INTRODUCTION

Thermodynamics lecture notes

Prepared by B.Sreenivas

INTRODUCTION

1. What is thermodynamics?

2. How the laws of TD were formulated?

3. Where we found the applications of Thermodynamic laws and principles?

4. How does the subject of thermodynamics differ from the concept of heat transfer?

5. Is thermodynamics a misnomer for the subject?

6. What do you understand by microscopic and macroscopic approaches in thermodynamics?

7. What is thermodynamic system? Explain the types

8. What is meant by boundary, universe and surroundings?

9. What is the difference between a closed system and open system?

10. An open system defined for a fixed region and a control volume are synonymous. Explain.

11. Define an Isolated system.

12. Define the terms

a. Thermodynamic properties

b. State

c. Change of state

d. Path

e. Process

f. Cycle

13. What are intensive and extensive properties? Give four examples for each.

14. What do you mean by homogeneous and heterogeneous systems?

15. Explain what you understand by thermodynamic equilibrium.

16. Explain mechanical, chemical and thermal equilibrium

17. What is a quasi-static process/ what is its characteristic feature?

18. What is the concept of continuum? How will you define density and pressure using this concept?

19. Explain the role of concept of continuum in microscopic and macroscopic approaches.

20. Define Force, Energy, Power, Specific volume and density?

21. Define the following:

a. Barometric or atmospheric pressure

b. Gauge pressure

c. Absolute pressure

d. Vacuum

22. What are different pressure gauges, transducer

23. Units and dimensions

24. Problems: Refer to problem sheet # 1.1

PROBLEM SHEET # 1.1

1. Convert the following readings of pressure to kPa, assuming that the barometer reads 760mm of Hg:

(a) 90 cm Hg gauge(b) 40 cm Hg Vacuum (c) 1.2 m H2O gauge (d) 3.1 bar

2. A 30 m high vertical column of a fluid of density 1878 kg/m3 exists in a place where g = 9.65 m/s2. What is the pressure at the base of the column?

Ans: 544 kPa

3. Assume that the pressure p and the specific volume v of the atmosphere are related according to the equation pv1.4 = 2.3 x 103, where p is in N/m2 abs and v is in m3/kg. The acceleration due to gravity is constant at 9.81 m/s2. What is the depth of atmosphere necessary to produce a pressure of 1.0132 bar at the earths surface? Consider the atmosphere as a fluid column.

Ans: 64.8 km

4. The pressure of steam flowing in a pipe line is measured with a mercury manometer, shown in figure 1. Some steam condenses into water. Estimate the steam pressure in kPa. Take the density of mercury as 13.6x 103kg/m3, density of water as 103kg/m3, the barometer reading as 76.1 cm Hg, and g as 9.806 m/s2.

5. A vacuum gauge mounted on a condenser reads 0.66 m Hg. What is the absolute pressure in the condenser in kPa when the atmospheric pressure is 101.3 kPa?

Ans: 8.8 kPa

6. The basic barometer can be used to measure the height of a building. If the barometric readings at the top and at the bottom of a building are 730 and 760 mm Hg respectively. Determine the height of the building. Assume an average air density of 1.18 kg/m3.

7. The forced draught fan supplies air to furnace of the boiler at draught of 30 mm of water. Calculate the absolute pressure of air supply if the barometer reads 760 mm Hg in kgf/cm2, bar and kPa.

Figure 1

INTRODUCTION

Why do we need to study thermodynamics?

Knowledge of thermodynamics is required to design any device involving the interchange between heat and work, or the conversion of material to produce heat (combustion).

1. What is thermodynamics?

Thermodynamics is a basic science that deals with energy. In other words, thermodynaamics may be defined as the study of energy, its forms and transformations and its interaction with matter. Thermodynamics also deals with various properties of substances and the changes in these properties as a result of energy transformations. Precisely thermodynamics is

(i)The study of the relationship between work, heat, and energy.

(ii)Deals with the conversion of energy from one form to another.

(iii)Deals with the interaction of a system and it surroundings.

The name thermodynamics stems from the Greek words therme (heat) and dynamics (power), which is most descriptive of the early efforts to convert heat into power. Today the same name is broadly interpreted to include all aspects of energy and energy transformations, including power production, refrigeration and relationships among the properties of matter.

2. How the laws of TD were formulated?

Thermodynamic laws were formulated from the day-to-day experiences and experimental observations. These laws govern the principles of energy conversion.

3. Where we found the applications of Thermodynamic laws and principles?

We can see the application of thermodynamics in every item, starting from household appliances to high-tech rockets. In fact, the human body itself is an interesting application area of thermodynamics.

The application of the thermodynamic laws and principles are found in all fields of energy technology, notably in

(i) Steam and nuclear power plants

(ii) Internal combustion engines

(iii) Gas turbines

(iv) Air conditioning

(v) Refrigeration

(vi) Gas dynamics,

(vii) Jet propulsion

(viii) Compressors

(ix) Chemical process plants such as refineries

(x) Combustion of hydrocarbon fuels such as coal, oil and natural gases

(xi) Use of passive and active solar energy units, power plants using geothermal sources beneath the ground, wind and tidal generation units (direct energy conversion devices)

(xii) Inside the space suit of astronauts

(xiii) In air-separation plants that produce oxygen for use in the steel manufacturing industry

(xiv) In our search for solutions to problems in connection with energy crises, shortages of fresh water and garbage disposal in the cities and

(xv) In our search for a better quality of life.

4. How does the subject of thermodynamics differ from the concept of heat transfer?

(i) Thermodynamics is the science, which deals mainly with the relation between heat and other forms of energy whereas heat transfer is concerned with the analysis of rate of heat transfer.

(ii) Thermodynamics deals with systems in equilibrium so it cannot be expected to predict quantitatively the rate of change in process which results from non-equilibrium states, viz., the temperature non-equilibrium (gradient) which is a must for heat transfer to take place.

5. Is thermodynamics a misnomer for the subject?

The science of thermodynamics deals with systems existing in thermodynamic equilibrium states, which are specified by properties. Infinitely slow quasi-static processes executed by systems are only meaningful in thermodynamic plots. The name thermodynamics is thus said to be a misnomer, since it does not deal with the dynamics of heat, which is non quasi-static. The name thermostatics then seems to be more appropriate. However, most of the real processes are dymanic and non quasi-static, although the initial and final states of the system might be in equilibrium. Such processes can be successfully deal with by the subject. Hence, the term thermodynamics is not inappropriate.

6. What do you understand by microscopic and macroscopic approaches in thermodynamics?

Behavior of matter can be studied either by macroscopic or microscopic.

In the macroscopic approach, a certain quantity of matter is considered, without the events occurring at the molecular level being taken into account. Macroscopic thermodynamics is only concerned with the effects of the action of many molecules, and these effects can be perceived by human senses.

For example, the macroscopic quantity, pressure, is the average rate of change of momentum due to all the molecular collisions made on a unit area. The effects of pressure can be felt. As the macroscopic point of view is not concerned with the action of individual molecules and the force on a given unit area can be measured by using, e.g., a pressure gauge.

These macroscopic observations are completely independent of the assumptions regarding the nature of matter. The macroscopic thermodynamics is also called as classical thermodynamics.

From the microscopic point of view, matter is composed of myriads of molecules. If it is a gas, each molecule at a given instant has a certain position, velocity, and energy and for each molecule these change very frequently as a result of collisions. The behavior of gas is described by summing up the behavior of each molecule. This study is also called as statistical thermodynamics.

7. What is thermodynamic system? Explain the types

A thermodynamic system is defined as a quantity of matter or a region in space upon which attention is concentrated in the analysis of a problem.

Figure1: A thermodynamic system

There are three classes of systems

(a) Closed system

(b) Open system(c) Isolated system

(a) Closed system: A closed system is a system of fixed mass. There is no mass transfer across the system boundary. There may be energy transfer into or out of the system.

Figure2: A closed system

Example: A certain quantity of fluid in a cylinder bounded by a piston constitutes a closed system.

(b) Open system (control volume): An open system is a system of fixed volume in space. In which matter crosses across the boundary of the system. There may be energy transfer also.

Figure3: An open system

Examples: Most of the engineering devices are open systems e.g., Thermodynamic analysis of an air compressor, jet engine etc.

Figure 4: Air compressor

Figure5: Jet engine

(c)Isolated system: In this system there is no interaction between the system and the surroundings. It is of fixed mass and energy, and there is no mass or energy transfer across the system boundary.

Figure 6: An isolated system

Figure 7: Water Vapour in internal equilibrium with liquid water: An isolated system

8. What is meant by boundary, universe and surroundings?

Surroundings: Everything external to the system is called surroundings or the environment.

Boundary: The system is separated from the surroundings by an envelope known as system boundary. The boundary may be either fixed or moving.

Example for a moving boundary is: a moving piston in a cylinder having fixed mass of charge.

Universe: A system and its surroundings together comprise a universe.

9. What is the difference between a closed system and open system?

Closed systemOpen system

1.It is a system of fixed mass or matter1. It is a system of fixed volume

2.No mass transfer but Energy transfer takes place2. Both matter and energy transfer may takes place.

3. System boundary may be fixed or moving.3. It is of fixed volume and hence is also called control volume. The boundary of the volume is bounded by a surface known as control surface.

10. An open system defined for a fixed region and a control volume are synonymous. Explain.

For thermodynamic analysis of an open system, attention is focused on a certain volume or region in space, across which both matter as well as energy transfer, takes place. When there is matter flow, then the system is considered to be a volume of fixed identity, the control volume. There is thus no difference between an open system and a control volume.

11. Define an Isolated system. (See for the answer from the answer of Q7)12. Define the terms

a. Thermodynamic properties:

Every system has certain characteristics by which its physical condition may be described. Such characteristics are called properties of the system. These are all macroscopic in nature, means they are identifiable/observable characteristic. A thermodynamic property refers to a characteristic, which is relevant to thermodynamics that is, which is concerned with the interaction of energy in the form of heat and work between a system and its surroundings. E.g., Volume, pressure, temperature etc.

b. State

The thermodynamic state of a system/substance at any given instant of time is its condition as characterized by certain identifiable/observable thermodynamic properties, i.e., the set of properties completely determine the state of a system.

c. Change of state

Properties are the coordinates to describe the state of a system. They are the state variables of the system. Any operation in which one or more of the properties of a system changes is called a change of state.

d. Path

The succession of states passed through during a change of state is called path of the change of state

e. Process

When the path is completely specified, the change of state is called a process, e.g., a constant pressure process

f. Cycle

A thermodynamic cycle is defined as a series of state changes such that the final state is identical with the initial state.

Figure: Initial state and final state of gas in a cylinder (a) cylinder piston arrangement (b) on p-v diagram to illustrate path, process and cycle

13. What are intensive and extensive properties? Give four examples for each.

Properties may be divided into two types., viz., extensive and intensive.

The properties that depend on the extent of the system/substance are known as extensive properties. The properties like length, volume, mass, energy etc., are extensive properties.

The properties that do not depend on the extent of the system/substance are known as intensive properties. The properties like pressure, temperature, density etc., are extensive properties. Further the ratio of two extensive properties of a homogeneous system (mass per unit volume) or specific extensive properties (extensive properties per unit mass) are intensive properties.

To illustrate it further, consider a homogeneous substance forming a system existing in a given state as shown in figure. One can divide this substance into a number of subdivisions, say, A, B, C, D, E, F and G. Each subdivision has different mass and different volume, but it has the same pressure and the same density and hence the same state. Thus, mass and volume depend on the extent of the system whereas pressure and density do not depend on its extent. We see that an intensive thermodynamic property has the same value for the system as a whole as well as for each subdivision or point of the system.

Figure: Subdivisions of a system

14. What do you mean by homogeneous and heterogeneous systems?

A quantity of matter homogeneous throughout in chemical composition and physical structure is called a phase. Every substance can exist either in any one of the three phases, viz., solid, liquid and gas or combination of phases.

A system consisting of a single phase is called homogeneous system, while a system consisting of more than one phase is known as a heterogeneous system.

15. What is meant by pure substance.

A pure substance is defined as one that is homogenous and invariable in chemical composition thoughout its mass. The relative proportions of the chemical elements constituting the substance are also constant.

Atmospheric air, steam-water mixture and combustion products of a fuel are regarded as pure substances. But the mixture of air and liquid air is not a pure substance, since the relative proportions of oxygen and nitrogen differ in the gas and liquid phases in equilibrium.

The state of a pure substance of given mass can be fixed by specifying two properties, provided the system is in equilibrium. This is known as the two-property reul. The stat thus be represented as a point on thermodynamic property diagrams . Once any two properties of a pure substance are known, other properties can be determined from the available thermodynamic relations.16. Explain what you understand by thermodynamic equilibrium.

Equilibrium: In any system, when there can be no spontaneous change in any macroscopic property registered, then the system is said to be exist in an equilibrium state. Thermodynamics studies mainly the properties of physical systems that are found in equilibrium states.

Thermodynamic equilibrium: A system is said to exist in a state of thermodynamic equilibrium when no change in any macroscopic property is registered, if the system is isolated from its surroundings.

An isolated system always reaches in course of time a state of thermodynamic equilibrium and can never depart from it spontaneously.

A system will be in a state of thermodynamic equilibrium, if the conditions for the following three types of equilibrium are satisfied.

(a) Mechanical equilibrium.

(b) Chemical equilibrium.

(c) Thermal equilibrium.17. Explain mechanical, chemical and thermal equilibrium

(a) Mechanical equilibrium: In the absence of any unbalanced force within the system itself and also between the system and the surroundings, the system is said to be in a state of Mechanical equilibrium. If an unbalanced force exists either the system alone or both the system and the surrounding will undergo a change of state till mechanical equilibrium is attained.

(b) Chemical equilibrium: If there is no chemical reaction or transfer of matter from one part of the system to another such as diffusion or solutions, the system is said to exist in a state of chemical equilibrium.

(c) Thermal equilibrium: When a system existing in mechanical and chemical equilibrium separated from its surroundings by a diathermic wall (diathermic means which allows heat to flow) and if there is no spontaneous change in any property of the system, the system is said to exist in a state of thermal equilibrium. When this is not satisfied the system will undergo a change of state till thermal equilibriums is restored.18. What is a quasi-static process/ what is its characteristic feature?

Let us consider a system of gas contained in a cylinder (as shown in figure 1). The system --- is in equilibrium state represented by the properties p1 v1 l1. The weight on the piston just balances the upward force exerted by the gas. If the weight is removed there will be an unbalanced force between the system and the surroundings and the gas under pressure, the piston will move up till it hits the stops Figure l Transition between two

Figure 2 Plot representing the Equilibrium states by an unbalanced force

transition between two

equilibrium sates

The system again comes to an equilibrium state, being described by the properties p2 v2 l2. But the intermediate states passed through by the system are nonequilibrium sates which cannot be described by thermodynamic coordinates. Figure 2 show points 1 and 2 as the ---- and final equilibrium sates joined by a dotted line, which has get no meaning otherwise. Now if the single weight on the piston is made up of many very small pieces of weights (figure 3) and these weights are removed one by one very slowly from the top of the piston, at any instant of the upward travel of the piston, if the gas system is isolated, the departure of the state of the system from the thermodynamic equilibrium state will be infinitesimally small. So every state passed through by the system will be an equilibrium state. So every state passed through by the system will be an equilibrium state. Such a process, which is but a locus of all the equilibrium points meaning almost Infinite slowness is the characteristic feature of a quasi-static process. A quasi-static process is thus a succession of equilibrium states. A quasi-static process is also called a reversible process.19. What is the concept of continuum? How will you define density and pressure using this concept?

From the macroscopic (classical thermodynamics) point of view, we are always concerned with volumes which are very large compared to molecular dimensions. Even a very small volume of a system is assumed to contain a large number of molecules so that statistical averaging is meaningful and a property value can be assigned to it. Disregarding the behaviour of individual molecules, matter here is treated as continuous. From the continuum stand point we can speak of properties at a point.Density: For example let us consider the density of a fluid at a point P (figure), which is surrounding by small size volume --- and let the mass contained by this volume be -- . We suppose that at first is rather large and is subsequently shrunk about the point P. If we plot ---- against the average density tends to approach an asymptote as increases (figure 2) However, when sv becomes so small as to contain relatively few molecules, the average density fluctuates substantially with time as molecules pass into and out of the volume in random motion, and so it is impossible to speak of a definite value of --- The smallest volume which may be regarded as continuous is The density p of the system at a point is thus defined as Pressure:

Pressure is the normal force exerted by a system against unit area of the bounding surface if (A21. Explain the role of concept of continuum in microscopic and macroscopic approaches.

From the microscopic view, we are always concerned with volumes that are very large compared to molecular dimensions, and therefore, with systems that contain many molecules. Because we are not concerned with the behaviour of individual molecules, we can treat the substance as being continuous, disregarding the action of individual molecules; this is called a continuum. The concept of continuum, of course, is only a convenient assumption that loses validity when the mean free path of the molecules approaches the order of magnitude of the dimensions of the vessel , as, for example in highly rarefied gases encountered in high-vacuum technology in rocket fights at high altitude and in election tubes and ballistic missiles. At about 200,000m alutude (high vacuum) the mean molecular path of a molecule may be as large as 35 m ie approximately equal o the vehicle itself in such circumstances the fluid cannot be treated as continuum. The microscopic point of view can be applied for the study.In most engineering applications, the assumption of continuum is valid and convenient, and goes hand in hand with the macroscopic view. Hence except for few exceptions, we can conclude that thermodynamics is a continuum science.

22. Define Force, Energy, Power, Specific volume and density?

Force (F) acting on a body is defined by Newtons II law of motion as the product of mass and acceleration.

F = md units: (Kg) (m/s2) = N

The weight of the body (W) is the force with which the body is attracted to the centre of the earth. It is the product of its mass (m) and the local gravitational acceleration (g) ieW = mg (N)

Energy: It is the capacity to exert a force through a distance and is defined as the product of force and distance.

E = F d Nm or J

The energy per unit mass is the specific energy the unit of which is J/Kg

Power: The rate of energy transfer or storage is called power. The unit of power is watt (W) IW = J/s and 1KW = 1000W and 1MW = 10 W

Specific volume (v): Volume (V) is the space occupied by a substance and is measured in M or litre 11 = 103 m3 The specific volume (v) of a substance is defined as the volume per unit mss and is measured in m3 / Kg.

Density ((): Is the mass per unit volume of a substance.

( = Kg/m3

It may be on the basis of mass or in respect of mole

A mole of a substance has a mass numerically equation the molecular weight of the --- substance. For example one g mol of oxygen has a mass of 32 g and 1Kg mol (1Kmol) of nitrogen has a mass of 28Kg. The symbol --- is used for molar spec-- volume (m3/Kmol).

23. Define the following:

a. Barometric or atmospheric pressure( P --): This is the pressure exerted by the atmospheric air. It is called barometric pressure as it is measured by a barometer ( a manometer which measure atmospheric pressure)The standard atmosphere pressure is defined as the pressure produced by a column of mercury 760mm high, the mercury density being 13.6x 103 Kg/m3 and the acceleration due to gravity being 9.81 m/s2 , the standard atmospheric pressure is 101 325 KN/m2 or 1.01325 bar or 76 cm of Hg.

b. Gauge pressure (P gaugs): The pressure measured from the gauge and instrument such as Bourdon and manometers is called the gauge pressure. The gauge actually measures the difference between the fluid pressure and the pressure of atmosphere surrounding the gauge. c. Absolute pressure (P abs): The pressure of a system is its pressure above absolute zero or relative to a perfect vacuum. The pressure relative to a perfect vacuum is called absolute pressure.Hence Absolute pressure = Atmospheric pressure + gauge pressure

Pabs = P-- - Pgauge N/m2d. Vacuum pressure (P abc): If the pressure of the fluid to be measured is less than the atmospheric pressure, the gauge will read on the negative side of the atmospheric pressure and is known as vacuum rarefaction or negative gauge pressure.Hence

Pabs = P--- Patm Pgauge N/m2

For example 16cm vacuum will be

xl 013 = 0.08bar24. What are different pressure gauges, transducerDifferent types of pressure gauges are

(a) Bourdon gauge as shown in figure (a), which measures the difference between the system pressure inside the tube and atmospheric pressure. It relies on the deformation of a bent hollow tube of suitable material which, when subjected to the pressure to be measured on the inside (and atmospheric pressure on the outside), tends to unbend. This moves a pointer through a suitable gear and lever mechanism against a call brated scale.

(b) Manometers: The manometer is a sensitive, accurate and simple device but it is limited to fairly small pressure differentials and, because of the inertia and friction of the liquid, is not suitable for fluctuating pressures, unless the rate of pressure change is small. The different types of manometers are

(i) Open U-tube indicating gauge pressure (shown in figure (b))

(ii) Open U-tube indicating vacuum (shown in figure (c))

(iii) A closed U-tube indicating absolute pressure (Shown in figure (d))

(iv) A barometer indicating atmospheric pressure.

If Z is the difference in the heights of the fluid columns in the two limbs of the U-tube (figure 2 and 3), ( the density of the fluid and g is the acceleration due to gravity then.

=

If the fluid is mercury having ( = 13,616kg/m2, one metre head of mercury column is equivalent to a pressure of 1.3366 bar, as shown below.

1m Hg = (gZ = 13,616xp.81x1= 1.3366x105 N/m2= 1.3366 barTransducer: A diaphragm type pressure transducer along with a cathode ray oscilloscope can be used to measure rapidly fluctuating pressures.25. Units and dimensions

26. Problems: Refer to problem sheet # 1.1

TEMPERATURE

1. Explain Zeroth law of thermodynamics? Explain how it forms the basis for temperature measurement.

2. Define thermometric property.

3. What is a thermometer?

4. What is a fixed point?

5. How many fixed points were used prior to 1954? What are these?

6. What is the standard fixed point in thermometry? Define it.

7. Why is a gas chosen as the standard thermometric substance?

8. State the advantages of gases over liquids as a thermometer liquids

9. What is an ideal gas?

10. What is the difference between the universal gas constant and a characteristic gas constant?

11. What are the principles of gas thermometer?

12. What is a constant volume gas thermometer? Why it is preferred to a constant pressure gas thermometer? Explain with the help of a neat sketch.

13. What do you understand by the ideal gas temperature scale?

14. Explain the Kelvin scale of temperature using the constant volume gas thermometer.

15. How can the ideal gas temperature for the steam point be measured?

16. What are the requirements of temperature scales?

17. What is the Celsius temperature scale?

18. Give the principle of working of (i) Electric resistance thermometer

(ii) Thermocouple

19. What is the advantage of a thermocouple in temperature measurement?

20. Explain the international practical temperature scale. What are its uses?

21. Write a note on scales of temperature

22. What are the requirements of temperature scales?

23. Problems: Refer to problem sheet # 1.2

WORK AND HEAT TRANSFER

Work

1. How can a closed system and its surroundings interact? What is the effect of such interactions on the system?

2. When work is said to be done by a system?

3. What are positive and negative work interactions?

4. What is displacement work?

5. Under what conditions is the work done equal to ?

6. What do you understand by path function and point function? What are exact and inexact differentials?

7. Show that work is a path function but not a property.

8. How does current flowing through a resistor represent work transfer?

9. What do you understand by flow work? Is it different from displacement work?

10. Why does free expansion have zero work transfer?

Heat

11. What is heat transfer? What are its positive and negative directions?

12. What are adiabatic and diathermic walls?

13. What is an integrating factor?

14. Show that heat is a path function but not a property.

15. What is the difference between work transfer and heat transfer?

16. Does heat transfer inevitably cause a temperature rise?

17. Define (a) Specific heat(b) heat capacity(c) latent heat of fusion

(d) latent heat of vaporization

(e) latent heat of sublimation

18. Problems: Refer to problem sheet # 1.3

FIRST LAW OF THERMODYNAMICS

1. State the first law for a closed system undergoing a cycle?

2. Write a note on joule experiments in establishing the first law?

3. Which is the property introduced by the first law?

4. State the first law for a closed system undergoing a change of state.

5. Show that energy is a property of a system.

6. What are the modes in which energy is stored in a system?

7. Define internal energy. How is energy stored in molecules and atoms?

8. What is the difference between the standard symbols of E and U?

9. What is the difference between heat and internal energy?

10. Define enthalpy. Why does the enthalpy of an ideal gas depend only on temperature?

11. Define specific heat at constant volume and constant volume.

12. Why should specific heat not be defined in terms of heat transfer?

13. Which property of a system increases when heat is transferred: (a) at constant volume, (b) at constant pressure?

14. What is a PMM1? Why is it impossible?

FIRST LAW APPLIED TO FLOW PROCESS

1.

Boundary

System

Surroundings

Boundary

System

Surroundings

Energy in

Energy out

No mass transfer

dm = 0

dE ( 0

Cylinder

System

Gas

Piston

Energy

Boundary

System

Surroundings

Energy in

Energy out

dm ( 0

dE ( 0

Mass in

Mass in

Air compressor

Motor

Work

Heat

Air out

Air in

Control volume

Control surface

C

T

Air

Combustion products

System boundary or control surface

Fuel

Surroundings

System

dm = 0

dE = 0

No mass or energy transfer

Water Vapour

Liquid water

Surroundings

Adiabatic wall

( No heat transfer)

Boundary

System

Surroundings

P

v

a

b

1

2

a,b : state points

a-b : change of state

a to b : path ,process

1-2-1: cycle

1

P1, v1

2

P2, v2

E

D

B

C

F

GA

A

System boundary

MED, MVGRCE, VZM

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