Transcript Introduction to Engineering Calculations

Chapter 1
Introduction to Engineering
Calculations
What’s in this chapter?
• Bioprocess Engineering Profession
• Units and Dimension
• Conversions of Unit
• Systems of Units
• Force, Weight and Mass
Introduction
 Describe the basic techniques for the handling
of units and dimensions in calculations.
• Describe the basic techniques for expressing
the values of process variables and for setting
up and solving equations that relate these
variables.
• Develop an ability to analyze and work
engineering problems by practice.
Bioprocess Engineering
Profession
BIOCHEMIST
VS
BIOPROCESS ENGINEER
Role of Bioprocess Engineering
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exploit advances in biology to create new products
design biochemical processes & operate plants
develop energy resources,
protect the environment.
Develop new, environmentally benign, and safer processes
to make the biochemical products that people depend on.
• Work in research and development laboratories,
creating polymeric materials with improved performance
and durability.
• Work in manufacturing, making vaccines and antibiotics.
• Invent new ways to keep our food and water supplies safe.
CHEMICAL PROCESS
RAW MATERIALS
SEPARATION PROCESS
INTERMEDIATE PRODUCT
REACTION PROCESS
INTERMEDIATE PRODUCT
SEPARATION PROCESS
FINAL PRODUCT
Bioprocess Engineer’s Task
You need to:
– Minimize production of unwanted
byproducts
– Separate the good (product) from the
bad (byproducts)
– Recover the unused reactants
– Maximize profit, minimize energy
consumption, minimize impact on the
environment
OPPORTUNITIES FOR BIOPROCESS
ENGINEERS
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pharmaceuticals
polymers
energy
food
consumer products
biotechnology
electronic and optical materials.
Units and Dimensions
Objectives:
• Convert one set of units in a function or equation
into another equivalent set for mass, length,
area, volume, time, energy and force
• Specify the basic and derived units in the SI and
American engineering system for mass, length,
volume, density, time, and their equivalence.
• Explain the difference between weight and mass
• Apply the concepts of dimensional consistency to
determine the units of any term in a function
Units and Dimensions
• Dimensions are:
– properties that can be measured such as
length, time, mass, temperature,
– properties that can be calculated by
multiplying or dividing other dimensions, such
as velocity (length/time), volume, density
• Units are used for expressing the dimensions
such as feet or meter for length, hours/seconds
for time.
• Every valid equation must be dimensionally
homogeneous: that is, all additive terms on both
sides of the equation must have the same unit
Conversion of Units
• A measured quantity can be expressed in terms of any
units having the appropriate dimension
• To convert a quantity expressed in terms of one unit to
equivalent in terms of another unit, multiply the given
quantity by the conversion factor
• Conversion factor – a ratio of equivalent values of a
quantity expressed in different units
• Let’s say to convert 36 mg to gram
36 mg
1g
1000 mg
=
0.036 g
Conversion
factor
Dimensional Equation
1. Write the given quantity and units on the left
2. Write the units of conversion factors that cancel
the old unit and replace them with the desired
unit
3. Fill the value of the conversion factors
4. Carry out the arithmetic value
Dimensional Equation
• Convert 1 cm/s2 to km/yr2
1 cm
s2
h2
day2
m
km
s2
h2
day2
yr2
cm
m
1 cm
36002 s2
242 h2
3652 day2
1m
1 km
s2
1 2 h2
12 day2
12 yr2
100 cm
1000 m
(3600 x 24 x 365)
100 x 1000
2
km
yr2
=
9.95 x 109 km/ yr
2
Systems of Units
•
Components of a system of units:
– Base units - units for the dimensions of mass, length,
time, temperature, electrical current, and light intensity.
– Multiple units- multiple or fractions of base unit
•
E.g.: for time can be hours, millisecond, year, etc.
– Derived units - units that are obtained in one or two ways;
a) By multiplying and dividing base units; also referred to
as compound units
•
Example: ft/min (velocity), cm2(area), kg.m/s2 (force)
b) As defined equivalent of compound unit (Newton = 1
kg.m/s2)
Systems of Units
• 3 systems of unit:
a) SI system
b) American engineering system
c) CGS system
Base Units
Base Units
Quantity
SI
Symbol
American
Symbol
CGS
Symbol
meter
m
foot
ft
centimeter
cm
Mass
kilogram
kg
pound mass
lbm
gram
g
Moles
grammole
mole
pound mole
lbmole
gram-mole
mole
Time
second
s
second
s
second
s
Temperature
Kelvin
K
Rankine
R
Kelvin
K
Length
Multiple SI Units
Multiple Unit Preferences
tera (T) = 10
12
centi (c) = 10
-2
giga (G) = 10
9
milli (m) = 10
-3
mega (M) = 10
6
micro (μ) = 10
-6
kilo (k) = 10
3
nano (n) = 10
-9
Derivatives SI Units
Derived SI Units
Quantity
Unit
Symbol
Equivalent to the Base Unit
Volume
Liter
L
0.001m3 = 1000 cm3
Force
Newton
(SI)
Dyne
(CGS)
N
1 kg.m/s2
1 g.cm/s2
Pressure
Pascal
Pa
1 N/m2
Energy/
Work
Joule
Calorie
J
cal
1 N.m = 1 kg.m2/s2
4.184 J =4.184 kg.m2/2
Power
Watt
W
1 J/s = 1 kg.m2/s3
Force and Weight
• Force is proportional to product of mass and acceleration
• Usually defined using derived units ;
1 Newton (N)
=
1 kg.m/s2
1 dyne
=
1 g.cm/s2
1 Ibf
=
32.174 Ibm.ft/s2
• Weight of an object is force exerted on the object by
gravitational attraction of the earth i.e. force of gravity, g.
• Value of gravitational acceleration:
g
= 9.8066 m/s2
= 980.66 cm/s2
= 32.174 ft/s2
Force and Weight
• gc is used to denote the conversion factor from a natural
force unit to a derived force unit.
gc
=
1 kg.m/s2
1N
= 32.174 lbm.ft/s2
1 lbf
ANY
QUESTION?