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CONSECUTIVE 15 ANNA UNIVERSITY QUESTION PAPER

B.E./B.Tech. DEGREE EXAMINATIONS, NOV./DEC. 2011Regulations 2008

Third Semester Mechanical EngineeringME2202 Engineering Thermodynamics

( Common to PTME 2202 Engineering Thermodynamics for B.E.(Part

-Time) Third Semester Mech - Regulations 2009; Use of approved

thermodynamic tables, Mollier diagram, Psychometric chart and Refrigerant

property tables are permitted in the examination.)

Time: Three Hours Maximum: 100 marks

Answer ALL Questions

Part A - (10 x 2 = 20 marks)

1. Distinguish between the terms 'state' and 'process' of thermodynamics.2. Show that energy of an isolated system is always constant.

3. What is a cyclic heat engine?4. What do you mean by entropy generation?

5. What is a pure substance? Give examples.

6. Why is Carnot cycle not practicable for a steam power plant?

7. What is equation of state? State the van der Waals equation for a real gas of m kg.

8. What is the partial pressure of carbon dioxide in a container that holds 5 moles of carbon

dioxide, 3 moles of nitrogen and 1 mole of hydrogen and has a total pressure of 1.05 atmospheres?

9. What is a psychrometer?

10. Sketch the Cooling and Humidifying process on a skeleton Psychrometric chart.Part B - (5 x 16 = 80 marks)

11. (a) (i) Define the following terms:

(1) Thermodynamics(2) Macroscopic approach

(3) Continuum(6)

(ii) 25 people attended a farewell party in a small room of size 10 x 8 m and have a 5 m ceiling.

Each person gives up 350 kJ of heat per hour. Assuming that the room is completely sealed off

and insulated, calculate the air temperature rise occurring in 10 minutes. Assume Cv of air

0.718 kJ/kg K and R = 0.287 kJ/kg K and each person occupies a volume of 0.05 m3. Take p

= 101.325 kPa and T = 20C. (10)OR

11. (b) (i) Considering a system which changes its state, prove that the internal energy is a

point function. (8)

(ii) Air flows at the rate of 0.5 kg/s through an air compressor, entering at 7 m/s,, 100 kPa and 0.95m3/kg and leaving at 5 m/s, 700 kPa, and 0.19 m

3/kg. The internal energy of air leaving is 90 kJ/kg

greater than that of the air entering. Cooling water in the compressor jackets absorbs heat from the air

at the rate of 58 kW. (1) Compute the rate of shaft work input to the air in kW (2) Find the ratio of the

inlet pipe diameter to outer pipe diameter. (8)

12. (a) (i) An engine is supplied with 1120 kJ/s of heat. The source and sink temperature aremaintained at 560K and 280K. Determine whether the following cases represent the reversible,

irreversible or impossible heat engines.

(1) 900 kW of heat rejected

(2) 560 kW of heat rejected

(3) 108 kW of heat rejected(8)
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(ii) A heat pump working on the Carnot cycle takes in heat from a reservoir at 5C and delivers

heat to a reservoir at 60C. A heat engine is driven by a source at 840C and rejects heat to a reservoirat 60C. The reversible heat engine, in addition to driving the heat pump, also drives a machine that

absorbs 30 kW. If the heat pump extracts 17 kJ/s from the 5C reservoir, determine (1) the rate of heatsupply from the 840C source, and (2) the rate of heat rejection to the 60C sink. (8)

OR

12. (b) (i) Derive an expression for the change in entropy of a perfect gas during polytropicprocess in terms of T1 and T2. (8)

(ii) 2 kg of water at 90C is mixed with 3 kg of water at 10C in an isolated system. Calculate the

change of entropy due to the mixing process. (8)

13. (a) Two streams of steam, one at 2 MPa, 300C and the other at 2 MPa, 400 C, mix in asteady flow adiabatic process. The rates of flow of the two streams are 3 kg/min and 2 kg/min

respectively. Evaluate the final temperature of the emerging steam, if there is no pressure drop due to

the mixing process. What would be the rate of increase in the entropy of the universe? This steam

with negligible velocity now expands adiabatically in a nozzle to a pressure of 1 kPa. Determine the

exit velocity of the stream and exit area of the nozzle.(16)

OR13. (b) (i) Define specific steam consumption, specific heat rate and work ratio. (6)

(ii) In a Rankine cycle, the steam at inlet to turbine is saturated at a pressure of 35 bar and the

exhaust pressure is 0.2 bar. The flow rate of steam is 9.5 kg/s. Determine (1) the pump work (2) the

turbine work (3) Rankine efficiency (4) condenser heat flow (5) work ratio and (6) specific steamconsumption. (10)

14. (a)(i) A vessel of volume 0.3 m3

contains 15 kg of air at 303 K. Determine the pressure exerted

by the air using, (1) Perfect gas equation (2) van der Waals equation. Take critical temperature of air

as 132.8 K. Critical pressure of air is 37.7 bar. (6)

(ii) A perfect gas mixture consists of 4 kg of N2 and 6 kg of CO2 at a pressure of 4 bar and a

temperature of 25C. For N2: Cv = 0.745 kJ/kgK and Cp = 1.041 kJ/kgK. For CO2: Cv = 0.653

kJ/kgK and Cp = 0.842 kJ/kgK. Find Cp , Cv and R of the mixture. If the mixture is heated at constant

volume to 50C, find the changes in internal energy, enthalpy and entropy of the mixture.(10)

OR14. (b) (i) Derive and explain the Maxwell's relations. (8)

(ii) Derive the T dS equation taking T and p as independent variables. (8)

15. (a) Atmospheric air at 1.0132 bar has a DBT of 32C and a WBT of 26C. Find(i) the

partial pressure of water vapour (ii) the specific humidity (iii) the dew point temperature (iv) the

relative humidity (v) the degree of saturation (vi) the density of the air in the mixture (vii) the density

of the vapour in the mixture (viii) the enthalpy of the mixture. (8x2 = 16)OR

15. (b) (i) Explain the process of heating with humidification of air, with the help of sketches of

schematic of air duct with the elements involved as well as the representation on psychrometric chart.(6)

(ii) 1 kg of air at 40C DBT and 50% relative humidity is mixed with 2 kg of air at 20C DBT and

20C dew point temperature. Calculate the specific humidity, enthalpy and the dry bulb temperature

of the mixture. (10)

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B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2011

Third Semester

Mechanical EngineeringME 2202 ENGINEERING THERMODYNAMICS (Regulation 2008)

(Common to PTME 2202 Engineering Thermodynamics for B.E (Part-Time) Mechanical

Engineering Third Semester - Regulation 2009)

Time : Three hours Maximum : 100 marks

Answer ALL questionsPART A (10 x 2 = 20 marks)

1.Calculate the actual pressure of air in the tank if the pressure of compressed air

measured by manometer is 30 cm of mercury and atmospheric pressure is 101 kPa. (Take g

= 9.78 m/s2)

2. What is meant by 'Hyperbolic Process'?

3. List out the generic types of irreversibilities.4. State : Carnot Theorem and Its Corollaries.

5. What do you understand from the word 'Dryness fraction'?

6. What are the ways by which Rankine cycle efficiency may be improved?

7. State : Dalton's law of partial pressures.8. What do you mean by Compressibility factor?

9. Define : Relative humidity.

10. What do you understand from the Dew point temperature?

PART B (5 x 16 = 80 marks)

11. (a) A gas contained in a cylinder is compressed from 1 MPa and 0.05 m3 to

2 MPa. Compression is governed by pF" constant. Internal energy of gas is given by; U =7.5 PV

-425, kJ. where P is pressure in kPa and V is volume in m3. Determine heat, work and change in

internal energy assuming compression process to be quasistatic. Also find out work interaction, if the

180 kJ of heat is transferred to system between same states.Also explain why it is different fromabove? (16)

Or

(b) In a gas turbine installation air is heated inside heat exchanger up to 750 C from ambient

temperature of 27 C. Hot air then enters into gas turbine with the velocity of 50 m/s and leaves at 600

C. Air leaving turbine enters a nozzle at 60 m/s velocity and leaves nozzle at temperature of 500 C

For unit mass flow rate of air determine the following assuming adiabatic expansion in turbine and

nozzle, (16)(i) Heat transfer to air in heat exchanger (ii) Power output from turbine (iii) Velocity

at exit of nozzle. Take up for air as 1.005 kJ/kg K.

12. (a) A reversible heat engine operates between two reservoirs at 827 C and 27C.

Engine drives a Carnot refrigerator maintaining -13C and rejecting heat to reservoir at 27C. Heat

input to the engine is 2000 kJ and the net work available is 300 kJ. How much heat is transferred to

refrigerant and total heat rejected to reservoir at 27 C? (16)

Or

(b) (i) How do you differentiate the Exergy (Availability) and energy based upon their

characteristics? (4)

(ii) Determine the rate of power loss due to irreversibility in a heat engine operating betweentemperatures of 1800 K and 300 K. Engine delivers 2 MW of power when heat is added at the rate of

5MW. (12)

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13. (a) In a closed vessel the 100 kg of steam at 100 kPa, 0.5 dry is to be brought to apressure of 1000 kPa inside vessel. Determine the mass of dry saturated steam admitted at 2000 kPa

for raising pressure. Also determine the final quality.Or

(b) A steam power plant running on Rankine cycle has steam entering HP turbine at 20 MPa, 500

C and leaving LP turbine at 90% dryness. Considering condenser pressure of 0.005 MPa andreheating occurring up to the temperature of 500 C determine, (16)

(i) The pressure at which steam leaves HP turbine (ii) The thermal efficiency, (iii)

Work done.

14.(a)In 5 kg mixture of gases at 1.013 bar and 300 K the various constituent gasesare as follows, 80% N2, 18% O2, 2% CO2. Determine the specific heat at constant pressure, gas

constant for the constituents and mixture and also molar mass of mixture taking y = \A for N2 and

O2 and = 3.1 for CO2. Universal gas constant =8314J/kg.K. (16)

Or

(b) Derive the Clausius Clapeyron equations and Vander Waal's equations.(16)

15.(a) For the atmospheric air at room temperature of 30 C and relative humidity of 60%determine partial pressure of air, humidity ratio, dew point temperature, density and enthalpy of air.

(16)

Or

(b) Two streams of moist air, one having flow rate of 3 kg/s at30 C and 30% relative humidity,other having flow rate of 2 kg/s at 35Cand 85% relative humidity get mixed adiabatically. Determine

specific humidity and partial pressure of water vapour after mixing. Take CP, Stream = 1.86 kJ/kg.K.

(16)
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B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2010Third Semester

Mechanical EngineeringME 2202 ENGINEERING THERMODYNAMICS (Regulation 2008)

(Common to PTME 2202- Engineering Thermodynamics for B.E. (Part-Time) Third Semester

Mechanical Engineering Regulation 2009)Time : Three hours Maximum : 100 Marks

(Use of Standard Thermodynamic tables, Mollier diagram,

Psychrometric Chart and Refrigerant Property Tables is permitted)

Answer ALL questions

PART A (10 x 2 = 20 Marks)

1. What are point and path functions? Give some examples.

2. Distinguish between stored energies and interaction energies.

3. What is the difference between a refrigerator and a heat pump?

4. How do the values of the integrals compare for a reversible and irreversible process

between the same end states?5. Why are the temperature and pressure dependent properties in the saturated mixture

region?

6. What are the four processes that make up the simple ideal Rankine cycle?

7. Using the definitions of mass and mole fractions derive a relation between them.8. What does Joule Thomson coefficient represent?

9. How do constant-enthalpy and constant wet bulb temperature lines compare on the

psychrometric chart?

10. Moist air is passed through a cooling section where it is cooled

and dehumidified. How do the specific humidity and the relative humidity of air change during

this process?

PART B (5 x 16 = 80 Marks)

11. (a) A rigid tank containing 0.4 m3 of air at 400 kPa and 30C is connected by a valve to a

piston cylinder device with zero clearance. The mass of the piston is such that a pressure of 200 kPa isrequired to raise the piston. The valve is opened slightly and air is allowed to flow into the cylinder

until the pressure of the tank drops to 200 kPa. During this process, heat is exchanged with the

surrounding such that the entire air remains at 30C at all times. Determine the heat transfer for this

process. (16)

Or

(b) The electric heating system used in many houses consists of simple duct with resistance wire.

Air is heated as it flows over resistance wires. Consider a 15 kW electric heating system. Air entersthe heating section at 100 kPa and 17C with a volume flow rate of 150 m3/min. If heat is lost from the

air in the duct to the surroundings at a rate of 200 W. determine the exit temperature of air.(16)

12. (a) Air is compressed by an adiabatic compressor from 100 kPa and 12 C to a

pressure of 800 kPa at a steady rate of 0.2 kg/s. If the isentropic efficiency of the compressor is 80

percent, determine the exit temperature of air and the required power input to the compressor.(16)

Or

(b) A 200 m3

rigid tank initially contains atmospheric air at 100 kPa and 300 K and is to be used as

storage vessel for compressed air at 1 Mpa and 300 K. Compressed air is to be supplied by a

compressor that takes in atmospheric air at Po = 100 kPa and To = 300 K. Determine the minimum

work required for this process. (16)

13. (a) (i)A 0.5 m3

vessel contains 10 kg refrigerant 134a at -20C. Determine the pressure, the
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total internal energy and the volume occupied by the liquid phase. (6)

(ii) A rigid tank with a volume of 2.5 m3

contains 15 kg of saturated liquid vapour mixture ofwater at 75C. Now the water is slowly heated. Determine the temperature at which the liquid in the

tank is completely vaporized. Also, show the processes on T-v diagram with respect to saturationlines. (10)

Or

(b) Consider a steam power plant that operates on a reheat Rankine cycle and has a net poweroutput of 80 MW. Steam enters the high-pressure turbine at 10 MPa and 500C and the low-pressure

turbine at 1 MPa and 500C. Steam leaves the condenser as a saturated liquid at a pressure of 10 kPa.

The isentropic efficiency of the turbine is 80 percent, and that of the pump is 95 percent. Show the

cycle on a T-s diagram with respect to saturation lines, and determine

(i) the quality (or temperature, if superheated) of the steam at the turbine exit,(ii) the thermal efficiency of the cycle, and

(iii) the mass flow rate of the steam. (16)

14. (a) (i)A rigid tank contains 2 kmol of N2 and 6 kmol of CO2 gases at 300 K and 15 MPa.

Estimate the volume of the tank on the basis of

(1) the ideal-gas equation of state,(2) compressibility factors and Amagat's law, and

(3) compressibility factors and Dalton's law. (8)

(ii) An insulated rigid tank is divided into two compartments by a partition. One compartment

contains 7 kg of oxygen gas at 40C and 100 kPa, and the other compartment contains 4 kg ofnitrogen gas at 20C and 150 kPa. Now the partition is removed, and the two gases are allowed to

mix. Determine

(1) the mixture temperature and

(2) the mixture pressure after equilibrium has been established.(8)

Or

(b) (i) Using the ideal-gas equation of state, verify

(1) the cyclic relation and (2) the reciprocity relation at constant P. (4)

(ii) Show that the internal energy of an ideal gas and an incompressible substance is a

function of temperature only, u = u(T). (6)

(iii) Derive expressions [puloP)T and {phiov)T in terms of P, v, and T only (6)

15. (a) (i) A 5 m x 5 m x 3 m room contains air at 25C and 100 kPa at a relative humidity of 75

percent. Determine

(1) the partial pressure of dry air,

(2) the specific humidity,

(3) the enthalpy per unit mass of the dry air, and

(4) the masses of the dry air and water vapour in the room. (8)(ii) The dry and the wet-bulb temperatures of atmospheric air at 1 atm (101. 325 kPa) pressure are

measured with a sling psychrometer and determined to be 25C and 15C respectively. Determine

(1) the specific humidity,(2) the relative humidity, and

(3) the enthalpy of the air using thermodynamic relations. (8)

Or

(b) (i)What is sensible heat? How is the sensible heat loss from a human body affected by the (1)

skin temperature,(2) environment temperature, and (3)air motion? (6)

(ii) Saturated air leaving the cooling section of an air-conditioning system at 14C at a rate of 50

m3/min is mixed adiabatically with the outside air at 32C and 60 percent relative humidity at a rate of

20 m3

/min. Assuming that the mixing process occurs at a pressure of 1 atm, determine the specifichumidity, the relative humidity, the dry bulb temperature, and the volume flow rate of the mixture.

(10)
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B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010 ,

Third Semester

Mechanical Engineering

ME2202 ENGINEERING THERMODYNAMICS

(Regulation 2008)

Time: Three hours Maximum: 100 Marks

(Use of Standard Thermodynamic Tables, Mollier Diagram, Psychometric Chart and

Refrigerant Property Tables is permitted)


PART A (10 x 2 = 20 Marks)

1. What do you understand by flow work? Is it different from displacement work?2. Which property of a system increases when heat is transferred:

(a) At constant volume(b) At constant pressure?

3. What do you understand by dissipative effects? When work is said, to be dissipated?4. Isentropic process need not be necessarily an adiabatic process - Justify.5. What is.critical state? Define the term critical pressure, critical temperature and critical

volume of water.

6. Why is Carnot Cycle not practicable for a steam power plant?7. Write down the Vender Waals equation of state. How does it differ from the ideal gas

equation of state?

8. Define Joule - Kelvin effect. What is inversion temperature?9. Define specific humidity. How does it differ from relative humidity?10. What is evaporative cooling? Will it work in humid climates?


11. (a) (i) The resistance of the windings in a certain motor is found to be 75 ohms atroom temperature (25C). When operating under full load under steady state conditions,

the motor is switched off and the resistance of the windings is immediately measuredagain and found to be 90 ohms. The windings are made of copper whose resistance at

temperature at t C is given by Rt = R0 [1+0.00393t] where Ro is the resistance at

0C. Find the temperature by the coil during full load. (8)

(ii) At the beginning of the compression strode of a two-cylinder

internal combustion engine the air is at a pressure of 101.325 kPa. Compression reduces

the volume by 1/5 of its original volume, and the law of compression is given by pv1.2

=

constant. If the bore andstroke of each cylinder is 0.15 m and 0.25 m respectively,

determine the power absorbed in kW by compression strokes when the engine speed

is such that each cylinder undergoes 500 compression strokes per minute. '

(8)Or
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(b) (i) The properties of a system, during a reversible constant pressure non-flow process atP = 1.6 bar changed from v1=0.3m

3/kg,T1 =20C to v2 = 0.55m3/kg, T2 =260C. The

specific heat of the fluid is given by Cp = [1.5+(75/T+45)] kJ/kgC where T is in C.Determine, the heat added, work done, change in internal energy and change inenthalpy per

kg of fluid. (8)

(ii) A nozzle is a device for increasing the velocity of a steadily flowing stream. At the inlet to

a certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and the velocity is 60 m/s. At

the discharge end, the enthalpy is 2762 kJ/kg. The nozzle is horizontal and there is negligible

heat loss from it.

(1) Find the velocity at exit from the nozzle.(2) If the inlet area is 0.1 m2 and the specific volume at the inlet 4 is 0.187 m3/kg,

find the mass flow rate.

(3) If the specific volume at the nozzle exit is 0.498 m3/kg, find the exit area of the

nozzle. (8)

12. (a) (i) Show that the efficiency of a reversible engine operating between twogiven constant temperatures is the maximum. (8)

(ii) A heat pump working on the Carnot cycle takes in heat from a reservoir at 5C and

delivers heat to a reservoir at 60C. The heat pump is driven by u reversible heat engine whichtakes heat from reservoir at 840C and rejects heat to a reservoir at 60C. The reversible heat

engine also drives a machine that absorbs 30 kW. If the heat pump extracts 17 kJ/s from the

reservoir at 5C, determine

(1) The rate of heat supply from 840C source, and

(2) The rate of heat rejection to 60C sink. (8)

Or

(b) (i) Determine the maximum work obtainable by using one finite body at temperature T and

a thermal energy reservoir at temperature To, T>T0. (8)

(ii) An aluminium block (cp =400J/kgK) with a mass of 5 kg is initially at 40C in

room air at 20C. It is cooled reversibly by transferring heat to a completely reversible cyclic

heat engine until the block reaches 20C. The 20C room air serves as a constant temperature

sink for the engine. Compute

(1) The change in entropy for the block,

(2) The change in entropy for the room air,

(3) The work done by the engine. (8)

13. (a) (i) Steam flows through a small turbine at the rate of 5000 kg/h entering at 15 bar 300Cand leaving at 0.1 bar with 4% moisture. The steam enters at 80 m/s at a point 2 m abovethe discharge and leaves at 40 m/s. Compute the shaft power assuming that the device is

adiabatic but considering kinetic and potential energy changes. Calculate the diameter of

the inlet and discharge tubes (8)

(ii) Steam expands isentropically in a nozzle from 1 MPa, 250C to 10 kPa.The steam flow

rate is 1 kg/s. Find the velocity of steam at the exit from the nozzle, and the exit area of the

nozzle-. Neglect the velocity of steam at inlet to the nozzle. The exhaust steam from the

nozzle flows into a condenser and flows out as saturated water. The cooling water enters thecondenser at 25C and leaves at 35C. Determine the mass flow rate. (8)

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Or

(b) (i) With a neat diagram explain the regenerative Rankine cycle with open feedwater heater(ii) In a thermal plant operating on a Rankine cycle, superheated steam at 50

bar and 500C enters a turbine, the isentropic efficiency of which is 0.8. Thecondenser pressure is 0.05 bar and it delivers saturated liquid to a feed pump, the isentropic

efficiency of which is 0.7. Determine the thermal efficiency of the power plant and the mass

flow rate of steam required for 50 MW net power generation. (8)

14. (a) (i)Explain how real gases deviate from an ideal gas behaviour? (4)(ii) Why does isothermal compression need minimum work and adiabatic

compression need maximum work?

(iii)A certain quantity of air initially at a pressure of 8bar and 280C has a volume of

0.035 m3. It undergoes a cycle consisting of the following processes:

(1) Expands at constant pressure to 0.1 m3.

(2) Follows polytropic process with n = 1.4

(3) A constant temperature process which completes the cycle.Evaluate the heat received and rejected in the cycle and cycle efficiency. (8)

Or

(b) (i) Derive the Clapeyron equation. (8)(ii) Over a certain range of pressures and temperatures the equation of a certain

substance is given by, the relation

V = (RT/p) - (C/T3)

where C is constant. Derive an expression for:

(1) The change of enthalpy.

(2) The change of entropy of this substance in an isothermal Process

15. (a) (i) Explain the process of cooling and dehumidification. (8)(ii) Explain with an example evaporative cooling. (8)

Or(b) (i) Two streams of air 25C, 50% RH and 25C, 60% RH are mixe

adiabatically to obtain 0.3 kg/s of dry air at 30C. Calculate the amounts of air drawn from

both the streams, and humidity ratio of the mixed air. (6)

(ii) An air-conditioned room requires 30 m3/min of air at 1.013 bar, 20C, 52.5%

RH. The steady flow conditioner takes in air at 1.013 bar, 77%RH, which it cools to adjust the

moisture content and reheats to room temperature. Find the temperature to which the air iscooled and thermal loading on both the cooler and heater. Assume that a fan before the cooler

absorbs 0.5 kW, and that the , condensate is discharged at the temperature to which the air is

cooled. (10)
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B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2009

Third Semester

Mechanical Engineering

ME 2202 ENGINEERING THERMODYNAMICS

(Regulation 2008)

Time: Three hours Maximum:100 Marks

(Use of Standard Thermodynamic Tables, Mollier Diagram, Psychometric

Chart and Refrigerant Property Tables is permitted)


PART A

1. What is the difference between the classical and the statistical approaches tothermodynamics?

2. State the zeroth law of thermodynamics3. What is the Kelvin-Planck expression of the second law of thermodynamics?4. Why is the second law, called a directional law of nature?5. Why is excessive moisture in steam undesirable in steam turbines?6. Why is the Carnot cycle not a realistic model for steam power plants?7. What does the Joule Thomson coefficient represent?8. In a gas mixture , which component will have the higher partial pressure-the one withthe higher mole number or the one with the larger molar mass?9. What is the difference between dry air and atmospheric air?10. When are the dry bulb and dew bulb temperature identical?


11. (a)A reciprocating air compressor takes in 2 m3/min air at 0.11 MPa, 293 K which itdelivers at 1.5 MPa, 384 K to an after cooler where the air is cooled at constant

pressure to 298 K. The power absorbed by the compressor is 4.15 kW. Determinethe heat transfer in (i)the compressor (ii) the cooler. State your assumptions

(16)Or

b) In a turbo machine handling an incompressible fluid .with a density of 1000 kg/m3

the conditions of the fluid at the rotor entry and exit are as given below :

Inlet Exit

Pressure 1.15 MPa 0.05

Velocity 30 m/sec 15.5 m/sec

Height above datum 10 m 2 mIf the volume flow rate of the fluid is 40m3/s, estimate the net energy transfer from the

fluid as work. (16)

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12. (a) The interior lighting of refrigerators is provided by incandescent lampswhose switches are actuated by the opening of the refrigerator door. Consider a refrigerator

whose 40W.light bulb remains on continuously as a result of a malfunction the switch. If therefrigerator has a coefficient of performance of 1.3 and the cost of electricity is Rs. 8 per kWh,

determine the increase in the energy consumption of the refrigerator and its cost per year if the

switch is not fixed. (16)Or

(b) (i) A Carnot heat engine receives 650 kJ of heat from a source of

unknown temperature and rejects 250 kJ of it to a sink at 297 K. Determine the

temperature of the source and the thermal efficiency of the heat engine.

` (6)(ii) A Carnot heat engine receives heat from a reservoir at 1173 K at a rate of 800

kJ/min and rejects the waste heat to the ambient air at 300 K. The entire work output of the

heat engine is used to drive a refrigerator that removes heat from the refrigerated space at 268

K and transfers it to the same ambient air at 300 K. Determine the maximum rate of heat

removal from the refrigerated space and the total rate of heat rejection to the ambient air (8)

13. (a) Consider a steam power plant operating on the ideal Rankine cycle Steam enters

the turbine at 3 MPa and 623 K and is condensed in the condenser at a pressure of 10 kPa.

Determine (i) the thermal efficiency of this power plant, (ii) the thermal efficiency if steam is

superheated to 873 K instead of 623 K, and (iii) the thermal efficiency if the boiler pressure israised to 15 MPa while the turbine inlet temperature js maintained at 873 K. (16)

Or

(b) Consider a steam power plant operating on the ideal reheat Rankine cycle. Steam enters

the high-pressure turbine at 15 MPa and 873K and is condensed in the condenser at a pressure

of 10 kPa If the moisture content of the steam at the exit of the low-pressure turbine is not to

exceed 10.4 percent, determine (i) the pressure at which the steam should be reheated and (ii)

the thermal efficiency of the cycle. Assume the steam is reheated to the inlet temperature of

the high-pressure turbine. (16)

14. (a)(i)Using the Clapeyron equation, estimate the value of the enthalpy of vaporization ofrefrigerant R 134a at 293 K, and compare it with the tabulated value.

(10)

(ii) Show that Cp - Cv = R for an ideal gas. (8)

Or

(b) (i) Show that the Joule-Thomson coefficient of an ideal gas is zero. (6)

(ii) Using the cyclic relation , and the first Maxwell relation, derive the other

three Maxwell relations (10)15. (a) (i) What is the lowest Temperature that air can attain in an

Evaporative cooler if it enters at 1 atm, 302 K, and 40 percent relative humidity? (4)

(ii) Consider a room that contains air at 1 atm, 308 K. and 40 percentrelative humidity. Using the psychrometric chart, determine: the specific humidity, the

enthalpy, the wet-bulb temperature, the dew-point temperature and the specific volume of

the air. (12)

Or

(b) An air-conditioning system is to take in outdoor air at 283 K and 30 percent

relative humidity at a steady rate of 45 m3/min and to condition it to 298 K and 60 percent

relative humidity. The outdoor air is first heated to 295 K in the heating section and then

humidified by the injection of hot steam in the humidifying section. Assuming the entireprocess takes place at a pressure of 100 kPa, determine (i) the rate of heat supply in the heating

section and (ii) the mass flow rate of the steam required in the humidifying section.

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B.E/B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010.

Third Semester Mechanical Engineering

ME 1201 ENGINEERING THERMODYNAMICS (Common to B.E. Production

Engineering) , (Regulation 2004)

(Common to B.E. (Part-Time) Second Semester Mechanical Engineering -Regulation 2005)

Time : Three hours Maximum marks : 100 marks

Answer ALL questions.

(Use of Steam Tables, Mollier diagram and Fsychrometric charts permitted).

PART A (10 x 2 = 20 marks)

1. What are point functions and path functions? Given examples.2. State the zeroth law of thermodynamics. Also give the thermodynamic

definition of work.

3. Enunciate the Kelvin-Planck statement of second law of thermodynamics.4. Give the expression for the COP of a heat pump in terms of source and sink temperatures.5. Define a pure substance.6. One kg ice melts at constant atmospheric pressure and at 0C to form liquid water. If the

latent heat of fusion of ice is 333.3 kJ/kg, calculate the entropy change during thisprocess.

7. What is the use of generalised compressibility chart?8. State any two applications of Clausius-Clapeyron equation. -9. Sketch the adiabatic saturation process on T-s diagram.10. Sketch the evaporative cooling process on a skeleton psychrometric chart.


11. (a) (i) State the first law of thermodynamics for a cycle and apply the

same to reversible cycles to prove that property energy exists. (8)

(ii) A gas of mass 1.5 kg undergoes a quasistatic expansion which follows the relationship,

p = a + bV where a and b are constants.The initial and final pressures are 1000

kPa and 200 kPa respectively and the corresponding volumes are 0.2 m

3

and 1.2 m

3

. The specificinternal energy of the gas is given by, u = l.5pv -85 kJ/kg where p is in kPa and v is in m3/kg.

Calculate the work done during the process. (8)

Or

(b) Air flows steadily at the rate of 0.5 kg/s through an air compressor entering at 7 m/s velocity,

100 kPa pressure, and 0.95 m3/kg specific volume, and leaving at 5 m/s, 700 kPa, and 0.19 m

3/kg. The

internal energy of air leaving is 90 kJ/kg greater than that of the air entering. .Cooling water in the

compressor jackets absorb heat at the rate of 58 kW. Calculate the rate of shaft work input to the

compressor. (16)

12. (a) (i) Prove that the Kelvin-Planck statement and Clausius statement ofsecond law of thermodynamics are equivalent. (8)

(ii) Represent the Carnot cycle on p-V and T-s planes and deduce an expression for

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thermal efficiency in terms of temperature. (8)

Or

(b) (i) Prove that the change in entropy during a polytropic process is

givenby S2-S1 =Cv(n-k/n-l)loge(T2/T1). Where k is the ratio of specific heats and n is the

index of compression or expansion. (8)

(ii) A closed system consists of 1 kg of air which is initially at 1.5 bar

and 67C The volume doubles as the system undergoes a process according to the law PV1.2 = C.

Find the work done, heat transfer and change in entropy. (8)

13. (a) In a steam generator compressed liquid water at 10 MPa, 30C enters a

30 mm diameter tube at the rate of 3 litres/sec. Steam at 9 MPa, 400C exits the tube. Find the rate

of heat transfer to the water. (16)

Or

(b) (i) Explain the factors which affect the thermal efficiency and quality of turbine exhaust ofRankine cycle. Justify your discussion using T-s diagrams. (8)

(ii) Sketch the Rankine regenerative cycle with one feed heater as schematic and T-s diagrams and

deduce the; expression for the thermal efficiency. (8)

14. (a) (i) Deduce the Maxwell's relations (8)

(ii) From the third relation of Maxwell deduce the Clausius-Clapeyron equation. (8)

. Or

(b) A mixture of 2 kg oxygen and 2 kg Argon is in an insulated piston cylinder arrangement at 100

kPa, 300 K. The piston compresses the mixture to half its initial volume. Find the final pressure,

temperature and piston work. Molecular weight of oxygen is 32 and argon is 40. Ratio of specific

heats for oxygen is 1.39 and for Argon, is 1.667. (16)

15. (a) (i) Define the Terms. Dew point, specific humidity, relative humidity, wet

bulb temperature. (4)

(ii) Describe how a psychrometric chart is constructed. Explain using pertinent equations for all

properties represented on it. (12)

Or

(b) Air at 40C DBT and 27C WBT is to be cooled and dehumidified by passing it over arefrigerant coil to give a final condition of 15C and 90% RH. Find the amounts of heat and moisture

removed per kg of dry air. (16)

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B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2009.

Third SemesterMechanical Engineering

ME 1201 ENGINEERING THERMODYNAMICS (Common to Production Engineering)(Common to B.E. (Part-Time) - Second Semester - Mechanical Engineering

- Regulation 2005)

(Regulation 2004) Time : Three hoursMaximum : 100 marks

(Use of standard thermodynamic tables, Mollier diagram, Psychrometric chart and Refrigerant

property tables permitted)

Answer ALL questions.PART A (10 x, 2 = 20 marks)

1. What is meant by Continuum? Identify its importance.

2. What is the requirement for the thermal equilibrium? Which law governs it?

3. Classify the following as point or path function: Heat, Enthalpy, Displacement work,

Entropy.4. Why is the COP of an heat pump is higher than that of a refrigerator, if they both operate

between the same temperature limits?

5. What is the triple point of water? Give the values of properties at that point.

6. What is meant by latent heat of vaporization?7. Is water vapour an ideal gas? Why?

8. If atmospheric air (at 101325 Pa) contains 21% oxygen and 79% nitrogen (vol. %), what

is the partial pressure of oxygen?

9. If the vapour pressure in the open atmosphere is 2.38 kPa atmospheric pressure is 100

kPa, calculate the specific humidity.

10. How do relative humidity, specific humidity, dew point temperature and wet bulb

temperature change during sensible cooling?


11. (a) (i) Distinguish between the reversible process and the cyclic process. (4)

(ii) Air contained in the cylinder and piston arrangement comprises the system. A cycle is

completed by four process 1-2, 2-3, 3-4 and 4-1. The energy transfers are listed below.

Complete the table and determine the network in kJ. Also check the validity of the first law of

thermodynamics. (8 + 2 + 2)

Process Q (kJ) W (kJ) U (kJ)1-2 40 ? 25

2-3 20 -10 ?

3-4 -20 ? ?

4-1 0 +8 ?

Or

(b) (i) Derive the suitable expression for the ideal compressor from the

steady flow energy equation and specify the assumptions under which such equation is

applicable. (4)

(ii) Calculate the power developed and diameter of the inlet pipe, if a gas enters into the gas

turbine at 5 kg/s, 50 m/s with an enthalpy of 0.9 MJ/kg and leaves at 150 m/s with an enthalpy of0.4 MJ/kg. The heat loss to the surrounding is 0.025 MJ/kg. Assume 100 kPa and 300 K at the

inlet. (8 + 4)

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12. (a) (i) Deduce the efficiency of Carnot cycle in terms of temperature fromits p-V diagram.

(4)(ii) Air is compressed from 100 kPa and 300 K to 5 bar isothermally and then it receives heat

at constant pressure. It is finally returns to its initial condition by a constant volume path. Plot theCycle on p-V and T-s diagram and calculate the net heat and work transfer.

(2 + 2 + 4 + 4)

Or

(b) (i)Bring out the concept of the Entropy and importance of T-s diagram.

(4)

(ii) Five kg of water at 303 K is mixed with one kg of ice at 0C. The system is open to

atmosphere. Find the temperature of the mixture and the change of entropy for both ice and water.Assume Cp of water as 4.18 kJ/kg-K and Latent heat of ice as 334.5 kJ/kg. Comment on the result

based on the principle of increase in entropy (4 + 4 + 4)

13. (a) (i) What is dryness fraction and degree of superheat (4)

(ii) Wet steam of 0.5 MPa and 95 % dry occupies 500 litres of volume. What is its internal

energy? If this steam is heated in a closed rigid vessel till the pressure becomes 1 MPa, find the heatadded. Plot the process on the Mollier chart. (5 + 5 + 2)

Or

(b) A regenerative cycle with three open feed water heaters works between 3 MPa, 450C and 4

kPa. Assuming that the bleed temperatures are chosen at equal temperature ranges, plot the process onh-s diagram and determine the efficiency of the cycle.

14. (a) (i) State the equation of state for van der wall's gas and explain the

importance of each term; Also bring out the limitations of the equation (3 + 3 + 2)

(ii) A gas mixture consists of 12 kg of methane, 5 kg of nitrogen and 3 kg of oxygen. Determine

the molecular mass and gas constant of the mixture. If the total pressure is 100 kPa, calculate their

partial pressures. (3 + 3 + 2)

Or

(b) (i) What is compressibility factor? Explain its significance. (2 + 2)

(ii) Deduce the expression for the Joule Thomson coefficient and hence plot the variation oftemperature with pressure for various enthalpies, marking all zones and boundaries. (8 + 4)

15. (a) (i) Deduce the relationship for specific humidity in terms of total

pressure and vapour pressure. (4)

(ii) If a room of 75 m3

contains air at 25C and 100 kPa at 75% relative humidity, determine the

partial pressure of dry air, specific humidity, enthalpy, mass of dry air and water vapour in the room.

(3 + 3 + 3 + 3)Or

(b) (i) How is the ratio of dry air flows related to specific humidity and enthalpy in an

adiabatic mixing? (4)(ii) In a power plant, cooling water leaves the condenser and enters a wet cooling tower at 35C at

a rate of 100 kg/s. water is cooled to 22.8C in the cooling tower by air that enters the tower at

101.325 kPa and 20C and 60% relative humidity and leaves saturated at 30C. Neglecting the fan

power, determine the volume flow rate of air in to the cooling tower and mass flow rate of the

required make up water. (8+4)

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B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2009.

Third Semester Mechanical Engineering

ME 1201 ENGINEERING THERMODYNAMICS (Common to B.E. Production

Engineering)

(Regulation 2004)

(Common to B.E. (Part-Time) Second Semester Mechanical Engineering) Time : Three

hours Maximum: 100 marks(Use of standard thermodynamic tables, Mollier diagram, Psychometric chart are

permitted)

Answer ALL questions. PART A (10 x 2 = 20 marks)1. What do you understand by flow work? Is it different from displacement work?2. What is PMM 1 ?3. Give the criteria of reversibility, irreversibility and impossibility of a

thermodynamic cycle.

4. What is meant by availability?5. Draw the phase equilibrium diagram for a pure substance on T-S plot with relevant

constant property line.

6. What is the effect of regeneration of a steam power plant?7. What is "Compressibility Factor"?8. State Dalton's law of partial pressures.9. Define dew point temperature.10. What is adiabatic saturation process?


11. (a) A gas of mass 1.5 kg undergoes a quasi-static expansion which follows a

relationship p =a + bV, where a and b are constants. The initial and final pressures are 1000 kPa

and 200 kPa respectively and the corresponding volumes are 0.20 m3 and 1.20 m3. The specific

internal energy of the gas is given by the relation: u = 1.5 pv 85 kJ/kg, where p is in kPa and v is

in m3/kg. Calculate the net heat transfer and the maximum internal energy of the gas attained during

expansion.

Or(b) A nozzle velocity is a device for increasing the velocity of a steadily flowing stream. At the

inlet to a certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and the velocity is 60 m/s. At

the discharge end, the enthalpy is 2762 kJ/kg. The nozzle is horizontal and there is negligible heat

loss from it. (i) Find the velocity at exit from the nozzle. (ii) If the inlet area is 0.1m2 and the specific

volume at inlet is 0.187 m3/kg, find the mass flow rate, (iii) If the specific volume at the nozzle exit is

0.498 m3/kg, find the exit area of the nozzle.

12. (a) (i) What are the causes of irreversibility of a process? (4)

(ii) A reversible heat engine operates between two reservoirs at temperatures of 600C and 40C.

The engine drives a reversible refrigerator which operates between reservoirs at temperatures of 40Cand - 20C. The heat transfer to the engine is 2000 kJ and the net work output of the combined engine

refrigerator plant is 360 kJ. (1) Evaluate the heat transfer to the refrigerant and the net heat transfer to

the reservoir at 40C. (2) Reconsider (1) given that the efficiency of the heat engine and the COP of

the refrigerator are each 40% of their maximum possible values. (12)

Or

(b) (i) Ten grams of water at 20C is converted into ice at -10C at constant atmospheric pressure.

Assuming the specific heat of liquid water to remain constant at 4.2 J/gK and that of ice to be half of

this value, and taking the latent heat of fusion of ice at 0C to be 335 J/g, Calculate the total entropychange of the system. (14)

(ii) Why is entropy transfer associated with heat transfer and not with work transfer? (2)

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13. (a) (i) Why do the isobars on Mollier diagram diverge from one another? (4)

(ii) A large insulated vessel is divided into two chambers, one containing 5 kg of dry saturatedsteam at 0.2 MPa and the other 10 kg of steam, 0.8 quality at 0.5 MPa. If the partition between the

chambers is removed and the steam is mixed thoroughly and allowed to settle, find the final pressure,steam quality and entropy change in the process (12)

Or

(b) In a reheat cycle, the initial steam pressure and the maximum temperature are 150 bar and550C respectively. If the condenser pressure is 0.1 bar and the moisture at the condenser inlet is 5%,

and assuming ideal processes, determine (i) the reheat pressure, (ii) the cycle efficiency, and (iii) the

steam rate.

14. (a) Two vessel, A and B, both containing nitrogen, are connected by a valve

which is opened to allow the contents to mix and achieve an equilibrium, temperature of 27C.Before mixing the following information is known about the gases in two vessels.

Vessel-A Vessel -B

p = 1.5 MPa p = 0.6 MPa

t = 50C t = 20C

Contents = 0.5 kg mol Contents = 2.5 kg mol

Calculate the final equilibrium process, and the amount of heat transferred to the surroundings. Ifthe vessel had been perfectly insulated, calculate the final temperature and pressure which would

have been reached. Take = 1.4.

Or

(b) Derive the Maxwell's equations.

15. (a) (i) . Explain the process of cooling and dehumidification. (4)

(ii) Air at 20C, 40% RH is mixed adiabatically with air at 40C, 40% RH in the ratio of 1 kg of

the former with 2 kg of the latter (on dry basis). Find the final condition of air (12)

(b) For a hall to be air-conditioned, the following conditions are given:

Outdoor condition - 40C dbt, 20C wbt

Required comfort conditions - 20C dbt, 60% RH

Seating capacity of hall - 1500

Amount of outdoor air supply - 0.3 m3/min/person

If the required condition is achieved first by adiabatic humidification and then by cooling,estimate (i) the capacity of the cooling coil in tonnes, and (ii) the capacity of the humidifier in kg/h.

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B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2008.Third Semester

(Regulation 2004)Mechanical Engineering


(Common to Production Engineering)(Common to B.E. (Part-Time) - Second Semester - Regulation 2005) Time: Three hours

. Maximum: 100 marks

(Use of standard thermodynamic tables, Mollier diagram, Psychrometric chart and Refrigerant

property tables permitted)



1. Define a thermodynamic system. Classify the followingsystems as open/closed/isolated : (a) Mixture of ice and water in a metal

container (b) A wind mill.2. Define heat and thermodynamic definition of work. ,3. Give Clausius statement of Second Law of Thermodynamics.4. What is the principle of increase of Entropy?5. Define quality of steam. What are the methods of determining quality of steam?6. Give the flow and T-s diagrams of the regenerative Rankine cycle with single open

feed water heater.

7. Explain the following terms : (a) Mole fraction, (b) Mass fraction.8. Write the Maxwell's equations and also give the basic relations from which these are

derived.

9. What do you understand by dry bulb and wet bulb temperatures?10. Draw a psychrometric chart and show the following processes on

it :

(a) sensible cooling, (b) latent heating, (c) heating and dehumidification and (d)cooling and humidification.


11. (a) (i) A van der Waal gas is compressed reversibly at

constant temperature from volume V1 to V2. The equation of state is given by

P =(RT/V-b)-(a/V2) . Determine the work done per mole of the gas. (8)

(ii) Define a new thermodynamic scale say degree N, in which the freezing point and boiling point

of water are 100N and 300N respectively. Correlate this temperature scale with centigrade scale.(8)

Or

(b) (i) Apply steady flow energy equation for a nozzle. State theassumptions made. (6)

(ii) A gas occupies 0.3 m3 at 2 bar. It executes a cycle consisting of processes : (1) 1-2; constant

pressure with work interaction of 15 kJ. (2) 2-3; compression process which follows the law

PV = Constant, and U3 = U2 (3) 3-1; constant volume process, and change in internal energy is 40

kJ. Neglect change in KE and PE. Draw PV diagram for the process and determine network transfer

for the cycle. Also . show that first law is obeyed by the cycle. (10)

12. (a) (i) Derive Clausius inequality and mention the criteria for reversibility of a cycle.(6)

(ii) A reversible heat engine operates between two reservoirs at 820C and 27C. Engine drives a
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reversible refrigerator which operates between reservoirs at temperatures of 27C and -15C. The

heat transfer to the engine is 2000 kJ and network available for the combined cycle is 300 kJ. (1) Howmuch heat is transferred to the refrigerant and also determine the total heat rejected to the reservoir at

27 C. (2) If the efficiency of the heat engine and COP of the refrigerator are each 40% of theirmaximum values, determine heat transfer to the refrigerator and also heat rejected to the reservoir at

27C. (10)

Or(b) (i) Show that there is a decrease in available energy when heat is transferred through

a finite temperature difference. (6)

(ii) In a closed system air is at a pressure of 1 bar, temperature of 300 K and volume of 0.025 m3.

The system executes the following processes during the completion of thermodynamic cycle : 1-2;

constant volume heat addition till pressure reaches 3.8 bar, 2-3; constant pressure cooling of air; 3-1;isothermal heating to initial state. Determine the change in entropy in each process. Take Cv = 0.718

kJ/kgK. R = 287 J/kgK.

(10)

13. (a) (i) Draw and explain phase equilibrium diagram for a pure substance

on P-T coordinate. Also indicate different regions on the diagram. (8)

(ii) Steam at a pressure of 15 bar and 250C expands according to the law PV1.25 = C to a pressureof 1.5 bar. Evaluate the final conditions, work done, heat transfer and change in entropy. The mass of

the system is 0.8 kg. (8)

Or

(b) (i) Why is Carnot cycle not practicable for a steam power plant? (4)(ii) In a steam power plant the condition of steam at inlet to the steam turbine is 20 bar and 300C

and the condenser pressure is 0.1 bar. Two feed water heaters operate at optimum temperatures.

Determine: (1) The quality of steam at turbine exhaust; (2) network per kg of steam, (3) cycle

efficiency, and (4) the steam rate. Neglect pump work (12)

14. (a) (i) Write a short note on Generalized Compressibility chart. (6)

(ii) A mixture of Ideal gases consists of 2.5 kg of N2 and 4.5 kg of CO2 at a pressure of 4 bar and

a temperature of 25C. Determine :

(1) Mole fraction of each constituent,

(2) Equivalent molecular weight of the mixture,(3) Equivalent gas constant of the mixture,

(4) The partial pressure and partial volumes,

(5) The volume and density of the mixture. (10)

Or

(b) (i) Derive van der Waal's equation in terms of reduce parameters. (8)

(ii) Derive TdS equations taking Temperature, volume and temperature, pressure as independent

properties (8)15. (a) Atmospheric air at 1.0132 bar has a DBT of 32C and a WBT of 26C. Compute (i) the

partial pressure of water vapor, (ii) the specific humidity, (iii) the dew point temperature (iv) the

relative humidity, (v) the degree of saturation, (vi) the density of air in the mixture, (vii) the density ofvapour in the mixture and (viii) the enthalpy of the mixture. Use thermodynamic table only. (16)

Or

(b) (i) Explain the process of cooling dehumidification of air. (8).

(ii) 30 m3/min of moist air at 15C DBT and 13C WBT are mixed with 12 m3/min of moist air at

25C DBT and 18C WBT. Determine DBT and WBT of the mixture assuming the barometric

pressure is one atmospheric. (8)

B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2008.

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Third Semester


ME 1201 ENGINEERING THERMODYNAMICS(Common to Production Engineering)

(Common to B.E. (Part-Time) - Second Semester - Regulation 2005) Time : Three hours

Maximum : 100 marks(Use of standard thermodynamic tables, Mollier diagram, Prychrometric chart and

Refrigerant property tables permitted)



1. Define 'process' and 'cycle' with one example each.2. Distinguish between heat and temperature.3. What do you understand by the concept of entropy?4. What is loss of availability? How is it related to entropy of universe?5. If water is at 65C at 1 atm, what is the state of water? What is its specific enthalpy?6. Plot the standard Rankine cycle on T-s diagram and label all the processes assuming the

steam to be dry and saturated at the end of expansion.

7. Have you ever encountered any ideal gas? If so, where?8. What is coefficient of expansion?9. If the relative humidity of air is 60% at 30C, what is the partial pressure of water

vapour?

10. What is thermodynamic wet bulb temperature?PART B (5 x 16 = 80 marks)

11. (a) (i) Derive an expression for the work transfer in an isothermal process. (2 + 2)

(ii) Identify any four reasons for irreversibility in a process. (4)

(iii) A Work done by substance in a reversible non-flow manner is in accordance with

V = (15/p) m3, where p is in bar. Evaluate the work done on or by the systemas pressure increases

from 10 to 100 bar. Indicate whether it is a compression process or expansion process. If the change in

internal energy is 500 kJ, calculate the direction and magnitude of heat transfer. (6 + 2)

Or

(b) (i) Define internal energy and prove that it is a point function. (3 + 4)

(ii) Establish the relationship between the specific heat at constant pressure and specific heat at

constant volume. (3)

(iii) In a Gas turbine installation, the gases enter the turbine at the rate of 5 kg/sec with a velocityof 50 m/sec and enthalpy of 900 kJ/kg and leave the turbine with 150 m/sec. and enthalpy of 400

kJ/kg. The loss of heat from the gases to the surroundings is 25 kJ/kg. Assume R = 0.285 kJ/kg K,

Cp = 1.004 kJ/kg K and inlet conditions to be at 100 kPa and 27C. Determine the diameter of theinlet pipe. (6)

12. (a) (i) State Carnot theorem (3)

(ii) An inventor claims to have developed an engine which receives 1000 kJ at a temperature of

160C. It rejects heat at a temperature of 5C and delivers 0.12 kWh of mechanical work. Is this a

valid claim? Justify your answer through Classius inequality. (3 + 2)

(iii) A refrigerator operating between two identical bodies cools one of the bodies to a temperature

T2. Initially both the bodies are at temperature T1. Deduce the expression for the minimum specificwork input, taking their specific heat as c. (8)

Or

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(b) (i) Deduce the expression for the Entropy change in terms of pressure and temperature.

(6)(ii) One kg of ice at -10C is allowed to melt in atmosphere at 30C. The ice melts and the water

so formed rises in temperature to that of atmosphere. Determine the entropy change of ice, theentropy change of surrounding, the entropy change of universe and write your comment based on

principle of increase in entropy. The specific heat of ice is 2 kJ/kg-K and its latent heat is 335 kJ/kg.

(3 + 3 + 3 + 1)

13. (a) (i) Draw p-V-T surface for any substance that contracts on freezing

and get p-T plot out of them. (4 + 2)

(ii) 3 kg of steam at 18 bar occupy a volume of 0.2550 m3. During a constant volume process, the

heat rejected is 1320 kJ. Determine final internal energy. Find dryness fraction and pressure, changein entropy and work done. (10)

Or

(b) (i) Briefly explain the process of super-heated steam formation with the help of T-s

diagram. (6)

(ii) A steam power plant runs on a single regenerative heating process. The steam enters the

turbine at 30 bar and 400C and steam fraction is withdrawn at 5 bar. The remaining steam exhausts at0.10 bar to the condenser. Calculate the efficiency, steam fraction and steam rate of the power plant.

Neglect pump work. (6 + 2 + 2)

14. (a) (i) Prove that the total pressure is a sum of partial pressures. (4)(ii) A closed vessel has a capacity of 0.5 m3. It contains 20% nitrogen and 20% oxygen 60%

carbon dioxide by volume at 20C and 1 MPa. Calculate the molecular mass, gas constant, mass

percentages and the mass of mixture (12)

Or

(b) (i) Derive Tds relations in terms of temperature & pressure changes and temperature

& volume changes. (10)

(ii) Describe Joule Kelvin effect with the help of T-p diagram. (6)

15. (a) (i) Describe the adiabatic cooling process and deduce the expression for itsenthalpy. (4 + 4)

(ii) Air at 20C, 40% relative humidity is missed adiabatically with air at 40C, 40% RH in the

ratio of 1 kg of former with 2 kg of latter (on dry basis). Find the final condition (humidity and

enthalpy) of air (8)

Or

(b) (i) Draw the cooling and dehumidification process and explain Sensible Heat Factor, Bypass

Factor and effectiveness of coil with respect to it. (6)(ii) A steam of air at 101.32 kPa. 18C, and a relative humidity of 30% is flowing at the rate of

14.15 m3/min. A second stream at 101.32 kPa. 38C and a relative humidity of 50% is flowing at the

rate of 8.5 m3/min. The two streams are mixed adiabatically to form a third stream at 101.32 kPa.

Determine the specific humidity, the relative humidity and the temperature of the third stream.

(4 + 3 + 3)
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Third Semester(Regulation 2004)

Mechanical EngineeringME 1201 ENGINEERING THERMODYNAMICS

(Common to Production Engineering)

(Common to B.E. (Part-Time) - Second Semester - Regulation 2005) Time : Three hoursMaximum : 100 marks

(Use of standard thermodynamic tables, Mollier diagram, Psychrometric chart and

Refrigerant property tables permitted)

Answer ALL questions.PART A (10 x 2 = 20 marks)

1. What is a PMM1? Why is it impossible?2. Is it correct to say 'total heat' or 'heat content' of a closed system?3. Why the second law of thermodynamics is called a directional law of nature?4. The coefficient of Performance (COP) of a heat pump is 5. Find the COP of a refrigerator

if both are reversible devices interacting between same source temperature and sink

temperature.

5. Define saturation state of a system.6. Why Carnot cycle is not practicable for a steam power plant?7. What do you mean by equation of state?8. State the Dalton's law of partial pressure.9. Define dew point temperature10. What is sensible heating?


11. (a) (i) A blower handles 1 kg/sec of air at 293 K and consumes a power of15 kW. The inlet and outlet velocities of air are 100 m/sec and 150 m/sec respectively.

Find the exit air temperature, assuming adiabatic conditions. Take Cp of air as 1.005kJ/kg-K. (9)

(ii) A room for four persons has two fans, each consuming 0.18 kW power and three 100

W lamps. Ventilation. air at the rate of 0.0222 kg/sec enters with an enthalpy of 84 kJ/kg

and leaves with an enthalpy of 59 kJ/kg. If each person puts out heat at the rate of 0.175

kJ/sec, determine the rate at which heat is to be removed by a room cooler, so that a

steady state is maintained in the room. (7)

Orb. (i) One litre of hydrogen at 273 K is adiabatically compressed to one-half of its initialvolume. Find the change in temperature of the gas, if the ratio of two specific heats for

hydrogen is 1.4 (4)(ii) The velocity and enthalpy of fluid at the inlet of a certain nozzle are 50 m/sec and

2800 kJ/kg respectively. The enthalpy at the exit of nozzle is 2600 kJ/kg. The nozzle is

horizontal and insulated so that no heat transfer takes place from it. Find

i. Velocity of the fluid at exit of the nozzleii. Mass flow rate, if the area at inlet of nozzle is 0.09 m2

iii. Exit area of the nozzle, if the specific volume at the exit of the nozzle is 0.495m3/kg. (12)

12. (a) (i) Give the Clausius statement of second law (3)(ii) A house hold refrigerator is maintained at a temperature of 275 K. Every time the
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door is opened, warm material is placed inside, introducing an average of 420 kJ, but

making only a small change in the temperature of the refrigerator. The door is opened 20times a day, and the refrigerator operates at 15% of the ideal COP. The cost of work is

Rs 2.50 per kWhr. What is the bill for the month of April for this refrigerator? Theatmosphere is at 303 K. (13)

Or

(b) (i) What is a thermal energy reservoir (3)(ii) Establish the inequality of Clausius (13)

13. a. A cyclic steam power plant is to be designed for a steam temperature atturbine inlet of 633 K and an exhaust pressure of 8 kPa. After isentropic expansion of

steam in the turbine, the moisture content at the turbine exhaust is not to exceed 15%.Determine the greatest allowable steam pressure at the turbine inlet, and calculate the

Rankine cycle efficiency for these steam conditions. Estimate also the mean temperature

of heat addition (16)

Or

b. In a reheat steam cycle, the maximum steam temperature is limited to 773 K. Thecondenser pressure is 10 kPa and the quality at turbine exhaust is 0.8778. Hadthere been no reheat, the exhaust quality would have been 0.7592. Assuming ideal

processes, determine (i) reheat pressure (ii) the boiler pressure (iii) the cycle

efficiency (iv) the steam rate (16)

14. (a) (i) A certain gas has CP = 0.913 and Cv = 0.653 kJ/kg K. Find the molecularweight and the specific gas constant R of the gas. (4)

(ii) Derive the Clausius- Clapreyon equation. (12)

Or

(b) (i) Derive Maxwell's equations (11)

(ii) Prove Tds =CvdT +T (p/T)v dV . (5)

15. (a) In a laboratory test, a sling psychrometer recorded dry bulb and wet bulbtemperatures as 303 K and 298 K respectively. Calculate (i) vapour pressure (ii) relative

humidity (iii) specific humidity (iv) degree of saturation (v) dew point temperature (vi)

enthalpy of the mixture. (16)Or

(b) (i) 1 kg of air at 313 K dry bulb temperature and 50% relative humidity is mixed with

2 kg of air at 293 K dry bulb temperature and 293 K dew point temperature. Calculate the

temperature and specific humidity of the mixture. (10)

(ii) Show the following processes on a skeleton psychrometric chart

a. dehumidification and coolingb.

heating and humidification (6)

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BE./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2007.Third Semester



(Common to Production Engineering)(Common to BE. (Part-Time) Second Semester)

(Regulation 2005)

Time : Three hours

Maximum : 100 marks

Use of Steam Tables, Mollier Chart, Psychrometric Chart permitted.Answer ALL questions.


1. What is meant by internal energy?2. A rigid tank is insulated around both its sides and ends. It is separated initially into two equal

volumes by a partition. When one side contains 1 kg of gas at 100 kPa and 345C, the other side

remains evacuated. If the partition is removed, find final pressure and temperature.

3. What do you understand by a reversible process?4. What are the two major conclusions deduced from the Carnot principles?5. Define triple point and identify the triple point of water.6. Steam in a pipeline with a pressure of 1000 kPa flows through a throttling calorimeter where

pressure is 100 kPa and temperature is 120C. What is the initial quality of steam if enthalpy

remains constant during throttling?

7. What is equation of state? Write the same for an ideal gas.8. What is the significance of compressibility factor?9. What is specific humidity and how do you calculate it?10.What is meant by adiabatic saturation temperature?


11. (a) (i) Deduce the expression for the displacement work in an isothermal process (4)(ii) Three grams of nitrogen gas at 6 atm and 160C is expanded adiabatically to

double its initial volume, then compressed at constant pressure to its initial volume

and then compressed again at constant volume to its initial state. Calculate the net

work done on the gas. Draw the p-V diagram for the process. Specific heat ratio of

nitrogen is 1.4. (10 + 2)Or

(b) (i) Describe steady flow energy equation and deduce suitable expression forthe expansion of gas in a gas turbine with suitable assumptions (8)

(ii) Air expands by isentropic process through a nozzle from 784 kPa and 220C to an

exit pressure of 98 kPa. Determine the exit velocity and the mass flow rate, if the exit

area is 0.0006 m2. (8)

12. (a) (i) What are the conditions for reversibility? Explain. (4)(ii) An heat exchanger circulates 5000 kg/hr of water to cool oil from 150C to 50C.

The rate of flow of oil is 2500 kg/hr. The average specific heat of oil is 2.5 kJ/kgK.

The water enters the heat exchanger at 21C. Determine the net change in the entropydue to heat exchange process, and the amount of work obtained if cooling of oil is

done by using the heat to run a Carnot engine with sink temperature of 21C. (8 + 4)

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Or

(b) (i) Deduce Clausius inequality and interpret it. (4 + 2)(ii) An ideal gas of 0.12 m3 is allowed to expand isentropically from 300 kPa and

120C to 100 kPa. 5 kJ of heat is then transferred to the gas at constant pressure.Calculate the change in entropy for each process. Assume = 1.4 and

Cp =1.0035 kJ/kg-K. If these two processes are replaced by a reversible polytropic

expansion, find the index of expansion between original and final states. What will bethe total changes in entropy? (4 + 4 + 2)

13. (a) (i) Draw p-T diagram and label various phases and Transitions.Explain the process of isobaric heating above triple point pressure with the help of p-T

diagram. (4 + 4)(ii) 2 kg of water at 200C are contained in a 20 m3 vessel. Determine the pressure,

enthalpy, mass and volume of vapour within the vessel (8)

Or

(i) Draw Rankine cycle with one open type feed water heater. Assume the condition of

the steam before entering the turbine to be superheated. Sketch the cycle on T-s

diagram. (6)(ii) In an ideal reheat cycle, the steam enters the turbine at 30 bar and 500C. After

expansion to 5 bar, the steam is reheated to 500C and then expanded to the condenser

pressure of 0.1 bar. Determine the cycle thermal efficiency, mass flow rate of steam.

Take power output as 100 MW. (6 + 4)

14.(a) (i) Deduce Maxwell's relations (6)(ii) Explain the Joule Thomson effect with the help of T-p diagram and derive the

expression for Joule Thomson coefficient. Show that the value of this coefficient for

an ideal gas is zero. (4 + 4 + 2)

Or

(b) (i) What are the differences between real and ideal gases (4)

(ii) Write down the van der Waal's equation of state for real gases and how is it

obtained from ideal gas equation by incorporating real gas corrections? (2 + 4)

(iii) A tank contains 0.2 m3

of gas mixture composed of 4 kg of nitrogen, 1 kg ofoxygen and 0.5 kg of carbon-di-oxide. If the temperature is 20C, determine the total

pressure, gas constant and molar mass of the mixture (6)

15.(a) (i) Draw the psychrometric chart and show any two psychrometricprocesses on it. (6)

(ii) A sample of moist air at 1 atm and 25C has a moisture content of 0.01% by

volume. Determine the humidity ratio, the partial pressure of water vapour, the degreeof saturation, the relative humidity and the dew point temperature. (10)

Or

(b) (i) Describe the process of adiabatic mixing of two streams and deduce the ratio ofmasses of two streams in terms of humidity and/or enthalpy (10)

(ii) The temperature of the windows in a house on a day in winter is 5C. When the

temperature in the room is 23C, and the barometric pressure is 74.88 cm Hg, what

would be the maximum relative humidity that could be maintained in the room

without condensation on the window panes? Under these conditions, find the partial

pressure of the water vapour and air, the specific humidity and the density of the

mixture. (6)

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Third Semester Mechanical EngineeringME 1201 ENGINEERING THERMODYNAMICS

(Common to Production Engineering and B.E. (Part-Time) -Second Semester - Regulation2005)(Regulation 2004)

Time : Three hours

Maximum : 100 marksStandard steam table, Mollier chart, Psychometric-charts are permitted.



1.What is the convention for positive and negative work?2.What are the corollaries to the first law of Thermodynamics?3.Given Kelvin-Planck statement of the second Law of Thermodynamics.4.What is a process involved in a Carnot cycle, sketch the same in P-V and T-S diagram.5.Define critical pressure and temperature for water.6.Sketch the Rankine cycle on a P-V plane and name the various process.7.State the Avagodro's law and state its significance.8.Write the Maxwell's questions and its significance.9.Explain the terms (a) Specific humidity (b) Dew point temperature.10.What is adiabatic mixing and write the equation for that?


11. (a) In an isentropic flow through nozzle, air flows at the rate of 600 kg/hr. At inlet to

the nozzle, pressure is 2 MPa and temperature is 127C. The exit pressure is 0.5 MPa. Initial air

velocity is 300 m/s .Determines (i) Exit velocity of air (ii) Inlet and exit area of nozzle.

Or

(b) A centrifugal pump delivers 2750 kg of water per minute from initial pressure of 0.8 bar

absolute to a final pressure of 2.8 bar absolute. The suction is 2 m below and the delivery is 5 m above

the centre of pump. If the suction and delivery pipes are of 15 cm and 10 cm diameter respectively,make calculation for power required to run the pump.

12. (a) A heat engine operating between two reservoirs at 100 K and 300 K is used to

drive heat pump which extracts heat from the reservoir at 300 K at a rate twice that at which engine

rejects heat to it. If the efficiency of the engine is 40% of the maximum possible and the co-efficient

of performance of the heat pump is 50% of the maximum possible, make calculations for the

temperature of the reservoir to which the heat pump rejects heat. Also work out the rate of heatrejection from the heat pump if the rate of supply of heat to the engine is 50 kW.

Or

(b) One kg of air is contained in a piston cylinder assembly at 10 bar pressure and 500 Ktemperature. The piston moves outwards and the air expands to 2 bar pressure and 350 K temperature.

Determine the maximum work obtainable. Assume the environmental conditions to be 1 bar and

290 K.Also make calculations for the availability in the initial and final states.

13. (a) 1 kg of steam initially dry saturated at 1.1 MPa expands in a cylinder following

the law PV1.13 = C. The pressure at the end of expansion is 0.1 MPa. Determine

(i) The final volume

(ii) Final dryness fraction(iii) Work done

(iv) The change in internal energy

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(v) The heat transferred.

Or(b) Steam at a pressure of 2.5 MPa and 500C is expanded in a steam turbine to a condenser

pressure of 0.05 MPa. Determine for Rankine cycle (i) The thermal efficiency of Rankine cycle (ii)Specific steam consumption. If the steam pressure is reduced to 1 MPa and the temperature is kept

same 500C. Determine the thermal efficiency and the specific steam consumption. Neglect feed

pump work.

14. (a) Derive Tds Equation when

(i) T and V independent

(ii) T and P independent

(iii) P and V independent.Or

(b) Explain and derive the

(i) Joules Thompson co-efficient (ii) Clausius Clapeyron equation.

15. (a) A room 7m x 4m x 4m is occupied by an air water vapour mixture at 38C. The

atmospheric pressure is 1 bar and the relative humidity is 70%. Determine humidity ratio, dew pointtemperature mass of dry air and mass of water vapour. If the mixture of air-water vapour is further

cooled at constant pressure until the temperature is l0C. Find the amount of water vapour condensed.

Or

(b) Air at 20C, 40% RH is mixed adiabatically with air at 40C 40% RH in the ratio of 1 kg of theformer with 2 kg of later. Find the final condition of air. Draw the process in chart also as diagram.

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B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2006.

Third Semester ,Mechanical Engineering


(Common to Production Engineering)

(Regulation 2004)

Time : Three hours Maximum : 100 marksStandard Steam Table, Mollier chart, Psychrometric charts are permitted.


PART A (10 x 2 = 20 marks)1. What is t he relationsh ip between a system and its environment when the system is (a)

Adiabatic (b) Isolated?2. What is meant by enthalpy'?3. State the Clausius statement of Second Law of Thermodynamics.4. State few examples of irreversible process.5. What is a pure substance? Give examples.6. How evaporation differs from boiling?7. State Dalto n's law of partial pressures. On what assu mptions this law is based?8. What is an equation of state?9. Define the Carnot cycle with P-V and T-S diagram.10. What is specific humidity? When does it become maximum?


11.(i)Derive the general energy equation for a steady flow system and apply the equation to anozzle and derive an equation for velocity at exit. (8)(ii) In an air compressor, air flows steadily at the rate of 0.5 kg/sec. At entry to the

compressor, air has a pressure of 105 kPa and specific volume of 0.86 m3

/kg and at exit ofthe compressor those corresponding values are 705 kPa and 0.16 m3/kg. Neglect Kinetic

and Potential energy change. The Internal energy of air leaking the compressor is

95 kJ/kg greater than that of air entering. The cooling water in the compressor absorbs

60 kJ/sec. of heat from the air. Find power required to derive the compressor. (8)

12.(a) Two kg of air at 500 kPa, 80C expands adiabatically in a closed systemuntil its volume is doubled and its temperature becomes equal to that of the surroundings

which is at 100 kPa, 5C for this process, determinei. The maximum work

ii. The change in availability andiii. The irreversibility.

For air taken, Cv 0= 0.718 kJ/kg K, u = Cv T Where Cv is constant and PV = mRT where P

is pressure in kPa, V volume in m3, m mass in kg, R a constant equal t o 0.287 kJ/kg

K and T temperature in K. (16)

Or

b. Establish the inequality of Clausius and express Entropy change inirreversible process. (16)

13.(a) In a single heater regenerative cycle the steam enters the turbine at30 bar, 400

C and the exhaust pressure is 0.10 bar . The feed water heater is a direct

- contact type, which operates at 5 bar. Find

i. the efficiency and the steam rate of the cycle, and

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ii. the increase in mean temperature of heat addition, efficiency andsteam rate as compared to t he Rankine cycle (with outregeneration) Neglect pump work. (16)

Or(b) One kg of steam is contained in an elastic balloon of spherical shape which

supports an internal pressure proportional to its diameter. The initial condition of

steam is saturated vapour at 110C. Heat is transferred to steam until pressurereaches 200 kPa. Determine:

i. Final temperatureii. Heat transferred. Take Cps = 2.25 kJ/kg K (16)

14. (a) Entropy is a function of any two properties like P and V, P and T etc., for a puresubstance with the help of Maxwell's Equation. Prove

i. Tds =Cy.dT + T[/k].dvii. Tds = Cp.dT-V.dp.Tiii. Tds = [KCy /].dp+ [Cp/v] .dv. (16)

OR(b) Determine change of Internal Energy and change of entropy when the gas obeys Vander

Waal's equation. (16)

15. (a) The atmospheric air at 30C DBT and 75% RH enters a cooling coil at t he rate of200 m3/rmn. The coil dew point temperature. is 14C and the by-pass factor is 0.1

determine

i. The temperature of air leaving the coilii. Capacity of the cooling coil in TR

iii. The amount of water vapour removediv.

Sensible heat factor for the process. (16)Or

(b) The volume flow rate of air is 800 m3/min of re-circulated at 22C DBT

and 10C dew point temperature is to be mixed with 300 m3/min of fresh

air at 30C DBT and 50% RH. Determine the enthalpy, Specific volume,

Humidity ratio and dew point temperature of the mixture. (16)

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B.E/E.TECH. DEGREE EXAMINATIONS, NOVEMBER/DECEMBER 2005ME 1201- ENGINEERING THERMODYNAMICS

Third semester,Mechanical engineering(Common to Production engineering)

Time: three hours

maximum: 100marksANSWER ALL QUESTIONS.

PART A- (10X2=20MARKS)

1. What is heat?2. Prove that cp-c v=R.3. State zeroth law of thermodynamics. What is its app

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