Question

Hydrogen gas is maintained at 3 bars and 1 bar on opposite sides of a plastic membrane which is .3 mm thick. The temperature is 25C, and the diffusion coefficient of hydrogen in the plastic at 25C is 9x10-8 m2/s. The solubility of hydrogen in the plastic membrane is 1.5x10-3 kmol/m3. What is the mass diffusive flux (in kg/m2.s) of hydrogen on the membrane

Answer 1

The mass diffusive flux of hydrogen on the membrane is 0.05886 kg/m^2.s.

Step-by-step explanation:

To calculate the mass diffusive flux of hydrogen on the membrane, we can use Fick's law of diffusion. The formula is:

Flux = (Diffusion Coefficient * Concentration Difference) / Membrane Thickness

First, let's calculate the concentration difference. The partial pressure difference can be calculated by subtracting the lower pressure from the higher pressure. So, in this case, the concentration difference is 3 bars - 1 bar = 2 bars.

Now, let's convert the concentration difference from bars to kmol/m3. The conversion factor is 0.0981 kmol/m3 per bar. So, the concentration difference is 2 bars * 0.0981 kmol/m3/bar = 0.1962 kmol/m3.

Plugging the values into the formula: Flux = (9x10-8 m2/s) * (0.1962 kmol/m3) / (0.3 mm)

Next, let's convert the thickness of the membrane from mm to m. The conversion factor is 0.001 m per mm.

So, the mass diffusive flux = (9x10-8 m2/s) * (0.1962 kmol/m3) / (0.3 mm * 0.001 m/mm) = 0.05886 kg/m2.s. Therefore, the mass diffusive flux of hydrogen on the membrane is 0.05886 kg/m2.s.