Abstract
This paper describes the problems encountered in the design, operation, and calibration of a small momentum balance fitted within an isokinetic sampling probe located in the test section of a wet steam ‘wind’ tunnel. The probe is suitable for use in air, dry steam, or wet steam. It has an opening of ½ in diameter, a maximum diameter of 1¼ in, and a length of 4½ in, and will detect momentum forces greater than 0·001 lbf. The signal is transmitted by causing the impulse cage to compress a bellows. Turpentine enclosed therein raises the level of its meniscus in a capillary tube and the change in level is observed with a micrometer microscope. An electrical superheating calorimeter is employed in series with the impulse-measuring probe to determine the stagnation enthalpy of the sample. Results are reported for air and steam. For steam the ranges of the respective variables are: pressure, 20–25 inHg vacuum; velocity, 200–500 ft/s; and wetness, 0–10 per cent by weight. Owing to the small size of the momentum cage it was not possible to isolate the contribution to the total momentum made by the entrained liquid.
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