Page:Journal of the American Society of Mechanical Engineers, Volume 33.pdf/674

WILLIS H. CARRIER, Figs. 11 and 12, was used in different experiments. A differential draft gage and pitot tube indicated the velocity of the air through the oriﬁce and over the wet-bulb thermometer No. 4.

74This velocity could be varied any desired amount between 1000 and 4000 ft. per min. by adjustment of the motor rheostat. It was found that the static pressure in the box agreed substantially with the velocity head at the thermometer bulb so that no further measurements of the former were recorded. Thermometer No. 1 indicated the dry-bulb temperature of the air in the box, thermometer No. 2, the dry-bulb temperature of the air outside, and thermometer No.3, the calorimeter temperature. Thermometers Nos. 3 and 4 were calorimeter thermometers especially constructed for this test by the Taylor

Instrument Company. They were in the fahrenheit scale, graduated to tenths of a degree, and calibrated to $1⁄40$ deg. They were also carefully compared.

75Experiment No. 1. This test was made in order to determine the effect of an air blast of known intensity upon the readings of thermometers No. 3 and No. 4. The need of the determination was evident as the velocities were not necessarily the same upon the two bulbs nor in the same relative direction. Moreover, it was evident that a portion of the heat of the air was converted into mechanical energy of the air current; also that a portion of this, at least, was re-converted into heat by impact on the bulb. This temperature error, if any, would be proportional to the velocity head; therefore a maximum condition of 1-in. velocity head and static pressure were taken. Both thermometers and the calorimeter were perfectly dry. The apparatus was run under constant