A transition from heterogeneous to homogeneous nucleation in the turbulent mixing CNC

A new method for changing the supersaturation in the Turbulent Mixing CNC has been developed and used to examine the transition from heterogeneous nucleation of test particles to homogenous nucleation of working fluid: dibutylphthlate (DBP). Supersaturation was controlled by changing the DBP vapor pressure in the nozzle flow by saturating only a predetermined part of the flow, while the total flow and temperature remain constant. This approach allows for the changing of the initial DBP vapor pressure, while keeping the flow structure and temperature field unchanged. The DBP concentration in the outlet of the vapor generator was measured experimentally for different ratios of saturated and bypass flows and found to be close to estimated values. Experimental results for transitions from heterogeneous nucleation to homogeneous nucleation are presented for NaCl and WOx particles at various DBP vapor pressures. With an increasing of the DBP vapor pressure, the concentration of enlarged particles increases until it reaches a plateau. At higher initial values of DBP pressure, homogeneous nucleation prevails, and the number concentration of particles follows a curve typical for homogeneous nucleation recorded in the absence of nuclei. Nuclei with different mobility diameters were activated at different values of vapor pressure. There are significant differences in the slopes of particle activation curves for NaCl and WOx particles. The reasons for such differences are a subject for continuing research.