Water flow measurements

Water flow measure- Turbine flow meters Magnetic P... 

A lake can also illustrate a theoretically valid, but not useful, control volume. Consider a control volume that comprised only the northern half of the lake the southern boundary of the control volume would then be a surface cutting vertically across the entire lake from the water surface to the lake sediments. Measurement of chemical transport across this boundary would be immensely difficult it would require detailed water flow measurements at an impossibly large number of sites, given that the speed and direction (i.e., the velocity) of water currents in a lake typically vary from place to place and time to time. Such a control volume would not simplify estimates of chemical inputs and outputs. 

What happens if the steam pressure is allowed to build up too fast in the drum Program the microcomputer so that it admits a small amount of steam at first, then gradually opens the steam control valve during a five-minute interval while watching the pressure in the drum. After drum pressure reaches specified limits, program the microcomputer to activate the timer. When the time is complete, the control valve in the steam line will be almost closed. Water will then be admitted through the three-way valve to start the cooling cycle. A water flow measurement sensor must be added to the system to notify the microcomputer that water flow has been established before steam is cut off completely. 

Figure 3.5A. Segmented anode fuel cell. The flow channels and divisions of the anode are shown. The basic setup for temperature control, reactant feed, and relative humidity and water flow measurements for the segmented anode fuel cell was the same as the one employed with the differential PEM fuel cell.

Other Instruments, In addition to the foregoing reactor instruments, all of which measure radiation, there are various temperature and water flow measurements to be mentioned. Each of. the 37 sampling tubes is actually part of a triple-function assembly sampling tube, pitot tube for flow measurement, and thermocouple for water temperature measurement. Knowledge of distribution of water flow velocity and temperature is of obvious value. There... 

U.S. Bureau of Reclamation. 1997. Water Measurement Manual. Washington, D.C. U.S. Government Printing Office. A useful handbook on methods of water flow measurement, and so on, available for downloading at http //www.usbr.gov/pmts/hydraulics lab/pubsl wmm/ (accessed November 3,2010). 

The porous texture and the perneability of an organic and syimetrical ultrafiltration membrane, aged in different solvents, are determined by water thermoporometry and water flow measurement, respectively. 

The water quality (air content) and the water flow influenced the measurements using one channel. Therefore the four channel system was first tested in the laboratory with a stationary tube. The best results were obtained using tap water and a well controlled flow in a water-filled chamber. A great difference in the concentration of air in the different grades of water was obvious, and the tap water was superior to soft water during these measurements. 

The use of tracers enables efficient and reliable measurements of oil, gas and water flow in industrial process units and pipe line systems under production conditions thus fundamentally being non-destructive testing methods. Typical problems which can be efficiently assessed by tracer studies include ... 

Flow measurements using tracers are performed in all piping systems carrying oil, gas or water including separators, compressors, injector systems, and flares. Calibration of elsewhere difficult accessible flow meters is regularly performed by the tracer methods, which are based on international standards. Tracer flow measurements are also well suited for special purposes... 

Current Meters. Various vane designs have been adapted for open-channel flow measurement. The rotating element is partially immersed and rotates rather like a water wheel. Operation is similar to that of vane anemometers. 

Sodium and chloride may be measured using ion-selective electrodes (see Electro analytical techniques). On-line monitors exist for these ions. Sihca and phosphate may be monitored colorimetricaHy. Iron is usually monitored by analysis of filters that have had a measured amount of water flow through them. Chloride, sulfate, phosphate, and other anions may be monitored by ion chromatography using chemical suppression. On-line ion chromatography is used at many nuclear power plants. 

For flow measurement of steam and water mixtures with a Herschel-type venturi in 2V2-in- and 3-in-diameter pipes, see Collins and Gacesa, y. Basic Eng., 93, 11-21 (1971). 

A good method for a simple calibration facility is a system where a constant airflow is produced by using two water containers and an arrangement of a virtually constant pressure head, The constant water flow into the second container displaces an equal airflow out of the container (Fig. 12.21). With this arrangement the difficult measurement of a small airflow is changed into a much easier and accurate measurement of a small water flow. 

A. L. Winternitz, C. F. Fischl. A simplified integration technique for pipe-flow measurement. Water Power, June 1957, pp. 225-234. 

The metabolic rate can be measured in several ways. When no external work is being performed, the metabolic rate equals the heat output of the body. This heat output can be measured by a process called direct calorimetry. In this process, the subject IS placed m an insulated chamber that is surrounded by a water jacket. Water flows through the jacket at constant input temperature. The heat from the subject s body warms the air of the chamber and is then removed by the water flowing through the jacketing. By measuring the difference between the inflow and outflow water temperatures and the volume of the water heated, it is possible to calculate the subject s heat output, and thus the metabolic rate, in calories. 

Stemerding (S16) has reported dispersion measurements in a column filled with 13-mm Raschig rings with water and air in countercurrent flow. The dispersion coefficient was observed to be essentially independent of the water flow rate and dependent on the air flow rate only. For increasing air flow rates, the dispersion coefficient passed through a maximum. 

The breakthrough came with stopped-flow techniques, applied first by Ritchie and Wright (1971a, 1981b). Stopped-flow measurements allow evaluation of observed rates in more detail. It was possible to show that the forward reaction occured not only with hydroxide ions but also with water molecules, followed by fast deprotonation by hydroxide ions. The mechanism of the latter reaction will be discussed in Sections 5.2 and 5.3. 

Water flows at between 3000 and 4000 cm3/s through a 50 mm pipe and is metered by means of an orifice. Suggest a suitable size of orifice if the pressure difference is to be measured with a simple water manometer. What is the approximate pressure difference recorded at the maximum flowrate ... 

Celata et al. (2006) studied experimentally the drag in glass/fused silica microtubes with inner diameter ranging from 31 to 259 jam for water flow with Re > 300. The drag measurements show that the friction factor for all diameters agrees well with predictions of conventional theory A = 64/Re (for the smallest diameter 31 pm, the deviations of experimental points from the line A = 64/Re do not exceed... 

Hao et al. (2007) investigated the water flow in a glass tube with diameter of 230 Lim using micro particle velocimetry. The streamwise and mean velocity profile and turbulence intensities were measured at Reynolds number ranging from 1,540 to 2,960. Experimental results indicate that the transition from laminar to turbulent flow occurs at Re = 1,700—1,900 and the turbulence becomes fully developed at Re > 2,500. 

An experimental study of the laminar-turbulent transition in water flow in long circular micro-tubes, with diameter and length in the range of 16.6-32.2 pm and 1-30 mm, respectively, was carried out by Rands et al. (2006). The measurements allowed to estimate the effect of heat released by energy dissipation on fluid viscosity under conditions of laminar and turbulent flow in long micro-tubes. 

The micro-channels utilized in engineering systems are frequently connected with inlet and outlet manifolds. In this case the thermal boundary condition at the inlet and outlet of the tube is not adiabatic. Heat transfer in a micro-tube under these conditions was studied by Hetsroni et al. (2004). They measured heat transfer to water flowing in a pipe of inner diameter 1.07 mm, outer diameter 1.5 mm, and 0.600 m in length, as shown in Fig. 4.2b. The pipe was divided into two sections. The development section of Lj = 0.245 m was used to obtain fully developed flow and thermal fields. The test section proper, of heating length Lh = 0.335 m, was used for collecting the experimental data. 

On the other hand Bao et al. (2000) reported that the measured heat transfer coefficients for the air-water system are always higher than would be expected for the corresponding single-phase liquid flow, so that the addition of air can be considered to have an enhancing effect. This paper reports an experimental study of non-boiling air-water flows in a narrow horizontal tube (diameter 1.95 mm). Results are presented for pressure drop characteristics and for local heat transfer coefficients over a wide range of gas superficial velocity (0.1-50m/s), liquid superficial velocity (0.08-0.5 m/s) and wall heat flux (3-58 kW/m ). 

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