Binary condensation in a supersonic nozzle

We present data from the first systematic studies of binary condensation in supersonic nozzles. The apparatus used to conduct the experiments is descr ibed in detail, and the important issues of stability and reproducibility o f the experiments are discussed. Experiments were conducted with water, eth anol, propanol, and binary mixtures of these compounds. Onset was determine d in the temperature range of 190-215 K, and for each mixture composition t he pressures of the condensible species at an onset temperature of 207 K we re determined. For the ideal ethanol-propanol mixtures, the onset pressures at constant temperature vary almost linearly between those of the pure com ponents. In contrast the isothermal onset pressures for the nonideal water- ethanol and water-propanol mixtures lie below the straight line joining the pure component values. This large reduction in the total pressure of conde nsible at onset for the aqueous alcohol mixtures is indicative of a strong mutual enhancement in the particle formation process. (C) 2000 American Ins titute of Physics. [S0021-9606(00)51441-X].