AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
High Temperature Condensation Particle Counter
Kanchit Rongchai, Nick Collings, JACOB SWANSON, University of Cambridge
Abstract Number: 494 Working Group: Instrumentation and Methods
Abstract Condensation Particle Counters (CPCs) are commonly used to measure the number concentration of airborne nanoparticles in various applications. A typical CPC consists of three major stages. They are: a saturation stage, a condensational growth stage and an optical particle counter (OPC). The working temperature of a typical CPC is around ambient or slightly higher.
This work is concerned with the development of a CPC that operates at such a high temperature that volatile material is not measured, due to it being evaporated. The obvious application is measurement from internal combustion engines, where the European legislated particle number method (PMP) requires a complex system for the removal of volatile material, prior to measurement by a conventional CPC.
The study involves theoretical modelling, design, construction and testing of a high temperature CPC. Di-Ethyl-Hexyl-Sebacat (DEHS) has initially been chosen as the “working” fluid, because it is non-toxic, is a liquid at room temperature and has a high boiling point. The saturator and condenser would be held at approximately 210˚ C and 190˚ C respectively.
The supersaturated region in the condenser where particles are grown, is modelled by numerically solving heat and mass transfer equations based on the finite difference method. The model was found to be in good agreement with an alternative model due to Stolzenburg and McMurry (1991). Particle growth was modelled by the heat and mass balance at the droplet surface. The simulations suggest that the high-temperature CPC will be able to grow and detect fine particles.
When a step decrease in particle concentration was introduced at the aerosol inlet, the high-temperature CPC has been shown to successfully grow and detect NaCl particles and ambient particles.
Stolzenburg, M. R., and McMurry, P. H. (1991) An Ultrafine Aerosol Condensation Nucleus Counter, Aerosol Science and Technology, 14:1, 48–65.