Anemometers turbine

Gup and Vane Anemometers. A number of flow meter designs use a rotating element kept in motion by the kinetic energy of the flowing stream such that the speed is a measure of fluid velocity. In general, these meters, if used to measure wind velocity, are called anemometers if used for open-channel Hquids, current meters and if used for closed pipes, turbine flow meters. 

The vane anemometer is an old invention. It can be likened to a small wind turbine with 4-10 rotating blades and a handle, as in Fig. 12.20. Earlier constructions were fully mechanical, where the spindle rotation was transmitted to a pointer through a series of gears. In modern vane anemometers, an electrical sensor records the spindle rotation and the signal is processed, giving the velocity on a digital display. Such an instrument usually is able to integrate the mean velocity over a time interval. 

The flow patterns for single phase, Newtonian and non-Newtonian liquids in tanks agitated by various types of impeller have been repotted in the literature.1 3 27 38 39) The experimental techniques which have been employed include the introduction of tracer liquids, neutrally buoyant particles or hydrogen bubbles, and measurement of local velocities by means of Pitot tubes, laser-doppler anemometers, and so on. The salient features of the flow patterns encountered with propellers and disc turbines are shown in Figures 7.9 and 7.10. 

Another challenge is selecting an appropriate location for the turbine, due to the highly localized nature of wind. Low-cost anemometers may help alleviate this problem, but time must be spent to collect a sufficient amount of data [10]. Areas particularly suited to wind power because of their typical high wind velocities include coastlines, high ground, and mountain passes [12]. Wind power does not need water, so it is suitable for dry areas. 

Among the renewable energy processes, it is the wind turbines that benefit the most from the measurement of wind direction and velocity. Doppler-type sensors are used to determine the wind velocity and to obtain three-dimensional air motion profiles and also in the balancing of HVAC systems and measuring of the velocity of wet and dirty gases in industry. For a more detailed discussion of Pitot tubes and thermal flowmeters, also refer to the Sections 3.9.7.2 and 3.9.10. Here, the focus is on mechanical- and Doppler-type anemometers. 

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. 

Inferential meters include instruments in which the volumetric flow rate is inferred by the movement of a turbine, propeller, or impeller. The fluid impinging on a blade causes it to rotate at an angular velocity that is proportional to the flow rate. The early anemometers made with plates and cups are examples. These types of meters are becoming less and less common due to the need to calibrate and compensate for effects like viscosity. According to Crabtree (2009), the Coriolis and ultrasonic meters are replacing the turbine meters in most industrial applications. 

Flowrate Differential pressure devices pitot tube, orifice plate, venturi meter Turbine meter Rotameter Hot wire anemometer... 

The scattered light is imaged onto a detector, where it is superimposed with part of the laser beam. The detector output contains the difference-frequency spectrum Ao) = cjoi — (i> = ( l + s) v, which is electronically monitored with a heterodyne technique. One example is an airborne CO2 laser anemometer that was developed for measuring wind velocities in the stratosphere in order to improve long-term weather forecasts [15.124]. Further examples are measurements of the velocity profiles in the exhaust of turbine engines of planes, in pipelines for gases and liquids, or even in the arteries of the human body. 

Compression of gases and air to achieve high pressures with relatively low volumes is by positive displacement compressors of either the piston or rotary type, while for large volumes at lower pressures centrifugal compressors are used as for example in gas turbines. Gas flows can be measured by means of a vane or hot wire (heated head) anemometer, by measuring the pressure difference across an orifice, or through the use of pitot tubes. 

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