We establish an analytical model, as well as perform Computational Fluid Dynamics (CFD) simulations to investigate the evaporation-condensation process in Condensation Particle Counters (CPCs). Via a systematic analysis of the effect of geometrical and operational parameters on the saturation profile in CPCs, we unveil that the insulation in these measurement devices is of key significance for the detection efficiency. Furthermore, we demonstrate that our analytical model can reliably predict the mass fraction of working fluid in the gas phase at the outlet of the saturator. This is of key importance for the efficient screening of working fluids, as well as the optimization of both geometry and operation parameters of CPCs. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.