How to Improve Accuracy of Existing Ultrasonic Water Meters

In present paper, the focus is given to possible ways of increasing accuracy for existing ultrasonic time-of-flight water meters. We will consider transducers with coaxial reflectors working at laminar, transitional and turbulent regimes within their measurement range. Considering error curves of such meters, we can easily resume that they are non-linear and not simply corrected using only one polynomic function. Measurements in laboratory and field conditions demonstrate that there is a shift in the ultrasonic meter’s calibration factor. The deviation of readings starts at Re = 5 000–10 000 and the maximum value is reached at Re = 160. Great inaccuracies referred to the transition from laminar flow to turbulent take place abruptly, which lead to undesirable errors. To understand this phenomenon, the theoretical basis of ultrasonic measurements was analyzed and revealed that typical algorithm for determination of the calibration factor is very questionable since it contains simplified information about velocity profile distribution. Trying to fix this problem, we applied computational fluid dynamics (CFD) modelling of ultrasonic meters with different variants of flow straighteners. Ranges of applicability of a particular turbulence model for a correct description of the velocity profile and other flow parameters in metrological purposes have been evaluated. Due to applied techniques, the flow profile sensitivities of various meter configurations are investigated at different Reynolds numbers comparing to real experiments. To get an improved ultrasonic meter design recirculation zones and flow separation regions inside the flow transducer have been eliminated. As a result, the accuracy of the ultrasonic water meter has increased. Simulations demonstrated reasonable agreement to the error curves obtained on the calibration facility for a whole measurement range.

Study of a Modified Obstruction Free Pressure Sensor Based Flow Transducer Using Hall Sensors

In the present paper, a modified obstruction free pressure sensor-based flow transducer has been developed using Hall sensors. This technique is a modified version of the earlier inductive method. In this transducer, the fluid pressure in the pipeline is taken as the flow sensing parameter, and various drawbacks of the earlier inductive technique are eliminated. A prototype unit of the transducer is developed and studied in the present work. The transducer consists of two identical C-type Bourdon gauges, each fitted with an identical permanent magnet and Hall sensor assembly to sense the fluid pressure under flow condition and static pressure under no flow condition. The difference between the two Hall sensor outputs is found to vary nonlinearly with flow rate. The mathematical relations describing the working of the prototype unit are derived in the paper. The static characteristic curves of the proposed flow transducer are determined experimentally and reported in the paper. The characteristic curves are found to follow the derived equations to a very good extent with negligible percentage deviation from best-fit nonlinear characteristic.

Key Research Insights into Dependence Between Turbine Flow Transducer Conversion Coefficients and Reynolds Number

The paper focuses on the key findings of the first experimental studies on assessing the dependence of the relative deviation of the conversion coefficients of the turbine flow transducer KTFT on the physicochemical properties of oil and oil products, as well as test conditions. The studies were carried out on a specialized calibration stand and on three systems for measuring the quantity and quality indicators of oil / oil products, operated in the main pipeline transport under various climatic conditions. Relying on the obtained experimental data, we assessed the influence of test conditions on KTFT and established correlation dependences between the kinematic viscosity, density, temperature and excess pressure. The study shows that the kinematic viscosity and density of the working medium, i.e., oil / oil products, as well as the Reynolds number Re, have the greatest influence on KTFT. Furthermore, with a change in the volumetric flow rate and kinematic viscosity at one object, it is possible to predict the change in KTFT in the entire range of the volumetric flow rate, relying on Re values. Findings of research show that the tested turbine flow transducer DN 250-1.6 can be operated when Re > 7600

Pannexin 1 Channels Control the Hemodynamic Response to Hypoxia by Regulating O2-Sensitive Extracellular ATP in Blood

Pannexin1 (Panx1) channels export ATP and may contribute to increased concentration of the vasodilator ATP in plasma during hypoxia in vivo. We hypothesized that Panx1 channels and associated ATP export contributes to hypoxic vasodilation, a mechanism that facilitates the matching of oxygen delivery to tissue metabolic demand. Male and female mice devoid of Panx1 (Panx1-/-) and wild-type controls (WT) were anesthetized, mechanically ventilated, and instrumented with a carotid artery catheter or femoral artery flow transducer for hemodynamic and plasma ATP monitoring during inhalation of 21% (normoxia) or 10% oxygen (hypoxia). ATP export from WT vs. Panx1-/- erythrocytes (RBC) was determined ex vivo via tonometer experimentation across progressive deoxygenation. Mean arterial pressure (MAP) was similar in Panx1-/- (N=6) and WT (N=6) mice in normoxia, but the decrease in MAP in hypoxia seen in WT was attenuated in Panx1-/- mice (-16±9% vs -2±8%; P<0.05). Hindlimb blood flow (HBF) was significantly lower in Panx1-/- (N=6) vs. WT (N=6) basally, and increased in WT but not Panx1-/- mice during hypoxia (8±6% vs -10±13%; P<0.05). Estimation of hindlimb vascular conductance using data from the MAP and HBF experiments showed an average response of 28% for WT vs -9% for Panx1-/- mice. Mean venous plasma ATP during hypoxia was 57% lower in Panx1-/- (N=6) vs WT mice (N=6) (P<0.05). Mean hypoxia-induced ATP export from RBCs from Panx1-/- mice (N=8) was 82% lower than from WT (N=8) ( P<0.05). Panx1 channels participate in hemodynamic responses consistent with hypoxic vasodilation by regulating hypoxia-sensitive extracellular ATP levels in blood.

Paediatric exhaled CO2 detector causes leaks

ObjectiveTo assess leakage caused by the Pedi-Cap.MethodsBench test I: Pedi-Caps were connected between the Neopuff and a test lung and placed underwater to detect the leak. Bench test II: the disposable Avea VarFlex Flow Transducer measured the leak. Retrospective analysis: recordings of intubations in the delivery room were analysed.ResultsThe (rippled) male end of the Pedi-Cap is the origin of the leak. In bench test I, 32% of the Pedi-Caps caused inevitable extensive leaks and 34% caused leaks that diminished after sealing the end. In bench test II (n=44) and the retrospective analysis (n=17), the flow transducer measured 22% (18–60) and 39% (8–82) leakage, respectively. Leakage decreased after removal of the Pedi-Cap (before vs after; 17% (7–75) vs 4% (2–10), p=0.004).ConclusionThe Pedi-Cap causes the leak which can compromise respiratory support. We recommend to remove the Pedi-Cap directly after change of colour and to be cautious when using the device as evaluation tool.