In a certain area of ​​the apparatus, where the pressure is 1 atm and the temperature is 200 ° C, the analysis of the gas is 33.33% NH 3 (A), 16.67% N 2 (B), and 50% H 2 (C) by volume. The conditions are such that the ammonia diffuses from the gas stream to the catalyst surface; also the Reaction products diffuse in the opposite direction, as if there were molecular diffusion to through a 1 mm thick gaseous film under a laminar regime.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.