n-Pentanol-helium homogeneous nucleation rates

An international collaboration to examine the effects of different experimental systems on nucleation measurements has resulted in a series of nucleation experiments on the n-pentanol-helium system. In particular, using a laminar flow diffusion chamber, nucleation rate data were obtained for temperatures between 258 and 266 K and total pressures of 0.10, 0.20, and 0.30 MPa. These results are compared with other data on nucleation measured experimentally using an expansion wave tube, a two-piston expansion chamber, a flow diffusion chamber, and a static diffusion chamber. The influence of the carrier gas pressure on nucleation rates was explored. It was concluded that the critical embryo phase transitions should be detectable in an analogous manner to the recently reported phase transitions in the glycerin-carbon dioxide system. The experimental detection of the melting point is suggested as a critical test for the ability of an experimental system to provide adequate measurements of nucleation rates. For example, the glycerin melting point can be used for these tests. A reference equation for nucleation rates of n-pentanol-helium is proposed as a practical test of any experimental measurement system for total pressures of 0.10, 0.20, and 0.30 MPa. The use of this equation is recommended even if the reference equation is not completely accurate, because it provides a scale for comparison of the results for different research groups and methods. (C) 2000 American Institute of Physics. [S0021-9606(00)50322-5].