MET 211 introduction-to_thermdynamics_1-4_

Chapter 2

Part 1 of 4

Thermodynamics is the Science of

energy transfer and effect of this

transfer on the substance properties.

Dr.Khaled S. Al-zahrani


Examples:

Heat energy Mechanical energy

Petrol Engine

Mechanical energy Electrical energy

Generator

Electrical energy Mechanical energy

Electric motor

Chemical energy Electrical energy

Full cell

Electrical energy Cooling effect

Refrigerator

Heat energy Electrical energy

Electrical power generator

The working Substance

The working substance: Absorbs heat or rejects heat.

Does work or work is done on it.

Compressed or expanded

Heated or cooled

So that the desired energy transfer is achieved.

Examples:

O Steam in steam turbine

O Fuel in car engine

O Air in air compressor



Pure Substance: Homogeneous composition

Constant chemical structure over phase change

Examples:

Water

Gold

Copper

Pure Substance

Constant chemical structure

over phase change

Examples:

Water

Gold

Copper

Mixture

Combination of two or more

substances

Examples:

Brass

Coffee

Soil


System:


Type of Systems: Closed

Open

Isolated

Adiabatic


Closed System:

Non-Flow system, only ENERGY flow across the boundary.


Open System:

Flow system, only ENERGY & MASS flow across the boundary.


Isolated System:

Non-Flow or heat system, NO ENERGY or MASS flow across

the boundary.


Adiabatic System:

No HEAT transfer across the system boundaries.


Thermodynamic Properties

Properties is a measurable characteristics of a system

Examples:

Pressure

Volume

Temperature

Density

Enthalpy

Entropy

Specific heat

Any Thermodynamic System can be described with help of its properties


System State

• The thermodynamic system is described in terms of certain values of

some properties.

• Any Two independent properties can completely fix the state of the

system

Thermodynamic Process

• A process is defined as the succession of specified changes in

the state of the system

• If the value of one of the properties is kept constant the process

is known by the properties which is kept constant.


Examples of thermodynamics process

Isobaric process P = C

Isochoric process V = C

Isothermal process T = PV = C

Isentropic process S = C

P

V

P = C

V =

C

T = PV = C


Cyclic Process

If a system undergoes various processes in succession in

such way that at the end of the last process it returns to its

original state.


0th 1st 2ed 3ed


0th Zeroth Law

A B B C

A C

Thermal Equilibrium


Joules experiment


Conservation of energy

E Initial + E entering = E final + E leave

Forms of Energy:

1. Gravitational Energy PE= g×Z = 9.81×Z

2. Kinetic Energy KE = 𝑪𝟐

𝟐

3. Displacement Energy DE = Pv

4. Internal Energy U

5. Heat Energy H

6. Work Energy W


Displacement Energy

Work done = Force × Distance

Pressure× Area

= P × A × L

If v = A × L then

= P× v

Force = F

Distance = L

Pressure = P

Area = A

Specific volume = v


Heat Energy

• Received +ve

• Rejected -ve

Work Energy

• Done By the fluid +ve

• Done On the fluid -ve

Q

+ve

-ve

W +ve

-ve


Rudolf Clausius (1822 – 1888)


0th 1st

Closed System Open System

2ed 3ed


Closed System:

Forms of energies:

Internal Energy U motion of Atoms

Kinetic Energy KE Movement

Potential Energy PE Elevation

Total Initial Energy Ei E1= U1 + K𝑬𝟏 + PE1

Total Final Energy Ef E2= U2 + K𝑬𝟐 + PE2

Conservation of energy law

Ei + Ee = Ef + El

Q W

U1 + Q = U2+W

Q = (U2 –U1) + W

Q - W = (U) Non-Flow Energy Equation


Examples:

U = ?

Q = +2500 Kj

W= +1400 Kj

From the 1st Law:

U = Q – W

= 2500 -1400

= +1100 kJ

The total energy is increasing


Examples:

Q = ?

= -700 Kj


Examples:

Q = ?

= -700 Kj


Examples:

W = ?

= +250 Kj/Kg


Examples:

U = ?

= +45 Kj/Kg


Examples:

Q = ?

= -120Kj/Kg

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