Surface area density

In some specific cases one would like to convert the chemisorption data into an averaged particle size. In that case, the number of surface atoms per unit surface area (density of surface atoms) is an essential parameter. Since this number depends on the type of the crystallographic plane, (see Table 3.7), one also needs information on the types of crystallographic planes exposed to the gas phase. This is also important for another reason the adsorption stoichiometry may depend on the crystallographic plane. 

Figure 42. (a) The droplet surface area density, S, as a function of droplet... 

Thomason, L. W L. R. Poole, and T. Deshler, A Global Climatology of Stratospheric Aerosol Surface Area Density Deduced from Stratospheric Aerosol and Gas Experiment II Measurements 1984-1994, J. Geophys. Res., 102, 8967-8976 (1997). 

The rapid growth of interest in powders and their surface properties in many diverse industries prompted the writing of this book for those who have the need to make meaningful measurements without the benefit of years of experience. It is intended as an introduction to some of the elementary theory and experimental methods used to study the surface area, porosity and density of powders. It may be found useful by those with little or no training in solid surfaces who have the need to quickly learn the rudiments of surface area, density and pore-size measurements. 

Grade of sihca used (particle size, surface area, density, surface chemistry, etc.)... 

Consider a body of arbitrary shape of mass m, volume J, surface area density p, and specific heat initially at a uniform temperature 7) (Fig. 4-2). At time t = 0, the body is placed into a medium at temperature T., and heat transfer takes place between the body and its environment, with a heat transfer coefficient h. For the sake of discussion, we assume that 7) > 7), but the analysis is equally valid for the opposite case. We assume lumped system analysis to be applicable, so lhat the temperature remains uniform wilhin the body at all times and changes with time only, T T t). 

In (his chapter, we considered the variation of temperature with time as well as position in one- or multidimensional sysKhls, We first considered the lumped systems in which tlte lempcr. itiire varies with time but remains uniform throughout the system at any time. The temperature of a lumped body of arbitrary shape of mass in, volume L/, surface area density p, and specific heat ioitially at a uniform temperature T, that is exposed to convection at time r 0 in a medium at temperature Tr. with a heal transfer coefficient h is expressed as... 

Higli-temperatuie calcination of a-Al203 affects some physical properties, in particular specific surface area, density and mechanical properties of the agglomerates which influence the grinding process (Hlavac and Bartuska, 1964). 

Liquid and solid particles observed in the atmosphere are generally a mixture of water, sulfuric acid and nitric acid with potentially the presence of traces of other chemical compounds like HC1 (see Table 5.9 in Section 5.7). The determination of the pseudo first-order rate coefficient kx (see Eq. (2.65)) for uptake by such particles in the stratosphere requires an accurate estimate of the surface area density available and of the reaction probability involved. 

The mean surface area density A can be calculated if the size distribution of the particles present in the atmosphere is known. For spherical particles... 

Figure 5.65. Median meridional distribution of the sulfate aerosol surface area density (/im2cm-3) for the period 1985-1994, based on observations by the SAGE II satellite. From Thomason et al, 1997.

A gas-to-fluid heat exchanger is referred to as a compact heat exchanger if it incorporates a heat transfer surface having a surface area density above about 700 m2/m3 (213 ft2/ft3) on at... 

Determine the surface geometrical properties on each fluid side. This includes the minimum free flow area A , heat transfer surface area A (both primary and secondary), flow lengths L, hydraulic diameter Dh, heat transfer surface area density P, the ratio of minimum free flow area to frontal area o, fin length and fin thickness for fin efficiency determination, and any specialized dimensions used for heat transfer and pressure drop correlations. 

For the solution to this problem, there are four unknowns—two flow rates or Reynolds numbers (to determine correct heat transfer coefficients and friction factors) and two surface areas—for the two-fluid crossflow exchanger. Equations 17.128, 17.129, 17.130 for <7 = 1, 2, and 17.132 are used to solve iteratively the surface areas on each fluid side UA in Eq. 17.128 is determined from NTU computed from the known heat duty or and C G in Eq. 17.130 represents two equations for fluids 1 and 2 [101] and the volume of the exchanger in Eq. 17.132 is the same based on the surface area density of fluid 1 (hot) or fluid 2 (cold). 

Heat transfer surface area density, a ratio of total heat transfer area on one side of... 

The major physical properties of ceramic powders constitute size distribution of primary particles and agglomerates, specific surface area, density, porosity, and morphology (e.g., shape, texture, and angularity). 

Particle morphology Crystallographic Properties Thermal methods of analysis Particle size distribution Surface area Density... 

Solubility, surface area, density, volatility, and melting point of the core material... 

Steel surface area density and layout (beam soffits have higher steel density than sides so may be separate zones). 

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