Consider the hydrogen-removal process described in .51,

Chapter 14, Problem 14.52

(choose chapter or problem)

Consider the hydrogen-removal process described in 14.51, but under conditions for which themass diffusivity of the hydrogen gas (A) in the sheetmaterial (B) is DAB?1.8?10?11m2/s (instead of 2.6?10?8m2/s). With the smaller value of DAB, auniform concentrationmay no longer be assumed toexist in the material during the removal process.(a) If the sheet material is left exposed to the airstreamfor a very long time, what is the final content ofhydrogen in the material (kg/m3)?(b) Identify and evaluate the parameters that describethe transient mass diffusion process in the sheet.Hint: The situation is analogous to that of tran-sient heat conduction in a plane wall.(c) Determine the time required to reduce the hydro-gen mass density at the center of the sheet totwice the limiting value calculated in part (a).(d) Assuming a uniform concentration at any time dur-ing the removal process, calculate the time requiredto reach twice the limiting density calculated in part(a). Compare the result with that obtained from part(c), and explain the differences.