Information Technology Reference
In-Depth Information
CHAPTER EIGHT
PRESSURE CHANGERS
Aspen Plus offers six different types of pressure changers. The Pump, Compressor,
and Multistage Compressor models actively change pressure as a result of the addition
of some form of work to the block which is converted to action on a stream. The
three other models — valve, pipe (single segment with fittings), and pipeline (multiple
segments with fittings) — are stationary objects that incorporate resistance to flow which
must be overcome by use of a pump or compressor.
8.1 PUMP BLOCK
The Pump block typically is used to calculate the power required to pump a fluid up to
a specified pressure. The Pump block can be used to model a hydraulic turbine as well.
In this variation the block calculates the power produced when the discharge pressure
is specified. Alternatively, the power input can be specified and the pump will calculate
the discharge pressure. Figure 8.1 shows the Pump and Turbine input options. Details
of the calculations are well documented in Aspen Plus's Help under Pump Reference.
An example of the use of a pump and a hydraulic turbine may be found at Chapter
Eight Examples/pumps. For cases in which meaningful pumping applications are not
needed, a Heater block can be used to specify the state of a stream.
8.2 COMPR BLOCK
Details of single-stage compressor modeling can be found in Aspen Plus's Help under
the Compr Reference, with a variety of links to all variants. An excellent overview
may be found by following the link Mollier method, Compressor Background. These
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