SEGMENTED THERMAL-DIFFUSION CHAMBER FOR CONTINUOUS MEASUREMENTS OF CN

A new segmented thermal diffusion chamber for measurement of CN has been constructed and found to operate satisfactorily. In the segmented chamber aerosol laden air is passed through a vertical cylindrical tube consisting of hot and cold segments with water saturated walls. Air in the center of the tube reaches a temperature and water vapor pressure midway between the temperature and vapor pressure of the hot and cold segments. This produces a supersaturation in a manner similar to that which generates supersaturations in a static thermal diffusion chamber operated at the same temperature difference. An analysis of this chamber shows that introducing the sample along the axis and surrounding it with filtered sheath air will prevent the sample from encountering fluctuating supersaturations which exist along the walls and give the dilution necessary for use with optical counters. © 1979.