Biomedical Engineering Reference
In-Depth Information
FIGURE 8-62
Conductivity of
human tissue as a
function of
frequency. [Adapted
from (Shiba, Nukaya
et al., 2006).]
FIGURE 8-63
Maximum SAR as a
function of
frequency [Adapted
from (Shiba, Nukaya
et al., 2006).]
8.7
PUMP TYPES
Turbo pumps, also known as dynamic or roto-dynamic pumps, produce a head and a flow
by increasing the velocity of the liquid through the device with the help of a rotating
vane impeller. In broad terms there are two classes of turbo pumps. In the first class,
there is a pronounced change in radius from the inlet to the discharge. These are known as
centrifugal pumps. The other main class, axial pumps, creates a flow that is mostly parallel
to the axis of rotation. Mixed-flow pumps lie somewhere between the two extremes, with
the flow proceeding along a conical surface of revolution.
Positive displacement pumps operate by alternately filling a cavity and then displacing
a given volume of liquid. The positive displacement pump delivers a constant volume of
liquid for each cycle irrespective of the discharge pressure. They can be classified as
follows:
•
Rotary pumps: gear, lobe, screw, vane, regenerative (peripheral), and progressive
cavity.
•
Reciprocating pumps: piston, plunger, and diaphragm.
