Macroscopic (or classical thermodynamics):

In this approach, a certain quantity of matter is considered, without taking into

account the events occurring at the molecular level.

This macroscopic approach to the study of thermodynamics that does not require

knowledge of the behaviour of individual particles.

Macroscopic thermodynamics is only concerned with the effects of the action of many

molecules, and these effects can be perceived by human senses.

The macroscopic observations are completely independent of the assumptions

regarding the nature of matter.

Example: A moving car, a falling stone from a cliff, etc.

Microscopic (or statistical thermodynamics):

From the microscopic viewpoint, matter is composed of a large number of small

molecules and atoms.

This microscopic approach to the study of thermodynamics that require knowledge of

the behaviour of individual particles.

Microscopic thermodynamics is concerned with the effects of the action of many

molecules, and these effects cannot be perceived by human senses.

The microscopic observations are completely dependent on the assumptions regarding

the nature of matter.

Example: Individual molecules present in air, etc.

o Intensive - Properties that do not depend on the amount of the matter present.

Luster - How shiny a substance is.

Melting/Freezing Point - The temperature at which the solid and liquid

phases of a substance are in equilibrium at atmospheric pressure.

Boiling Point - The temperature at which the vapor pressure of a liquid

is equal to the pressure on the liquid (generally atmospheric pressure).

Density - The mass of a substance divided by its volume

o Extensive - Properties that do depend on the amount of matter present.

Mass - A measurement of the amount of matter in a object (grams).

Weight - A measurement of the gravitational force of attraction of the

earth acting on an object.

Volume - A measurement of the amount of space a substance occupies.

CONDUCTION

If heat is applied directly to one part of a solid object, the electrons become excited.

This causes molecular collisions which travel along the object, heating as it passes

through. This transfer of heat within a solid is known as conduction.

CONVECTION

Conduction between objects, where one is a gas or liquid, is called convection. As

gasses or liquids are heated, the excited molecules achieve a fluid motion.

RADIATION

The transmission of energy across space is called radiation. Radiation does not depend on the

presence of matter and can occur across a vacuum.

Energy means: the all energy (losses + gained)

Exergy means the maximum energy u can gain.

Energy is the capacity that can be converted by the system

to be work

Exergy is the useful energy that can be derived or used by

the system

Enthalpy describes the energy it takes for a substance to change from one phase to another

(i.e. solid to liquid.) Entropy deals with the actual disorder of particles and substances (i.e.

more disorder of the particles as a solid substance is heated to a liquid.)

Entropy is define as the degree of disorderliness of a molecule/substance while Enthalpy is

the energy it take a substance to change from one state to another.

Question: What is Dalton's Law of Partial Pressures?

Dalton's law of partial pressures is used to determine the individual pressures of each gas in a

mixture of gases.

Answer: Dalton's law of partial pressures states:

The total pressure of a mixture of gases is equal to the sum of the partial pressures of the

component gases.

PressureTotal = PressureGas 1 + PressureGas 2 + PressureGas 3 + ... PressureGas n

An alternative of this equation can be used to determine the partial pressure of an individual

gas in the mixture.

If the total pressure is known and the number of moles of each component gas are known, the

partial pressure can be computed using the formula:

Px = PTotal ( nx / nTotal )

where

Px = partial pressure of gas x PTotal = total pressure of all gases nx = number of moles of gas x

nTotal = number of moles of all gases This relationship applies to ideal gases, but can be used

in real gases with very little error.

There are four processes in the Rankine cycle. These states are identified by numbers (in

brown) in the above Ts diagram.

Process 1-2: The working fluid is pumped from low to high pressure. As the fluid is a

liquid at this stage, the pump requires little input energy.

Process 2-3: The high pressure liquid enters a boiler where it is heated at constant

pressure by an external heat source to become a dry saturated vapour. The input

energy required can be easily calculated using mollier diagram or h-s chart or

enthalpy-entropy chart also known as steam tables.

Process 3-4: The dry saturated vapour expands through a turbine, generating power.

This decreases the temperature and pressure of the vapour, and some condensation

may occur. The output in this process can be easily calculated using the Enthalpy-

entropy chart or the steam tables.

Process 4-1: The wet vapour then enters a condenser where it is condensed at a

constant pressure to become a saturated liquid.

Steam power plant is a thermal power plant consists of main components and auxiliary

components as well as other systems. The main component consists of four components,

namely:

- Boiler

- Steam Turbine

- Condenser

- Generator

Boiler

Boiler has the function to convert water into steam. The process of change of water to vapor

done by heating the water in the pipes with heat from burning fuel. Combustion processes

carried out continuously in the combustion chamber with fuel and air flow from the outside.

The resulting steam is superheat steam which have high temperature and high pressure.

Steam production quantities dependent on the surface area of heat transfer, flow rate, and the

heat of combustion is given. Boiler construction consisting of water-filled pipes called a

water tube boiler

Steam Turbine

Steam turbine working to change the heat energy contained in the steam into rotary motion.

Steam with high pressure and temperature were directed to push turbine blades mounted on

the shaft, so the shaft rotates. Due to perform work on the turbine, the pressure and

temperature of steam coming into the turbine down to saturated vapor. This steam then flows

to the condenser, while the rotary power is used to turn a generator. Today almost all of the

steam turbine is a type of condensing turbine

Condenser

Condensers are devices to convert steam into water. The changes done by the steam flow into

a room containing tubes. Steam flows outside tubes, while the cooling water flowing inside

the tubes.

This is called surface condenser condenser. Usually for coolant use sea water.

Heat transfer rate depends on the flow of cooling water, sanitation tubes and the temperature

difference between the steam and cooling water. The process of change into water vapor

occurs at saturated pressure and temperature, in this case the condenser is under vacuum.

because the cooling water temperature equal to the outside temperature, the maximum

temperature condensate water near the outside air temperature. if the rate of heat transfer

interrupted it will affect the pressure and temperature.

Generator

The main purpose of the activities at a plant is electricity. Electrical energy generated from

the generator. Function generator converts mechanical energy into electrical energy in the

form of a round with the principle of magnetic induction.

Generator consists of stator and rotor. stator consists of the casing which contains coils and a

rotor magnetic field station consists of a core containing a coil

The zeroth law of thermodynamics states that if two thermodynamic systems are each in

thermal equilibrium with a third, then all three are in thermal equilibrium with each other.

There are two classical statements of the second law of thermodynamics:

Kelvin & Planck

"No (heat) engine whose working fluid undergoes a cycle can absorb heat from a single

reservoir, deliver an equivalent amount of work, and deliver no other effect"

Clausius

"No machine whose working fluid undergoes a cycle can absorb heat from one system, reject

heat to another system and produce no other effect"

Both statements of the second law place constraints on the first law by identifying that energy

goes downhill.

What is the difference between Compressible Fluids and Incompressible Fluids?

• Compressible fluids are found in reality. In fact, all of the fluids found in nature are

compressible. Incompressible fluids are a concept developed for ease of calculations.

• Compressible fluids reduce in volume when an external pressure is applied, but

incompressible fluids do not change the volume.

• The fluid dynamic calculations for the incompressible fluids are very easy compared to the

calculations involving compressible fluids.

The dual cycle consists of following operations:

1. 1-2 Adiabatic compression

2. 2-3 Addition of heat at constant volume.

3. 3-4 Addition of heat at constant pressure.

4. 4-5 Adiabatic expansion.

5. 5-1 Rejection of heat at constant volume.

Rankine Cycle

1-2-3 Isobaric Heat Transfer. High pressure liquid enters the boiler from the feed

pump (1) and is heated to the saturation temperature (2). Further addition of energy

causes evaporation of the liquid until it is fully converted to saturated steam (3).

3-4 Isentropic Expansion. The vapor is expanded in the turbine, thus producing work

which may be converted to electricity. In practice, the expansion is limited by the

temperature of the cooling medium and by the erosion of the turbine blades by liquid

entrainment in the vapor stream as the process moves further into the two-phase

region. Exit vapor qualities should be greater than 90%.

4-5 Isobaric Heat Rejection. The vapor-liquid mixture leaving the turbine (4) is

condensed at low pressure, usually in a surface condenser using cooling water. In well

designed and maintained condensers, the pressure of the vapor is well below

atmospheric pressure, approaching the saturation pressure of the operating fluid at the

cooling water temperature.

5-1 Isentropic Compression. The pressure of the condensate is raised in the feed

pump. Because of the low specific volume of liquids, the pump work is relatively

small and often neglected in thermodynamic calculations.

Thermal conductivity (λ) is the intrinsic property of a material which relates its ability to conduct

heat. Heat transfer by conduction involves transfer of energy within a material without any motion

of the material as a whole.