MODEL QUESTION PAPER (CIE)

 Test/Date and Time Semester/year Course/Course Code Max Marks Ex: I test/6 th week of sem 10-11 Am VSEM APPILED THERMAL ENGG. 20 Year: 2016-17 Course code:15ME52T Name of Course coordinator :                                                                                             Units:1,2 Co: 1,2   Note:  Answer all questions Question no Question MARKS CL CO PO 1 Explain Barrel type Steam Calorimeters with a neat sketch. OR Explain Separating type Steam Calorimeters with a neat sketch 5 U 2 2 2 Make use of the given data find the quantity of heat required to produce 1kg of steam at a pressure of 6 bar at a temperature of 250C, under the following conditions. a)  When the steam is wet having a dryness fraction 0.9, b) when the steam is dry saturated, c)when it is superheated at a constant pressure at 2500C assuming the mean specific heat of superheated steam to be 2.3 kJ/kg0K. 5 A 1 2 3 Choose    the different system of producing draught in a boiler and mention their advantages and disadvantages 5 A 2 2 4 Explain the various types of draughts used in usual practice. OR Compare the advantages of high pressure boiler over low pressure boiler. 5 U 2 2

MODEL QUESTION PAPER (SEE)

V- Semester Diploma Examination

Course Title: APPLIED THERMAL ENGINEERING

Time: 3 Hours]                                                                                                     [Max                                                                                                  Marks:                                                                                                        100

Note: Answer any SIX from PartA and any SEVEN from Part B

PART-A                                                                                                 6x5=30 marks

1.    List the advantages of superheated steam

2.     Explain Barrel type Steam Calorimeters with a neat sketch

3.     List the various types of draughts used in usual practice.

4.    List the different types of steam - condensers.

5.     List the function of cooling tower in a modem condensing plant

6.    Explain the Working of simple De-Laval turbine with line diagram

8.    List the desirable properties of a secondary refrigerant.

9.     Explain Single stage reciprocating air compressor with line diagram

PART-B                                                                                                   7x10=70 marks

1.         Steam at 18 bar and dryness 0.9 is heated at constant pressure until dry and saturated. Find the increase in volume, heat supplied and work done per kg of steam. If the volume is now kept constant, find how much heat must be extracted to reduce the pressure to 14 bar.

2.         Make use of the steam table,find the following : (i) Enthalpy and volume of 1 kg of steam at 12. 1 bar and dryness fraction 0.9, and (ii) Enthalpy and volume of 1 kg of steam at 12. 1 bar and 225’C. Take the specific heat at constant pressure for superheated steam as 2.1 kJ/kg K.

3.         i) Compare high pressure boiler and low pressure boiler

ii) Explain the function of the safety valve

4.         Outline the sketch and explain the working of a La-mount boiler

5.         Outline the sketch and explain counter-flow low level jet condenser and list the advantages.

6.         A convergent-divergent nozzle is required to discharge 2 kg of steam per second. The nozzle is supplied with steam at 7 bar and 1800C and discharge takes place against the back pressure of 1 bar. The expansion up to throat is isentropic and the frictional resistance between throat and exit is equivalent to 63 kJ/kg of steam. The approach velocity to the nozzle is 75 m/s and throat pressure is 4 bar. Estimate (a) Suitable areas of throat and exit, (b) Overall efficiency of the nozzle based on enthalpy drop between inlet pressure, temperature and exit pressure.

7.           An impulse turbine with a single row wheel is to develop 99.3 kW, the blade speed being 150 m/sec. A mass of 2 kg of steam per second is to flow from the nozzles at a speed of 350 m/sec. The velocity coefficient of the blades may be assumed to be 0.8 while the steam is to flow axially after passing through the blades ring. Determine the

nozzle angle, and the blade angles at inlet and exit assuming no shock. Estimate also the diagram efficiency of the blading.

8.           The steam leaves the nozzle of a single-stage impulse wheel turbine at 900 m/sec. The nozzle angle is 20°, the blade angles are 30° at inlet and outlet, and friction factor is 0.8. Calculate : (a) the blade velocity, and (b) the steam flow in kg per hour if the power developed by the turbine is 257'kW.

9.         a) Explain winter Air Conditioning with neat sketch.

b) Explain Summer Air conditioning with neat sketch

10.    It is desired to compress 17m3 of air per minute from 1 bar (100 kN/m2) and 21'C to a delivery pressure of 7 bar (700 kN/m2) in a single-stage, single-acting air compressor. Calculate the power required to drive the compressor and the heat rejected duhng compression to cooling water if the compression is (a) Isentropic (y = 1.4 for air), and

(b)  Isothermal.

MODEL QUESTION BANK

Diploma in Mechanical Engineering V Semester

Course title: APPILED THERMAL ENGINEERING

Note: The paper setter is of liberty to set the questions on his/her desecration based on cognitive levels notified for that unit. They has to follow only blue print of SEE question paper format. The model question bank is only for reference to students/course coordinator to initiate the process of teaching-learning only.

CO-1: Determine steam properties and dryness fractions.

REMEMBER

1.         What is meant by saturation temperature and saturation pressure?

2.       Define the following terms : (i) Saturated steam, (ii) Dry saturated steam, (Hi) Wet steam, (iv) superheated steam, (v) Dryness fraction of steam, (vi) Specific volume of steam, and (vii) Saturated water.

3.         List the advantages of superheated steam

4.         Define Internal energy of steam.

UNDERSTAND

1.      Explain the process of formation of steam at a constant pressure from water.

2.      Explain how the wet steam, dry saturated steam and superheated steam is produced.

3.      Explain T-H diagram during steam formation.

4.      Explain steam tables and their uses.

5.      Explain Carnot cycle with Sketch

6.      Explain with sketch Rankine cycle

7.      Explain Barrel type Steam Calorimeters with a neat sketch.

8.      Explain Separating type Steam Calorimeters with a neat sketch

9.      Explain Throttling type Steam Calorimeters with a neat sketch

10.  Explain combined Separating & Throttling type Steam Calorimeters with a neat sketch

11.   Compare enthalpy and internal energy of steam

12.   Outline the Limitations of Calorimeter.

13.  Explain the following terms : (i) Saturated steam, (ii) Dry saturated steam, (Hi) Wet steam, (iv) superheated steam, (v) Dryness fraction of steam, (vi) Specific volume of steam, and (vii) Saturated water.

14.  Explain the following terms as referred to steam : (i) Enthalpy of water, (ii) Enthalpy of evaporation, (iii) Superheat, (iv) Specific volume, and (v) Enthalpy of dry saturated steam.

15.   Compare saturated steam and dry saturated steam.

APPLICATION

1.        Make use of the given data find the quantity of heat required to produce 1kg of steam at a pressure of 6 bar at a temperature of 250C, under the following conditions.

a)   When the steam is wet having a dryness fraction 0.9, b)when the steam is dry saturated, c)when it is superheated at a constant pressure at 2500C assuming the mean specific heat of superheated steam to be 2.3 kJ/kg0K.

2.        Steam enters an engine at a pressure of 12bar with 670C of superheat. It is exhausted at  a pressure of 0.15bar and 0.95dry. Find the drop in enthalpy of steam.

3.        Make use of the given data find the internal energy of 1kg of superheated steam at a pressure of 10bar and 2800C.

If this steam be expanded to a pressure of 1.6bar and 0.8dry, determine the change in internal energy. Assume specific heat of superheated steam as 2.3 kJ/kg0K.

4.        A vessel contains 20kg of steam at a pressure of 8 bar. Find the amount of heat, which must be rejected, so as to reduce the quality of steam in the vessel to be 70%.

5.        Steam at 18 bar and dryness 0.9 is heated at constant pressure until dry and saturated. Find the increase in volume, heat supplied and work done per kg of steam. If the volume is now kept constant, Analyze how much heat must be extracted to reduce the pressure to 14 bar.

6.        Analyze how much heat is needed to convert 5 kg of water at 40'C into 90 per cent dry (or 10 per cent wet) steam at 5 bar (500 kPa) ? Take specific heat of water as 4. 187 kJ/kg K.

7.        Analyze how much heat is needed to convert 4 kg of water at 20’C into steam at 8 bar (800 kPa) and 200'C. Take kp of superheated steam as 2.1 kJ/kg K and specific heat of water as 4.187 kJ/kg K.

8.        Make use of the given data ,Find the volume of one kilogram of steam at a pressure of 15 bar (15 MPa) in each of the following cases : (i) when steam is dry saturated, (ii) when steam is wet having dryness fraction of 0.9, and (iii) when steam is superheated, the degree of superheat being 40'C.

9.        Analyze the condition of steam in each of the following cases : (i) at a pressure  of 10 bar and temperature 200‘C, (ii) at a pressure of 8 bar and volume 0.22 m /kg, and (iii) at a pressure of 12 bar, if 2,688 kJ/kg are required to produce it from water at 0 ‘C.

10.   Utilize steam table,and find (i) Enthalpy and volume of 1 kg of steam at 12. 1 bar and dryness fraction 0.9, and (ii) Enthalpy and volume of 1 kg of steam at 12. 1 bar and 225’C. Take the specific heat at constant pressure for superheated steam as 2.1 kJ/kg K.

11.   Wet steam of mass 25 kg and occupying a volume of 0.49 m at 75 bar has a total heat (enthalpy) increase of 1,500 kJ when superheated at constant pressure. Determine : (i) Initial quality of steam, (ii) Final quality (degree of superheat) of steam, and (HI) Increase in volume of steam after superheating. Assume kp for the superheated steam to be 2-1 kJ/kg K.

12.   Steam enters a steam engine at a pressure of 12 bar with 67‘C of superheat and is exhausted at 0.15 bar and 094 dry. Calculate the drop in enthalpy from admission to exhaust, and volume of 1 kg of steam at admission and exhaust conditions. Take kp of superheated steam as 2.1 kJ/kg K.

13.   Make use of the given data, find the external work done during evaporation, internal latent enthalpy and internal energy per kg of steam at a pressure of 15 bar (1,500 kPa) when the steam is (i) 09 dry, and (ii) dcy saturated.

14.0.025 m3 of steam at 3.5 bar and dryness fraction 08 is converted into dry saturated steam at 11 bar. By how much are the enthalpy and internal energy changed ?

15. The internal energy of 1 kg of steam at a pressure of 14 bar (1.4 MPa) is 2,420 kJ. Calculate the dryness fraction of this steam. Find the increase in internal energy if this steam is superheated at constant pressure to a temperature of 295'C. Take kp of superheated steam as 2.3 kJ/kg K.

16. Inspect at what fraction of enthalpy of 1 kg of steam at 10 bar  and 0.9  dry represents the internal energy ? What is the change in internal energy when the pressure and temperature of this steam is raised to 13 bar and 250'C ? Take kp of superheated steam as 2.1 kJ/kg K.

CO-2: Classify and explain boilers, boiler mountings and accessories

REMEMBERING

1.      Define steam boiler and list its function.

2.      List the types of boilers according to various factors

3.      List the advantages of a Lancashire boiler

4.      List the advantages of Cochran boilers

7.      List the advantages of water-tube boilers over fire-tube boilers and tank boilers.

8.      List the boiler mountings.

9.     List the different mountings and accessories with which the Babcock and Wilcox water-tube boiler is fitted

10.     List the various types of draughts used in usual practice.

UNDERSTANDING

1.        Explain the following terms used in boiler practice : (a) Boiler shell, (b) Fire grate,

(c)  Furnace, (f) Mountings, (g) Blowing-off

2.      Expline the method of obtaining draught in the boiler.

3.      Compare ‘water-tube’ and Fire-tube' boilers.

4.      Explain the function of the safety valve .

5.      Explain the function of the Fusible plug.

6.      Outline the neat sketch of the Babcock and Wilcox water tube boiler.

7.        Compare Natural draught and artificial draught.

8.        Compare Forced draught and induced draught.

9.     Compare how an artificial draught is considered advantageous over a natural draught

10.   Explain the terms mechanical draught and balanced draught.

11.   Explain the working principle of the steam jet draught.

12.   Compare the advantages of high pressure boiler over low pressure boiler.

13.   Compare high pressure boiler and low pressure boiler.

APPLICATION

1.      Construct neat sketch and explain the Lancashire boiler.

2.      Construct neat sketch and explain the Co-chran boiler

3.      Construct neat sketch and explain the locomotive boiler.

4.     Choose the different system of producing draught in a boiler and mention their advantages and disadvantages.

5.      Construct neat sketch and explain the La-mount boiler.

6.      Construct neat sketch and explain the working of a Benson boiler

REMEMBERING

1.        List the function of a condenser in a modem steam condensing power plant.

2.        list the different types of steam - condensers.

3.          List the function of cooling tower in a modem condensing plant.

4.        Define the term ‘Nozzle efficiency.

UNDERSTANDING

1.      Outline the Sketch and explain the working of Surface Condenser

2.      Outline the Sketch and explain the working of Jet Condenser

3.      Construct neat sketch of a barometric jet condenser and explain its working

4.      Compare the merits and demerits of surface condensers over jet condensers

5.      Construct neat sketch of a counter-flow low level jet condenser and explain its working.

6.      Construct neat sketch and explain the operation of an evaporative condenser

7.      Construct neat sketch and explain the working of any one type of cooling tower.

8.      Explain the function of a steam nozzle. Explain the types of nozzles with sketch.

9.      Explain the term critical pressure as applied to steam nozzles.

10.  Explain the term “critical pressure" as applied to steam nozzles. Why are the turbine nozzles made divergent after the throat.

11.   Explain he causes of supersaturated flow in nozzles.

12.  Explain the supersaturated expansion of steam and give some idea of the limits within which this condition is possible.

13.   Explain the Types of steam nozzles with neat sketches

14.    Explain the Effect of friction on the flow of steam through convergent-divergent steam nozzles.

15.   Explain the Effect of supersaturated flow in steam nozzles.

APPLICATION

1.        A nozzle is to be designed to expand steam at the rate of 0.10kg/s from 500kpa, 2100C to 100kpa. Neglect inlet velocity of steam. For a nozzle efficiency of 0.9, determine the exit area of the nozzle.

2.        Steam enters a convergent – divergent nozzle at 2 MPa and 4000C with a negligible velocity and mass flow rate of 2.5 kg/s and it exists at a pressure of 300 kPa. The flow is isentropic between the nozzle entrance and throat and overall nozzle efficiency is 93 percent. Determine (a) throat, and (b) exit areas.

3.        In a convergent-divergent nozzle, the steam enters at 15 bar and 3000C and leaves at a pressure of 2 bar. The inlet velocity to the nozzle is 150 m/s. Find the required throat and exit areas for mass-flow rate of 1 kg/s. Assume nozzle efficiency to be 90 percent and Cps= 2.4 kJ/kgK

4.        Determine the throat and exit diameters of a convergent-divergent nozzle, which will discharge 820 kg of steam per hour at a pressure of 8 bar superheated to 220 0C into a chamber having a pressure of 1.5 bar. The friction loss in the divergent portion of the nozzle may be taken as 0.15 of the isentropic enthalpy drop.

5.        A convergent-divergent nozzle is required to discharge 2 kg of steam per second. The nozzle is supplied with steam at 7 bar and 1800C and discharge takes place against the back pressure of 1 bar. The expansion up to throat is isentropic and the frictional

resistance between throat and exit is equivalent to 63 kJ/kg of steam. The approach velocity to the nozzle is 75 m/s and throat pressure is 4 bar. Estimate (a) Suitable areas of throat and exit, (b) Overall efficiency of the nozzle based on enthalpy drop between inlet pressure, temperature and exit pressure.

6.        A turbine having a set of 16 nozzles receives steam at 20 bar and 400 0C. The pressure of steam at the nozzle exit is 12 bar. If the discharge rate is 260 kg/min and the nozzle efficiency is 90 %, calculate the cross-sectional area at the nozzle exit. If the steam has a velocity of 80 m/s at entry to the nozzle, find the percentage increase in discharge.

7.        The steam is supplied to a nozzle at a rate of 1 kg/s from an inlet condition of 10 bar, dry saturated and exit at 1 bar pressure. The efficiency of the nozzle for the convergent portion is 95 percent and that of the divergent portion is 90 percent. Determine (a) throat and exit diameters of nozzle (b) length of nozzle, if divergent cone angle of the nozzle is 140. (c) The power in kW correspondence to exit velocity of the steam

8.        A convergent-divergent nozzle is required to discharge 350 kg of steam per hour. The nozzle is supplied with steam at 8.5 bar and 90% dry and discharges against a back pressure of 0.4 bar. Neglecting the effect of friction, find the throat and exit diameters.

CO-4: Understand the working of steam Turbines

1.      Compare Impulse and reaction turbines.

2.      Explain the principle of working of impulse turbine.

3.      Explain the Working of simple De-Laval turbine with line diagram

4.      Outline the velocity diagram of a impulse turbine blades.

5.      Explain the need for compounding.

6.      Explain Blade efficiency and diagram efficiency.

7.        Explain why steam turbines are compounded

8.      Explain the Pressure compounding with diagrams

9.      Explain the Velocity compounding with diagrams

10.   Explain the Pressure-Velocity compounding with diagrams.

11.   Explain the working of an Impulse reaction turbine.

13.   Explain Parson’s reaction turbine.

APPLICATION

1.                        Steam issues from the nozzle of a simple impulse turbine with a velocity of 900 m/sec. The nozzle angle is 20°, the mean diameter of the blades is 25 cm and the speed of rotation is 20,000 r.p.m. m The mass flow through the turbine nozzles and blading is

0.18 kg of steam per sec. Draw the velocity diagram and derive or calculate the following : (a) Tangential force on blades, (b) Axial force on blades, (c) Power developed by the turbine wheel, (d) Efficiency of the blading, and (e) Inlet angles of

2.                        The rotor of an impulse turbine is 60 cm diameter and runs at 9,600 r.p.m. The nozzles are at 20° to the plane, of the wheel, and the steam leaves them at 600 m/sec. The blades outlet angle are 30° and the friction factor is 0.8. Calculate the power developed per kg of steam per second and the diagram efficiency.

3.                        An impulse turbine with a single row wheel is to develop 99.3 kW, the blade speed being 150 m/sec. A mass of 2 kg of steam per second is to flow from the nozzles at a speed of 350 m/sec. The velocity coefficient of the blades may be assumed to be 0.8 while the steam is to flow axially after passing through the blades ring. Determine the nozzle angle, and the blade angles at inlet and exit assuming no shock. Estimate also the diagram efficiency of the blading.

4.                        The steam leaves the nozzle of a single-stage impulse wheel turbine at 900 m/sec. The nozzle angle is 20°, the blade angles are 30° at inlet and outlet, and friction factor is 0.8. Calculate : (a) the blade velocity, and (b) the steam flow in kg per hour if the power developed by the turbine is 257'kW.

5.                        The outlet area of the nozzles in a simple impulse turbine is 15-5 err? and the steam leaves them 0.91 dry at 1.4 bar and at 920 m/sec. The blade angles are 30° at inlet and exit, and the blade velocity is 0.25 of the steam velocity at the exit from the nozzle. The friction factor is 0.8. Find : (a) the nozzle angle, (b) the power developed, (c) the diagram efficiency, and (d) the axial thrust on the blading.

6.                        A single stage impulse rotor has a blade ring diameter of 57.5 cm and rotates at a speed of 10,000 r.p.m. The nozzles are inclined at 200 to the direction of motion of the blades and the velocity of the issuing steam is 1050 m/sec. Determine the inlet blade angle in order that the steam shall enter the blades passage without shock. Assume a friction coefficient of the blading equal to 0.85 and that the inlet and outlet angles are equal. Find also: (a) the power developed at the blades for a steam supply of 1,350 kg per hour, (b) the diagram efficiency, and (c) the loss of kinetic energy due to blade friction.

CO5: Operate air compressors and observe the parameters affecting the performance

REMEMBERING

1.      List the types of air compressors.

2.      List the applications of the air compressor.

3.     List the advantages of multi stage reciprocating air compressor.

UNDERSTANDING

1.      Explain the uses of compressed air.

2.      Classify the air compressor.

3.      Explain Single stage reciprocating air compressor with line diagram.

4.      Explain multi stage compression with line diagram.

5.      Compare Reciprocating compressor with Rotary compressors.

6.      Explain with Sketch the operation of a single-stage centrifugal compressor

7.      Explain with Sketch the operation of a Screw compressor(oil free).

APPLICATION

1.                    A single-cylinder, single-acting reciprocating air compressor has a cylinder of 24 cm diameter and linear piston speed of 100 metres per minute. It takes in air at 100 kPa (100 kN/m2) and delivers at 1 MPa ( 1 MN/rrP), Determine the indicated power of the

compressor. Assume the law of compression to be pv1.25 = constant ture of air at inlet is 288 K. Neglect clearance effect.

2.                    A single-acting, single-stage air compressor developing indicated power of 11 kW, runs at 200 r.p.m. and has a linear piston speed of 100 metres per min. If the suction pressure and temperature are 100 kPa and 15‘C respectively and delivery pressure is 1,000 kPa, calculate the dimensions of the compressor cylinder. Assume the law of compression to be pv1.25 = constant. Neglect clearance effects.

3.                    A single-acting, single-stage air compressor is belt driven from an electric motor at 300

r.p.m. The cylinder diameter is 20 cm and the stroke is 24 cm. The air is compressed from one atmosphere to 8 atmospheres and the law of compression is pv1.25 = constant. Find the power of the electric motor if the transmission efficiency is 96 per cent and the mechanical efficiency of the compressor is 85 per cent Neglect clearance effect.

4.                    It is desired to compress 17m3 of air per minute from 1 bar (100 kN/m2) and 21'C to a delivery pressure of 7 bar (700 kN/m2) in a single-stage, single-acting air compressor. Calculate the power required to drive the compressor and the heat rejected during compression to cooling water if the compression is (a) Isentropic (y = 1.4 for air), and

(b) Isothermal.

CO6: Know the mechanism of refrigeration, and its types and different air conditioning system

REMEMBER

1.      Define Refrigeration, Refrigerating effect, Tonne of refrigeration and COP.

2.      Name the common refrigerants in use.

3.      List the desirable properties of a secondary refrigerant.

4.      Define Air Conditioning and list the types of air conditioning.

5.     Define Dry air, Saturated air, Dry bulb temperature, Wet bulb temperature, Dew point temperature, Relative humidity, Absolute humidity, Specific humidity.

UNDERSTANDING

1.         Explain Vapour compression refrigeration with flow diagram.

2.         Explain Vapour absorption refrigeration with flow diagram.

3.       Explain the factors affecting the choice of refrigerants commonly used in refrigerating machines.

4.         Explain winter Air Conditioning with neat sketch.

5.         Explain Summer Air conditioning with neat sketch.

6.         Explain Year round air conditioning with neat sketch.