Anemometers hot-film

Nonintrusive Instrumentation. Essential to quantitatively enlarging fundamental descriptions of flow patterns and flow regimes are localized nonintmsive measurements. Early investigators used time-averaged pressure traverses for holdups, and pilot tubes for velocity measurements. In the 1990s investigators use laser-Doppler and hot film anemometers, conductivity probes, and optical fibers to capture time-averaged turbulent fluctuations (39). 

Hot film anemometer An instrument for the measurement of fluid velocity similar to the hot wire anemometer, but more robust as it consists of a thin quartz rod covered with a film of platinum rather than a wire. 

Hot-filament chemical vapor deposition (HFCVD), 17 214-215 Hot-fill market, 20 50-52 Hot-film anemometers, 11 676 Hot flocking, 7 59... 

Schowalter and coworkers [49-51 ] developed a hot film anemometer to measure wall slip [49]. This particular experimental technique attempted to correlate the pressure and hot film oscillation with the alternation of boundary condition in slit capillary flow of monodisperse polybutadiene (PB). 

Figure 7.4 Typical times series of a hot-film anemometer for (a) low (a = 2%) and (b) high (a = 13%) void fractions.

Thomae [544] measured the turbulent flow field in an unbaffled stirred tank of V = 1.6 m by determining the vector of the momentary flow velocity by point for point determination with a constant temperature hot-film anemometer. From these paths of equal flow velocity, so-called isotachs, and paths of equal turbulence, so-called isotarachs, were derived for the turbine and for the propeller stirrer. It was also found that u and u increased linearly with Re up to Re = 4 x 10 u cc u oc nd. However, relatively low values were found for the ratio u /u 0.18 for the turbine stirrer and ca. 0.09 for the propeller stirrer. 

Blackwelder, R. F., Hot-wire and hot-film anemometers, Methods of Experimental Physics 18, Part A, pp. 259-314, 1981. 

Paulsen, P.K. and Hasenkam, J.M. 1983. Three-dimensional visualization of velocity profiles in the ascending aorta in dogs, measured with a hot film anemometer. /. Biomech. 16 201-210. 

FIGURE 56.4 Velocity profiles obtained with a hot-film anemometer probe in the descending thoracic aorta of a dog at normal arterial pressure and cardiac output. The velocity at r = time/(cardiac period) is plotted as a function of radial position. Velocity w is normalized by the maximum velocity Wm and radial position at each time by the instantaneous vessel radius R(f). The aortic valve opens at t = 0. Peakvelocity occurs 11% of the cardiac period after aortic valve opening. (From Ling, S.C., Atabek, W.G., Letzing, W.G. et al. 1973. Circ. Res. 33 198. With permission.)... 

Ling, S.C., Hubbard, P.G. (1956). The hot-film anemometer A new device for fluid mechanics. Journal of Applied Sciences 23(9) 890-891. 

Paulsen, P. K., Nissen, T., Patient Safety Unit for a Hot-Film Anemometer, Used for Blood-Velocity Determination in Humans, Medical Biology Engineering Computing, Vol. 20,1982, pp. 625-627. 

The water was operated in batch mode. The velocity measurements were performed with a hot-film anemometer. 

Torvik [173] also used a hot-film anemometer and measured velocities, void fractions, and turbulent kinetic energy of a bubble column with diameter 0.29 m and height 4.52 m. Both the air and the water were operated in continuous modes in the column. The liquid superficial velocity was low. Results at level 2.6m above gas distributor at different gas velocities are shown in Fig. 8.5. 

Gasche [46], Gasche et al. [47], Grienberger [50], Grienberger and Hofmann [51], Hillmer [59] and Hillmer et al. [60] also studied the flow in fwo-phase bubble colunms using a hot-film anemometer. 

Thermal hot-wire and hot-film anemometers (HFA) have been available for measuring instantaneous single phase fluid velocity for about a century. The small size of the sensor and good frequency response makes them especially suitable for turbulence investigations. These techniques are thus commonly used in many engineering disciplines. 

The main advantages of laser Doppler anemometry (LDA) relative to pitot tubes and hot-film anemometers (HFA) include ... 

The gas and liquid velocities at key points are measured by hot film anemometers. The locations of the hot film probes are rotated in several similar experiments to get fiill information on velocity distributions. The amount of entrained droplet flow and droplet sizes are measured by several isokinetic sampling probes. The Thermal-hydraulic and Reactor Safe Laboratory has recently developed the isokinetic sampling probe to measure the droplet entraimnent rate and droplet size distribution. For droplet size distribution, the droplets are collected into a oil bath and the CDC pictures of the suspensions are obtained. Using digital image processing system... 

Instrument Pitot static probe Conductivity probe Hot film anemometer (liquid)... 

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