Electrostatic precipitators (ESPs) are used to clean particles from gas flows such as the exhaust from a power plant boiler or a municipal waste incin-erator. They work by applying a charge to the particles, which then move at their terminal velocity in 'response to the electrostatic force that results from an applied voltage. In this problem, you are to do the following (con-ditions and equations that apply to the entire problem are given at the end of the problem):
(a) To Calculate the terminal velocity, it is first necessary to clearly identify the forces acting on the particle. Draw a picture similar to that in Figure 4-16 and identify the forces acting on a particle passing through the ESP. Note: Neglect gravity in this calculation-assume that the only external force acting on the particle is the electrostatic force. Since buoyancy is a result of the gravitational force, neglect buoyancy also.
(b) Calculate the terminal drift velocity (w) of particles in response to the electrostatic force as a function of particle diameter. Report your so-lution as an equation that gives the w in units of cm/s, and specify the units of Dp that you are using.
(c) Calculate the terminal drive velocity for particles of the following di-ameters: 0.5 gm and 10.0 µm.
(d) For comparison, calculate the gravitational settling velocity for the same particle sizes.
(e) By comparing your answer for part (a) to the Stokes ; settling velocity equation, determine the particle size for which the gravitational settling velocity is equal to the drift velocity in the ESP. Express your answer in units of µm.
