introduction chapter Eme or thermodynamics

Prepare by:-Shivkumar PanjabiPrepare by:-Shivkumar Panjabi

Prime movers is a device which uses natural resources to convert their energy into mechanical energy or useful work.

Prepare by:-Shivkumar Panjabi 2


Fuel Flow of river water Atoms Renewable energy sources


1. mechanical energy2. Thermal (heat) energy3. electromagnetic energy4. electrical energy5. nuclear energy6. chemical energy


“the ability to do work” The combination of energy and matter

make up the universe: ◦ Matter is substance, and energy is the

mover of substance.



PotentialEnergy

KineticEnergy

All Energy

GravitationPotentialEnergy

ElasticPotentialEnergy

ChemicalPotentialEnergy

energy of position or energy in storage.

◦ Water behind a dam◦ Hammer over head◦ Food on the plate

energy of motion, the form capable of doing work ◦ Flowing water◦ A falling hammer◦ Electrons

regenerating ATP in a bio’l cell


Mass- the amount of matter an object has.

Matter- something that has mass and takes up space.

Weight- is the amount of mass of an object, it is dependent upon gravity.


Force is an action that can change motion.◦A force is what we call a push or a pull,

or any action that has the ability to change an object’s motion.

◦Forces can be used to increase the speed of an object, decrease the speed of an object, or change the direction in which an object is moving.


is equal to the force that is exerted times the distance over which it is exerted.

W = F x d The unit of work combines the unit of

force (N) with the unit of distance (m) Newton-meter (N-m) aka Joule.


measures the rate of work done. or the rate at which energy is

expended. Power is the amount of work done,

divided by the time it takes to do it. Power (watts) = work (joules) / time

(sec) P = W/t



The normal stress (or “pressure”) on the feet of a chubby person is much greater

than on the feet of a slim person.

Some basic pressure gages.

Pressure: A normal force exerted by a fluid per unit area

Absolute pressure: The actual pressure at a given position. It is measured relative to absolute vacuum (i.e., absolute zero pressure).

Gage pressure: The difference between the absolute pressure and the local atmospheric pressure. Most pressure-measuring devices are calibrated to read zero in the atmosphere, and so they indicate gage pressure.

Vacuum pressures: Pressures below atmospheric pressure.


Throughout this text, the pressure P will denote absolute pressure unless specified otherwise.

Temperature is a measure of hotness or coldness Ice point: A mixture of ice and water that is in equilibrium

with air saturated with vapor at 1 atm pressure (0°C or 32°F).

Steam point: A mixture of liquid water and water vapor (with no air) in equilibrium at 1 atm pressure (100°C or 212°F).

Triple point of water- A mixture of ice,liquid water and water vapor (with no air) in equilibrium(0.01°C)

Celsius scale: in SI unit system Fahrenheit scale: in English unit system Thermodynamic temperature scale: A temperature scale

that is independent of the properties of any substance. Kelvin scale (SI) Rankine scale (E)


A constant-volume gas thermometer would read -273.15°C at absolute zero pressure. Known as absolute zero temperature

Energy as Heat• Heat is the energy transferred between

objects that are at different temperatures

• Though energy has many different forms, all energy is measured in units called joules (J).


0Q


Signs for heat, Q and work, W

Sign convention for heat, Q :

Q = positivepositive value

Q = negativenegative value

Heat flow into the system

Heat flow out of the system

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Surroundings(environment)

System

0W

(a)


System

0W

(b)

0Q


Sign convention for work, W:

W = positive value

W = negative value

Work done by the system

Work done on the system


System

0W


System

0W

The two most commonly used are-1.Specific heat at constant volume (CV) It is the amount of heat required to raise the temperature of unit mass of a gas through 1°C, when volume is kept constant. t2.Specific heat at constant pressure (CP) It is the amount of heat required to raise the temperature of unit mass of a gas through 1°C, when the pressure of the gas is kept constant

However, CP > CV and CP / CV = γ. γ is called the ratio of specific heats.At constant volume, ΔQ = m CV θAt constant pressure, ΔQ = m CP θPrepare by:-Shivkumar Panjabi 19

Internal energy -The internal energy of a gas is the kinetic energy of thermal motion of its molecules.

Enthalpy is the sum of the internal energy of a system plus the product of the system’s volume multiplied by the pressure that the system exerts on its surroundings

Enthalpy: H = U + PV

Entropy definition:- A measure of disorder of the system.- ΔS is equal to the heat Q it absorbs, divided by T.

T

dQdS rev


input

outputefficiency


Brake power –brake power of engine is the power available at engine output shaft.

Indicated power –indicated power is a power developed inside engine cylinder by burning fuel.

Friction power – F.P.= I.P.-B.P.

Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.


1. Zeroth law of thermodynamics If two systems are at the same time in equilibrium with a third system, they are in equilibrium with each other.Practically, this means that all three systems are at the same temperature.

AB

C

Since A and B are at equilibrium and B and C are at equilibrium, A and C are also at equilibrium according to the zeroth law

Statement:- Energy can not be created or destroyed and

the total energy of a system is always constant.

Mathematical formula for a closed system:

Where; ∆U: change in internal energy Q: heat transferred to the system. W: work done by the system.


WUQ

This is sometimes called the "first form" of the second law, and is referred to as the Kelvin-Planck statement of the second law.

It is impossible to extract an amount of heat QH from a hot reservoir and use it all to do work W . Some amount of heat QC must be exhausted to a cold reservoir.


3. Second law of thermodynamics:Clausius statement-it is impossible to have a device that operating in a cycle produce no effect other than transfer heat from a body at lower temperature to a body at higher temperature.I.Second law in terms of heat flow: Heat flows spontaneously from hotter to colder objects but not vice versa.II.Second law in terms of heat engines: It is impossible to construct an engine which has 100% efficiency or a system in which the heat added to the system is solely used to perform work.

a. Open; mass & heat can transferb. Closed; no mass transfer

c. Isolated; no mass or heat transfer


System: A quantity of matter or a region in space chosen for study. Surroundings: The mass or region outside the systemBoundary: The real or imaginary surface that separates the system from its surroundingsUniverse = System + Boundary


Example: Piston and cylinder - a closed system

m

Gas at pressure, p

Piston


Example: The gas turbine engine - an open system

Shaft Work Output

Combustor

Fuel Flow In

Air Flow In

Exhaust Gases Out

Compressor Work Out


Property: Any characteristic of a system.

Some familiar properties are pressure P, temperature T, volume V, and mass m.

Properties are considered to be either intensive or extensive.

Intensive properties: Those that are independent of the mass of a system, such as temperature, pressure, and density.

Extensive properties: Those whose values depend on the size—or extent—of the system.

Specific properties: Extensive properties per unit mass.


Criterion to differentiate intensive and extensive properties.

Thank you for your attention

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introduction chapter Eme or thermodynamics