Hot Film Calibration System Using a Free Jet in Water (original) (raw)
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Progress in hot-film anemometry for hypersonic flow
Experimental Thermal and Fluid Science, 1996
m A robust microsensor hot-film probe has been developed to obtain continuous turbulence measurements in moderately severe hypersonic environments. This probe represents a significant advancement of an existing concept. Optimization for hypersonic flow is achieved through sensor placement, the use of high-temperature materials, and state-of-the-art microphotolithographic fabrication techniques. Tests in Mach 6 air and Mach 11 helium flows have been very promising. The probe has exhibited excellent characteristics, including a frequency response that is a factor of 5 higher than that of previous hot-film sensors. The qualitative spectra of the anemometer fluctuations has been smooth and repeatable. Despite these improvements, heat conduction into the substrate still complicates the probe response. A review of the physics of this problem is presented along with a plan for the characterization of the response via several dynamic calibration techniques.
Study of Hot Wire Anemometry and Flow Measurement Elements
2015
In industries,flow of any fluid varies over a very wide range.It ranges from very low to very high velocity. Because of this variation, various types of flow measurement elements have been developed. Out of all these, hot wire anemometer, orifice meter and rotameter are widely used. Responses of fluids with different densities and sensors with different diameters have been studied. Since these components are delicate to heat exchange between the component and its composition, temperature and environment, their responses vary with conditions provided. Using hot-element sensor we also measured the concentration of gas components in a mixture of two known gases. This method is based on thermal conductivity of mixture. Thermal conductivity of mixture depends on individual thermal conductivities of gases of mixture and individual fractional concentration of that gases. Taking different types of probes and different types of fluid we compare the behavior of sensor so that we can determine...
Investigation on the determination of flow direction using two parallel cylindrical hot film sensors
Measurement, 2010
Measurement of instantaneous air flow velocity with high frequency can be carried out by using a hot wire anemometer (HWA). HWA works on the basis of heat transfer rate from hot wire to the fluid flow, therefore directional identification of the air flow using hot wire anemometer is a difficult task. By using two parallel cylindrical hot film sensors a probe was built. By considering the wake and heat effect of the upstream sensor on the downstream sensor, direction of the air flow can be identified. In this work, the wake and heat effect resulting from the upstream sensor to the velocity measurement, by the downstream sensor was studied. This measured velocity is dependent of the following factors namely; air velocity, upstream sensor overheat ratio, distance between the two sensors and turbulence intensity of the flow. As a result it was found that the manufactured probe with sensor distance of 1 mm apart is capable of measuring reverse flow measurements of up to 20 m/s for a moderate turbulent flow. (M.A. Ardekani), mohamedami-ny@merc.ac.ir (M. Aminy), khoshnevis@Sttu.ac.ir (A. Khoshnevis).
Hot-wire calibration in subsonic/transonic flow regimes
1995
A different approach for calibrating hot-wires, which simplifies the calibration procedure and reduces the tunnel run-time by an order of magnitude was sought. In general, it is accepted that the directly measurable quantities in any flow are velocity, density, and total temperature. Very few facilities have the capability of varying the total temperature over an adequate range. However, if the overheat temperature parameter, a(sub w), is used to calibrate the hot-wire then the directly measurable quantity, voltage, will be a function of the flow variables and the overheat parameter i.e., E = f(u,p,a(sub w), T(sub w)) where a(sub w) will contain the needed total temperature information. In this report, various methods of evaluating sensitivities with different dependent and independent variables to calibrate a 3-Wire hot-wire probe using a constant temperature anemometer (CTA) in subsonic/transonic flow regimes is presented. The advantage of using a(sub w) as the independent variabl...
Proceedings of SPIE - The International Society for Optical Engineering, 2010
Investigations of the flow behavior are currently carried out experimentally on models of hydraulic turbines. Quantities such as unsteady velocity can be acquired using PIV or LDV techniques, static wall pressure using steady or unsteady pressure transducers and wall shear stress using hot-film anemometry. More rarely acquired however, the unsteady total pressure at different locations in the flowstream would give more information on the flow dynamics and would be a key component for setting boundary conditions for CFD simulations. Following the example of classical Pitot tubes, which can only give averaged pressure values though, we have developed a five-hole pressure probe with embedded sensors that can measure unsteady values of total pressure, local flow velocity and direction. The probe head is designed to have a minimum impact on the flowstream, and the miniature sensors are placed in a cross configuration compared to the probe's support axis.
Application of hot-wire (-film) flowmeters to water velocity measurements in wells
Journal of Hydrology, 1982
Hot wires have long been used for the measurement of air speeds, where they are particularly suitable for relatively small velocities. Unfortunately, it has not been possible to use them in water with the same precision and ease as in air. One of the main drawbacks of hot wires (films) when they are used in water measurements is that they become unstable because of the contamination of the wire (film) by dissolved gases, dirt and chemicals in the water, and they are very sensitive to ambient temperature fluctuations. The present paper discusses the practical problems in using the hot-wire (-film) flowmeter for velocity measurements in water wells.
Experimental Investigations on Low Speed Turbulence Using Hot-Wire Anemometer
2013
Objective of this study is to measure the turbulence characteristics of air flow through rectangular channel in the developing regime. IFA 300 Constant Temperature Anemometer system is used for turbulence measurements. Calibration of IFA 300 Constant Temperature Anemometer is carried out in a low speed open jet wind tunnel using known velocity of air. Calibration constants are determined as per the King's Law. Measurements are carried out at different Reynolds Numbers for the analysis of variation of velocity from wall to core region. The turbulence measurement includes variation of turbulent intensity and turbulence kinetic energy for different Reynolds Numbers. The results obtained from hot wire anemometer are compared with analytical methods available in literature. Fast Fourier Transform is also carried out for establishing the chaotic nature of turbulent flow. Turbulence intensity, turbulence kinetic energy and normal stress are found to decrease from wall to core region of rectangular channel.
Three-component constant temperature anemometer CTA3-2: Calibration and application
The study deals with three-component hot-wire anemometer designed and manufactured in ITAM SB RAS. The paper presents the calibration technique of designed and manufactured three-wire probes and describes the data obtained in testing experiments on measurements of steady and unsteady parameters of the flow in subsonic turbulent jet.
Mass flow-rate control unit to calibrate hot-wire sensors
Experiments in Fluids, 2007
Hot-wire anemometry is a measuring technique that is widely employed in fluid mechanics research to study the velocity fields of gas flows. It is general practice to calibrate hot-wire sensors against velocity. Calibrations are usually carried out under atmospheric pressure conditions and these suggest that the wire is sensitive to the instantaneous local volume flow rate. It is pointed out, however, that hot wires are sensitive to the instantaneous local mass flow rate and, of course, also to the gas heat conductivity. To calibrate hot wires with respect to mass flow rates per unit area, i.e., with respect to (qU), requires special calibration test rigs. Such a device is described and its application is summarized within the (qU) range 0.1-25 kg/m 2 s. Calibrations are shown to yield the same hot-wire response curves for density variations in the range 1-7 kg/m 3. The application of the calibrated wires to measure pulsating mass flows is demonstrated, and suggestions are made for carrying out extensive calibrations to yield the (qU) wire response as a basis for advanced fluid mechanics research on (qU) data in density-varying flows.