Simultaneous Flowmetry Research Articles

Applications and Perspectives of Ultrasonic Multi-Gas Analysis with Simultaneous Flowmetry

We have developed ultrasonic instrumentation for simultaneous flow and composition measurement in a variety of gas mixtures. Flow and composition are respectively derived from measurements of the difference and average of sound transit times in opposite directions in a flowing process gas. We have developed a sound velocity-based algorithm to compensate for the effects of additional gases, allowing the concentrations of a pair of gases of primary interest to be acoustically measured on top of a varying baseline from ‘third party’ gases whose concentrations in the multi-gas mixture are measured by other means. Several instruments are used in the CERN ATLAS experiment. Three monitor C3F8, (R218), and CO2 coolant leaks into N2-purged environmental envelopes. Precision in molar concentration of better than 2 × 10−5 is routinely seen in mixtures of C3F8 in N2 in the presence of varying known concentrations of CO2. Further instruments monitor air ingress and C3F8 vapor flow (at high mass flows around 1.1 kg s−1) in the 60 kW thermosiphon C3F8 evaporative cooling recirculator. This instrumentation and analysis technique, targeting binary pairs of gases of interest in multi-gas mixtures, is promising for mixtures of anesthetic gases, particularly in the developing area of xenon anesthesia.

A Custom Online Ultrasonic Gas Mixture Analyzer With Simultaneous Flowmetry, Developed for the Upgraded Evaporative Cooling System of the ATLAS Silicon Tracker

We describe a combined ultrasonic instrument for continuous gas flow measurement and simultaneous real-time binary gas mixture analysis. In the instrument, sound bursts are transmitted in opposite directions, which may be aligned with the gas flow path or at an angle to it, the latter configuration being the best adapted to high flow rates. The combined flow measurement and mixture analysis algorithm exploits the phenomenon whereby the sound velocity in a binary gas mixture at known temperature and pressure is a unique function of the molar concentration of the two components. The instrument is central to a possible upgrade to the present ATLAS silicon tracker cooling system in which octafluoropropane (C F ) evaporative cooling fluid would be replaced by a blend containing up to 25% hexafluoroethane (C 2 F 6 ). The instrument has been developed in two geometries following computational fluid dynamics studies of various mechanical layouts. An instrument with 45 crossing angle has been installed for commissioning in the ATLAS silicon tracker cooling system. It can be used in gas flows up to 20 000 l.min -1 and has demonstrated a flow resolution of 2.3% of full scale for linear flow velocities up to 10 m.s in preliminary studies with air. Other instruments are currently used to detect low levels of C 2 F 8 vapor leaking into the N 2 environmental gas surrounding the ATLAS silicon tracker. A long-duration continuous study of more than a year has demonstrated a sensitivity to mixture variation of better than 5.10 -5 .

Voiding disorders after radical hysterectomy

The authors report the reaction on bladder function observed in 15 women suffering from cervical cancer in stages I and II after the Wertheim-Meigs radical hysterectomy. All the patients were given various tests before and after operation: urodynamic investigations using uroflowmetry, gas cystometry completed by a urecholine denervation test, cystosphinctermanometry with simultaneous flowmetry, simultaneous recording of bladder and urethral pressures with flowmetry, and urethral closure pressure profile with microtip transducers (Millar Instruments). On the basis of the results, the authors maintain that the damage caused by the operation affects not only the detrusor but also the normal sphincter function as suggested, in fact, by the symptoms observed in the patients (dysuria and stress incontinence). The preoperative urodynamic study was of no help in foreseeing the amount of damage caused by the operation to the normal bladder-sphincter function. On the other hand, the study proved essential postoperatively in clarifying the pathophysiology of the voiding disorders complained of by the patients and, above all, in deciding upon the best plan of management.