p4.9-12 - velocity. c.) Estimate the error in your...

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4.9-12 A hot wire anemometer is used to measure the velocity of an air flow. The device consists of a wire with length L = 1 cm and diameter D = 0.5 mm. The nominal operating conditions are at an air velocity u = 50 ft/s with ambient temperature T = 20ºC and atmospheric pressure. The wire is energized with a current in order to maintain the temperature of the wire Δ T = 5 K above the ambient temperature. The ohmic dissipation, g ± , in the wire is related to the velocity of the air. a.) What is the ohmic dissipation in the wire at the nominal conditions? b.) Plot the air velocity as a function of ohmic dissipation - this is your calibration curve for the device, you will measure the generation and use this plot to infer the air
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Unformatted text preview: velocity. c.) Estimate the error in your measurement related to uncertainty in the measurement of generation if you can measure the ohmic dissipation to within g = 2 mW. d.) Estimate the error in your measurement related to uncertainty in the measurement of the temperature difference if you can measure T to within T = 0.2 K. e.) You neglected radiation in your calculation - estimate the error that might be induced by radiation from the hot wire. f.) Can your hot wire be used to measure the velocity of oxygen rather than air? Estimate the error associated with using your correlation from (b) with oxygen....
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This note was uploaded on 08/11/2008 for the course ME 364 taught by Professor Rothamer during the Summer '08 term at Wisconsin.

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