A2. A flux of gas (species A) is to be transported by diffusion (without any con

Question

A2. A flux of gas (species A) is to be transported by diffusion (without any convection) across a layer of solid material Three distinct materials are under consideration for achieving this. The first material (material1) is a homogeneous but permeable solid. The diffusivity of species A through this homogeneous solid is DAH and the thickness of the material is zH The second material (material 2) is a porous material, with (Fickian) diffusion taking place through the network of pores, rather than through the solid itself. The diffusivity of the gas species A through the pores is DAP, which is 100 times greater than DAH, but the thickness of the material zp2 is 10 times zH. Moreover the pore space of the material only accounts for 32% of its total volume, and the flow paths through the material are tortuous-to cross from one side of the material to the other, gas flows along a path that is 3.0 times the thickness of the material itself. Low porosity and high tortuosity imply that the effective diffusivity of the porous material The third material (material 3) is again a porous material, and again (Fickian) diffusion takes place through the pores rather than through the solid itself. The thickness of the material zPs is 1.2 times zP2. It is somewhat more porous (the porosity is 40%) and flow paths are slightly less tortuous (flow paths are just 2.9 times the thickness of the material itself) Which of the following correctly identifies the materials producing the highest and lowest fluxes of species A? is less than DAP (a) material 1: highest, material 2: lowest (b) material 1: highest, material 3: lowest (c) material 2: highest, material 1 (d) material 2: highest, material 3: lowest (e) material 3: highest, material 1: lowest (f) material 3: highest, material : lowest 2: lowest

Explanation / Answer

e) is correct because from the statements stated it easy to observe material 2 high flux than material 1 because in the statement it self said the diffusivity in 2nd material is 100 times larger than diffusivity in 1st material and similarly material 3 has high flux than material 2 because material 3 has more porosity and less tortuous.

So this can be simply shown as flux2>flux1 and flux3>flux2

so flux3>flux2>flux1

there fore material-3 has highest and material-1 has lowest flux.

so now i think if you have clarity on the question based on the above answer.dont forget to upvote to my answer plese.

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