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CHAPTER 1Introduction To
Thermodynamics
ERT 206/4ERT 206/4ThermodynamicsThermodynamics
Miss. Rahimah Bt. Othman
Email: [email protected]
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.(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.
THERMODYNAMICS: Definition
THERMO =
DYNAMICS =
HEAT AND TEMPERATURE
MOTION
* 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: Definition
- 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)
1.These must be separated from the mixture and purified to result in product of societal, commercial, or medicinal value.
•These is the area where thermodynamics plays a central role in bioprocess eng.
•Separation processes, e.g. distillation are designed based on information from thermodynamics
OHHCOCHOOHHC 223252
THERMODYNAMICS: Example
- 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)
• 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;
Total volume, divided by the mass or number of moles of the system to yield specific or molar volume.
M
mn Mnmor
mVV t
nVV t
m
VV
t
n
VV
t
• Specific volume:
• Molar volume: or
or
SI unitSI unit Metric engineering Metric engineering system unitssystem units
Newton (N) Kilogram force (kgf)
F = ma mag
Fc
1
21c
2
c
s f kg m kg .80665 9 g
ms 9.80665 x kg 1 x g
1 kgf 1
* Note : The kilogram force is equivalent to 9.80665 N
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.
212
55.74792.9
730sNm
ms
N
g
Fm
Solution
With a = g, Newton’s law is : F = mg. Hence;
Because the newton N has the unit kg m s-2,
kgm 55.74
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;
N 124.5 kgms 124.5 )F(or
ms 1.667 x kg 74.55)()( 2-
2
moon
moonmgmoonF
• Temperature is commonly measured with liquid-in-glass thermometers, wherein the liquid expands when heated.
• 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 unitSI unit Metric engineering system unitsMetric 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.
ghA
gAh
A
mg
A
FP
A
mg
A
FP
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
22
Ncm77.76)1)()(4/1(
295.60 pressure Gauge
N 295.60)82.9)(14.6(
A
F
mgF
The absolute pressure is therefore;
kPa 4.867 or
Ncm 74.86)013332.0)(748(77.76 2
P
P
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,
bar 0.8009 kPa 80.09 Ncm 8.009 cmkgms 8.009or
cmgms 8,009ms 9.784 x gcm 13.53 x cm 60.5 222
2223
P
P
• Work, W is performed whenever a force acts through a distance.
t
t
V
V
t
t
t
PdVW
PdVdW
A
VPAddW
FdldW
2
1
* Note: The minus sign ‘-’ the volume change is positive, and the minus sign is required to make the work negative.
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.