Dependence of the performance of TSI 3020 condensation nucleus counter on pressure, flow rate, and temperature

Abstract

A theoretical study has been carried out to investigate the performance of the TSI 3020 condensation nucleus counter (CNC) at various pressures and flow rates by assuming a parabolic velocity profile in the condenser tube and solving the heat and mass transfer equations using the finite difference method. Calculations have been performed for pressures ranging from 0.03 to 10 atm and sampling flow rates from 0.5 to 50 mL/s. The results indicate that the counting efficiency of the CNC is a function of pressure and flow rate due to changes in heat and mass transfer rates. The counting efficiency can be correlated with a single parameter, ζ, which combines the effects due to pressure, sampling flow rate, and the length and diameter of the condenser tube. The cut size of the instrument, Dp50, defined as the particle size at which the counting efficiency is 50%, has been found to vary with pressures, reaching a minimum at a pressure of approximately 1 atm. The cut size of the CNC has been found to be most sensitive to the temperature difference between the saturator and condenser but relatively insensitive to the flow rate and the saturator temperature. © 1990 Elsevier Science Publishing Co., Inc.