Chapter 4 - Quantitative Relations Between Transfer Processes

Abstract

In most of the unit operations encountered in the chemical and process industries, one or more of the processes of momentum, heat, and mass transfer are involved. Thus, in the flow of a fluid under adiabatic conditions through a bed of granular particles, a pressure gradient is set up in the direction of flow, and a velocity gradient develops approximately perpendicularly to the direction of motion in each fluid stream; momentum transfer then takes place between the fluid elements that are moving at different velocities. If there is a temperature difference between the fluid and the pipe wall or the particles, heat transfer will take place as well, and the convective component of the heat transfer will be directly affected by the flow pattern of the fluid. In a very turbulent fluid, the rates of transfer per unit area of both momentum and mass are high, and as the pressure drop rises, the rates of transfer of both momentum and mass increase together. In some cases, momentum, heat, and mass transfer all occur simultaneously. In this chapter, it will be shown that not only the processes of momentum, heat, and mass transfer are physically related but also quantitative relations between them can be developed.