LAUSR

Abstract Thermally diffusive laminar-flow condensation particle counters (CPCs) often utilize alcohol or water as the working fluid to condense and grow particles large enough for optical detection. Different CPC structures (including saturator and condenser) have been designed to accommodate different characteristics of alcohol and water. This study presents a convertible CPC that can use both alcohol and water without modifying the CPC structure or wick material. It utilizes a laminar-flow design including a heated saturator followed by a cooled condenser. When using butanol as the working fluid, the CPC cutoff size was measured to be 10 nm and 7 nm for laboratory-generated NaCl and Ag particles, respectively, at the saturator temperature of 39 °C and the condenser temperature of 17.5 °C. For water, the CPC cutoff sizes are 3 nm for NaCl particles and 2.8 nm for Ag particles at the saturator temperature of 41.5 °C and the condenser temperature of 5 °C. When the ambient dew point temperature is above the condenser temperature, the water CPC can collect moisture from the air to make it self-sustained. Numerical simulation confirmed the spatial distribution of saturation ratios for butanol and water vapors under the setting conditions. The output power of the optical detector is set to be 5 mW for butanol and 25 mW for water to obtain pulse heights generated by particles high enough to achieve high signal-to-noise ratios. The convertible CPCs using butanol and water were used for measuring atmospheric particles in comparison to a commercial butanol CPC and obtained consistent results. Copyright © 2024 American Association for Aerosol Research Graphical Abstract