Download What does thermodynamic mean?

College of Engineering
Spring Session- 2016
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
CHAPTER1: Basic Definitions, Zeroth, First, and Second Laws of Thermodynamics
1.1.
Definitions
What does thermodynamic mean?
It is a Greeks word which means a motion of the heat.
Water is a liquid substance……
Liquid is a fluid substance which is structured in a little close atoms and molecules.
Air is a gas substance……
Gas is a fluid substance which is structured in a less close atoms and molecules.
What does Newtonian fluid mean?
Newtonian fluids is the fluids in which shear stress is directly proportional to deformation rate,
such as water, oil, air, etc.
What does Non-Newtonian fluid mean?
Non-Newtonian fluids is the fluids in which shear stress is not directly proportional to
ketchup, etc.
deformation rate, such as toothpaste,
̇ du
γ = dy [s −1 ] = Shear rate
Fig.1.1 Shear stress vs shear rate
What does the viscosity mean, classify the type of the viscosity?
The viscosity is a material properties which resists any external force.
The viscosity can be distinguished into two types:
1. Kinematic viscosity is a substance property.
2. Dynamic viscosity is the ability of a matter to resist a body’s motion.
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College of Engineering
Spring Session- 2016
1.2.
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
Theories (Basic Concepts)
Before discussing the behavior of the fluid, the basic concepts is to understand employing
Newton’s laws in case of the fluid flow.
1.2.1. Newton’s First Law:
W = mg
Where m is a the mass of a substance, g is thegravitational acceleration
(g = 9.81
m
ft
or
32.2
)
s2
s2
1.2.2. Newton’s Second Law
A body moves in a uniform velocity unless is exerted by an external force.
⃗ = ma⃗
F
Where, m is the mass of a body and 𝑎 is the acceleration
a⃗ =
dv
dx
, the velcoity is v = .
dt
dt
1.2.3. Normal and shear stress:
The normal stress is the normal force acts perpendicular on a body’s surface area.
σ=
F⊥
A
The shear stress is the tangential force acts on a body’s surface area.
τ=
F⫽
A
1.2.4. First Law of thermodynamics (Conservation of Energy)
The conservation of energy is also called first law of thermodynamics says” The energy can’t be
created or destroyed, but it can change from form to anther forms of energy”
Closed System: the amount of mass in a system is fixed but the volume changes.
∑ Qk − ∑ Wk = ∆E, ΔE = ΔU + ΔPE + ΔKE
k
k
Open system: the amount of the mass flowrate in a system changes but the volume is fixed, i.e.
mass flowrate crosses a system boundary.
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College of Engineering
Spring Session- 2016
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
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1
∑ Qi + ∑ Wi + Hi + ṁVi2 + ṁgZi = ∑ Qe + ∑ We + He + 𝑚̇𝑉𝑒2 + ṁgZe
2
2
i
i
e
e
Conservation of Mass
Conservation of mass states that for any system closed to all transfers of matter and energy (both
of which have mass), the mass of the system must remain constant over time, as system mass
cannot change quantity if it is not added or removed.
∂ṁ
= ∑ ṁ e − ∑ ṁ i
∂t
e
i
1.3.
Thermodynamics Properties, Fluid Mechanics and Heat Quantities
Concepts:
Specific volume is the total volume per unit mass (unit volume/unit mass).
𝑣=
V
m
Density is the amount of matter in a body per unit volume (unit mass/unit volume).
ρ=
m
V
Specific gravity is the ratio of a substance density to the water density at 4ᵒC.
SG =
ρ
ρ@4°C
Sensible heat is the amount of heat required to change the temperature of a substance.
Latent heat is the amount of heat required to change the phase.
Sublimation is the change from solid to gas without passing through the liquid phase.
Pressure is the force exerted on a surface area (force per unit area).
Surface tension is the apparent interfacial tensile stress that acts whenever a liquid has a density
interface.
λ=
Force
A unit length
Entropy is a thermodynamics property which is used to measure of a disorder molecules.
S=∫
Qrev
T
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College of Engineering
Spring Session- 2016
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
Enthalpy is a thermodynamics property which contains the internal energy of a substance plus
the pressure energy.
H = U + PV
Heat flux is the total rate of heat per unit area.
q" =
Q
A
Incompressible fluid is flows in which variations are negligible, such as water, oil, etc.
Compressible fluid is flows in which variations are not negligible, such as gases.
Units and dimensions
Table 1.1 Primary SI Units
Table 1.2 Some derived units
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College of Engineering
Spring Session- 2016
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
Table 1.3 Some conversion factors in SI units
Define
1. 0th law of thermodynamics?
Ans.” If the two bodies are in the thermal equilibrium with a third body, they are also in
thermal equilibrium with each other. “
2. 1st law of thermodynamics?
Ans. “The energy cannot created and destroyed but it changes from form to another”
3. 2nd law of thermodynamics?
Ans. “ The energy has quality as well as a quantity, and actual processes occur in the
direction of decreasing quality of energy. “
4. A system in thermodynamics?
Ans.”
5. Open system and closed system?
Ans.”
6. Isothermal and adiabatic process?
Ans.”
7. Isobaric and Isochoric process?
Ans.”
8. Isentropic process?
Ans.”
9. Process and State?
Ans.”
10. Specific quantity?
Ans.”
11. Cycle and critical point?
Ans.”
12. A pure substance?
Ans.”
13. Saturated liquid and saturated vapor?
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College of Engineering
Spring Session- 2016
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
Ans.”
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14. Compressed liquid?
Ans.”
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15. Superheated?
16. Latent and sensible heat?
Ans. “Latent heat is the amount of heat required to change the phase of a pure substance,
and the sensible heat is the amount of heat required change the temperature of a pure
substance.”
17. Sublimation
Ans. “A Phase which passes from the solid phase directly into the vapor phase.”
18. Nuclear, chemical, and thermal energy?
Ans.”
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What is a turbine? What is a pump? What is a compressor?
Ans.”
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Which the following system is closed system or open system?
System
Vessel
Tank
Piston Cylinder
Compressor
Turbine
Pump
Radiator
Condenser
Boiler
Open
Closed
Explain?
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College of Engineering
Spring Session- 2016
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
Evaporator
Expansion V/V
Deaerator
Heat Exchanger
Heater
Define
1. Force, Pressure, Energy, and Power?
Ans. “
2. Torque, Kinetic Energy, Potential Energy, and Mechanical Energy?
Ans. “
3. Enthalpy, Entropy, and Energy?
Ans.”
4. Internal Energy, Total Energy?
Ans. “
P
P
T
T
ρ
ρ
½m
½m
½V
½ V
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Fig.1.2. Intensive and Extensive Quantities
5. Manometer and Parameter?
Ans. “
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6. Work and specific heat?
Ans. “
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7. Properties, Extensive properties and Intensive properties?
Ans. “
“Intensive properties are those that are independent of the size of a system, and Extensive
properties are those whose values depend on the size or extend of the system. “
8. Molar mass, mole and molecular weight?
Ans. “
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9. Thermal equilibrium, mechanical equilibrium, Phase equilibrium, and chemical
equilibrium?
Ans. “
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10. A pure substance, Specific properties, density, and mass?
Ans.” A pure substance is a substance that has a fixed chemical composition,
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College of Engineering
Spring Session- 2016
THERMODYNAMICS II - ME 272
Dr. Saeed J. Almalowi, [email protected]
,
11. Path, Process, and Quasi-static (equilibrium) process?
Ans.”
Table1.1. Units Conversion Table (UCT)
Pressure
1kPa = 100bar
1atm=10.325 kPa
1MPa=1000 kPa
1atm = 14.696 psia
Work and Energy
1Btu (British thermal unit) = 1.055 kJ
1lbf = 32.174 Ibm. ft/s2
1hp =2545 Btu/hr
Temperature
T(K)=T(C)+273
T(R) = T(F)+460
T(R) =1.8T(K)
T(F)= 1.8 T(C)+32
Length and Volume
1 m =100cm
1km =1000m
1cm=10 mm
1ft =12 in
1m3=1000 Liter ‘L’
1cm3=0.001 L
1ft3=28.32 L
1 in3=0.0164 L
Time
1 hr (hour) = 3600 sec (second)
1 hr = 60 min (minute)
1s = 1000 ms (millisecond)
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