Information Technology Reference
In-Depth Information
Figure 8.2
Compr options.
It is also necessary to specify the mechanical efficiency, defined by
IHP
=
Fh
(8.5a)
IHP
η
m
BHP
=
(8.5b)
where
F
is the molar flow rate,
h
the enthalpy change, IHP the indicated horsepower,
BHP the brake horsepower, and
η
m
the mechanical efficiency.
The Aspen Plus Compr block can be used to model a compressor or turbine. Three
models of compressors are available: a polytropic centrifugal, a polytropic positive
displacement, and an isentropic compressor, each with variants as shown in Figure 8.2.
If a turbine is chosen, isentropic is the only possibility. Some examples of Compr
applications are given at Examples/compressor.
8.3 MCompr BLOCK
Details of multistage compressor modeling can be found in Aspen Plus's Help under
the MCompr Reference, and the link specifying MCompr. These sections should be
read prior to using the block. The MCompr block can be used to model six types of
compressors, as shown in Figure 8.3. The tabs Specs and Cooler are used to specify the
various efficiencies and the stage outlet conditions, respectively. The Convergence tab
is used to select the allowed phases in the compressor and cooler stages. An example
of a MCompr application is given at Examples/mcompr.
8.4 PIPELINES AND FITTINGS
The Pipe block calculates the pressure drop in a single run of pipe. Pipe permits the
connection of fittings. The flow is assumed to be uniform along the axis and can
