The surface charge on these particles is – 2 mv, in aqueous solution at 30 c. it is expected that the suspension may be exposed to temperatures as high as 120 f. for reference, we need a stability ratio of at least 10^4 to ensure no flocculation.

determine the height of the energy barrier (in j) that is necessary to keep a suspension of polystyrene nanospheres of diameter 100 nm from being flocculated.

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.