# ME Subjects – Concepts Simplified

## Topics on Mechanical Engineering Courses

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## MCQ-DIESEL CYCLE

DIESEL CYCLE

It consists of two isentropic processes, one isobaric and one at constant volume processes. The sequence of processes is as follows:

(i) Compression isentropic.

(ii) Heat is supplied at constant pressure.

(iii) Expansion is isentropic.

(iv) Heat rejection is at constant volume.

It  uses diesel fuel. It is also called a compression cycle. In this only air is compressed with a high compression ratio (11:1 to 20:1).Fuel on injection gets ignited due to high temperature of compressed air. It is used in heavy vehicles like trucks, buses and railways.

MCQ-DIESEL CYCLE

1. Diesel cycle consists of
1. Two isentropic and two iso- baric processes
2. Two iso-thermal and two iso-baric processes
3. Two isentropic and two iso-thermal processes
4. None

ANS: (iv)

1. Diesel cycle consists of

(i) Two adiabatic and two iso-thermal processes

(ii) Two isentropic and two constant volume processes

(iii) Two isobaric and two iso-thermal processes

(iv)None

ANS: (iv)

1. Heat is added in the Diesel cycle at

(i) Constant temperature

(ii) Constant pressure

(iii) Constant entropy

(iv)None

ANS: (ii)

4. Heat is added in Diesel Cycle at

(i) Constant enthalpy

(ii) Constant volume

(iii) Constant entropy

• None

ANS: (iv)

5. Compression in an Diesel cycle is

1. Isobaric
2. Isothermal
3. Isenthalpic
4. None

ANS: (iv)

6. Compression in an Diesel Cycle is

1. Isometic
2. Isentropic
3. Iso-baric
4. None

ANS: (ii)

7. Heat rejected in an Diesel Cycle is

1. Isobaric
2. Iso-thermal
3. Isenthalpic
4. None

ANS: (iv)

8. Heat rejected in an Diesel Cycle is

1. Isometric
2. Isentropic
3. Isenthalpic
4. None

ANS; (i)

9. Expansion in an Diesel Cycle is

1. Isobaric
2. Iso-thermal
3. Iso-metric
4. None

ANS: (iv)

10. Expansion process in an Diesel Cycle is

1. Constant volume
2. Constant pressure
3. Constant entropy
4. None

ANS: (iii)

11. Efficiency of an Diesel Cycle is dependent of

1. Compression ratio
2. Cut off ratio
3. Both compression and cut off ratio
4. None

ANS: (iii)

12. Efficiency of an Diesel Cycle is independent of

2. Heat rejection
3. Properties of the working substance
4. None

ANS: (iv)

13. The efficiency of the Diesel Cycle is given by

1. 1-1/( γ-1)
2. 1+ 1/( γ-1)
3. 1 –γ/(γ-1)
4. None

ANS: (iv)

14. The efficiency of the Diesel Cycle is given by

1. 1-1/r( γ-1) [(αγ -1) / γ(α – 1)]
2. 1+ 1/r( γ-1) [(αγ -1) / γ(α – 1)]
3. 1 –γ/r(γ-1)
4. None

ANS: (i)

15. Diesel cycle is a

1. Carnot Cycle
2. Steam Cycle
3. Otto Cycle
4. None

ANS: (iv)

16. Diesel cycle is a

1. Petrol Cycle
2. Steam Cycle
3. Diesel Cycle
4. None

ANS: (iii)

17. Diesel cycle is

1. Compression Cycle
2. Otto Cycle
3. Spark ignition cycle
4. None

ANS: (i)

18. Fuel in a Diesel Cycle is burnt with

• Compression alone
• With steam
• With Diesel
• None

ANS: (i)

19. Fuel in a Diesel Cycle is burnt with

1. Expansion alone
2. With a spark
4. None

ANS: (iv)

20. For the same compression ratio,

Efficiency of Diesel cycle is

1. Greater than that of Otto cycle
2. Less than that of Otto cycle
3. Equal to that of Otto cycle
4. None

ANS: (ii)

21. Compression ratio in an Diesel Cycle is

1. 3:1 to 5:1
2. 7:1 to 10:1
3. 11:1 to 20:1
4. None

ANS : (iii)

22. Heat rejected in Diesel as well as in Otto Cycles is

1. Isobaric
2. Isothermal
3. Isentropic
4. None

ANS: (iv)

23. Heat rejected in Diesel as well as in Otto Cycles is

1. Isobaric
2. Isothermal
3. Isochoric
4. None

ANS: (iii)

## MCQ ZEROTH LAW OF THERMODYNAMICS

ZEROTH LAW OF THERMODYNAMICS

It states that if two thermodynamic systems A and B are in thermal equilibrium with a third system C, then system A and B are also in thermal equilibrium with each other. It is a pre-requisite for the three laws of thermodynamics. It was invented later than the three laws of thermodynamics. That is why it is called zeroth law of thermodynamics. It is a law of thermal equilibrium. Body temperature being measured by a thermometer is there only when thermometer and body are in thermal equilibrium with each other.

MCQ ZEROTH LAW OF THERMODYNAMICS

1. Heat coming from any source is of
1. Same kind
2. Different kind
3. May be same as well as different
4. None

ANS: (i)

1. Zeroth law establishes
1. Chemical equilibrium
2. Mechanical equilibrium
3. Chemical as well as mechanical equilibrium
4. None

ANS: (iv)

1. Zeroth law establishes
1. Chemical equilibrium
2. Mechanical equilibrium
3. Thermal equilibrium
4. None

ANS: (iii)

1. It is called Zeroth law because it was invented
1. Earlier than first law
2. Earlier than second law
3. Earlier than third law
4. None

ANS: (iv)

1. It is Zeroth law because it was invented
1. Later than first law
2. Earlier than second law
3. Earlier than third law
4. None

ANS: (i)

1. Temperature is a
1. Isentropic quantity
2. Mechanical quantity
3. Chemical quantity
4. None

ANS: (iv)

1. Temperature is a
1. Physical quantity
2. Mechanical quantity
3. Iso-thermal quantity
4. None

ANS: (i)

1. Temperature is a
1. Isentropic quantity
2. Isenthalpic quantity
3. Iso-baric quantity
4. None

ANS: (iv)

1. Zeroth law is a law of
1. Conservation of mass
2. Conservation of energy
3. Conservation of mass and energy
4. None

ANS: (iv)

1. Zeroth law is a law of
1. Reversibility
2. Ir-reversibility
3. Reversibility as well as ir-reversibility
4. None

ANS: (iv)

1. Zeroth law deals with
1. Pressure
2. Volume
3. Enthalpy
4. None

ANS: (iv)

1. Zeroth law deals with
1. Work
2. Heat
3. Work as well as heat
4. None

ANS: (iv)

1. Measurement of temperature in thermodynamics is linked to the
1. First law of thermodynamics
2. Second law of thermodynamics
3. Third law of thermodynamics
4. None

ANS: (iv)

1. Measurement of temperature with a thermometer is linked to the
1. First law of thermodynamics
2. Second law of thermodynamics
3. Third law of thermodynamics
4. None

ANS: (iv)

1. During thermal equilibrium, there is
1. No mass transfer
2. No energy transfer
3. No momentum transfer
4. None

ANS: (ii)

1. Thermal equilibrium is there if
1. Pressure changes with time
2. Volume changes with time
3. Temperature changes with time
4. None

(iv)

1. Thermal equilibrium is there if
1. Pressure remains constant
2. Temperature remains constant
3. Volume remains constant
4. None

ANS: (ii)

1. Among three systems, glass of ice, glass of hot water and environment, which type of equilibrium these will achieve with the passage of time
1. Chemical equilibrium
2. Mechanical equilibrium
3. Thermal equilibrium
4. None

ANS: (iii)

1. In the freezer of a refrigerator, there are four different item at the same temperature. Which law of thermodynamics is applicable?
1. First law
2. Second law
3. Zeroth law
4. None

ANS: (iii)

## MCQ SECOND LAW THERMODYNAMICS

SECOND LAW OF THERMODYNAMICS

There are two statements of Second Law.

Planck’s statement

There is no heat engine in the universe which can convert a certain quantity of heat into equivalent amount of work.

Clausius statement

Heat cannot flow from a body at lower temperature to a body at higher temperature without the use  of an external agent. This heat transfer from low to high temperature is refrigeration and this needs energy. Heat transfer from high to low temperature is by itself. Thus, second law talks of irreversibility.

MCQ SECOND LAW THERMODYNAMICS

1. It is a law of
• Reversibility
• Irreversibility
• Reversibility as well as ir-reversibility
• None

ANS: (ii)

1. A heat engine can convert following % of heat into work
• 25 %
• 50 %
• 75 %
• None

ANS: (iv)

1. Heat flowing from high temperature body to low temperature body is
• Refrigeration
• Heat Transfer
• Refrigeration as well as heat transfer
• None

ANS: (ii)

1. Heat flowing from low temperature body to high temperature body is
• Refrigeration
• Heat Transfer
• Refrigeration as well as heat transfer
• None

ANS: (i)

1. There is no heat transfer in the
• Isen-tropic process
• Iso-baric process
• None

ANS: (iv)

1. Entropy is a measure of
• Disorder
• Order
• Both order as well as disorder
• None

ANS: (i)

1. Heat transfer depends on
• Entropy difference
• Enthalpy difference
• Internal energy difference
• None

ANS: (iv)

1. Heat transfer depends on
• Temperature difference
• Pressure difference
• Internal energy difference
• None

ANS: (i)

1. A Carnot cycle is a
• Refrigeration cycle
• Power consuming cycle
• Power producing cycle
• None

ANS: (iii)

1. A Carnot cycle consists of
• Ir-reversible processes
• Reversible processes
• Ir-reversible and reversible processes
• None

ANS: (ii)

1. COP is maximum for a
• Carnot cycle
• Otto cycle
• Diesel cycle
• None

ANS: (iv)

1. Work input is maximum for a
• Isen-tropic compression
• Iso-baric compression
• Iso-metric compression
• None

ANS: (iv)

1. Work input is maximum for a
• Isothermal compression
• Iso-enthalpy compression

• None

ANS: (i)

1. During a reversible process, the entropy reduces to
• 5
• 75
• 95
• None

AND: (iv)

1. During an ir-reversible process, the entropy reduces to
• 5
• 75
• 95
• None

AND: (iv)

1. Second law of Thermodynamics is also known as the law of

(i) Decreased entropy

(ii) Increased entropy

(iii) Decreased as well increased entropy

• None

ANS: (ii)

1. Second law of thermodynamic lead to the discovery of
• Internal energy
• Enthalpy
• Entropy
• None

ANS: (iii)

1. Efficiency of a heat engine is governed under which law of thermodynamics
• Third
• (zeroth
• First
• None

ANS: (iv)

1. Efficiency of a heat engine is governed under which law of thermodynamics
• Second
• (zeroth
• First
• None

ANS: (i)

1. Second Law of Thermodynamics deals with
• Quality of energy
• Quantity of energy
• Both quality and quantity of energy
• None

ANS: (i)

1. A process feasibility is governed by which law of thermodynamics
• First
• Second
• Third
• None

ANS: (iv)

1. A process feasibility is governed by which law of thermodynamics
• First
• Second
• Both First and Second
• None

ANS: (iii)

1. Mathematically second law of thermodynamics is represented by
• ∆s Univ > 0
• ∆s Univ < 0
• ∆s Univ£ 0
• NONE

ANS: (i)

## FILLING BLANKS-REFRIGERATION

Filling blanks in refrigeration is possible only if one has deep understanding and clarity about the topic. Filling blanks will further increase knowledge which will help to apply in real life applications.

FILLING BLANKS-REFRIGERATION

Fill in the blanks in refrigeration is from university question papers

1. The high pressure is from —————— to ———————–in a refrigeration system.
2. The condition of refrigerant at the inlet of evaporator is ————–liquid and vapor.
3. At the outlet of evaporator, the condition of refrigerant  is ——— and —— vapor.
4. Inlet of the compressor, the condition of refrigerant is ———-pressure and —–temperature vapor.
5. Refrigerant condition at the outlet of compressor is high————- and high———vapor.
6. The refrigerant at the inlet of condenser is ————– pressure and ———temperature vapor.
7. The state of refrigerant at the outlet of condenser is high ———— and high———– liquid.
8. The condition of refrigerant at the inlet of expansion valve is ——-pressure and ——temperature liquid.
9. The condition of refrigerant at the inlet of evaporator is ————–liquid and vapor.
10. The condition of refrigerant at the inlet of evaporator is saturated ———and —– vapor.
11. The most commonly used Freon R—and R—have been banned,
12. The most commonly used refrigerant in industry is ———————.
13. The most commonly used refrigerants in window air conditioner is ————-.
14. The condenser is the ——–pressure side of a refrigeration system.
15. The low pressure side starts from ————–expansion valve and ends at ———–of compressor.
16. The high pressure starts —————- of compressor and ends at the ——————–expansion valve.
17. The function of the compressor is to increase ————— and —————.
18. Refrigeration is a process of ——————–.
19. The process of refrigeration is used to protect —————–against spoilage.
20. The growth of bacteria is greater in a ————————-atmosphere.
21. The growth of bacteria can be stopped by ———————.
22. Refrigeration is based on the principle that ————causes cooling.
23. Refrigeration capacity is expressed in —————–.
24. One ton of refrigeration is equal to ——————kJ/day.
25. One ton of refrigeration is equal to ——————kJ/hour.
26. The machine which produces refrigeration is called ————————system.
27. The most popular system for producing refrigeration is ———————-.
28. The refrigeration system which is equipped with ——————is called a vapor compression refrigeration system.
29. The system which produces cooling with water is called ————————-.
30. The temperature decrease in the room due to a desert cooler is ——————–0
31. ————-energy is used to run the vapor absorption refrigeration system.
32. In the absorption refrigeration system, the refrigerant is separated from the absorbent in the ——–.
33. In the absorption system, absorbent absorbs the refrigerant in the —————–.
34. Mechanical refrigeration system is also called ——————————.
35. The low pressure of the refrigeration system is also called ——————-, suction pressure and evaporator pressure.
36. The high pressure of the refrigeration system is also called ——————-, discharge pressure and condensing pressure.
37. The compressor in the refrigeration system compresses the vapors and increases its —————-and —————.
38. The oil separator separates the ——————-from the compressed refrigerant.
39. The condenser is air cooled, water cooled and ———————— cooled.
40. The condenser changes the vapor refrigerant into a ———————-state.
42. Expansion valve changes high pressure liquid refrigerant into —————liquid.
43. Accumulator —————–the liquid which comes from the evaporator.
44. Muffler reduces the suction and discharge —————— of the compressor.
45. —————pipe is used in the ammonia vapor absorption refrigeration system.
46. There is no ————–part in the vapor absorption refrigeration system.
47. Gases which are charged in the Electrolux refrigerator are —————-and —————–.

1. Compressor, Expansion valve,
2. Saturated,
3. Dry, saturated,
4. low, low
5. pressure, temperature
6. high, high
7. pressure, temperature,
8. high, high
9. liquid, saturated,
10. saturated,
11. 12 , 11,
12. Ammonia,
13. R-22,
14. high,
15. middle, inlet
16. outlet, middle
17. Pressure temperature,
18. (Cooling),
19. (Food stuff),
20. (Hot and humid),
21. (Cooling),
22. (Evaporation),
23. Tons of refrigeration),
24. (302400),
25. (12600),
26. (refrigeration),
27. (Vapor compression refrigeration system),
28. (Compressor),
29. (Desert cooler),
30. (100C),
31. (Heat),
32. (Generator),
33. (Absorber),
34. (Vapor compression refrigeration system),
35. (Back pressure),
37. (Temperature and pressure),
38. (Lubricating oil),
39. (Evaporative),
40. (Liquid),
41. (Storage),
42. (Low pressure),
43. (Stores),
44. (sound),
45. (Steel),
46. (Moving),
47. (Ammonia and Hydrogen).

CONDUCTION

It is one of mode of heat transfer. It takes place in solids by physical contact. It depends on the thermal conductivity. Thus there is more heat conduction in metals. There is least conduction in non metals. l

1. Discuss thermal diffusivity.

Thermal diffusivity is expressed as the thermal conductivity divided by the by the product of density and specific heat. In a substance with high thermal diffusivity, heat moves rapidly through the solid. It is  because the substance conducts heat quickly relative to its volumetric heat capacity. If it is higher, then less time is required for certain heat transfer to take place through the solid.

Further, thermal diffusivity is typically measured in mm²/s. Its symbol is α. The thermal diffusivity of a material indicates the rate of heating and rate of cooling of a material under transient conditions. The physical signiﬁcance of this quantity lies in the fact that the inverse of thermal diffusivity is a measure of time. This is he time required to establish the thermal equilibrium in the specimen.

The rate of change of temperature depends on its numerical value.

METHODS TO FIND THERMAL DIFFUSION

(i) Flash Method

(ii) Infrared detectors

(iii) Intrinsic thermo-couples

1. Difference between thermal conductivity and thermal diffusivity?

Thermal conductivity (k) represents its ability to conduct heat. Whereas thermal diffusivity (α) indicates how fast the heat is conducted?

1. List at least four examples of multi-dimensional heat conduction.
1.  Cooling of I.C. Engines
2.  Heat transfer in air conditioning ducts.
3.  Heat transfer in an industrial chimney.
4.  During various heat treatment processes.
1. List the methods used in the analysis of 2 Dimensional steady state conductive heat transfers.

There are four methods.

1.  Analytical method
2. Graphical Method
3. Analogical Method
4. Numerical Method
1. List the methods used in the analysis of 3 dimensional steady state conductive heat transfers.

There are three methods.

1.  Analytical method
2. Analogical Method
3. Numerical Method

1. what are the assumptions used in Lumped capacity analysis?
1.  Solid materials have infinite (very large) value of ‘k’.
2.  The conductance resistance or internal resistance is negligible as compared to convective resistance or external resistance.
3.  Temperature is assumed to be constant at a given time in such solids.
4.  Thus rate of change of internal energy is linked with convective heat exchange at the surface of the solid.
1. What is a conduction shape factor?

In Convection          q. =h A dT

In conduction,          q. = -k A (dT/dx)

Compare and write conduction equation as       q.  = k S dT

Here S is the shape factor and S = – k/dx in conduction

S =h in convection

1. What is LUMPED CAPACITY?

It the product of Biot number and Fourier number as given below.

hAst /ρVC = (hV/ (kAs)) (As2kt/ (ρV2C)) = (hLc/k) (αt/Lc2))

1. List some of the areas which are covered under the discipline of heat transfer.

(i) Fins in compressors, in motors, on condensers and evaporators, on transformers

(ii) Heat exchanger like condenser, evaporator and a boiler

(iii)Transfer of  Heat  from the Sun, from fire, from furnaces, from radiators.

1. State the assumptions used in Fourier law of heat conduction.
1.  Conduction under steady state conditions.
2.  The heat flow is 1 dimensional.
3.  The temperature gradient is constant and the temperature profile is linear.
4.  There is no internal heat generation.
5.  The bounding surfaces are at respective constant temperature.
6.  The material is homogeneous and isotropic (The value of ‘k’ is constant in all directions).
1. List some essential features of Fourier Law.
1.  This law is applicable to solids, liquids and gases.
2.  Fourier law is based on experimental data and hence cannot be derived from first principle.
3.  Heat transfer is vector expression and indicates that the rate of flow of heat in the temperature decreasing direction.
4.  It gives the definition of thermal conductivity, a transport property.
1. What is thermal contact resistance?.

When two solid bodies come in contact, heat flows from the hotter body to the colder body. There is a temperature drop at the common surfaces in contact. It is due to the thermal contact resistance existing because of imperfect contact between the two contacting surfaces. Further it is due to irregular surfaces. Thermal contact resistance is the ratio of temperature drop and the average heat flow across the contacting surfaces.

## BOOT STRAP AND REDUCED AMBIENT AIRCRAFT COOLING SYSTEMS

AIR REFRIGERATION

It is used in aircrafts of the entire world. There are different cooling arrangements for the air conditioning of aircrafts. Here boot strap and reduced ambient cooling systems are discussed here.

BOOT STRAP AND REDUCED AMBIENT AIRCRAFT COOLING SYSTEMS

Boot Strap Air Refrigeration System: Two systems

1. Without evaporative cooling,
2. With evaporative cooling FIG. BOOT STRAP SYSTEM ON TEMPERATURE ENTROPY CHART

In this, there are two compressors, two heat exchangers and one turbine. Normally second compressor is run by the expansion turbine. In case of evaporative cooling in Boot strap, another water cooled heat exchanger is placed after the second heat exchanger in Fig. above.

Reduced Ambient Air Refrigeration System Fig. REDUCED AMBIENT AIRCRAFT COOLING SYSTEM ON TEMP ENTROPY CHART

It uses two turbines and one compressor. Turbine 1 uses rammed air. The air from turbine 1 enters the heat exchanger. Turbine 2 uses air after the heat ex-changer for further cooling.

Turbine 1 has input and output points as 2 and 4.

Cooled air from turbine 1 enters the first Heat exchanger at point 4.

Heat exchanger has input at points 3 and 5.

CAUTION: RAMMED AIR IS NOT USED IN THE HEAT EXCHANGER BECAUSE RAMMED AIR IS FED TO TURBINE 1.

Turbine 2 has input and output points as 5 and 6.

Procedure of calculation is similar to the BOOT STRAP SYSTEM.

## CLOSE COILED HELICAL SPRING -AXIAL TORQUE

### CLOSE COILED HELICAL SPRING -AXIAL TORQUE

This torque will rotate the free end with respect to the fixed end. Thus it will change the coil diameter and will be mainly producing the bending effect. Therefore such springs are designed on the basis of pure bending. Further helix angle ‘α’ is small.

Let φ be the total angle through which the free end of the spring turns relative to the free end when the axial couple is applied.

Use bending equation for its analysis

M/I = σ/y = E/R

σ =(M/I) y

Then M = EI/R

Here R is the radius of the coil

L= 2πRn

where n is the number of turns in the spring

Bending equation gives 1/R =M/EI

Thus Φ = ML/EI

Work done =W= (1/2) Mφ = M2L/2EI

I = πd4/64

Substituting the value of ‘I’ in Φ, we get

Φ =M 2πRn/(E πd4/64) =128R n M/Ed4

Maximum stress in the spring wire due to axial couple will be

Bending stress, σ

σ= (M/I)y=[M/(π/64d4)] x d/2= 32M/πd3

ALTERNATIVELY FROM STRAIN ENERGY

Same expression can also be achieved from the strain energy.

Strain energy in bending is given by

U bending = M2L/2EI

(1/2)M Ф = M2L/2EI

Ф =ML/EI= M 2πRn/(2E (π/64)d4 )

Ф =128MRn/Ed4 = 64WDn/Ed4

Bending stress, σ

σ= (M/I)y=[M/(π/64d4)] x d/2= 32M/πd3

Shear stress ԏ =0

Principal stress σ1 = σb

Maximum shear stress

ԏmax = σb/2

Angle of twist ϴ =0

Axial deflection δ =0

Resilience

U =M2L/2EI

But M/I =σ/y

M = σI/y = σ I/(d/2)= 2σI/d

M2 =( 2σI/d)2 = 2σ2 I2/d2

Therefore= U =(2σ2 I2/d2 )L/2EI = 2σ2 (π/64)d4/E d2 = U =(σ2/8E)(π/4)d2 L =(σ2/8E)(Volume of spring wire)

Resilience = u = U/V =  σ2/8E

Stiffness

Stiffness of spring  = k =  M/Ф Ed4/64Dn

FINAL RESULTS

Stress σ = 32M/πd3

Rotation of free end = Ф =64WDn/Ed4

Resilience = u= σ2/8E

Axial deflection = δ =0

## MCQ FIRST LAW OF THERMODYNAMICS

MCQ FIRST LAW OF THERMODYNAMICS

1. Total energy of the universe is
• (a) Increasing
• (b) Decreasing
• (c) Increasing as well as decreasing
• (d) None

Ans: (d)

1. As per First Law of Thermodynamics, energy can be
• (a) Created
• (b) Destroyed
• (c) Created as well as destroyed
• (d) None

Ans:(d)

1. As per First Law of Thermodynamics, energy cannot be
• (a) Created
• (b) Destroyed
• (c) Created as well as destroyed
• (d) None

Ans:(c)

1. Total energy of the universe is

(a) Increasing

(b) Decreasing

(c) Constant

(d) None

Ans: (c)

1. An intensive property is
• (a) Independent of volume
• (b) Independent of density
• (c) Independent of mass
• (d) None

1. Which of the following is an intensive property?
• (a) Volume
• (b) Enthalpy
• (c) Entropy
• (d) None

Ans: (d)

1. Which of the following is an intensive property?
• (a) Volume
• (b) Enthalpy
• (c) Temperature
• (d) None

Ans: (c)

1. Which of the following is NOT an intensive property?
• (a) Volume
• (b) Pressure
• (c) Temperature
• (d)None

Ans: (a)

1. Heat supplied to a system is
• (a) Work done –Change in internal energy
• (b) Work done +Change in internal energy
• (c) Work done Change in internal energy
• (d) None

Ans : (b)

1. Conversion of heat energy into mechanical work is
• (a) 100 %
• (b) 80%
• (c) 50%
• (d) None

Ans: (d)

1. Conversion of heat energy into mechanical work is
• (a) >100 %
• (b) <100%
• (c) =100%
• (d) None

Ans: (b)s

1. The temperature of a system is
• (a) Extensive property
• (b) Intensive property
• (c) Extensive as well as intensive property
• (d) None

Ans: (b)

1. Force is an
• (a) Extensive property
• (b) Intensive property
• (c) Extensive as well as intensive property
• (d) None

Ans: (a)

1. First law of thermodynamics is a law of
• (a) Conservation of enthalpy
•  (b)Conservation of entropy
• (c) Conservation of internal energy
• (d) None

Ans: (d)

1. First law of thermodynamics is a law of
• (a) Conservation of enthalpy
• (b) Conservation of entropy
• (c) Conservation of energy
• (d) None

Ans: ( c)

1. Which Property is related to the First Law of Thermodynamics?

(a)Enthalpy

(b) Entropy

(d)None

Ans: ( c )

1. An open system has
• (a) Only Mass transfer
• (b) Only Energy transfer
• (c) Mass as well as energy transfer
• (d) None

Ans: (c )

1. An closed system has
• (a) Only Mass transfer
• (b) Only Energy transfer
• (c) Mass as well as energy transfer
• (d) None

Ans: (a )

1. An isolated system has
• (a) Only Mass transfer
• (b) Only Energy transfer
•  (c)Mass as well as energy transfer
• (d) None

Ans: (d )

1. An isolated system has
• (a) No Mass transfer
• (b) No Energy transfer
• (c) No Mass and no energy transfer
• (d) None

Ans: (c )

1. Among the system, boundary and surrounding, the order is
• (a) System, surrounding and boundary
• (b) Surrounding, system and boundary
• (c) System, boundary and surrounding
• (d) None

Ans: (c )

1. A system consists of
• (a) System, boundary and surrounding
• (b) Pressure, temperature and volume
• (c) Intensive, extensive and internal energy
• (d) None

Ans: (a)

1. In a thermodynamic process, which one is NOT a path function?
• (a) Work done
• (b) Heat supplied
• (c) Internal energy
• (d) None

Ans: (c )

1. In a thermodynamic process, which one is a path function?
• (a) Work done
• (b) Enthalpy
• (c) Internal energy
• (d) None

Ans: (a )

1. First law of Thermodynamics deals with the Law of
• (a) Conservation of momentum
• (b) Conservation of mass
• (c) Conservation of internal energy
• (d) None

Ans : (d)

1. Increase in enthalpy causes
• (a) Increase in volume
• (b) Increase in pressure
• (c) Increase in mass
• (d) None

Ans: (d)

1. During an exothermic reaction, There is
• (a) Increase in enthalpy
• (b) Decrease in enthalpy
• (c) Remains constant
• (d) None

Ans : (b)

1. During an exothermic reaction, There is
• (a) Increase in mass
• (b) Decrease in mass
• (c) Mass remains constant
• (d) None

Ans : (b)

1.  Unit of enthalpy is
• (a) kJ/kg K
• (b) kJ/m3+
• (c) kJ/kg
• (d) None

Ans: (c )

1. I. unit of temperature is
• (a) 0C
• (b) 0K
• (c) 0F
• (d) None

Ans: (d)

1. I. unit of temperature is
• (a) C
• (b) K
• (c) F
• (d) None

Ans: (b)

1. I. unit of mass is
• (a) g
• (b) kg
• (c) lb
• (d) None

Ans: (b)

1. I. unit of pressure is
• (a) Pascal
• (b) mm of Hg
• (c) bar
• (d) None

Ans: (c)

1. Example of a open thermodynamic system is
• (a) Refrigerator
• (b) Air conditioner
• (c) Compressor in a refrigerator
• (d) None

Ans: ( c)

1. Example of a closed thermodynamic system is
• (a) Evaporator in a Refrigerator
• (b) Condenser in an Air conditioner
• (c) Compressor in a refrigerator
• (d) None

Ans: ( d)

1. Which is the thermodynamic system in a human body ?
• (a) Open system
• (b) Closed system
• (c) Isolated system
• (d) None

Ans: (a)

1. The S.I. unit of power is

(a) Newton

(b) Pascal

(c) Joule

(d) None

Ans: (d)

1. Which of the following is NOT a point function?
• (a) Temperature
• (b) Entropy
• (c) Pressure
• (d) None
• Ans: (d)
1. . Which of the following is NOT a point function?
• (a) Temperature
• (b) Entropy
• (c) Heat
• (d) None

Ans: (c)

1. Temperature remains constant in
• (a) Dalton’s Law
• (b) Charles Law
• (c) Raoult’s Law
• (d) None

Ans: (d)

1. Temperature remains constant in
• (a) Dalton’s Law
• (b) Charles Law
• (c) Boyle’s Law
• (d) None

Ans: (c)

M E Subjects – Mechanical Engineering Concepts Simplified

Various topics of Mechanical Engineering presented here are in a simple manner. Following courses can be easily understood as it is based on our vast teaching experience. Anybody can make things complex. It is really very difficult to make things/topics simple. Such an attempt has been made to make every article simple to read, simple to understand and simple to reproduce. Matter has been taken from the literature available. but every effort has been made to make it as simple as possible. Matter has been written in small sentences and in a simple manner.

• Strength of Materials
• Heat Transfer
• Refrigeration and Air Conditioning
• Thermodynamics
• Fluid Mechanics
• Theory of Machines
• Mechanical Vibrations
• Internal and External Engines
• Engineering Drawing
• Manufacturing
• Multiple Choice Questions on each main as well as sub topics

• Strength of Materials
• Load, Force, Weight, Types of Loads, Stress, Strain, Unit Stress, Unit Strain, Modulus, Simple and Composite Bodies,Elastic Properties, Stiffness, Poisson’s Ratio, Elastic Constants, Relation between Elastic Constants, Plastic Properties, Yield Strength, Ultimate Strength, Breaking Strength
• Ductile materials, Brittle Materials, Ductility, Malleability, Hardness, Strain Energy, Toughness
• Thermal Stress, Thermal Strain
• Complex Stresses, Principal Stresses, Principal Strains, Principal Planes, Maximum Shear Stress, Planes of Maximum Shear Stress, Angle of Obliquity
• Shear Force Diagram, Bending Moment Diagram, Point of contra-flexure
• Type of beams  bending stress, bending strain in simple and composite beams, moment of inertia, section modulus, Moment of Resistance
• Combined Bending and Axial Loading, Middle Third Rule, Middle Quarter Rule
• Shear stresses in a beam
• Slope and Deflection
• Torsion: Stresses/ strains/ strain energy in circular shafts under Torsion/ (Torsion + bending Moment)/ (under Torque+ Bending Moment+ Axial Thrust)
• SPRINGS: Stress/ deflection/ stiffness/ strain energy in Laminated/ Close coiled/ Open coiled springs
• COLUMNS AND STRUTS: Stresses/ strains in Short, Medium and Long Columns, Slenderness Ratio, Buckling of a column, Equivalent length, Rankine formula, Euler formula, Eccentric loading, Eccentricity
•  Thin and Thick Walled Pressure Vessels (Cylindrical and Spherical)
• Strain Energy in Tension/ Compression/ Bending/ Torsion
• STIFFNESS: Tension stiffness/ compression stiffness/ bending stiffness/ torsion stiffness ,spring stiffness
• Heat Transfer – Difference between heat transfer and thermodynamics, Modes of heat Transfer (Conduction, Convection and Radiation )
• Fourier Law of Conduction(in Rectangular, Cylindrical and Spherical Coordinates)
• Newton’s Law of Convection
• Stefan’s- Boltzmann Law of Radiation
• Conductive Heat Transfer Coefficient (Thermal Conductivity), Convective Heat Transfer Coefficient, Radiation Heat Transfer Coefficient, Overall Heat Transfer Coefficient
• Practical Applications of Conduction, Convection, Radiation
• Thermal Resistance in Conduction, Convection, Radiation
• Fins and Heat Exchangers:  Types of fins and Heat Exchangers, Parallel and Counter-flow Heat Exchangers
• Laws of Radiation, Absorptivity, Reflectivity and Transmissivity, Surface Resistance, Space Resistance, Radiation Shape Factors, Shape Factor Algebra, Radiation Exchange between black and real bodies, Radiation Shields
• Refrigeration and Air Conditioning – Definition of Refrigeration, Air-Conditioning and Cryogenics, Methods of Refrigeration, Air- Conditioning and Cryogenics, Practical Applications of refrigeration, Air-Conditioning and Cryogenics
• Carnot and Reverse Carnot Cycle, Gas Refrigeration Cycle, Reverse Rankine Cycle, Cooling Effect, Heating Effect, Cooling Capacity, Heating Capacity, Work input, Coefficient of Performance
• Pressure – Enthalpy Chart,  Temperature-Entropy Chart, Vapor Compression Refrigeration Cycle, Vapor Absorption Cycle, Gas Refrigeration Cycle and its Types, Rate of Refrigerant Flow, Quality of Refrigerant After The Expansion Valve, Volumetric Efficiency
• Steam-Jet Refrigeration, Multi-compressor- Multi-Evaporator Refrigeration, Thermo-electric Refrigeration, Magnetic cooling
• Liquefaction of Air, Oxygen, Nitrogen, Hydrogen and Helium
• Refrigerants (Primary, Secondary, Tertiary, Organic, inorganic and Azeotrope) , Types of Refrigerants
• Compressors, Condensers, Expansion Devices, Evaporators, Pipes, Desiccants, Anti-freezes, Lubricating Oils, Liquid Suction Heat-Exchanger, Accumulator, Oil Separator, Receiver, Solenoid Valve and Defrosting
• Refrigerant and Air –Conditioning Controls-Capillary Tube, Automatic Expansion Valve, Thermostatic Expansion Valve, Low side Float Valve, High Side Float Valve, Thermostat, Low and High Pressure cut-outs and Cut-ins, Low and High Voltage Cut-outs and Cut-ins.

CONTINUED ON PAGE 2

## FLUID MECHANICS INTRODUCTION-2

FLUID MECHANICS INTRODUCTION-2

Fluid Mechanics is a science which deals all aspects of  fluids. It studies the fluids whether in motion or static. Fluid is a common name to liquids, vapors and gases.

Three parts of fluid mechanics

Fluid statics

It deals with forces applied by fluids at rest. This fluid force is pressure. Pressure is a normal force exerted by a fluid per unit area. It is called the static pressure of the fluid. Some laws are used in fluid statics. These laws are

Pascal’s law

It states that the pressure applied by an enclosed liquid will be transmitted equally in all directions.

Newton’s Law

It is applied to a static fluid. Thus, ΣF = ma = 0 for a static fluid.

ΣFx = ΣFy = ΣFz = 0. It deals with equilibrium of forces on a fluid.

Buoyancy Law (Archimedes’ principle)

States that a body completely or partially submerged in a fluid (liquid or gas) AT REST is acted upon by an upward buoyant force. The magnitude of which is equal to the weight of the fluid displaced by the body.

(b)Fluid Kinematics

Deals with fluids in motion without considering forces or energy acting. In this, we study displacement, velocity and acceleration. The other name of kinematics is geometry of motion. In this, we study ideal fluid, real fluid, in-compressible and compressible fluid. Thus, we also study various types of flows. For example,

(i) Laminar flow

(ii) Turbulent flow

(v) Uniform flow

(vi) Non-uniform flow

(vii) Rotational flow

(viii) Ir-rotational flow

(ix) One, two and three dimensional flows

There are two ways to study fluid mechanics. Out of Lagrangian and Eulerian methods, Eulerian method is used as it is relatively easy to apply. It concerns velocity field and continuity equation.

© Fluid Dynamics deals with fluids in motion with forces/energy acting on the moving fluids.

Three types of fluids

• Liquids are in-compressible. There is no effect of pressure and temperature. Examples of liquid are water, milk, kerosene oil, petrol, fatty oils etc.
• Vapor is compressible. Vapors are effected by pressure and temperature. It is studied only with the help of tabular data and charts.  Gas laws are not applicable to vapors. Examples of vapors are steam and refrigerants.
• Gases are compressible. These are effected by pressure and temperature. It is studied with gas laws and universal equation. Examples of gases are air, oxygen, nitrogen, hydrogen etc.

EXAMPLES OF MOVING FLUIDS

1. Water flowing in pipe lines at home or factory
2. Refrigerant flowing in a refrigerator or air conditioner
3. Water flowing in water turbines and pumps
4. Steam flowing in pipes to steam turbines
5. Gas flowing to gas turbines
6. Blood flowing in the human body

FLUID MECHANICS STUDY APPROACH

NOTE: Why we consider the motion of a fluid particle in a fluid motion?

There is a basic difference between the motion of a solid and the motion of a fluid. A solid body is compact and moves as one element. There is no relative motion between the particles of a solid body. Thus, we study the motion of the entire body. Therefore, there is no necessity to study the motion of any particle of a solid body. But in fluids, we consider the motion of individual particles. Because, there is relative motion between various fluid particles.

Prototypes help in the study of fluid mechanics. Further, prototypes are small size working objects for pumps, turbines, submarines, airplanes and dams. These prototypes should have geometric, dimensional, kinematic and dynamic similarities. Of course, study is carried out with empirical equations using dimensionless numbers.