2.
Chemical Engineering
Chemical engineering
essentially deals with the
engineering of chemicals,
energy and the processes
that create and/or convert
them.
Modern chemical
engineers are concerned
with processes that convert
raw materials or (cheap)
chemicals into more useful
or valuable forms.
3.
Job opportunities for Chemical
Engineers
Chemical engineering are employed across a huge variety
of sector including:
Chemical and allied products
Pharmaceuticals
Energy
Water
Food & drink
Oil & gas
Process plants & equipment
Biotechnology
Business and management
Consultancy
4.
Chemical engineer duties
Chemical engineers utilize
mass, momentum, and
energy transfer along with
thermodynamics and
chemical kinetics to
analyze and improve on
"unit operations in a
chemical plant."
5. Introduces basic chemical engineering unit operations.
Three main areas of unit operations are covered: Fluid
flow, heat transfer and mass transfer.
The principles of operation of major equipment and
machinery often found in the chemical process
industries are presented.
Fundamental engineering calculations are introduced,
and laboratory work is used to reinforce the
understanding of certain chemical engineering
phenomena.
Objective of the course
6. CLO 1- Explain the meaning of unit operations and identify
the various unit operations found in the plant
CLO 2- Explain the importance of piping systems, fittings
and devices used for metering of fluids
CLO 3- Describe the various types of machinery to move
fluids
CLO 4- Discuss the principles of operation of fired heaters
and heat exchange equipment
CLO 5- Discuss the principles of separation processes and
their equipment
LEARNING
OUTCOMES
7.
Introduction to the course.
Many examples are to be given to the students as well as
relevant articles on the subject.
SO1: Explain the meaning of unit operations
SO2: List the unit operations most likely found in the plant
If the schedule permits, a site visit to a chemical industry will
complement this learning outcome
L.O #1
9.
An oil refinery or petroleum refinery is
an industrial process plant where crude
oil is processed and refined into more
useful products such as petroleum
naphtha, gasoline, diesel fuel, asphalt
base, heating oil, kerosene and liquefied
petroleum gas.
OBJECTIVE OF OIL REFINERY
10.
Petroleum products are grouped into three categories: light
distillates, middle distillates and heavy distillates.
LIGHT DISTILLATES:
Liquefied petroleum gas (LPG), Gasoline (also known as petrol,
Naphtha
MIDDLE DISTILLATES:
Kerosene and related jet aircraft fuels, Diesel fuel
HEAVY DISTILLATES
Fuel oils, Lubricating oils, Paraffin wax, Asphalt and tar,
Petroleum coke
MAJOR PRODUCTS
12.
Pretreatment: Desalting before entering
the refinery to avoid corrosion problems:
Preheating of crude oil for separation by
distillation
Separation of crude oil into fractions by
atmospheric and vacuum distillation.
Chemical transformation
COMMON PROCESS UNITS
FOUND IN A REFINERY
14.
A desalter is a process unit in an oil refinery that removes salt from
the crude oil. The salt is dissolved in the water in the crude oil, not in
the crude oil itself.
The desalting is usually the first process in crude oil refining. The salt
content after the desalter is usually measured in PTB - pounds of salt
per thousand barrels of crude oil.
Usually desalting is necessary only when the salt content of a crude
oil is greater than 10 lb/ 1000bbl (expressed as NaCl)
But now almost all crude oils are desalted to increase the efficiency
of the refineries LISTEN...LEARN...THINK...GROW 14
CRUDE OIL DESALTING
17. Following the desalter, the crude oil is further heated by exchanging heat
with some of the hot, distilled fractions and other streams. It is then heated
in a fuel-fired furnace (fired heater) to a temperature of about 398 °C and
routed into the bottom of the first distillation unit.
LISTEN...LEARN...THINK...GROW 17
PREHEATING CRUDE OIL
18.
FURNACE
One of the major energy
demands within
refineries comes from the
need to heat the crude
feedstock upstream of
the crude distillation
column to obtain the
desired flash and
distillation yields.
20.
STEP III: ATMOSPHERIC AND
VACCUM DISTILLATION
The crude atmospheric and vacuum distillations are the first major
processing units in any refinery.
They are used to separate the crude oils into fractions according to
boiling point so that each of the processing units following will have
feedstock that meet their particular specifications.
Higher efficiencies and lower costs are achieved if the crude oil
separation is accomplished in two steps:
First by fractionating the total crude oil at essentially atmospheric
pressure;
Then by feeding the high-boiling bottoms fraction (topped or
atmospheric reduced crude) from the atmospheric still to a second
fractionator operated at a high vacuum
28.
Unit Operations are the basic physical
operations of chemical engineering in a
chemical process plant, that is, distillation,
fluid transport, heat and mass transfer,
evaporation, extraction, drying, crystallization,
filtration, mixing, size separation, crushing and
grinding, and conveying
What is unit operation?
29. 1.Fluid flow processes, including fluids transportation,
filtration, and solids fluidization.
2.Heat transfer processes, including evaporation,
condensation, and heat exchange.
3.Mass transfer processes, including gas absorption,
distillation, extraction, adsorption, and drying.
4.Thermodynamic processes, including gas liquefaction, and
refrigeration.
5.Mechanical processes, including solids transportation,
crushing and pulverization, and screening and sieving.
Chemical engineering unit
operations consist of five classes:
30.
1. Fluid Flow Process:
Fluid Transportation
Pipeline transport is
the transportation of
goods through a
pipe. Liquids and
gases are transported
in pipelines and any
chemically stable
substance can be sent
through a pipeline
31.
2.Heat transfer processes
Heat Exchanger
A heat exchanger is a
piece of equipment built
for efficient heat transfer
from one medium to
another. The media may
be separated by a solid
wall to prevent mixing
or they may be in direct
contact
32.
3.Mass Transfer Processes
Distillation
Distillation is a process of
separating the component
substances from a liquid mixture
by selective vaporization and
condensation.
Distillation may result in
essentially complete separation
(nearly pure components), or it
may be a partial separation that
increases the concentration of
selected components of the
mixture.
33.
4.Thermodynamic processes
Gas Liquefaction
Liquefaction is used for
analyzing the fundamental
properties of gas molecules
(intermolecular forces), for
storage of gases, for example:
LPG, LNG
At atmospheric pressure, very
low temperatures are required.
The natural gas is condensed
into a liquid at approximately
−162 °C (−260 °F).
34.
5. Mechanical processes
Crushing
Crushers may be used to
reduce the size, or change the
form, of waste materials so
they can be more easily
disposed of or recycled, or to
reduce the size of a solid mix
of raw materials (as in rock
ore), so that pieces of different
composition can be
differentiated.
38.
Mole is a unit of measurement used in chemistry to express
amounts of a chemical substance, defined as the amount of any
substance that contains as many elementary entities
Molecular mass or molecular weight refers to the mass of a
molecule. It is calculated as the sum of the mass of each
constituent atom multiplied by the number of atoms of that
element in the molecular formula
𝑀𝑜𝑙𝑒 =
𝑚𝑎𝑠𝑠
𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡
Mole & Molecular weight
40.
Hydrogen (H2) has two hydrogen atoms.
The atomic mass or molecular weight of hydrogen is 2.
The molecular weight of methane, molecular formula
CH4, is calculated as follows.
EXAMPLES
atomic mass total mass
C 12 12
H 1 4
CH4 16 Molecular weight
41.
1) How many moles of hydrogen (H2) have a mass of 8g
2) What is the molecular weight of water ( H2O) if 2 moles
contain 36 grams.
3) What is the total mass of 1 mole of ethane C2H6
Class activity
42.
What is Weight ?
Weight is a force we
get as we press against
other objects. You
press against a scale to
measure your weight.
What pulls you against
the scale?
SI Unit of weight is
Newton
44.
What is Volume ?
Volume is the quantity of
three-dimensional space
enclosed by some closed
boundary.
For example, the space that a
substance (solid, liquid, gas,
or plasma).
A measuring cup can be used
to measure volumes of
liquids.
SI unit of volume is m3
45.
Volume milliliter (mL) 1000 mL = 1 L
Cubic centimeter (cm³) 1 cm³ = 1 mL
Liter (L) 1000 L = 1 m³
Cubic meter (m³)
Common Units of Volume
46.
Prefix Symbol Factor Numerically Name
giga G 109 1 000 000 000 billion
mega M 106 1 000 000 million
kilo k 103 1 000 thousand
centi c 10-2 0.01 hundredth
milli m 10-3 0.001 thousandth
micro μ 10-6 0.000 001 millionth
nano n 10-9 0.000 000 001 billionth
Prefixes for Units
47. 47
Mass Density
Volume
Mass
SI Unit of Mass Density: kg/m3
DEFINITION OF MASS DENSITY
The mass density (Rho) is the mass m of a substance divided
by its volume V:
48. 48
Solids have
highest density
Aluminum 2 700
Brass 8 470
Concrete 2 200
Copper 8 890
Diamond 3 520
Gold 19 300
Ice 917
Iron (steel) 7 860
Lead 11300
Quartz 2 660
Silver 10 500
Wood (yellow pine) 550
Mass Densities of Common Substances
(Unit: kg/m3)
50.
1) A solid has a density of 917 kg/m3. What will be its mass in
a container of 3 m3 ?
2) Water occupies a volume of 5 m3. What is the mass
An unknown gas has a mass of 6.45 kg and occupies a volume
of 5 m3. What is the density? What is this gas?
Class activity
51.
If we know the total mass of the mixture and the
mass of each component, we can calculate the total
mass by dividing the mass of each component by the
total mass.
The total mass composition should be equal to 1
Mass composition
Components Mass (grams) Mass composition
Water 15 15/65= 0.23
Gasoline 40 40/65= 0.61
Salt 10 10/65= 0.16
Total 65 1.00
52.
Find the composition of a mixture containing
1ograms of sugar, 20 grams of water and 5 grams of
coffee.
Class activity
55.
55
Parts Of Piping Systems
Piping Systems include:
Pipe
Flanges
Fittings
Bolting
Gaskets
Valves
Hangers and supports
Insulations, coverings, coatings
56.
“Piping systems are like arteries and veins. They carry the
lifeblood of modern civilization.”
56
Piping Systems
57.
57
Piping Systems :Safety First
Primary Design Consideration is Safety
Evaluate Process Conditions
Temperature
Pressure
Chemical compatibility/Corrosion allowances
Vibration, flexing, bending
Expansion/Contraction due to temperature change
Environmental conditions
Evaluate the Effects of a Leak
Evaluate Performance in a Fire Situation
58.
58
Piping Systems : Special Requirements
Evaluate any Special Requirements
Sanitary requirements – “Cleanability”
Serviceability – ease of maintenance of equipment
Possible contamination of process fluid by piping materials,
sealants, or gasketing
Earthquake, Hurricane, Lightening, Permafrost
Lowest Cost over the Lifetime
59.
59
CM4120
Unit Operations Lab
Codes and Standards for Piping Systems
Codes and Standards simplify design, manufacturing, installation
process
Standards – provide design criteria for components
standard sizes for pipe
dimensions for fittings or valves
Codes – specific design/fabrication methodologies
Incorporated into local/regional statute
It’s the LAW
60.
60
Standards for Piping Systems
ASME Boiler and Pressure Vessel Code
ASME B31: Code for Pressure Piping
ANSI Standards – dimensions for valves, piping,
fittings, nuts/washers, etc.
ASTM Standards for piping and tube
API – Specs for pipe and pipelines
AWS, ASHRAE, NFPA, PPI, UL, etc.
61.
61
ASME B31 is the applicable standard for design
of most piping systems in chemical plants
B31.1 – Power plant boilers
B31.3 – Chemical plant and refinery piping
B31.4 – Liquid petroleum transport
B31.7 – Nuclear power plant radioactive
fluids
62.
62
ASME B31.3 – Chemical Plant and Refinery Piping Code
Includes:
Process piping in chemical and refinery plants
Process piping in pharmaceutical and food processing
Process piping in textile and paper plants
Boiler piping
63.
63
ASME B31.3 covers:
Materials and design
Fabrication
Erection and assembly
Support
Examination, inspection, and testing
Web reference: www.piping-toolbox.com
64.
64
Piping Systems : Standard Pipe Sizes
Diameters are “Nominal”
Sizes 12” and less, nominal size < OD
Sizes 14” and over, nominal size = OD
Wall thickness inferred thru “Schedule”
Schedule = P/S * 1000
Defined Schedules:
5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160
65.
65
Piping Systems: Standard Tubing Sizes
Steel tubing:
Diameters are Actual OD
Wall thickness is specified
Refrigeration Tubing
Single wall thickness available for each size
Actual OD
Copper Tubing – Nominal sizes
Type K, L, M
66.
66
Piping Systems Materials – Metallic piping
Carbon and low alloy steel
Ductile
Inexpensive and available
Easy to machine, weld, cut
Some drawbacks
67.
67
Piping Systems Materials – Metallic piping
Alloy Steels including “Stainless Steels”
Good corrosion resistance
More difficult to machine, weld, cut
Some drawbacks
68.
68
Piping Systems Materials – Metallic piping
Nickel, Titanium, Copper, etc.
Copper is used in residential and commercial applications
and is widely available
Other materials are expensive and difficult to machine,
weld, join
Some incompatibilities with each
69.
69
Piping Systems Materials – Non-Metallic piping
Thermoplastics
Wide range of chemical compatibility
Light weight
Easily cut and joined
Low temperature limits
Need extra supports
70.
70
Piping Systems Materials – Non-Metallic piping
Fiberglass Reinforced Pipe
Wide range of chemical compatibility
Easily cut and joined
Wider temperature limits than thermoplastics
Thermal expansion similar to carbon steel
Similar structural performance as carbon steel
75.
75
Piping Systems : Heat Tracing
Prevents flow problems in cold climates
Freeze protection
Loss of flow due to viscosity increase
Prevent condensation in vapor lines
Methods
Electric
Hot Fluids
76.
76
Piping Systems : Piping Supports
Prevent strain at connections
Must allow for expansion/contraction
Design for wind/snow and
ice/earthquake
Clearance for plant traffic and equipment
78. 78
Results of inadequate support:
May, 1974 – Leaking reactor removed from train of reactors and
temporarily replaced with a section of pipe
June, 1974 – Supports collapse, pipe breaks
28 dead, 89 injured, 1800 houses damaged, 160 shops and
factories damaged, large crater where plant stood
79.
79
CM4120
Unit Operations Lab
Piping Systems
Select in-line components
Determine insulation, coverings, coatings
Design and locate supports and hangers
80.
80
Piping Systems : Pipe Joints
Threaded
Welded
Soldered/ Brazed
Glued
Compression
Bell and spigot
Upset or expanded
86.
86
Piping Systems: Pipe Fittings
Forged
Cast
Malleable Iron
Pressure/Temperature Rated by “Class”
125, 250, or 2000, 3000, etc.
Need a look-up table to determine max. allowable P for the design
temperature
98.
Fluid Flow
• Mass flow rate: Av (kg/s)
• Continuity: 1A1 v1 = 2A2 v2
i.e., mass flow rate the same everywhere
e.g., flow of river
A1 1 A2 2v1 v2
99.
Paul E. Tippens
Fluid Motion
The lower falls at
Yellowstone National Park:
the water at the top of the
falls passes through a narrow
slot, causing the velocity to
increase at that point.
100.
Fluids in Motion
All fluids are assumed in this
treatment to exhibit streamline
flow.
• Streamline flow is the motion of a fluid in
which every particle in the fluid follows the
same path past a particular point as that
followed by previous particles.
101.
Since 1989 there were at least 23 distinct type of technologies
available for the measurement of flow in closed conduit.
The performance of flowmeters is also influenced by a
dimensionless unit called the Reynolds Number.
The Reynolds number is used for determined whether a flow is
laminar or turbulent. Laminar flow within pipes will occur
when the Reynolds number is below the critical Reynolds
number of 2300 and turbulent flow when it is above 4000.
TYPES OF FLOW
102.
Types of Flow
𝑅𝑒 =
𝜌.𝑑.𝑣
𝜇
𝜌 is the density in kg/m3
d is the diameter of the
pipe in m
V is the velocity of fluid
in m/s
𝜇 is the dynamic
viscosity in Pa.s
103.
1) The velocity of water in a pipe is 1.5 m/s. Calculate the
Reynolds number if the diameter is 0.1 m and the density and
viscosity are respectively 1000 kg/m3 and 0.001 Pa.s
2) What will be the velocity for a Reynolds number of 2000.
Class activity
104.
Quantity of a gas or liquid
moving through a pipe or
channel within a given or
standard period (usually a
minute or hour)
What is a Flow Rate ?
105.
What is mass flow rate
Mass flow rate is the
mass of a substance
which passes per
unit of time.
Its unit is kg/s
(kilogram per
second) in SI units,
106.
1) What is the mass flow rate of 5 kg of water passing through
a tube during 1 min ?
2) In 20 seconds, water passes a tube with a mass flow rate of
2kg/s. What is the mass of water?
Class work
107.
Volume flow rate
Volume flow rate,
rate of fluid flow or
volume velocity) is
the volume of fluid
which passes per unit
time.
The SI unit is m3/s
(cubic meters per
second.
𝑄 =
𝑉𝑜𝑙𝑢𝑚𝑒
𝑡𝑖𝑚𝑒
108.
Volume flow rate and
velocity
Volume flow rate
= Area x velocity
Q= A.v
A = Cross-sectional Area of Pipe
(SI: m2)
v = Velocity of the fluid in the
pipe (SI: m/s)
109.
1) In how many seconds, 3 m3 of water having flows with a
rate of 10 m3/s
2) Water flowing in a tube having a area of 10 cm2. If the flow
rate is 1 m3/s, what will be the velocity in m/s?
Class work
110.
Volume and mass flow
rates
Mass flow rate is equal
to the volumetric flow
rate times the density.
ṁ= ρ.Q
Since Q = A. v
ṁ=ρ.A . v
111.
A liquid having a density of 800 kg/m3 has a volumetric flow
rate of 50 m3/s. What is its mass flow rate is kg/s?
A fluid has a density of 1000 kg/m3 flows in a pipe of surface
are equals to 10 cm2. If the velocity is 1 m/s, what are the
volumetric and mass flow rates
Class activity
112.
Molecular flow rate is defined as mass flowrate divided by the
molecular weight.
N =
𝑀𝑎𝑠𝑠 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒
𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡
Molecular flow rate
113.
1) What is the molecular flow rate of water if the mass
flow rate is 100 kg/s and the molecular weight is 18
2) What is the mass flow rate of gasoline if the
molecular flow rate is 50 moles/s and the molecular
weight is 80.
Class activity
117.
Orifice plate
An orifice plate is a thin
plate with a hole in it,
which is usually placed
in a pipe. When a fluid
passes through the
orifice, it is forced to
converge to pass through
the hole, the velocity
increases and the fluid
pressure decreases
118.
Positive displacement
A positive displacement
meter is a type of flow
meter that requires fluid to
mechanically displace
components in the meter in
order for flow measurement
These devices consist of a
chamber(s) that obstructs
the media flow and a
rotating or reciprocating
mechanism that allows the
passage of fixed-volume
amounts.
121.
INTRODUCTION
The pump is mechanical device which conveys liquid
from one place to another place.
It can be defined as a hydraulic machines which
converts the mechanical energy into hydraulic energy
( Pressure) .
The pump is power absorbing machine.
The power can be supplied to the pump by a prime
mover like an electric motor, an internal combustion
engine or turbine..
122.
Pressure definition
Pressure is the action of one force
against another over, a surface. The
pressure P of a force F distributed
over an area A is defined as:
P = F/A
123.
Pressure References
Absolute pressure
The pressure is referenced to zero absolute. Absolute
pressure can only have a positive value.
Gauge pressure
The pressure is referenced to atmospheric pressure:
P ( gauge ) = P ( absolute) – Atmospheric pressure
Vacuum pressure
Any pressure lower than atmospheric pressure is called
vacuum pressure.
124.
UNITS OF PRESSURE
SI UNITS:
1Pa = 1N/M2=1KG/S2.M
1ATM (ATMOSPHERIC PRESSURE)= 100 kPa
1 ATM= 101 kN/M2
1ATM= 760 MM. HG
US UNITS:
1PSIA = 1LBF/IN2
1PSIA = 6894.7 Pa
1ATM= 14.696 PSIA
LISTEN..LEARN..THINK..ENJOY
YOURSELF
124
125.
1) A liquid in a pipe has an absolute pressure of 50 kPa. What
is the reading in the gauge if the atmospheric pressure is 101
kPa?
2) You read in a manometer a pressure of -10 kPa. What is the
absolute pressure ?
Convert 50 kPa into atm.
Convert 2 atm into Psi.
Class activity
126.
Head
Connect a tube to the
discharge of a pump and
measure the water height, that
the head of the pump.
Head is the height at which a
pump can raise water up.
More pressure the pump
delivers, the higher the head
will be in the figure.
127.
Pressure and Head
Head and pressure are interchangeable terms provided that
they are expressed in their correct units.
The conversion of all pressure terms into units of equivalent
head simplifies most pump calculations.
ℎ =
𝑃.𝑔 𝑐
𝜌.𝑔
128.
1) What is the head in m when the pressure is 98100 Pa and the
density of the liquid is 1000 kg/m3.
g = 9.81 m/s and gc= 1kg.m/s2
h = (98100 x 1)/ ( 1000x 9.81)= 10 m
2) what is now the pressure if the head is 5 m?
Example + activity
130.
Pump Performance Curve
Step #1, Horizontal Axis
The pump's flow rate is plotted on the horizontal
axis ( X axis)
Usually expressed in Gallons per Minute
Pump Flow Rate
131.
Pump Performance Curve
Step #2, Vertical Axis
Pump Flow Rate
The head the pump produces is
plotted on the vertical axis (Y axis)
Usually express in Feet of Water
Head
132.
Mapping the Flow and the Head
Pump Flow Rate
Most pump
performance curves
slope from left to
right
Performance Curve
Head
133.
Pump Performance Curve
Important Points
Shut-off Head is the maximum pressure
or head the pump can produce
No flow is produced
Pump Flow Rate
Head
Shut-off Head
135.
System Performance Curves
System Performance Curve is a mapping of the
head required to produce flow in a given
system
A system includes all the pipe, fittings and
devices the fluid must flow through, and
represents the friction loss the fluid experiences
136.
System Performance Curve
Step #1, Horizontal Axis
System Flow Rate
The System's flow rate in plotted on the horizontal axis
( X axis)
Usually expressed in Gallons per Minute
137.
System Performance Curve
Step #2, Vertical Axis
Pump Flow Rate
The head the system requires is plotted on the
vertical axis (Y axis)
Usually express in Feet of Water
Head
138.
System Performance Curve
Step #3, Curve Mapping
The friction loss is mapped onto the graph
The amount of friction loss varies with flow through
the system
Head
Pump Flow Rate
Friction Loss
139.
Head
Pump Flow Rate
The point on the system curve that intersects the pump curve is
known as the operating point.
141.
POSITIVE DISPLACEMENT
PUMPS:
RECIPROCATING PUMPS
Reciprocating pump
classification
Reciprocating pumps can be
classified based on
1. Sides in contact with water
a) Single acting Reciprocating
pump
b) Double acting reciprocating
pump
2. Numbers of cylinder used
a) Single cylinder pump
b) Two cylinder pumps
c) Multi-cylinder pumps)
142.
This machine consists of an
IMPELLER rotating within a
case (diffuser)
Liquid directed into the
center of the rotating
impeller is picked up by the
impeller’s vanes and
accelerated to a higher
velocity by the rotation of the
impeller and discharged by
centrifugal force into the case
(diffuser).
Centrifugal Pumps
144.
Diameter of
the Impeller
Thickness
of the impeller
Centrifugal Impellers
Thicker the Impeller- More Water
Larger the DIAMETER - More Pressure
Increase the Speed - More Water and Pressure
Impeller
Vanes
“Eye of the
Impeller”
Water
Entrance
145.
Two Impellers in Series
Direction of Flow
Twice the pressure
Same amount of water
146.
Multiple Impellers in
Series
Placing impellers in series increases the amount of
head produced
The head produced = # of impellers x head of one
impeller
Direction of Flow Direction of Flow
151.
What is a Compressor?
◦ A mechanical device that increases the pressure of a gas by
reducing its volume.
◦ Similar to a pump – Increases the pressure on a fluid and transport
it through a pipe.
What is key difference between a Fluid and a Gas?
◦ Compressibility – a gas is compressible
What happens to gas volume as it is compressed?
◦ Decreases
What happens to the Temperature of the Gas as it is
compressed?
◦ Increases
Compressors
152. Compressors are classified by how they work
Two Categories of Compressors
◦ Positive Displacement
◦ Dynamic
What is a Positive Displacement Compressor?
◦ A compressor that confines successive volumes of gas within a
closed space in which the pressure of the gas is increased as the
volume of the closed space is decreased.
Intermittent Flow
What is a Dynamic Compressor?
◦ A compressor using a rotating mechanism to add velocity and
pressure to gas.
Continuous Flow
Compressors
153.
Two types of Positive Displacement
Compressors:
Reciprocating
Rotary
Two Types of Dynamic Compressors
Centrifugal
Axial
Compressors
154.
Reciprocating Compressors
How does it work?
Piston movement in a cylinder connected to a rod and crankshaft
Downward piston motion, low pressure gas enters the chamber
Upward piston motion, gas is compressed and exits the chamber
Video
Reciprocating Compressors
155. Reciprocating Compressors
◦ High Horsepower Applications
Common in natural gas transmission lines.
Processes for high pressure delivery of gasses
◦ Air Conditioning Compressors
Some manufactures (Frigidaire™) use rotary compressors
AC Compressors (and other small appliance applications) are Hermetic
or Semi-Hermetic
Compressors
156.
Rotary Compressors
◦ How do they it work?
When a rotating mechanism spins past the inlet valve, it creates a
vacuum.
The fluid flows out of the valve behind it, filling the vacuum.
As it approaches the outlet valve, the chamber shrinks, creating more
pressure on the fluid.
The fluid has nowhere to go but out of the outlet valve, so it shoots out
of it.
Then the rotating mechanism continues on to draw more fluid at the
inlet valve.
◦ How it works Video
Rotary Compressors
157. Common Types of Rotary Compressors
◦ Screw
◦ Vane
◦ Scroll
Screw
◦ Two meshing helix screws
Rotors
◦ Compact and smooth running
◦ 2 types - Oil Free and Oil Flooded
Oil Free – No assistance from oil to cool and assist in sealing .
Oil Flooded – Oil injected to aid in sealing and provide cooling.
Separator downstream to capture the oil
Rotary Compressors
158.
Vane Compressors
◦ Vane housing on a off centered shaft
◦ Vanes slide in an out always making
contact with the compressor walls
◦ Gas enters in the largest opening
◦ Exits the smallest
◦ Good for low pressure applications
◦ Efficient
◦ Heat controlled by
oil injection
Vane Compressors
159.
Scroll Compressor
◦ How it works
2 Spirals
1 stationary, 1 orbits without rotating
1st orbit entraps inlet gas
Subsequent orbits compresses gas and exited out the center
Generally 2-3 orbits for a full cycle
Video
◦ Advantages
Compact
Steady flow
Low energy use
Quiet
Smooth operation
Scroll Compressors
160.
What is a Dynamic Compressor?
A compressor using a rotating mechanism to add
velocity and pressure to gas.
Continuous Flow
What are the Two Types of Dynamic Compressors?
Centrifugal
Axial
Dynamic Compressors
161.
Centrifugal Compressors
Rotating disk (impeller) forces gas to the rim of the
impeller, increasing velocity
The diffuser converts the velocity energy to pressure
energy.
Primarily used for continuous, stationary service in
industries such as refineries, chemical plants and snow
making operations
Single Stage and Multi-Stage Compressors
How a Centrifugal Compressor Works
Centrifugal Compressors
162.
Impeller
Most critical part of a centrifugal compressor
Compressor performance determined by impeller:
Size
Shape
Speed
3 types of Impellers
Closed
Most common
Shroud covering both sides of the blade
Center eye hole for gas to enter
Used in Multi-stage compressors
Semi –open
Open
Compressors
163.
Multi-Stage Compressors
Diaphragm
Specially designed casing wall separating
the stages
Gas passes through the difuser
Passes through the return channel in the
diaphragm
Controlling Axial Load on the Shaft
Bearing Review
Thrust Bearing
Multi Stage Compressors
164. Axial Compressors
Gas flows parallel to the axis of rotation
Unlike centrifugal that has radial components
Has rotating and stationary components
Rotating airfoil – rotor
Stationary airfoil – stator
Similar number of these on
a shaft
Video
Axial Compressors
165.
Axial Compressors
High Volume
High Efficiency
High Cost
Common Uses
Gas Turbines
Jet engines
Power stations
Nickname – “Superchargers”
Axial Compressors
167.
1) How many moles of carbon have a mass of 36g
2) What is the molecular weight of methane ( CH4) if 2 moles
contain 32 grams.
3) What is the total mass of 1 mole of propane C3 H8
Class activity
168.
1) A solid has a density of 1600 kg/m3. What will be its mass
in a container of 5.5 m3 ?
2) Water occupies a volume of 15 m3. What is the mass
An unknown gas has a mass of 3.45 kg and occupies a volume
of 3 m3. What is the density?
Class activity
169.
Find the mass composition of a mixture containing 20
grams of water , 35 grams of juice and 5 grams of
sugar.
Class activity
170.
1) The velocity of water in a pipe is 2 m/s. Calculate the
Reynolds number if the diameter is 0.15 m and the density and
viscosity are respectively 800 kg/m3 and 0.003 Pa.s
2) What will be the velocity for a Reynolds number of 4000.
Class activity
171.
1) What is the mass flow rate of 6 kg of water passing through
a tube during 45 seconds ?
2) In 10 seconds, water ( density = 1000 kg/m3) passes a tube
with a mass flow rate of 2m3 /s. What is the mass of water?
Class work
172.
1) In how many seconds, 5 m3 of water having flows with a
rate of 8 m3/s
2) Water flowing in a tube having a area of 7 cm2. If the flow
rate is 1.5 m3/s, what will be the velocity in m/s?
Class work
173.
A liquid having a density of 1000 kg/m3 has a volumetric flow
rate of 60 m3/s. What is its mass flow rate is kg/s?
A fluid has a density of 1000 kg/m3 flows in a pipe of surface
are equals to 2 m2. If the velocity is 1.5 m/s, what are the
volumetric and mass flow rates
Class activity
174.
1) What is the molecular flow rate of a liquid if the
mass flow rate is 70 kg/s and the molecular weight is
38
2) What is the mass flow rate of gasoline if the
molecular flow rate is 50 moles/s and the molecular
weight is 80.
Class activity
175.
1) A liquid in a pipe has an absolute pressure of 150 kPa. What
is the reading in the gauge if the atmospheric pressure is 101
kPa?
2) You read in a manometer a pressure of 40 kPa. What is the
absolute pressure ?
Convert 0.5 atm into Pa.
Convert 50 kPa into Psi.
Class activity
176.
1) What is the head in m when the pressure is 100100 Pa and
the density of the liquid is 800 kg/m3.
g = 9.81 m/s and gc= 1kg.m/s2
Example + activity