Roughness depth

Two 1-in-diameter bars of stainless steel [k = 17 W/m °C] are brought into end-to-end contact so that only 0.1 percent of the cross-sectional area is in contact at the joint. The bars are 7.5 cm long and subjected to an axial temperature difference of 300°C. The roughness depth in each bar LJ2) is estimated to be 1.3 fun. The surrounding fluid is air, whose thermal conductivity may be taken as 0.035 W/m - °C for this problem. Estimate the value of the contact resistance and the axial heat flow. What would the heat flow be for a continuous 15-cm stainless-steel bar ... 

When the joint pressure for two surfaces in contact is increased, the high spots of the surfaces are deformed so that the contact area A, is increased and the roughness depth L, is decreased. Discuss this effect in the light of the presentation of Sec. 2-11. (Experimental work shows that joint conductance varies almost directly with pressure.)... 

Therefore, and because the surfaces of all particulate matter are rough, the adhesion tendency increases with decreasing particle size of at least one of the adhesion partners. Figure 9 explains schematically the conditions. Microscopically, all surfaces of solids, even macroscopically smooth ones, are rough. The depth of roughness depends on the particle size. Below a certain particle size the specific (in reference to particle size) roughness depth of smooth surfaces is approximately constant. 

The application of average peak-to-valley height R and maximum roughness depth as a combination allows the detection of individual outliers. If Rmax is significantly higher than an extra high peak exists. 

Figure 34.16. Roughness depth profile of the surface of an aluminum casting without addition of an aerogelic nanoadditive.

The roughness depth ranges are shown in Table 4.2, which can be achieved using various machining processes. 

TABLE 4.2 Achievable Roughness Depths of Metal-Cutting Tools... 

The accuracy depends on the Initial roughness depth and on the unevenness, which must be removed. This means that it should be attempted to coat it as fine as possible when processing using machine tools, because no hand-operated lapping and polishing tool can work as accurately and as fast as a machine tool. 

The first system called LiSSA has been developed for interpretation of data from eddy-current inspection of heat exchangers. The data that has to be interpreted consists of a complex impedance signal which can be absolute and/or differential and may be acquired in several frequencies. The interpretation of data is done on the basis of the plot of the signal in the impedance plane the type of defect and/or construction is inferred from the signal shape, the depth from the phase, and the volume is roughly proportional to the signal amplitude. 

For a rough estimation of the optimum excitation frequency for a given test object, one can use the well known expression for the skin penetration depth S ... 

Salt acts as a completely mobile plastic below 7600 m of overburden and at temperatures above 200°C (2). Under lesser conditions, salt domes can grow by viscous flow. Salt stmctures originate in horizontal salt beds at depths of 4000—6000 m or more beneath the earth s surface. The resulting salt dome or diapir is typically composed of relatively pure sodium chloride in a vertically elongated, roughly cylindrical, or inverted teardrop-shaped mass. 

Typical overall coefficients to start a rough sizing are as below. Use these in conjunction with the NTU calculated for the process. The closer the NTU matches the plate (say between 2.0 and 3.0), the higher the range of listed coefficients can be used. The narrower (smaller) the depth of corrugation, the higher the coefficient (and pressure drop), but also the lower the abdity to carry through any particulate. 

For prehminary screening and easibility studies or for rough cost estimates, one may wish to employ a version of the isothermal method which assumes that the liquid temperatures in the tower are everywhere equal to the inlet-liquid temperature. In their analysis of packed-tower designs, von Stockar and Wilke [Ind. Eng. Chem. Fun-dam. 16, 89 (1977)] showed that the isothermal method tended to underestimate the reqmred depth of packing by a factor of as much as 1.5 to 2. Thus, for rough estimates one may wish to employ the assumption that the temperature is equal to the inlet-liquid temperature and then apply a design fac tor to the result. 

To recover oil from the continental shelf of arctic Canada and Alaska, drilling and production platforms must be built some miles offshore, in roughly 40 m of water. This is not a great depth, and would present no new problems were it not that the sea freezes in winter to a depth of around 2 m. Wind blowing across the surface of the ice sheet causes it to move at speeds up to 1 m s pressing it against the structure. Ice is... 

Similarly, contaminant concentrations in rivers or streams can be roughly assessed based on rate of contaminant introduction and dilution volumes. Estuary or impoundment concentration regimes are highly dependent on the transport mechanisms enumerated. Contaminants may be localized and remain concentrated or may disperse rapidly and become diluted to insignificant levels. The conservative approach is to conduct a more in-depth assessment and use model results or survey data as a basis for determining contaminant concentration levels. 

Surface Roughness Measurement, Formation by Sputtering, Impact on Depth Profiling... 

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