This document provides an overview of fundamental units in both the SI and English systems of measurement. It discusses various thermodynamic terms like enthalpy, internal energy, entropy, and heat. It also defines the three basic types of thermodynamic systems: open, closed, and isolated systems. Newton's second law of motion is expressed relating an object's acceleration to the net force acting on it and its mass. Gravity is defined using the proportional relationship between gravitational force, mass, and gravitational acceleration.

1. LECTURE UNIT 001
Fundamental Units:
SI units English / Engineering units
Length meters, m feet, ft
Time seconds, s seconds, sec
Mass kilogram, kg slugs, or pound mass, lbm
Force Newton, N pound force, lbf
Pressure Pascal, Pa psi
o o
Temperature C F
o
Absolute Temperature R K
Heat Energy N-m or J Btu
Power J/s or W Hp, ft-lbf/sec, Btu/hr
Nomenclatures:
H - Total Enthalpy (kJ, Btu) h - Specific Enthalpy (kJ/kg, Btu/lbm)
V - Total Volume (m3, ft3) v - Total Volume (m3/kg, ft3/lbm)
U - Total Internal Energy (kJ, Btu) u - Total Internal Energy (kJ/kg, Btu/lbm)
S - Total Entropy (kJ/K, Btu/oR) s - Total Entropy (kJ/kg.K, Btu/lbm. oR)
Q - Total Heat (kJ, Btu) q - Total Heat (kJ/kg, Btu/lbm)
A. Thermodynamics
That branch of science which deals with transformation of energy from one form to another, and the movement of energy
from one location to another.
B. Thermodynamic System
A that occupies a given , has a , and contains a
mass.
m
V
ILLUSTRATION: (Piston-cylinder arrangement)
TDC BDC
m
V
Q
C. Three Basic Types of Thermodynamic Systems
1. Open System or Steady Flow System
In this system, heat, work and mass (with its associated energy) all crosses the system boundary.
Win Wout
PE1 PE1
min TS mout
KE1 KE1
U1 U1
Wf1 Wf1
Qin Qout
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do nothing and succeed.”

2. ILLUSTRATION: (Steam Turbine)
PE1
KE1
U1
WT
Wf1 ST
1
(S=C)
2
PE2 KE2 U2 Wf2
2. Closed System or Non-Flow System
In this system, there is no mass flow, heat and work can cross the system boundary.
Win Wout
min = 0 TS mout = 0
Qin Qout
ILLUSTRATION: (Standard Vapor Compression Refrigeration System)
Qout
Condenser
mR mR
E.V.
mR
WC
Compressor
mR
Evaporator
Room
Qin
3. Isolated System
In this system nothing crosses the system boundary, (no heat, no work, no mass)
Win = 0 Wout = 0
min = 0 TS mout = 0
Qin = 0 Qout = 0
ILLUSTRATION: (Piston Cylinder Arrangement)
Matter
Anything that occupies space and has weight.
Isaac Newton’s Second Law of Motion
States that if an unbalanced force acts in a body:
1. The body will accelerate in the direction of the unbalanced force.
2. The acceleration will be proportional to the unbalanced force and inversely proportional to the mass of
the body.
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3. ILLUSTRATION:
goA goA
Where: Where:
FA mA FA mA
m A = mB m A > mB
and, and,
FA > FB FA = FB
goB goB
so, so,
goA > goB goA > goB
FB mB FB mB
thus, thus,
go F eq. 1 1
8
go eq. 2
8
m
Hence; combining eq. 1 and eq. 2
go F
8
m
Therefore;
F
go = gc
m
m go
F= Units: Eng’g units: lbf
gc kgm - m
SI units:
or N
Where: s2
F = force of gravity
m = mass of the substance, slugs or lbm, kgm
go = observed or local gravitational acceleration, ft , m
sec2 s2
gc = proportionality constant
gs = standard gravitational acceleration
Eng’g units SI units
32.2 lbm - ft kgm - m
gc = = 1
lbf - sec2 N - s2
ft m
gs = 32. 2 = 9.81 2
sec2 s
NOTE:
Use standard gravitational acceleration gs if the observed or local gravitational
acceleration go is not given.
1 kgf = 2.2 lbf = 9.81 N
FORMS OF ENERGY
Energies possessed by a body which has to be considered when analyzing a thermodynamic system.
Types or Forms of Energy
A. Stored Energy
Energies stored within the body which goes or dependent upon the flow of the mass.
1. Potential Energy (PE)
2. Kinetic Energy (KE)
3. Internal Energy (U)
4. Flow Work (Wf)
B. Transition Energy
Energies in transit (on the move) which are dependent upon the flow of the mass.
5. Heat (Q)
6. Mechanical Work (W)
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4. 1. Potential Energy (PE)
Stored energy due to its elevation above any arbitrary datum plane.
ILLUSTRATION:
m
2
F
z2 m
1
z1
F
Datum
DERIVATION:
2 2
dPE = F dz
1 1
PE = F ( z)
PE2 - PE1 = F (z2 - z1)
m go Units: Eng’g units: lbf - ft
PE = z)
gc ( SI units: N - m or J
Where:
m = mass of the substance
go = local or observed gravitational acceleration
gc = proportionality constant
z = change in elevation
NOTE:
Mechanical equivalent of heat energy
1 Btu = 779 lbf - ft
1 kcal = 428.1 kgf - m
2. Kinetic Energy (KE)
Stored energy of a body by virtue of its motion (velocity).
ILLUSTRATION:
1 2
dx
DERIVATION:
2 2
dKE = F dx
1 1
Where:
m go
F= gc
m
dv dx
= g
c dt dx
m
dv dx
=
gc dx dt
m
dv
= v
gc dx
So;
2
m
dv
KE = v
gc dx
1
m v2
v1+1
KE = g
c 1+1
m v1
v22 - v21
= gc 2
m
1 v2 Units: Eng’g units: lbf - ft
KE = gc
2 SI units: N - m or J
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5. 3. Internal Energy (U)
Stored energy due to its motion of molecules and forces of attraction between them.
ILLUSTRATION:
Change of
state
Q
Units: English Units: lbf - ft
U = (U2 - U1) = m Cv T
SI Units: J or
kJ
Where:
m = mass of the substance, units: lbm, kg
Cv = specific heat at constant volume, units: Btu , kJ
lbm - oR kg - K
T = change in Absolute temperature, units: oR, K
4. Flow Work (Wf)
Is the energy required to move the fluid across the boundary of the system.
ILLUSTRATION:
PE1
KE1
WSF
U1
n
Wf1
TS
PE1
KE1
U1
Wf1
Q
Units: English Units: lbf - ft
Wf = (P2V2 - P1V1) = PV
SI Units: J or
kJ
* Enthalpy (H)
combination energy or useful energy.
H = U + Wf
H = U + Wf
= mCv T + PV
= mCv T + mR T
= m (Cv + R)
But; R = Cp - Cv
Cp = Cv + R
Units: English Units: lbf - ft
H = mCp T
SI Units: J or
kJ
Where:
m = mass of the substance, units: lbm, kg
Btu , kJ
Cp = specific heat at constant pressure, units:
lbm - oR kg - K
T = change in Absolute temperature, units: oR, K
R = ideal gas constant Btu , kJ
lbm - oR kg - K
NOTE:
use Cp when dealing with enthalpy, H
use Cv when dealing with internal energy, U
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6. 5. Heat Energy, (Q)
Is the energy crossing a systems boundary because of a temperature difference between the system and surroundings.
ILLUSTRATION:
Change of
state
Q
Q = Tds General equation for Ideal gas or vapor process
Q=mC T
Where:
m = mass of the substance, units: lbm, kg
C = specific heat (depending upon the process involved
during the change of state),Btu
units: kJ ,
lbm - oR kg - K
o
T = change in Absolute temperature, units: R, K
6. Mechanical Work (W)
When force acts in the direction of motion.
s2
W= F ds
s1
Units: English Units: lbf - ft
W = (F)(s)
SI Units: J or
kJ
Where:
F = force acting on the object.
s = distance moved or the displacement of the object.
NOTE:
(+) W = work is done by the system (direction is going out of the system)
(-) W = work is done on the system (direction is going into the system)
(+) Q = heat is added on the system (direction is going into the system)
(-) Q = heat is rejected by the system (direction is going out of the system)
DIESEL ENGINE: EC
mair mexhaust
TDC
BDC
Flywheel
BP
Entropy, S
Property which measures the microscopic disorder or randomness of the molecules of a thermodynamic substance.
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