Thinning allowance

Proton Exchange Membrane Fuel Cells (PEMFCs) are being considered as a potential alternative energy conversion device for mobile power applications. Since the electrolyte of a PEM fuel cell can function at low temperatures (typically at 80 °C), PEMFCs are unique from the other commercially viable types of fuel cells. Moreover, the electrolyte membrane and other cell components can be manufactured very thin, allowing for high power production to be achieved within a small volume of space. Thus, the combination of small size and fast start-up makes PEMFCs an excellent candidate for use in mobile power applications, such as laptop computers, cell phones, and automobiles. 

The microinterferometric method employed in the study of kinetics of foam film thinning allows to establish experimentally the liquids that form or do not form foam films. If a liquid possesses even small affinity to produce a foam, a circular film with clearly pronounced Newton rings is formed when it is drawn out of the biconcave drop. Films from aqueous surfactant solution can be obtained even at very small decrease in the surface tension (Act < 10 4 N m 1). It is sufficient to ensure a tension gradient between the film center and periphery. 

In addition to the plate overage, the fabricator (or head manufacturer) also adds a thinning allowance to the head to ensure that the head meets the minimum thickness in all areas. Depending on the type of head, the diameter, and the thickness required, a thinning allowance can be determined. This can be as much as 1.5 in. for large-diameter hemi-heads over 4 in. thick The metal does not disappear during the forming process but may flow to the areas of most work. 

Typically, die designer will check the required shell thickness at elevations where a seam is required. Actual plate thicknesses used will include a thinning allowance to accommodate thinning which occurs in the pressing of die plates. The plates do not get lighter. The actual plate... 

The weight estimates should include a thinning allowance to account for the thicker plates utilized. Thinning allowance can be estimated as follows ... 

Fig. 20.7 Electrical double-layer EDL) mechanism, shaded in gray, at high ionic strength, it is thin, allowing co-ions and counterions to pass through the nanochannel. At low ionic strength, the EDL thickness increases, resulting in a counterion-selective nanochannels [65]...

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