Free Jet Calibration Stand

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For multihole pressure probes and hot wire anemometers, an appropriate calibration stand for delivering free air jet is available at the laboratory. It is supplied with pressurized air from the industrial compressor of the laboratory. The air is driven at first to a settling chamber, where the fluid is normalized/stabilized; it then flows into the convergent nozzle and at last to the atmosphere. The heating of the air is also feasible with the use of electrical resistances which are placed in the chamber.

Due to the way it is manufactured, the static pressure of the jet is always equal to the atmospheric, while the total/stagnation pressure can be measured with high accuracy at the maximum cross-sectional area of the convergent nozzle, since the losses of the total pressure during the acceleration of the flow in the convergent nozzle is negligible. Also, due to its symmetry the direction of the flow coincides with the axis of symmetry of the nozzle. These features allow the full estimation of the velocity, both in magnitude and direction, which enables the calibration through the use of this configuration.