This document discusses compressible flow and its applications in chemical engineering. It begins by defining compressible flow as fluid flow with significant changes in density, usually when the Mach number is greater than 0.3. It then discusses how to distinguish compressible fluids using the Mach number and provides some historical examples. The effects of compressibility, such as choked flow, shock waves, and changes in density with pressure changes are described. Finally, some applications of compressible flow in chemical engineering are mentioned, such as high-speed gas flow in pipes and nozzles and compressible gas flow in chemical processing industries.

2. Compressible flow
and its applications in chemical
engineering

3. CONTENTS
1. Introduction to compressible flow ?
2. How to distinguish compressible fluids through Mark
no. ?
3. Historical high-water marks
4. Effects of compressibility on flow
5. Applications of compressible in chemical Engineering

4. Compressible
flow :
 It is the branch
of fluid dynamics that
deals with flows
having significant
changes in
fluid density.
The fluid flow is
compressible when
the mach no: is
greater than 0.3 .

5. •Mach no: It is the ratio of
the speed of the flow to
the speed of sound .

6. Historical high-water
marks :
400 years earlier
6 ft long turbine
3ooo r.p.m
Carl
G.P

7. Chuck Yeager
mach no: (0.85 to 1.06)
43000 ft high
700 miles/hr
(1947)
Bell XS-

8. Compressibilit
y :
 Compressibility is a measure of the relative volume
change of a fluid or solid as a response to
a pressure (or mean stress) change. In its simple form,
the compressibility β may be expressed as
,

9.  If the density changes slowly, so that heat conduction
keeps the temperature T constant ( ISOTHERMAL
COMPRESSIBILITY ).
If the density changes rapidly, so that no heat can flow,
(dq=0, no heat transfer) is also isentropic (ds=0).

10.  Compressibility is property of fluids , liquid have very low values
of compressibility
 ( for water B = 5 X 10-10 PA−1 OR ATM−1 at 1 atm ) where as
gases have high compressibility. ( for Air B = 5 X 10-5 PA−1 OR
ATM−1 at 1 atm ) if the fluid element is assumed to have unit mass
, V is specific volume (volume per unit mass) and the density is Ρ =
1/ V . Than the given equation will reduce to

11. 1. From here we see that high speed flows generally involve large
pressure gradients . for a given change in pressure (dp) due to
flow , the resulting change in density (dΡ) will be small for liquids
(which have low values of B) therefore for the for the flow of
liquids relatively large pressure gradients can create high
velocities without much change in density. On the other hand for
the flow of gases with their attended large values of B moderate
to strong pressure gradients lead to substantial change in the

12. Effects of compressibility on flow
Choked flow : when the velocity of fluid is equal to the velocity of sound
that condition is known as chocked flow condition.
Sound waves / pressure waves : the rise and fall of pressure during the
passage causes pressure waves.
Shock waves: nearly discontinuous property change in supersonic flow
will cause shock waves.
A pressure ratio of 2 :1 will cause sonic flow

13. APPLICATIONS
High-speed flow of gasses in pipes, through nozzles
In turbines
 especially in relief valves.
Compressible gas flow with significant variation in
density along pipes is commonplace in the chemical
processing industries (CPI). In designing these pipes for
compressible flow, it is important to calculate the
pressure loss or maximum gas-handling capacity for