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Thermodynamics
CHAPTER 1
Introduction To Thermodynamics
Miss. Rahimah Bt. Othman
Email: rahimah@unimap.edu.my
COURSE OUTCOME 1 CO1)
1. Chapter 1: Introduction to Thermodynamics
Identify and analyze scope, dimensions and units, measure
of amount or size, force, temperature, pressure, work, energy
and heat.
2. Chapter 2: The First Law and Other Basic Concepts
3. Chapter 3: Volumetric properties of pure fluids
4. Chapter 4: Heat effects
5. Chapter 5: Second law of thermodynamics
6. Chapter 6: Thermodynamics properties of fluids
THERMODYNAMICS: Definition
* Thermodynamics Definition.
(from the Greek θέρμη therme, meaning "heat“ and δύναμις, dynamis,
meaning "power")
- is the study of energy conversion between heat and mechanical work,
and subsequently the macroscopic variables such as temperature, volume
and pressure.
THERMO =
HEAT AND TEMPERATURE
DYNAMICS = MOTION
THERMODYNAMICS: Definition
* Initially, thermodynamics is the study of the flow of heat to
produce mechanical energy that could be used for locomotive;
- after that is used for steam engines, turbines, pumps, air
conditioners etc.
* Because such equipment also used in chemical/ bioprocess
plant, it is also important for those engineers to learn the
fundamental of such equipment.
THERMODYNAMICS: Example
-
The production of chemicals, polymers, pharmaceuticals and other
biological materials, and oil and gas processing, all involve chemical or
biochemical reaction that produce a mixture of reaction product.
(e.g:Production of acetic acid from ethanol using Acetobacter aceti bacteria)
C2 H 5OH  O2  CH 3CO2 H  H 2O
1. These must be separated from the mixture and purified to result in
product of societal, commercial, or medicinal value.
2. These is the area where thermodynamics plays a central role in
bioprocess eng.
3. Separation processes, e.g. distillation are designed based on information
from thermodynamics
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
Dimensions and Units
- Dimension is recognize through our sensory perceptions and not
definable without the definition of arbitrary scales of measure,
divided into specific units of size.
- The units have been set by international agreement, and are
codified as the International System of Units (SI).
• Note: See Table 1.1 for Prefixes (eg: deca, hecto, kilo, etc.) of SI
units. (eg: 1 cm = 10-2 m, 1 kg = 103 g)
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
Measures of amount or size
• Three measures of amount or size are in common use:
Mass, m ;
Number of moles, n ; Total volume, Vt
• Mass, m divided by the molar mass M (molecular weight) to yield
number of moles;
m
n
M
or
m  Mn
Total volume, divided by the mass or number of moles of the system to
yield specific or molar volume.
• Specific volume:
Vt
V
m
• Molar volume:
Vt
V
n
or
V t  mV
or
V t  nV
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
Force
SI unit
Metric engineering
system units
Newton (N)
Kilogram force (kgf)
F = ma
1
F 
ma
gc
1 kgf

1
x 1 kg x 9.80665 ms  2
gc
gc

9 .80665 kg m kg f 1 s  2
* Note : The kilogram force is equivalent to 9.80665 N
Force Example 1.1
An astronaut weighs 730 N in Houston, Texas, where the local
acceleration of gravity is g = 9.792 ms-2. What are the astronaut’s mass
and weight on the moon, where g = 1.67 ms-2.
Solution
With a = g, Newton’s law is : F = mg. Hence;
m
F
730 N
1 2


74
.
55
Nm
s
2
g
9.792ms
Because the newton N has the unit kg m s-2,
m  74.55 kg
This mass of the astronaut is independent f location, but weight
depends on the local acceleration of gravity. Thus on the moon the
astronaut’s weight is;
F (moon)  mg (moon)  74.55 kg x 1.667 ms 2
or
F(moon)  124.5 kgms -2  124.5 N
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
Temperature
• Temperature is commonly measured with liquid-in-glass thermometers,
wherein the liquid expands when heated.
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
Pressure
• The pressure P exerted by a fluid on a surface is defined as the normal
force exerted by the fluid per unit area of the surface.
SI unit
Metric engineering system units
Pascal (Pa)
Kilogram force per square centimeter (kgf cm-2)
• The primary standard for pressure measurement is the dead-weight
gauge in which a known force is balanced by a fluid pressure acting
on a known area.
F mg

A
A
F mg Ahg
P 

 hg
A
A
A
P
Force Example 1.2
A dead-weight gauge with a 1 cm diameter piston is used to measure
pressures very accurately. In a particular instance a mass of 6.14 kg
(including piston and pan) brings it into balance. If the local acceleration
of gravity is 8.82 ms-2, what is the gauge pressure being measured? If
the barometric pressure is 748 Torr, what is the absolute pressure?
Solution
The force exerted by gravity on the piston, pan and weights is
F  mg  (6.14)(9.82)  60.295 N
F
60.295
2
Gauge pressure  

76
.
77
Ncm
A (1 / 4)( )(1) 2
The absolute pressure is therefore;
or
P  76.77  (748)(0.013332)  86.74 Ncm2
P  867.4 kPa
Force Example 1.3
At 27oC (300.15 K) the reading on a manometer filled with mercury is
60.5 cm. The local acceleration of gravity is 9.784 ms-2. To what pressure
does this height of mercury correspond?
Solution
Recall the equation in the preceding text, P = hρg. At 27 oC (300.15 K)
the density of mercury is 13.53 g cm-3. Then,
P  60.5 cm x 13.53 gcm 3 x 9.784 ms 2  8,009 gms 2cm 2
or
P  8.009 kgms 2cm 2  8.009 Ncm2  80.09 kPa  0.8009 bar
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
Work
• Work, W is performed whenever a force acts through a distance.
dW 
Fdl
Vt
dW   PAd
A
dW   PdV t
W
V2t
   t PdV t
V1
* Note: The minus sign ‘-’ the volume change is positive,
and the minus sign is required to make the work negative.
Dimensions and
Units
Measures of amount
or size
Force
Temperature
Thermodynamics
Pressure
Work
Energy
Heat
THANK YOU
TUTORIAL 1 - QUESTIONS
Problems : 1.3, 1.4, 1.11, 1.14, 1.22
Reference Book:
Smith, J.M., Van Ness, H.C. and Abbort, M.M., Introduction to
Chemical Engineering Thermodynamics, Seventh Edition,
McGraw-Hill, 2005.