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Index
Isothermal Flow
In this chapter a model dealing with gas that flows through
a long tube is described.
This model has a applicability to situations which occur
in a relatively long distance and where
heat transfer is relatively rapid so that the temperature
can be treated, for engineering purposes, as a constant.
For example, this model is applicable when a natural gas
flows over several hundreds of meters.
Such situations are common in large cities in U.S.A. where
natural gas is used for heating.
It is more predominant (more applicable) in situations
where the gas is pumped over a length of kilometers.
Figure 8.1:
Control volume for isothermal flow
 |
The high speed of the gas is obtained or explained by the combination
of heat transfer and the friction to the flow.
For a long pipe, the pressure difference reduces the density
of the gas.
For instance, in a perfect gas, the density is inverse of
the pressure (it has to be kept in mind that the gas undergoes an
isothermal process.).
To maintain conservation of mass,
the velocity increases inversely to the pressure.
At critical point the velocity reaches the speed of sound at the exit
and hence the flow will be choked
8.1.
Subsections
Next: The Control Volume Analysis/Governing
Up: gasDynamics
Previous: Isothermal Nozzle (T=constant)
Index
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