Nucleate of water

Example 2.9. The nucleation of water is analysed in an expansion chamber. A vapor at an initial pressure of 2330 Pa at 303 K is expanded to a final pressure of 1575 Pa. In this process it cools down to 260 K. At 260 K the equilibrium vapor pressure is 219 Pa. Thus, the supersaturation reaches P/Po = 7.2. What is the nucleation rate ... 

Figure 5.1 Gibbs energy of nucleation of water drops at different water vapor oversaturations of at 25°C. Curve 1 is plotted for oversaturation p/poo = 8.1 = 0.5...

P. P. Wegener, Gasdynamics of Expansion Flows with Condensation and Homogeneous Nucleation of Water Vapor, Chapter 4 of Nonequilibrium Flows, vol. 1, part 1, P. P. Wegener, ed.. New York Marcel Dekker, 1969. 

The nucleation of water and ice was monitored with an optical microscope whose objective was inserted into an opening in a purge box, as shown in Figure 2. The a-AhOs substrate was held by a sample holder against a peltier cooler with temperature monitoring by two thermocouples. 

Assuming homogeneous nucleation of water droplets, we need to find 7hom- Further assuming i om to be equal to the value observed for ice nucleation, i.e., 1.85nm (Table 14.2), Eq. (14.6) directly yields 7 hom = 15C. This would be a small undercooling. 

Boulaud, D., G. Madeleine, D. Vigla, and J. Bricard (1977). Experimental study on the nucleation of water vapor sulfuric acid binary system. J. Chem. Phys. 66, 4854-4860. 

The factor C is a statistical measure of the rate of formation of embryos that reach the critical size. It is proportional to the concentration of the individual particles and to the rate of collision of these particles with an embryo of the critical size required to form a stable nuclus. Its value for nucleation from solutions is not known. From analogy with nucleation of water drops from su r aturated water vapor, it is of the order of 10 nuclei/cm -s. Its accurate value is not important, because the kinetics of nucleation is dominated by the In a term in the exponent. 

FIGURE 10.14 Vapor pressure of sulfuric acid as a function of temperature using the Ayers et al. (1980) and Kulmala and Laaksonen (1990) estimates. (Reprinted with permission from Kulmala, M. and Laaksonen, A. Binary nucleation of water sulfuric acid system. Comparison of classical theories with different H2S04 saturation vapor pressure, J. Chem. Phys. 93, 696-701. Copyright 1990 American Institute of Physics.)... 

Kulmala, M., and Laaksonen, A. (1990) Binary nucleation of water sulfuric acid system. Comparison of classical theories with different H2SO4 saturation vapor pressures, J. Chem. Phys. 93,696-701. 

Oriani, R. A. Sc Sundquist, B. E. (1963). Emendations to nucleation theory and the homogeneous nucleation of water from the vapour. J. Chem. Phys. 38, 2082-9. [88]... 

A simulated homogeneous nucleation rate of 6.6 x 10 cm s was determined from our calculations. The values of the free energy barrier and the rate of nucleation are in reasonable agreement with experimental and simulation values obtained for the homogeneous nucleation of water and urea. Current woik in our group is focused on the study of nucleation of ILs near surfaces and inside pores. 

The second matter we wish to deal with is the time dependence of rii and /j. In Eqs. (1) and (4) we assumed that the concentrations and currents were time dependent. In this case Eqs. (1) or (4) cannot be solved analytically, although approximate solutions are possible. Abraham has carried out extensive computer calculations on the time dependence of the cluster concentrations and currents for homogeneous nucleation of water vapor. Typical results of his work are shown in Fig. 3. (The details of these calculations, boundary conditions, etc., have been discussed by Abraham and do not concern us here.) The crucial result of Abraham s calculations is that for typical gas phase... 

R. E. Heist and H. Reiss, Investigation of homogeneous nucleation of water vapor using a diffusion cloud chamber, J. Chem. Phys. 59,665-671 (1973). 

Wegener,P.P. Gas dynamics of expansion flows with condensation and homogeneous nucleation of water vapor, in Nonequilibrium Flows, Ch.4, Part 1,Ed.P.P.Wegener, Marcel Dekker, New York (1979). 

Chemical potential homogeneous nucleation of water-vapor condensation... 

For applications to vapor-liquid nucleation see McKenzie, M. E. Chen, B. Unravelling the peculiar nucleation meehanism for non-ideal binary mixtures with atomistic simulations, J. Phys. Chem. B 2006,110, 3511-3516 Chen, B. Siepmann, J. I. Klein, M. L. Simulating the nucleation of water/ethanol and water/nonane mixtures, mutual enhancement and two-pathway mechanism, J. Am. Chem. Soc. 2003, 125, 3113-3118. The latter paper has a reference and discussion to experimental measurements using a supersonic nozzle expansion technique. 

D. Barschdorf, Carrier gas effects on homogeneous nucleation of water vapor in a shock tube. Phys. Fluids 18(5), 529-533 (1975)... 

A smooth, clean surface will produce uniform nucleation of a vapor on the surface. A common test is to breathe on the surface and look at the nucleation pattern. This is called the black breath test. For example, nucleation of water on the mirror in a shower room shows up the swipes where the mirror surface has not been cleaned very well. Nucleation uniformity over... 

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