PRESSURE DROP CORRELATION The pressure losses accompanying the flow of fluids through packed columns are caused by simultaneous kinetic and viscous energy losses. The essential factors determining the energy loss, i.e. pressure drop, in packed beds are: 1. Rate of fluid flow 2. Viscosity and density of the fluid 3. Closeness and orientation of packing 4. Size shape and surface of the particlesThe Ergun equation is an estimation of the pressure drop through a packed bed due to thefollowing factors: rate of fluid flow, fluid properties such as viscosity and density, void fraction, and physical properties of the packing material. (1)Blake and Kozeny found that for viscous laminar flow, the pressure drop was proportional to the porosity of the packing material in the following manner:

(2)

They also determined how other factors effected equation (1), which resulted in the Blake-Kozeny equation:

= (3)where k1 is a dimensionless empirical constant that through many experiments was determined to equal to 150.

Since flow in the column can become turbulent, Burke and Plummer found that for turbulentflow the pressure change due to kinematic energy loss was proportional to the porosity of thepacking material in the following manner: (4)They also determined how other factors played an effect on equation (1), which resulted in the Burke-Plummer equation:

= (5)Where k2 is a dimensionless empirical constant that through many experiments was determined to equal to 1.75. Ergun made the assumption that the total pressure drop across a fluidized bed is due to the sum of the viscous and kinematic forces. Through many experiments Ergun concluded that his equation is valid for a wide range of Reynold numbers