GB829681A - Measurement of dewpoint - Google Patents

Abstract

829,681. Measuring humidity. GILLI, P. March 26, 1950, No. 9369/56. Class 40 (1) [Also in Group XX] A positively propelled current of moist gas is cooled below the dewpoint under controlled conditions and the temperature of the cooled gas is used for continuous evaluation of its dewpoint. In the form shown in Fig. 1 a sample of the gases from a flue 1 is continuously removed at 2 and returned at 10 by a blower 7. The gases are first reduced in temperature in a pipe 3 surrounded by a water jacket 4 maintained at a constant temperature by a heater 5 and thermostat 6. Alternatively, boiling water may be used. The gases are further cooled in a pipe 8 in a jacket 12 and finally cooled below the dewpoint in a pipe 9 in a jacket 11. Cooling air is passed successively through the jackets 11, 12, Fig. 2, shows the air continuously circulated by a blower 13 through jackets 11, 12 and a pipe 14 in a jacket 16. A thermostat 15, exposed to the air from the blower, is connected to a valve 17 controlling the supply of cooling water to the jacket 16. The temperature of the gas in the pipe 9 is a measure of the dewpoint and a temperature indicator may be calibrated directly. The indication may be furnished by the expansion of a tube within the tube 9 relatively to an Invar reference member or may be thermo-electric. The gas sample may be cooled in stages to indicate the dewpoints of different vapours in the gas. The same cooling air may produce the successively stages of cooling, or the gas itself, when cooled below the lower dewpoint may be used to cool itself to the upper dewpoint.