David Sinclair

Experimental Verification of Diffusion Battery Theory

The diffusion battery, an assembly of circular tubes or rectangular channels, is one of the best devices available for measuring the size and size distribution of submicron aerosols in the diameter range 0.002 to 0.2 µ m. The performance of these batteries is known from molecular diffusion theory, but until now has not been checked experimentally in this size range because of the lack of the necessary monodisperse aerosols. Experimental measurements on singly charged monodisperse aerosols from 0.01 µm to 0.1 µ m are described using a General Electric and a Pollak condensation nucleus counter to measure the aerosol penetration through the stages of a set of portable diffusion batteries in series. Particle sizes in the range tested could be selected at will by adjusting the voltage of an electric mobility classifier. The fraction of aerosol of a given size passing through each battery stage was found to agree closely with the penetration calculated from molecular diffusion theory for that size. This shows t...

Particle size sensitivity of condensation nucleus counters

Abstract The counting efficiency of condensation nucleus counters as affected by aerosol particle size has been studied by many investigators. Literature on this subject was reviewed and it was found that the size for 100% efficiency varies from 0.01 to 0.09 μm depending on the type of counter, the nature of the particle and the investigator. The minimum detectable diameter varies from 0.0014 to 0.005μm. Measurements made at the Environmental Measurements Laboratory (EML) showed that the efficiency of the Pollak and the TSI falls to about 15% at diameters of 0.005 μm. The General Electric and the Environment One do not show this effect, at least when compared with the EML continuous flow counter.

Measurement of Nanometer Aerosols

This paper is a review of my work during the past 18 years on nanometer, i.e., submicrometer, aerosols. These aerosols scatter negligible light so they are difficult to study and must be observed by indirect methods such as diffusion batteries and condensation nucleus counters. Several diffusion batteries are described: “cluster tube” batteries, 5.5 km of 1-mm-diam. straight tubing mounted in clusters; collimated holes structures containing 5.1 km of holes, 1/4 mm in diameter; honeycomb structures containing 3.5 km of holes 1/3 mm in diameter; screen batteries containing 55 stainless steel screens in 10 sections; reticulated vitreous carbon batteries containing 60 k interconnected pores per cm5. From theory, the diffusion battery is shown to be only slowly discriminating, so a series of batteries and measurements is required for particle size analysis. Measurements were made with a continuous flow condensation nucleus counter developed to provide the steady flow required by diffusion battery theory. The m...

Intrinsic Calibration of the Pollak Counter—A Revision

The “intrinsic” calibration of the Pollak condensation nucleus counter was reevaluated with the aid of a “tube bridge,” the device invented by Pollak for this purpose. This device allows measurement of the concentration of an aerosol and then another measurement when the concentration has been reduced to exactly one-half. This is accomplished by filtering out all of the aerosol from one of the two legs of the tube bridge, while maintaining the same flow rate in each. Seven hundred and eighty pairs of measurements were made over the concentration range of 102/cm3 to 106/cm3 using the aerosol in the laboratory ambient atmosphere, gold aerosol from a thermal generator, and carbon aerosol from the incomplete combustion of methane. The results gave the ratio, half to full aerosol, equal to 0.50 ± 5% over the range from 10/cm3 to 105/cm3. Above 105/cm3 the ratio increased to about 0.7 depending on the type of aerosol but not on the particle size. These values were obtained from Pollaks 1960 calibration tables ...

The Continuous Flow Condensation Nucleus Counter. II

The original version of the continuous flow counter has been improved and redesigned to run automatically with a rotary sequencing valve and data processing system. As previously described, the counter was developed at the Environmental Measurements Laboratory for use with diffusion batteries because they require a constant flow of aerosol for particle size measurement. The automated system is used extensively for measurement of the concentration and particle size distribution of indoor and outdoor aerosols. The operating conditions are evaluated to determine the effect of temperature deviation and alcohol dilution. Laboratory measurements of both the dew point and the light transmission show the diameter of the alcohol drops to vary from 13 μm at nucleus concentration of 1000/cm3 to 5.5 μm at 300,000/cm3. A recent calibration shows the new counter to be nearly 100% efficient for condensation nuclei ranging from 90 to 5 nm in diameter.

Temperature and Water Drop Size in the Pollak Counter

An extensive series of measurements was made of the performance of the Pollak counter during adiabatic expansion. Temperature was measured by a resistance wire, 0.0005-in. (0.0127-mm) diameter, which was stretched the length of the counter. The temperature drop, pressure drop, and the fog formed during wet adiabatic expansion were observed on an oscilloscope and photographed with a Polaroid camera. The temperature drop was observed to be 8°C, whether room aerosol (about 50,000 particles · cm−3, causing dense fog) or filtered air (slight fog) was introduced. A temperature drop of 16°C was observed during dry adiabatic expansion. To obtain this condition, prolonged drying with dry air from a tank was necessary to rid the Pollak counter of the 200 cm3 of water in the ceramic lining. The same temperature was observed whether room aerosol or Altered air was introduced, but no fog was formed in either case. The water drop size was also measured by three methods: direct observation of sedimentation; calculations...

Letter to the Editor: Reply to C. N. Davies and N. Egilmez Concerning the Nolan-Pollak Nucleus Counter

Please click here to find the Letter to the Editor to which this Response refers: http://dx.doi.org/10.1080/02786828608959082 In response to “Letter to the Editor Lagrangian Stochastic Particle Tracking” by Aliabadi and Rogak in Aerosol Science and Technology 45:313–314, 2011.