Nucleation at high pressure II: Wave tube data and analysis.

Nucleation rate data, obtained from expansion wave tube experiments, are reported for several vapor–gas mixtures at high pressure. Results are given for water–vapor in the presence of helium and nitrogen gas, and for n-nonane in helium and methane. For all these mixtures, carrier gas pressures of 10, 25, and 40 bar have been applied, with temperatures ranging from 230 to 250 K. An extended form of the nucleation theorem (in terms of the derivative of the nucleation rate with respect to carrier gas pressure) is derived, which appears to be very helpful in the interpretation of high pressure data. It can be used to obtain the carrier gas content of the critical nucleus directly from the pressure dependence of experimental nucleation rates. Combining this method with the theoretical considerations of part I of this paper [J. Chem. Phys. 111, 8524 (1999), preceding paper]: the nucleation behavior of water at high pressures of both helium and nitrogen can quantitatively be understood. For n-nonane in helium our "pressure perturbation approach" is also valid. For n-nonane in methane, however, this approach fails because of the high methane solubility in the liquid phase

Homogeneous nucleation rates for n-pentanol from expansion wave tube experiments

Within the scope of joint experiments by the international Nucleation Workshop Group, nucleation experiments on n-pentanol were carried out using a pulse-expansion wave tube. Data were obtained for nucleation at temperatures between 240 K and 260 K. Total pressures of the carrier gas (helium) during nucleation varied from 89 to 109 kPa. The results are presented in tabular form, to facilitate future comparison. Our results are consistent with existing data by Hrubý et al. Comparisons are made to the Kinetic Classical Theory (KCT) as well as to the semiphenomenological theory by Kalikmanov and Van Dongen (KvD–SPT). Although both theories predict nucleation rates that are apparently too low in the temperature range of interest, the KvD–SPT is approximately two orders of magnitude closer to the experimental result

Comment on "The nucleation behavior of supercooled water vapor in helium"

In a recent paper Peeters et al. published new experimental data on nucleation rates of water in the temperature range of 200–235 K. They reported about a drastic change in the nucleation rate at 207 K. An error in their experimental procedure has been found. The data of Peeters et al. have been reinterpreted. The jump in nucleation rate disappears and the corrected nucleation rate data are in good agreement with data found by Wölk and Strey with a different experimental facility

Evidence for an eastward flow along the Central and South American Caribbean Coast

11 pages, 8 figures, 2 tables.-- Full-text version available Open Access at: http://www.iim.csic.es/~barton/html/pdfs.htmlHydrographic transects suggest an eastward flow with a subsurface core along the entire southern boundary of the Caribbean Sea. The transport of the coastal limb of the Panama-Colombia Gyre (PCG), known as the Panama-Colombia Countercurrent, decreases toward the east (from ∼6 Sv off Panama), as water is lost into the recirculation of the PCG. Off Panama, the flow is strongest at the surface, but, off Colombia, it is strongest at around 100 m. A portion of the counterflow (∼1 Sv) continues eastward along the Colombian coast as far as the Guajira region (12°N, 72°W), where it submerges to become an undercurrent beneath the coastal upwelling center there. The eastward flow also occurs in the Venezuela Basin, beneath the coastal upwelling region off Cariaco Basin and exits the Caribbean through the Grenada Channel at around 200 m depth. Numerical simulations suggest that this flow, counter to the Caribbean Current, is a semi-continuous feature along the entire southern boundary of the Caribbean, and that it is associated with offshore cyclonic eddies. It probably constitutes part of the Sverdrup circulation of the Tropical North Atlantic cyclonic cell.This work had financial support of the Colombian Institute for the Development of Science and Technology COLCIENCIAS, project 96-044 and the Colombian Navy. Also, the Office of Naval Research provided funding for C. N. K. Mooers and E. D. Barton during manuscript preparation.Peer reviewe

Wave induced growth and evaporation of droplets in a vapor-gas mixture

Heterogeneous condensation and evaporation induced by an unsteady rarefaction wave and by the passage of a shock wave in a water-nitrogen mixture is studied. Time resolved measurements of modal droplet radius, droplets radius, droplet number density, pressure, and gas density are presented. Condensation on Cr2O3-particles of about 10 nm starts at a saturation ratio of 3.4. Typical droplet radii and droplet number densities are 1.5 µm and 1011 m-3. A shock wave with Mach number 1.36 causes full evaporation in 4 ms