Discuss the theories of interphasemass transfer:a. The Two film Theoryb.The Penetration Theoryc. The Boundary Layer Theoryd. The Surface Renewal Theory

a. The Two Film Theory: This theory was proposed by Lewis and Whitman in 1924. It assumes that mass transfer occurs through two stagnant films around the droplet. The resistance to mass transfer is assumed to be concentrated in these films. The concentration of the solute is assumed to be uniform across each film but varies from the interface concentration to the bulk fluid concentration. The rate of mass transfer is given by Fick's first law of diffusion.

b. The Penetration Theory: This theory was proposed by Higbie in 1935. It assumes that the fluid is perfectly mixed and that the solute penetrates into the fluid by a process of eddy diffusion. The concentration of the solute at the interface is assumed to be constant and equal to the saturation concentration. The rate of mass transfer is given by the equation derived from Fick's second law of diffusion.

c. The Boundary Layer Theory: This theory was proposed by Prandtl in 1904. It assumes that the fluid flow near the interface is laminar and that the velocity of the fluid varies from zero at the interface to the free stream velocity at the edge of the boundary layer. The concentration of the solute also varies across the boundary layer. The rate of mass transfer is given by the equation derived from the boundary layer equations.

d. The Surface Renewal Theory: This theory was proposed by Danckwerts in 1951. It assumes that the surface of the fluid is constantly being renewed by the process of eddy diffusion. The concentration of the solute at the interface is assumed to be constant and equal to the saturation concentration. The rate of mass transfer is given by the equation derived from the surface renewal theory.