Module 1
thermodynamics
Thermodynamics → Thermo + dynamics ( Heat + motion)
SYSTEM : is defined as a quantity of matter or region in space chosen for study.
SURROUNDINGS: is the mass or region outside the system.
BOUNDARY: is the real or imaginary surface that separates the system from its
surroundings
 mathematically has no thickness, thus it can neither contain any mass nor occupy any
volume in space.
 The BOUNDARY can be FIXED or MOVABLE.
Two basic kinds of systems are:
• CLOSED SYSTEMS (Control mass )
• OPEN SYSTEM (Control Volume)
CLOSED SYSTEM (CONTROL MASS):
consists of fixed amount of mass and no
mass can cross its boundary.
 Energy ( heat or work) can cross the boundary
 the volume of a closed system does not have to be fixed
ISOLATED SYSTEM : is a special case for a closed system where even the energy is not
allowed to cross the boundary ( e.g. closed adiabatic system)
OPEN SYSTEMS or CONTROL VOLUME is a properly selected region in space,
which usually encloses a device that involves mass flow such as a compressor, turbine or nozzle.

Both mass and energy can cross the boundary of a control volume
CONTROL SURFACE: is the boundaries of control volume, and they can be real or
imaginary.
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Module 1
thermodynamics
PROPERTIES OF A SYSTEM:
1- Intensive properties
 are those that are independent of the mass of a system, such as temperature,
pressure, and density.
2- Extensive properties
 are those whose values depend on the size—or extent—of the system. Total
mass, total volume, and total momentum
3- Specific properties
 are Extensive properties per unit mass Some examples of specific properties are
specific volume
Density: is defined as mass per unit volume
𝜌=
𝑚
𝑣
𝑘𝑔
( ⁄ 3)
𝑚
specific volume (ν) which is defined as volume per unit mass
𝑣 1
𝑣= =
𝑚 𝜌
specific gravity, or relative density is defined as the ratio of the density of a
substance to the density of some standard substance at a specified temperature.
 ρ (water) = 1000 (kg/m3).
𝑆𝐺 =
specific weight
𝜌
𝜌𝑤𝑎𝑡𝑒𝑟
is the weight of a unit volume of a substance
𝛾𝑠 = 𝜌𝑔 (𝑁⁄ 3
𝑚 )
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Module 1
thermodynamics
Describing a SYSTEM
 PROPERTIES of a fluid determine a STATE.
 When TWO (or more) INTENSIVE independent properties are
known, the exact state of the substance is known.
 When a property changes, a change of STATE occurs.
 Thus, a state of a substance can be defined by its PRESSURE and
TEMPERATURE.
Process:
is Any change that a system undergoes from one equilibrium state to another
Cycle: is A system is said to have undergone a cycle if it returns to its initial state at the end of
the process.
Thermal equilibrium The zeroth law
of thermodynamics : states that if two
bodies are in thermal equilibrium with a third body,
they are also in thermal equilibrium with each other.
𝑇𝑅 = 𝑇𝐹 + 460°
𝑇𝐾 = 𝑇𝐶 + 273°
9
℉ = ( × ℃) + 32°
5
5
℃ = (℉ − 32° )
9
Example :
Convert 0F into degrees Celsius (C).
5
℃ = (℉ − 32° )
9
C   0F  3 2 9 5
C    3 2 9 5 C
C = -17.78 
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Module 1
thermodynamics
Pressure is defined as a normal force exerted by a fluid per unit area.
Pascal (Pa) it has the unit of Newtons per square meter (N/m2)
𝑃𝐺𝑎𝑢𝑔𝑒 = 𝜌𝑔ℎ
The basic manometer.
The pressure in a fluid does not vary in the horizontal direction
within a fluid, the pressure at point 2 is the same as the
pressure at point 1.
𝑃𝐺𝑎𝑠 = 𝑃𝑎𝑡𝑚 + 𝜌𝑔ℎ
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Module 1
thermodynamics
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