1. Chapter 2 Thermodynamics:
System is defined as a quantity of matter or a region in space chosen for study. The mass or region outside the system is called the surroundings. Separated by Boundary. Systems may be considered to be closed or open. A closed system (also known as a control mass) consists of a fixed amount of mass, and no mass can cross its boundary but with energy exchange. special case, even energy is not allowed to cross the boundary, that system is called an isolated system. Open system, or a control volume Both mass and energy can cross the boundary of a control volume. that involves mass flow such as a compressor, turbine, or nozzle.

2. Any characteristic of a system is called a property
Any characteristic of a system is called a property. Some familiar properties are pressure P, temperature T, volume V, and mass m. density is defined as mass per unit volume. specific gravity, or relative density, and is defined as the ratio of the density of a substance to the density of some standard substance at a specified temperature (usually water at 4 C = 1000kg/m3). SG= density/ density water. Specific volume defined as the volume per unit mass: ν=V/m = 1/ ρ

3. Properties: Intensive properties are those that are independent of the size of a system, such as temperature, pressure, and density. Extensive properties are those whose values depend on the size—or extent—of the system such as : Mass m, volume V, and total energy E Divide the system into two equal parts with a partition, Each part will have the same value of intensive properties as the original system, but half the value of the extensive properties. specific properties. Some examples of specific properties are specific volume (v=V/m) and specific total energy (e=E/m).

4. Set of properties that completely describes the condition, or the state, of the system. Thermodynamics deals with equilibrium states. Equilibrium implies a state of balance. Thermal Equilibrium (temperature is the same through the system, Mechanical Equilibrium (no change in pressure throughout the system with time). phase equilibrium when the mass of each phase reaches an equilibrium level and stays there. chemical equilibrium if its chemical composition does not change with time.

5. - The state of a simple compressible system is completely specified by two independent, intensive properties.
- A system undergoes from one equilibrium state to another is called a process, and the series of states through which a system passes during a process is called the path of the process. Different types of Processes: The prefix iso- is often used to designate a process for which a particular property remains constant. An isothermal process, for example, is a process during which the temperature T remains constant; an isobaric process is a process during which the pressure P remains constant; and an isochoric (or isometric) process is a process during which the specific volume v remains constant.

6. The term steady implies no change with time
The term steady implies no change with time. The opposite of steady is unsteady, or transient.The term uniform, however, implies no change with location over a specified region.
the steady-flow process: a process during which a fluid flows through a control volume steadily. That is, the fluid properties can change from point to point within the control volume, but at any fixed point they remain the same during the entire process.

7. Pressure
final
path
initial
Volume

8. Forms of Energy: the total energy of a system in two groups: The macroscopic forms of energy are those a system possesses as a whole with respect to some outside reference frame, such as kinetic and potential energies . The microscopic forms of energy are those related to the molecular structure of a system and the degree of the molecular activity. The sum of all the microscopic forms of energy is called the internal energy of a system and is denoted by U.

9. The energy that a system possesses as a result of its motion relative to some reference called kinetic energy KE = ½ m v2 (kJ), The energy that a system possesses as a result of its elevation in a gravitational field is called potential energy PE = mgz
the total energy of a system consists of the kinetic, potential, and internal energies: E = U + KE + PE . Most closed systems remain stationary = stationary systems (no change in their kinetic and potential energies). ∆ E=∆U

10. Types of associated energies with U : 1) portion of the internal energy of a system associated with the kinetic energies of the molecules is called the sensible energy. 2) The internal energy associated with the phase of a system is called the latent energy (without a change in the chemical composition), 3) The internal energy associated with the atomic bonds in a molecule is called chemical energy, 4) of energy associated with the strong bonds within the nucleus of the atom itself is called nuclear energy.
The only two forms of energy interactions associated with a closed system are heat transfer (Q) and work (W). An energy interaction is heat transfer if its driving force is a temperature difference. Otherwise it is work. (Discussed later).

11. - Energy-Environment: The largest source of air pollution is the motor vehicles, and the pollutants released by the vehicles are usually grouped as hydrocarbons (HC), nitrogen oxides (NOx), and carbon monoxide (CO). Ozone and Smog (made up mostly of ground-level ozone (O3) + numerous other chemicals. Acid Rain and Green house Effect.

12. - Temperature & Zero law of Thermodynamics: when a body is contact with another body that is at a different temperature, heat is transferred from the body at higher temperature to the one at lower temperature until both bodies attain the same temperature (Thermal Equilibrium). The zeroth law can be restated as two bodies are in thermal equilibrium if both have the same temperature reading even if they are not in contact.

13. The temperature scales used in the SI and in the English system are the Celsius scale (C) and the Fahrenheit scale (F). The thermodynamic temperature scale in the SI is the Kelvin scale (K), whereas the thermodynamic temperature scale in the English system is the Rankine Scale (R).
∆T(K) = ∆T( C)
∆T(R) = ∆T( F)

14. To obtain absolute temperatures: T(K) = T( C) + 273.15
Kelvin scale is the ideal-gas temperature scale. The temperatures on this scale are measured using a constant-volume gas thermometer
To obtain absolute temperatures:
T(K) = T( C)
T(R) = T( F)
To convert between different scales:
T(R) = 1.8 T(K)
T( F) = 1.8 T( C) + 32
1 C
1 K
1.8 R
1.8 F

15. P
Experimental data
Gas (A)
Gas (B)
extrapolation
Gas (C)
Gas (D)
T ( C )

16. Pressure is defined as the force exerted by a fluid per unit area
newtons per square meter (N/m2), called a pascal (Pa).
1 Pa = 1 N/m2
1 bar = 100 kPa
1 atm = kPa bars
In the English system, the pressure unit is pound-force per square inch (lbf/in2, or psi), and 1 atm = psi
The actual pressure at a given position is called the absolute pressure, and it is measured relative to absolute vacuum (i.e., absolute zero pressure).

17. Pgage = Pabs - Patm (for pressures above Patm)
Pvac = Patm Pabs (for pressures below Patm)
P gage
P atm
P vac
P atm
P abs
P atm
P abs
P abs = 0
Absolute vacuum

18. The pressure P will denote absolute pressure unless specified
otherwise. Often the letters “a” (for absolute pressure) and “g”
(for gage pressure) are added to pressure units (such as psia and
psig)
Example: A vacuum gage connected to a chamber reads 5.8 psi at a location where the atmospheric pressure is 14.5 psi. Determine the absolute pressure in the chamber.
Solution: Pabs = Patm - Pvac = = 8.7 psi

19. Pressure in Depth : pressure in a fluid does not change in the horizontal direction. Pressure in a fluid increases with depth because more fluid rests on deeper layers, and the effect
of this “extra weight” on a deeper layer is balanced by an increase in pressure
∆P = P1 – P2 = ρgh = Pgage (h = pressure head)
Manometers:
P1 = P2 (horizontally) , But P2 = Patm + ρgh Figure (1)
Example: A manometer is used to measure the pressure in a tank. The fluid used has a specific gravity of 0.85, and the manometer column height is 55 cm. If the local atmospheric pressure is 96 kPa, determine the absolute pressure within the tank.

20. SG = Density substance / water density
Patm = 96kPa
P = ??
h = 55 cm
SG = 0.85
SG = Density substance / water density
Density of substance = 0.85 (1000kg/m3) =
850 kg/m3
P = Patm + ρgh = 96 kPa kg/m3 * 9.81 m2/s * 0.55m (1 kPa/1000N/m2) * ( 1 N / 1kg. m/s2) = kPa

21. Patm + ρ1gh1 + ρ2gh2 + ρ3gh3 = P1 P1+ ρ1g(a + h) - ρ2gh - ρ2ga = P2 2
Fluid 1 h2
Fluid 2
Fluid 3 h3 1
Fluid
P1+ ρ1g(a + h) - ρ2gh - ρ2ga = P2 1 2 a ρ1 h ρ2

22. P1 + ρwater gh1 + ρoil gh2 - ρmercury gh3 = Patm
Exp.1
P1 + ρwater gh1 + ρoil gh2 - ρmercury gh3 = Patm
Solving for P1 and substituting,
85.6 kPa + (9.81 m/s2)
[(13,600 kg/m3) (0.35 m) -(1000 kg/m3) (0.1 m) –
(850 kg/m3) (0.2 m)]
[(1 N/1 kg · m/s2)( 1 kPa/1000 N/m2)]
= kPa
Exp.2
P = Patm + W/A
= 0.97 bar + (60) (0.981)/(0.04)
[(1 N/1 kg · m/s2)(1bar//105 N.m2)]
= 1.12 bar
Oil 1 2 h1
Water h3 h2
Mercury
Patm = 0.97 bar
m = 60 kg
Patm
A = 0.04 m2
W = mg

23. BAROMETER AND THE ATMOSPHERIC PRESSURE
The atmospheric pressure (barometric pressure) is measured by a device called a barometer. As Torricelli measured the atmospheric pressure by inverting a mercury-filled tube into a mercury container that is open to the atmosphere. Note that the length and the cross-sectional area of the tube have no effect on the height of the fluid column of a barometer
Patm = ρgh

24. standard atmosphere, which is defined as the pressure produced by a column of mercury 760 mm in height at 0 C
(ρ= 13,595 kg/m3) and (g = m/s2) mmHg ...
1 mmHg = 1 torr = Pa
1 atm = 760 mm Hg = 760 mm torr
If water instead of mercury were used to measure the standard atmospheric pressure,
a water column of about 10.3 m..!!!
As we go up atm pressure drops..!!

25. Other Pressure Measurement Devices:
Mechanical instrument - Bourdon tube: consists of a hollow metal tube bent like a hook whose end is closed and connected to a dial indicator needle. When the tube is open to the atmosphere, the tube is undeflected, and the needle on the dial at this state is calibrated to read zero (gage pressure). When the fluid inside the tube is pressurized, the tube stretches and moves the needle in proportion to the pressure applied.
Electronic instrument - pressure transducers, made of semiconductor materials such as silicon and convert the pressure effect to an electrical effect such as a change in voltage, resistance, or capacitance. A) smaller and faster, B) more sensitive, reliable, and precise than their mechanical counterparts

26. Different types of pressure transducers: Gage pressure transducers (use the atmospheric pressure as a reference give a zero signal output at atmospheric, absolute pressure transducers are calibrated to have a zero signal output at full vacuum. Differential pressure transducers measure the pressure difference between two locations directly instead of using two pressure transducers and taking their difference. strain-gage pressure transducers The emergence of an electric potential in a crystalline substance when subjected to mechanical pressure is called the piezoelectric effect.