can compromise the acquisition of airspeed data, misguide pilots, and potentially cause catastrophic flight control failures. This article introduces a predictive methodology for identifying critical conditions that lead to icing on aircraft pitot tubes. Utilizing numerical simulation techniques, the methodology calculates the critical conditions for pitot tube icing across cruise flight regimes and atmospheric conditions, resulting in the generation of a critical condition envelope surface. By comparing these critical conditions against actual sensor data, a predictive danger zone can be established, offering an advanced warning system to ensure flight safety.

Small-volume omnidirectional intelligent airflow sensor with differential pressure measurement

Currently, instruments capable of simultaneously measuring airflow velocity and direction are costly and bulky, which presents a challenge in high spatial and temporal resolution in airflow measurement. To address these issues, this paper explores a method that uses artificial neural networks to calculate airflow velocity and direction, capable of measuring the velocity and direction of airflow within the range of 2–12 m/s with high spatiotemporal resolution. Based on the results of comparing the pressure difference response to wind speed in flow simulation, the airflow sensor is designed in a hexagonal prism shape, using low-cost, tiny MEMS pressure sensor chips, with an overall size of only 13 mm × 13 mm × 9 mm, and a power consumption of less than 1.2 mW. Performance tests in the wind tunnel showed that the average error in airflow velocity measurement was 0.20 m/s, and the average error in airflow direction measurement was 0.74°.

Guidelines for Predicting Airtightness in Residential Buildings under Climatic Pressure Conditions

This paper presents a generalized approach for predicting building airtightness based on pressure difference measurements. Furthermore, it provides practical guidelines for applying this method. Studies have proposed a method for predicting the airtightness of high-rise residential buildings in winter using the pressure difference caused by the stack effect. This method was validated using tests under various temperature differentials and building heights. However, practical guidelines for its implementation are lacking. To generalize the airtightness prediction method, a 95% confidence interval for the results was calculated using the blower door test. The applicable pressure difference was calculated based on the calculated results. For each building, the minimum differential pressure within a 95% confidence interval was at least 20 Pa. To provide guidelines for utilizing the proposed airtightness prediction method, acceptable conditions characterized by ΔH × ΔT ≥ 750 m∙°C were calculated. An acceptable condition, characterized by ΔH × ΔT ≥ 750 m∙°C, showed the highest agreement between predicted and measured values across all buildings. This study outlines practical guidelines for using the proposed methodology under these conditions. Overall, we present a straightforward method that relies solely on measuring pressure difference, thereby eliminating the need for a complex and challenging blower door test, typically used in real-world scenarios. By applying this method to predict airtightness in building conditions, the accuracy of predictions for energy use intensity and indoor air quality can be significantly improved.

Modification of the method for determining the flow coefficient K of an Iris damper with a flowmeter with consideration for its applicability in a wider measurement range

In industrial practice, among many types of measuring devices, a significant group comprises instruments for measuring velocity as well as single-phase and two-phase flow rates. Due to numerous measurement challenges, manufacturers of such equipment strive to obtain highly accurate measurement results while keeping the devices simple in structure and operation. Several measurement methods meet these criteria. One proposed measurement device based on pressure difference measurement is the commercial Iris damper with a flowmeter. The authors of a notable study conducted research on this flowmeter under atypical flow conditions. Additionally, they modified the method of determining the correction coefficient K for this type of flowmeter, which represents a novelty in their work. The obtained measurement results indicate the possibility of applying this measurement device in a significantly wider range of flow rates than specified by the manufacturer. The investigated Iris flowmeter can be a suitable instrument for measuring gas flow rates up to 600 l/s, while simultaneously exhibiting a measurement uncertainty of 0.5% of the measured value.

Performance characterization of a wireless sensors network system (WSNS) for measurements of hurricane wind effects on structures

This paper presents a new wireless sensors network system (WSNS) designed for high-resolution absolute pressure measurements, wind speed, and direction. The system is tailored to assess the impact of hurricane winds on residential structures, both in laboratory settings and field environments. Importantly WSNS stands out for its unique ability to provide waterproof, surface-mounted external pressure measurements. The system's performance is evaluated during deployment on a full-scale house model at the Wall of Wind facility. The WSNS sensors were installed on different surfaces of a single-story residential building model. The sensor locations mirrored the locations of surface pressure taps connected to a Scanivalve differential pressure measurement system. Due to the size and shape of the WSNS pressure module, a casing effect was observed, which may result in pressure offsets under certain wind speeds and directions, depending on the sensor's location and the conditions, including dry and light rain (50 mm per hour). The comparison between WSNS and Scanivalve indicates that the sensor's casing geometry does not cause significant differences in the time-averaged measurements for low-turbulence regions. Conversely, this is not true for high-turbulence regions, which should be marked for future deployments using smaller surface-mounted pressure taps.

Highly sensitive push-pull differential pressure sensor with multi-parameter measurement capabilities

A multi-parameter sensor comprising of a Fabry–Perot (FP) pair and a fiber-optic FP microcavity was proposed for simultaneous measurement of differential pressure (DP), static pressure (SP) and temperature. The push-pull FP pair is used to measure the differential pressure, and wide measurement range can be achieved by adjusting the dimensions of the diaphragm. The self-enclosed fiber-optic microcavity is utilized to measure the static pressure. For multi-parameter measurement, a matrix equation is proposed to solve the differential pressure, static pressure and temperature by fully considering the relationship of the FP cavity lengths and measurands. The performance of multi-parameter sensing is verified experimentally. The sensitivities of differential pressure, static pressure and temperature are 294.4822 nm/KPa, 353.08 nm/MPa and 42.4056 nm/°C, respectively, in variation of cavity lengths. The sensing characteristics show good linearity. Such a sensor could find important applications in the fields of process industry and oil industry, etc.

Flow Performance Analysis of Non-Return Multi-Door Reflux Valve: Experimental Case Study

Non-return multi-door reflux valves are essential in fluid control systems to prevent reverse flow and maintain system integrity. This study experimentally analyzes the flow performance of multi-door check valves under different operating conditions, focusing on pressure testing and evaluating their effectiveness in preventing backflow. A wide-ranging experimental setup was designed and implemented to simulate real-world scenarios, facilitating accurate measurement of flow rates, pressure differences, and valve response times. The collected experimental data were analyzed to evaluate the valve’s performance in terms of flow capacity, pressure drop, and hydraulic efficiency. Additionally, the effects of factors such as valve size, valve configuration, and fluid properties (water) on performance were considered. It was found that the non-return multi-door reflux valve has been proven effective and reliable in preserving system integrity and maintaining unidirectional flow at the same time during pressure testing. It exhibits no backflow, remains stable and constant across varied flow conditions, and demonstrates a low pressure drop and high flow capacity, making it suitable for critical pressure testing applications. The response curve revealed that valve opening takes longer to reach higher flow rates than closing, indicating pressure instability during transition periods. This non-linear relationship indicates possible irregularities in pressure drop response to flow rate changes, highlighting potential areas for further investigation.

Pressure Sensors for Evaluating Hand Grasp and Pinch.

This study addresses the need for highly sensitive tools to evaluate hand strength, particularly grasp and pinch strength, which are vital for diagnosing and rehabilitating conditions affecting hand function. Current devices like the Jamar dynamometer and Martin Vigorimeter, although reliable, fail to measure extremely low force or pressure values required for individuals with severe hand impairments. This research introduces a novel device, a modified Martin Vigorimeter, utilizing an ultra-soft latex chamber and differential pressure measurement to detect minute pressure changes, thus significantly enhancing sensitivity. The device offers a cost-effective solution, making advanced hand strength evaluation more accessible for clinical and research applications. Future research should validate its accuracy across diverse populations and settings, exploring its broader implications for hand rehabilitation and occupational health.

Relationships between ankle blood pressure indices and major adverse cardiovascular events in people with and without type 2 diabetes

BackgroundThe relationship between ankle blood pressure (BP) and cardiovascular disease remains unclear. We examined the relationships between known and new ankle BP indices and major cardiovascular outcomes in people with and without type 2 diabetes.MethodsWe used data from 3 large trials with measurements of ankle systolic BP (SBP), ankle-brachial index (ABI, ankle SBP divided by arm SBP), and ankle-pulse pressure difference (APPD, ankle SBP minus arm pulse pressure). The primary outcome was a composite of cardiovascular mortality, myocardial infarction, hospitalization for heart failure, or stroke. Secondary outcomes included death from cardiovascular causes, total (fatal and non-fatal) myocardial infarction, hospitalization for heart failure, and total stroke.ResultsAmong 42,929 participants (age 65.6 years, females 31.3%, type 2 diabetes 50.1%, 53 countries), the primary outcome occurred in 7230 (16.8%) participants during 5 years of follow-up (19.4% in people with diabetes, 14.3% in those without diabetes). The incidence of the outcome increased with lower ankle BP indices. Compared with people whose ankle BP indices were in the highest fourth, multivariable-adjusted hazard ratios (HRs, 95% CI) of the outcome for each lower fourth were 1.05 (0.98–1.12), 1.17 (1.08–1.25), and 1.54 (1.54–1.65) for ankle SBP; HR 1.06 (0.99–1.14), 1.26 (1.17–1.35), and 1.48 (1.38–1.58) for ABI; and HR 1.02 (0.95–1.10), 1.15 (1.07–1.23), and 1.48 (1.38–1.58) for APPD. The largest effect size was noted for ankle SBP (HRs 1.05 [0.90–1.21], 1.21 [1.05–1.40], and 1.93 [1.68–2.22]), and APPD (HRs 1.08 [0.93–1.26], 1.30 [1.12–1.50], and 1.97 [1.72–2.25]) with respect to hospitalization for heart failure, while only a marginal association was observed for stroke. The relationships were similar in people with and without diabetes (all p for interaction > 0.05).ConclusionsInverse and independent associations were observed between ankle BP and cardiovascular events, similarly in people with and without type 2 diabetes. The largest associations were observed for heart failure and the smallest for stroke. Including ankle BP indices in routine clinical assessments may help to identify people at highest risk of cardiovascular outcomes.Graphical abstractAnkle blood pressure indices and incidence of major cardiovascular outcomes. Expanded MACE, a composite of death from cardiovascular causes, myocardial infarction,hospitalization for heart failure, or stroke. BP, blood pressure; CV, cardiovascular; HHF, hospitalization for heart failure; HR, Hazard ratio (for the lowest fourth of blood pressure indice compared to the highest); MACE, major adverse cardiovascular events; MI, myocardial infarction; Total, fatal and non-fatal MI or stroke.

Measurement and prediction of void fraction and pressure drop during air drying process of wet particle packed bed

This study aimed at development of a pressure drop prediction method at a drying process by flowing air through a wet particle packed bed saturated with distilled water. At first, the pressure drop measurement during the drying process of the wet particle packed bead of glass sphere was carried out, and a method for predicting the pressure difference of the bed was proposed by investigating the effect of liquid saturation on the bed void fraction. It was clarified that the effect could be predicted by a simple model by considering liquid bridges formed between particles. Next, the liquid saturation when the measured pressure difference suddenly decreased was investigated as the residual saturation. The value was like that of past research. Finally, considering the effect of liquid saturation on the bed void fraction and the influence of the residual saturation on the relative permeability of liquid phase, more than 90 % of all pressure drop data could be predicted with an error of less than ±15 %. Furthermore, in the range where the gas-phase velocity was large, it was important to predict the pressure difference considering the change of the bed void fraction and the residual saturation.

Driving rain tightness and defects of prefabricated concrete sandwich walls with joints, windows and balconies

There have historically been, and still are, problems with water intrusion into new external walls of prefabricated concrete sandwich elements in Sweden to a varying extent. The aim of this study was to obtain documented knowledge and data on driving rain resistance, to provide a basis for improvements and calculations in a common kind of concrete sandwich system with façade components and sealing products. The study included inspections and air pressure difference measurement of façades in the field and driving rain resistance testing of experimental set-ups in a laboratory. Inspection showed that vertical joints between the concrete elements were often significantly too narrow and, at the same time, adhesion loosening of building mastic in these joints was common. TDV-tubes were often incorrectly placed or had a bad incline. Field measurements indicate no pressure equalization, which is also confirmed by lab measurements. Lab results indicated inward leakage at window-wall interface, even without wind pressure, through the TDV-tubes despite a sharp incline, in element joints with a new kind of application of pre-compressed joint sealing tape. The largest leakage flows were of 0.4% of the vertical water flow across a unit width of the façade at the given height.

Transonic Compressor Darmstadt Open Test Case: Experimental Investigation of Stator Secondary Flows and Hub Leakage

Abstract The future trend of clean sky aviation has led to a smaller core engine, resulting in highly loaded stages with increased relative tip gaps and leakage flows, which causes a reinforced influence of secondary flow phenomena. This article experimentally investigates the secondary flow effects in the 3D-optimized shrouded stator of the TUDa-GLR-OpenStage, representative of a transonic high-pressure compressor front stage, and its susceptibility to typical hub leakage flows. The impact of stator hub leakage on efficiency and total pressure ratio is investigated for several operating speeds, from subsonic to nominal transonic operating conditions. Steady five-hole probe and time-resolved virtual multi-hole probe measurements at different operating conditions at nominal speed are conducted to investigate the underlying loss mechanisms. The leakage mass flow is determined using the measured pressure difference within the fin seal. Steady results show that the optimized 3D stator effectively suppresses the hub corner separation compared to the predecessor 2D stator, but its performance is further limited by a near-tip separation. With the increased stator hub leakage (at a leakage-to-main flow ratio of about 0.4%), the compressor isentropic efficiency generally drops (by about −0.5%) at the full operating range due to an enhanced hub corner separation effect. However, the increased leakage also helps alleviate the tip-corner separation when operating near stall, leading to a smaller efficiency penalty under these conditions. Unsteady results reveal the sensitivity of transient compressor performance to the passing rotor wake, but limited interaction between this phenomenon and the increased leakage is observed. These findings provide insight into the stator hub leakage-related penalties on the compressor aerodynamics efficiency.

Thermal and hydraulic performance of volumetrically heated triply periodic minimal surface heaters

Advanced heat transfer surfaces, mainly Triply Periodic Minimal Surfaces (TPMSs) have great potential to increase heat transfer performance over traditional heat transfer surfaces due to their tortuous flow path and higher surface area-volume ratio. The emergence of additive manufacturing of nuclear fuel motivates experimental investigation of such advanced geometries in the context of a nuclear reactor core. This study employed a novel method to explore the performance of gyroid and diamond TPMS geometries. Volumetrically heated heaters were additively manufactured from conductive polymer filament, and airflow was used to simulate the convective heat transfer from the core within a nuclear reactor. The mass flow and volumetric generation rates were varied, local Nusselt number correlations were obtained using embedded thermocouples to measure the solid and fluid temperature, and friction factor correlations were developed using differential pressure measurements. The gyroid TPMS presented a friction factor 1.5 times higher than the diamond TPMS and 90 times that of the rod bundle. TPMS geometries showed Nusselt numbers 8–10 times higher than that of the rod bundle, also maintaining colder internal temperatures, which suggested that they could sustain 250–275 % higher power density than the rod bundle for a given centerline temperature. Hence, having the potential to greatly increase the safety margins and power output of a nuclear reactor core with similar volume.

Identifying steady and pulsatile two-phase flow regimes with pressure drop signals and acoustic emissions

Identifying two-phase flow regimes is vital for understanding phase-change heat and mass transfer processes. Traditionally, flow regime identification has relied on subjective flow visualization studies, which are then converted to flow regime maps applicable to specific operating conditions. However, these conventional, largely subjective, maps fall short in predicting abrupt changes in flow patterns that often occur during regular operation of vapor compression and absorption heat pumps and other thermal systems. Conventional flow regime maps are also inadequate for addressing the transient, intermittent, or periodic flow regimes that occur in boiling and condensation enhanced using acoustic and other emerging techniques. Therefore, there is a pressing need for alternative flow regime identification techniques that can adapt and reliably track rapid and local changes in two-phase hydrodynamics. Promising candidates for dynamic flow pattern classification include high-resolution pressure drop signals and acoustic emission spectra, which can provide insights into the local hydrodynamics within a flow channel. To assess the feasibility of these measurement techniques, differential pressure and condenser microphone measurements are recorded alongside high-speed videos of a two-phase flow of saturated R134a. The total mass flux and vapor quality are varied to understand the effects of phase velocity and liquid inventory on wave propagation in the channel. Additionally, forced oscillations are introduced to a steady two-phase flow to analyze their impact on flow patterns and their corresponding pressure drop and acoustic signals. Statistical analyses, including Gaussian mixture modeling, are employed to reveal characteristic pressure drop probability associated with each flow pattern, which form the basis for developing a model capable of predicting flow regimes in both steady and oscillating flows. The resulting framework introduces a new flow regime identification technique that can adapt to dynamic operating conditions, benefiting a wide range of thermal systems and phase-change processes.

Experiments and predictions for severe slugging of gas-liquid two-phase flows in a long-distance pipeline-riser system

Experiments concerning the flow regimes observed in gas-liquid two-phase flows in a long-distance pipeline-riser system were carried out and analyzed in this paper. The test loop with 0.075 m inner diameter consisted of a 314 m horizontal pipeline, followed by a 25 m downward-inclined pipe, and finally a 21.5 m riser pipe. An industrial-scale global flow regime map including 5 flow regimes was derived from differential pressure measurements in the riser and was used as a reference for improvements. Electrical capacitance volume tomography installed in the horizontal section was used to reconstruct the phase interface and calculate the average gas void fraction (GVF). An appropriate model for this system was selected by comparing the experimental GVF with different, widely used models. The occurrence of severe slugging flow (SS) can be predicted accurately using an improved model involving additional corrections that consider pipeline length, accurate GVF calculation, and gas density. This study supports the development of a suitable SS prediction model enabling safe design, operation, and control of practical systems.

Calibration of Thixotropic and Viscoelastic Shear-Thinning Fluids Using Pipe Rheometer Measurements

Some non-Newtonian fluids have time-dependent rheological properties like a shear stress that depends on the shear history or a stress overshoot that is a function of the resting time, when fluid movement is started. The rheological properties of such complex fluids may not stay constant while they are used in an industrial process, and it is therefore desirable to measure these properties frequently and with a simple and robust device like a pipe rheometer. This paper investigated how the time-dependent rheological properties of a thixotropic and viscoelastic shear-thinning fluid can be extracted from differential pressure measurements obtained at different flowrates along a circular pipe section. The method consists in modeling the flow of a thixotropic version of a Quemada fluid and solving the inverse problem in order to find the model parameters using the measurements made in steady-state conditions. Also, a Maxwell linear viscoelastic model was used to reproduce the stress overshoot observed when starting circulation after a resting period. The pipe rheometer was designed to have the proper features necessary to exhibit the thixotropic and viscoelastic effects that were needed to calibrate the rheological model parameters. The accuracy of rheological measurements depends on understanding the effects that can influence the observations and on a proper design that takes advantage of these side effects instead of attempting to eliminate them.

Vertical transmission of infectious aerosols through building toilet drainage system: An experimental study

The building's toilet drainage system has been identified as a potential route for the transmission of SARS-CoV-2 during outbreaks. This study employed agar-fluorescein sodium semi-solid as trace particles to investigate the possibility of vertical transmission of the SARS-CoV-2 in drainage system. In both scenarios, where floor drains were all properly sealed or dried out, simulated faeces containing fluorescein sodium were flushed into the toilet bowl. Air sampling was conducted in each restroom, and differential pressure measurements at the floor drain locations were taken. The experimental results showed that when all floor drains were properly sealed, the differential pressure at each floor drain was 0. The fluorescein sodium-traced aerosol did not transmit through the drainage system to various floors, which significantly reduced the risk of infection for users through this route. However, when all floor drains dried out, toilet users above the neutral pressure layer (NPL) were at a high risk of virus infection. Due to the increasing maximum negative pressure at the floor drain above the NPL with ascending floor levels, users on each floor above the NPL faced an elevated infection risk in restrooms. Specifically, users on the top floor were exposed to infectious aerosols roughly 1.6 times that of the first floor above the NPL. Conversely, owing to the increasing maximum positive pressure at the floor drain below the NPL with descending floor levels, users below the NPL experienced a comparatively lower infection risk. This finding has important implications for understanding the vertical transmission dynamics of SARS-CoV-2 in residential or public building and can inform the development of effective control measures.

Combined Ash and Soot Monitoring for Gasoline Particulate Filters Using a Radio-Frequency-Based Sensor

Increasingly stringent emission limits have made particulate filters necessary for gasoline engines. Similar to diesel applications, gasoline particulate filters (GPFs) can be monitored by differential pressure measurement or by the radio-frequency-based filter diagnosis (RF sensor). In addition to measuring the soot loading, ash detection is critical for monitoring the GPF over the entire vehicle lifetime. Because the RF sensor detects the filter loading through a change in the dielectric properties of the GPF, it can detect not only soot but also ash. In diesel applications, the RF sensor has already demonstrated its potential for ash detection. To verify the feasibility of simultaneous ash and soot monitoring for GPFs, filters were loaded with ash on an engine test bench and measured on a lab test bench under defined synthetic exhaust gas conditions. By evaluating resonant modes, soot and ash could be clearly distinguished, as ash mainly affects the resonant frequency, while soot also changes the quality factor due to its high dielectric losses. However, higher soot loadings could not be detected by the resonant parameters, but instead by a frequency-averaged transmission signal. While the presence of ash caused an offset in this signal, its sensitivity to soot was not affected. Thus, the influence of ash can be corrected if the signal in the soot-free filter state is known, e.g., from the behavior of the resonant parameters. Therefore, even with a continuously increasing ash loading over the lifetime of a vehicle, an accurate soot detection is possible with the RF sensor.