Kelvin effect

Joule-Thomson effect, Joule-Kelvin effect... 

This section represents a continuation of Section VII-5, which dealt primarily with the direct estimation of surface quantities at a solid-gas interface. Although in principle some of the methods described there could be applied at a solid-liquid interface, very little has been done apart from the study of the following Kelvin effect and nucleation studies, discussed in Chapter IX. 

Most studies of the Kelvin effect have been made with salts—see Refs. 2-4. A complicating factor is that of the electrical double layer presumably present Knapp [3] (see also Ref. 6) gives the equation... 

In general there are two factors capable of bringing about the reduction in chemical potential of the adsorbate, which is responsible for capillary condensation the proximity of the solid surface on the one hand (adsorption effect) and the curvature of the liquid meniscus on the other (Kelvin effect). From considerations advanced in Chapter 1 the adsorption effect should be limited to a distance of a few molecular diameters from the surface of the solid. Only at distances in excess of this would the film acquire the completely liquid-like properties which would enable its angle of contact with the bulk liquid to become zero thinner films would differ in structure from the bulk liquid and should therefore display a finite angle of contact with it. 

Kelvin effect The electrical potential gradient caused by a temperature gradient along a conducting wire. Also known as the Thomson Effect. 

Kelvin effect. It was found that in the case of oxygen, nitrogen, air, and carbon dioxide, there was a cooling effect, so that x is... 

The Joule-Kelvin effect may also be calculated from van der Waals equation. For an expansion from i to r2 at constant temperature, let the change of intrinsic energy be 112 — iii = Amt. 

Jochmann s equation, 164 Joule, 31 experiments with gases, 137 Kelvin effect, 164, 225 researches, 28, 51 theorem, 136... 

There are several basic physical-chemical principles involved in the ability of aerosol particles to act as CCN and hence lead to cloud formation. These are the Kelvin effect (increased vapor pressure over a curved surface) and the lowering of vapor pressure of a solvent by a nonvolatile solute (one of the colligative properties). In Box 14.2, we briefly review these and then apply them to the development of the well-known Kohler curves that determine which particles will grow into cloud droplets by condensation of water vapor and which will not. 

KELVIN EFFECT, VAPOR PRESSURE LOWERING, AND THE KOHLER CURVES... 

Kelvin effect. Recall that the change in free replace dr in Eq. (Z) energy of a gas due to a change in pressure (at... 

FIGURE 14-37 Basis of Kelvin effect for increased vapor pressure over small liquid droplets. 

As we have seen in Chapter 9, there are a variety of dissolved solutes in atmospheric particles, which will lower the vapor pressure of droplets compared to that of pure water. As a result, there is great interest in the nature and fraction of water-soluble material in atmospheric particles and their size distribution (e.g., Eichel el al., 1996 Novakov and Corrigan, 1996 Hoffmann et al., 1997). This vapor pressure lowering effect, then, works in the opposite direction to the Kelvin effect, which increases the vapor pressure over the droplet. The two effects are combined in what are known as the Kohler curves, which describe whether an aerosol particle in the atmosphere will grow into a cloud droplet or not under various conditions. 

This vapor pressure lowering by the solute acts simultaneously with, and counteracts, the vapor pressure increase due to the Kelvin effect [Eq. (BB)]. Multiplying the two, the net result for the vapor pressure above a solution containing a dissolved solute is given by... 

The Kelvin effect is not limited to spheres. For example, the neck of liquid between two supports is described by a paraboloid of revolution. In this case the radius of curvature of the concave surface is outside the liquid and therefore introduces a minus sign into Equation (40). In addition, the factor of 2 is not required to describe the Kelvin effect for this geometry. Example 6.2 illustrates a test of the Kelvin equation based on this kind of liquid neck. 

EXAMPLE 6.2 Use of the Kelvin Equation for Determining Surface Tension. Figure 6.5 shows a plot of experimental data that demonstrates the validity of the Kelvin effect. Necks of liquid cyclohexane were formed between mica surfaces at 20°C, and the radius of curvature was measured by interferometry. Vapor pressures were measured for surfaces with different curvature. Use these data to evaluate 7 for cyclohexane. Comment on the significance of the fact that the linearity of Figure 6.5 extends all the way to a p/p0 value of 0.77. 

In addition to proving the Kelvin effect, the data in Figure 6.5 show that the surface tension of cyclohexane may be regarded as constant down to a radius of curvature given by the reciprocal of the abscissa corresponding to p/p0 = 0.77, which is 4 nm. It is remarkable that the... 

Vapors in equilibrium with liquid in fine capillaries or pores will have depressed vapor pressure as a result of the Kelvin effect. In fact, if the pores are adequately small, the vapor will condense at pressures far below normal. By measuring the volume of nitrogen adsorbed at a relative pressure, i.e., p/po, of 0.99 and with prior knowledge of the surface area, the average pore diameter can be calculated. 

Kelvin effect, 153 mattress model of adsorption inhibition, 153-154 medical applications, 155 recrystallization- inhibition applications, 155 repeating tripeptide unit, 152 step pinning model of adsorption inhibition, 153-154 structure, 152 subtypes, 152... 

Kirmaier, C., Holten, D., and Parson, W. W., 1985b, Picosecond-photodichroism studies of the transient states in Rhodopseudomonas sphaeroides reaction centers at 5 kelvin Effects of electron transfer on the six bacteriochlorin pigments. Biochim. Biophys. Acta, 810 49n61. 

Figure 19. RH values observed for the efflorescence of ammonium sulfate (120 sec residence time) by heterogeneous nucleation as a function of mode diameter of the inclusions for corundum ( ) and hematite ( ). The hnes show F = 0.50 of the optimized fit to the active site model (Eqn. 24). Right axes show saturation ratios, S, of the aqueous phase with respect to crystalline ammonium sulfate and salt mole fractions, x, of the aqueous phase, as calculated from the model of Clegg et al. (1998) when assuming equihbrium between RH and water activity and omitting Kelvin effects. Adapted from Martin et al. (2001). Used by permission of the American Geophysical Unioa...

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