Condensation nucleus counter using mixing and cooling

摘要

A modified mixing-type condensation nuclei counter for measuring the size and number of small particles is presented. A gas stream is saturated with respect to a working fluid. The saturated gas at a first temperature is mixed in a growth chamber with a sample gas at a second temperature that is lower than the first temperature. The mixture of the saturated gas and the sample gas at different temperatures results in supersaturation of the mixed gas with respect to the working fluid. Particles in the sample gas act as nucleation sites for condensation of the working fluid. The particles are thus grown to a larger size and therefore are more easily measured by known light-scattering particle detection methods. The efficiency of the supersaturation process is made even more efficient by cooling the growth chamber to a third temperature which is lower than the second temperature or by turbulently mixing the saturated gas and the sample gas. False count rate is reduced by filtering the saturated gas before it is mixed with the sample gas to remove droplets of the working fluid from the saturated gas.