PERIYAR CENTENARY POLYTECHNIC COLLEGE PERIYAR NAGAR - VALLAM THANJAVUR. DEPARTMENT OF MECHANICAL ENGINEERING QUESTION BANK

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1 PERIYAR CENTENARY POLYTECHNIC COLLEGE PERIYAR NAGAR - VALLAM THANJAVUR. DEPARTMENT OF MECHANICAL ENGINEERING QUESTION BANK Sub : Design of Machine Elements Year / Sem: III/ V Sub Code : MEB 540 UNIT-I 1.Define any five mechanical properties metals with at least one example. 2.Explain how alloy steels are designated with an example. 3.What is free cutting steel? How it is designed? 4. A mild steel rod supports a tensile load of 50 KN. If the stress in the rod is limited to 100 N/mm 2, determine the size of the rod When the cross-s=section is (i) Circular (ii) Square (iii) rectangle with width = 3x thickness. 5.A steel rod of 100mm 2 Cross- sectional area is made up of stands (threads of rope) 1mm in diameter having an allowable tensile stress of 168 N/mm 2 and an ultimate strength of 130 KN. The factor of safety is 8. If 10 strands are broken along a pitch of the lay of strands, is the rope fit for further use, Why? 6.A knuckle joint is subjected to a pull of 80kn. If the maximum permissible tensile stress in the rods is 100N/mm 2 and the permissible shear in the pin is 80N/mm 2,Calculate the diameter of the rods of the pin. 7. A hydraulic press exerts a total load of 4MN which is carried by two steel rods of 2.5 m long supporting the upper head of the press. It the safe stree is 85 Mpa and E= 210 kn/mm 2, Calculate (i) The diameter of rods. (ii) Extension in each rod.

2 8.Design a sleeve and cotter joint to withstand a tensile load of 60KN. All parts of the joint are made of the same material and the permissible stresses are given below. f t = 60 N/mm 2 ; f c =125N/mm 2 ; f s = 70N/mm 2 9. A casting weighting 30 KN is lifted by means of an eye bolt of 30mm nominal diameter. The bolt extends 40mm into the casting. Determine direct tensile and shear stresses in the threaded portion of the bolt. 10.A square tie bar 20mm x 20mm in section carries a load. It is attached to a bracket by means of 6 bolts. Calculate the dia of the bolt if the maximum stress in the bar is 150 N/mm 2 and in the bolt is 75 N/mm 2

3 UNIT-II 1. A hollow shaft transmits 600kw at 500rpm. The maximum shear stress is 60N/mm 2.. Find the outside and inside diameter of the shaft, If the outer diameter is twice that of inside diameter. Assume maximum Torque is 20% great that the mean torque. 2.A Pair of wheels of a railway wagon carries a load of 50Kn on each axle box, acting at a distance of 100mm outside the wheel base. The gauge of the rails is 1.4m. Find the diameter of the axle between the wheels, if the permissible stress is 100N/mm 2. 3.A shaft made of mild steel is required to transmit 100kw at 300rpm. The supported length of the shaft is 3m. It carries 2 pulleys each weighing 1500N, supported at a distance of 1m from each ends respectively. Assume the safe value of stress as 60N/mm 2. Determine the diameter of the shaft. 4.A rectangular key 40mm length is required to transmit 10 KW at 900rpm. Determine the size of the key, If the permissible shear stress and crushing stress are limited to 65N/mm 2 respectively, Assume that the shaft and key are made of the same material. 5.Design a protective type flange coupling to connect two shafts to transmit 7.5kw at 720rpm. The permissible shear stress for the shaft, bolts and key materials is 33N/mm 2, Permissible crushing strength for bolt and key material is 60N/mm 2 and permissible shear stress for cast iron is 15N/mm 2. 6.A shaft is transmitting 97.5 KW at 180 Rpm. If the allowable shear stress in the material is 60 Mpa, find the suitable diameter for the shaft. The shaft is not to twist more than 1º in a length of 3m. Take G=80 Gpa. 7. A 15 KW 960 rpm motor has a mild steel shaft of 40mm diameter and the extension being 75mm. The permissible shear and crushing stresses for the mild steel are 56 Mpa and 112 Mpa. Design the key.

4 8.A shaft 30mm dia is transmitting power at a maximum shear stress of 80Mpa. If a pulley is connected to the shaft by means of key. find the dimension of the key so that the stress in the key is not to exceed 50 Mpa and the length of the key is 4 times the width of the key. 9. A flange coupling has to transmit 110kw at 200rpm. The allowable shear stress of the material is 40MPa and the safe stress may be taken as 30Mpa for the bolts. Assuming the maximum torque to be 15 percent greater than mean, determine the diameter of shaft, dia of the bolt, number of bolt and pitch circle dia of bolt.

5 UNIT-III 1.Select a flat belt from manufacturer s catalogue to transmit power of 15KW at 1200RPM. The speed of the driven pulley is 450 RPM. Max centre distance between the shaft is 2m. Assume steady load. 2.Select the crossed flat belt drive from the manufacturer s catalogue to transmit a power of 25KW at 960RPM. The speed of the drive pulley is 500RPM. Centre distance between shafts is 1.5m. Apply intermittent load. 3.Design V-belt to the following specification. Power to be transmitted =75Kw Speed of driving wheel =1440 rpm Speed of driven wheel =400 rpm Diameter of driving wheel=300mm Centre distance = 2500 mm Small pulley factor, K d = 1.14 Service factor,=1.3 Correction factor for length, K t = Design a V-belt drive and calculate the actual tensions from the following data. dia of driven pulley = 600 mm dia of driving pulley = 200 mm Centre distance between pulleys = 1000mm (approximately) Speed of driven pulley=400 Rpm Speed of driving pulley = 1200 Rpm Power transmitted = 10 KW (Don,t convert to w) Service-heavy duty -16 hours/day.

6 5. A belt drive consists of two V-belts in parallel on grooved pulley of the same size.the angle of groove is 30º.The cross-sectional area of each belt is 750mm 2 and coefficient of friction is The density of belt material is 1.2Mg/m 3 and the maximum stress in the material is 7MN/m 2. Calculate the power that can be transmitted between pulley of 300mm diameter rotating at 1500Rpm. Find also the shaft speed in speed in rpm at which the power transmitted would be maximum. 6.Write short notes on belt materials. 7.Sketch and name the different types of belts used in engineering field. 8.Draw the sketch and note the specifications. A design a fabric belt to transmit 11KW at 420RPM of an engine to a line shaft at 20 RPS. Engine Pulley diameter is 550mm and the centre distance is 2m. Assume coefficient of friction µ = 0.2 and number of plies =6. 9. Leather belt drive transmits 15KW power. The centre distance between the pulleys is twice the diameter of the big pulley. The speeds of big and small pulleys are 480 rpm and 1440rpm respectively. The belt should operate at a velocity of 20m/sec approximately and the stresses in the belt should not exceed 2.25 N/mm 2. The density of leather is 0.95 gm/cc and the co-efficient of friction is The thickness of the belt is 5mm. Calculate i) The diameters of pulleys ii) The length and width of belt iii) The belt tensions. 10.A leather belt 9mm thick transmits 26KW from a pulley one metre diameter running at 300rpm. The friction co-efficient between belt and pulley surface is 0.28 and the belt material weighs 9.3 x10 3 N/m 3. The angle of lap is 165º. If the stress in the belt is limited to 3N/mm 2. Determine the width of belt.

7 11. A power of 60ke at 750 rpm is to transmitted from an electric motor to a Compressor shaft at 300rpm by V belt. The approximate larger pulley diameter is 1500 mm. The approximate centre distance is 1650 mm. Cross sectional area is 350 mm 2 and density is 1000 kg/m 3, having an allowable tensile stress of 2 Mpa is allowable for use. Overload factor is 1.5. a=34º, µ = 0.28.

8 UNIT-IV 1.Design a journal bearing for a centrifugal pump from the following:- Load on the journal =20KN. Speed of journal =900 rpm. Diameter of journal =100mm. L/D=1.6. Type of oil used is SAE 10 for which the absolute viscosity at 55ºC.Maximum bearing pressure=1.5n/mm 2. Heat dizzipation co-efficient =1332 J/S/m 2 /ºC. Calculate the mass of lubricatinf oil required for artificial cooling, if rise in temp of oil is limited to 10ºC. ATake specific head of oil as 1710 J/kg k. 2.A journal bearing 300mm long and 150mm dia carries a radial load of 9KN at 1200 rpm. The power lost in friction is 6KW. Viscosity of oil at room temperature is Pa s. Find the diametral clearance, 3.A journal bearing 75mm long supports a load of 7500N on a 50mm diameter journal running at 750rpm. The diametral clearance is mm. determine the viscosity of oil if the operation temp. of the bearing surface is limited to 77ºC. The ambient temp=21ºc. Heat dissipating co-effcient =210W/m 2 / ºC. 4. An 80mm long journal bearing supports a load of 2800N on a 50mm diameter shaft. The bearing clearance of 0.05mm and the viscosity of the oil is kg/m-s at the operating temperature. If the bearing is capable of dissipating 80J/s, determine the maximum safe speed. 5.State and explain the different properties of materials used for sliding contact bearings. 6. A journal bearing is proposed for a centrifugal pump. The diameter of the journal is 150mm and the load on it is 40KN and its speed is 900 rpm. Design and given the complete calculations for the bearing. 7.Design a suitable journal bearing a centrifugal pump form the following data: Load on the bearing = KN Dia of the journal = 80 mm Speed = 1440 rpm Bearing characteristic number = 30x10-6 Permissible bearing pressure = 0.7 to 1.4 N/mm 2 Average atmospheric temp = 30º C Calculate the cooling requirements using lasche s equation. Use Mckee s equation for calculating the friction co-efficient of head dissipation, K = /m 2 /w for heavily Constructed bearing. Temperature rise, t º =6º C

9 11.The load on a 100mm fully hydro dynamic bearing is 900nN. Speed of journal is 320rpm. Take l/d=1,c/d= Temperature is 65º C. Minimum oil film thickness =0.022 (i) Select an oil that will closely accord with the stated conditions. For the selected oil, determine (ii) Power lost in friction (iii) Oil flow through the bearing (iv) Amount of leakage (v) temperature rise of oil when it passes through the bearing and (vi) maximum Oil pressure.

10 UNIT-V 1.A hand lever is mounted on a shaft. The maximum force of 150N is applied by the worker. The distance between the centre of the shaft to the point of load is 1m. Determine the diameter of the solid shaft, If the permissible shear stress is limited to 20N/mm 2. Determine the section of the lever near the boss, if the permissible stress is limited to 85N/mm 2. Assume rectangular cross-section with sides in the ratio 1:2 2.Design a hand lever of rectangular section subjected to a maximum load of 250N at the end of moment arms of 1.2m. The thickness of the lever is constant and is equal to times the width of lever near the boss., Permissible shear stress for the shaft material is 40N/mm 2 and the permissible bending stress for the lever material is 80N/mm 2 3. A foot lever is 1000mm from centre of shaft to point of applications of load of 900N. Calculate the diameter of the shaft, if the permissible shear stress for the shaft material is 75N/mm 2. Determine the dimension of the key if the safe shear stress for the key material is 80N/mm 2. Find the diamension of rectangular arm of the foot lever at 100mm from the centre of the shaft. Assume width of the lever near the boss as 3 times the thickness.allowable bending stress is 70N/mm 2. 4.A pinion runs at 600 rpm drives a gear at a speed ratio of 4:1. Allowable static stress of point and gear material is 85N/mm 2. Pinion has 16 teeth of module 8mm. Teeth are 20º F.D system. Face width 90mm. Find the power transmitted 5.A cranked lever has the following dimension. Length of the handle = 400mm, Length of the lever arm= 500mm, Overhang of the Journal=200mm. If the lever is operated by a single person exerting a maximum forces of 500N at a distance of 1/3 rd length of the handle from its free end. Find (i)diameter of the handle (ii) Cross section of the lever arm which is rectangular b= 2t. (iii) diameter of the journal. The permissible bending stress for the lever material may taken as 50Mpa and shear stress for the shaft material may taken as 50MPa and shear stress for the shaft material is 42MPa.

11 6.Design a cranked lever having a length of handle as 0.5m,length of lever arm as 0.45m and overhang of the journal as 0.1m. The lever is used for operating hoisting which and is operated by two persons exerting a maximum force of 500N at a distance of 0.4 times the length of the handle from free end. The bending stress in lever should not exceed 50N/mm 2 and shear stress in lever should not exceed 50N/mm 2. Shear stress in the should not exceed 40N/mm 2. 7.It is desired to transmit 10KW from a motor shaft running at 1440 rpm to alow speed reduction of 3:1. The teeth are 14 1/2º involute with 25 teeth on the pinion. The starting torque is 30% higher than the running torque. Both the pinion and gear are made of steel heat treated. Design a suitable spur gear drive to satisfy the above condition y= /tp for 141/2º involve gear. Assume module=6. Allowable static stress, f º =210MPa.

12 ******* PERIYAR CENTENARY POLYTECHNIC COLLAGE THERMAL ENGINEERING -11 SUBCODE:- MEB-510 QUESTION BANK DETAILS UNIT-1 PART A 1. What is the value of the boiling point of water? 2. What is value of the dryness fraction? 3. What are the types of calorimeter? 4. Write advantages of steam tables. 5. Define: wet steam. 6. Define: dry and saturated steam. 7. Define: superheated steam. 8. Define: enthalpy of water 9. Define: Dryness fraction. 10. Define: Internal energy of steam. 11. Define: enthalpy of evaporation. 12. Write the expression for enthalpy of super heated steam 13. Write the expression for entropy of wet steam 14. Write the expression for entropy of superheated steam 15. Write the expression for internal energy of super heated steam 16. Define external work of evaporation. 17. Define: Entropy of evaporation. 18. Define: Entropy of steam. 19. Define: density of steam. 20. What is phase diagram? 21. What you meant by heat of super heat? 22. State three conditions of steam. 23. write the expression for enthalpy of dry and saturated steam Part-B 1.Determine the specific volume, enthalpy, entropy, external work, internal latent heat and ineternal energy of steam 8bar and 95%dry. 2. Determine the specific volume, enthalpy, entropy, external work, internal latent heat and ineternal energy of dry saturatead steam at 150 C 3. Determine the specific volume, enthalpy, entropy, external work, internal latent heat and ineternal energy of steam 20 bar and 250C.assume CPs=2.1kj/kg k. 4.Find the amount of heat required to rise the temperature of 3kg of water at 40Cto generation temperature of 175C 5.Find the amount of heat required for 3kg of water at45c in order to convert it into steam at 4 bar and80%dry

13 6. Dry and saturated stream at heat at that a particular pressure has a total heat of 2750 kj/kg. if it is superheated until its total heat at that pressure is 3180kj/kg.Find degree of superheat. Assume Cps=2.2kj/kg k. 7. determine the entropy of super heated steam at a pressure of 14 bar and temperature of 250C.assume CPs=2.05kj/kg k. 8.In an experiment on wet steam in a barrel calorimeter, the following readings were taken. Steam pressure= 5.5bar Mass of copper calorimeter=1kg Mass of calorimeter+water=3.8kg, Mass of calorimeter+water+_steam=4kg, \ Initial temperature of water=10c Final temperature of water=50c Specific heat of copper=0.092kj/kg k. calculate dryness fraction of steam. 9. The following observation were recorded to find the Dryness Fraction of steam by combined separated and throttling calorimeter Total quantity of steam passed=36kg Water drained from separator=1.8kg Steam pressure before throttling=12 bar Pressure of steam after throttling =atmospheric pressure Temperature of steam after throttling =110C Specific heat of superheated steam =2.091 kj/kg k Determine the a) dryness fraction of steam entering into throttling calorimeter b)dryness fraction of steam in steam main 10. Explain the separating and throttling calorimeter UNIT -2

14 PART A 1. What is the function of air pre heater? 2. What is the function of super heater? 3. Write the function of economizer. 4. Write the advantages of high pressure boiler. 5. What is boilers? 6. What is high pressure boilers? give an example. 7. Give an example for high pressure boilers. 8. List the boilers mountings as per the Indian boiler act. 9. What is boilers mountings? 10. What is boiler accessories? 11. What is fire tube boilers? 12. What is water tube boilers? 13. What are the common external treatment given to boilers feed water? 14. State any two functions of boiler accessories. 15. What are two the common internal treatments given to the boiler feed water? 16. Name any two boiler accessories. 17. What is foaming in boilers? 18. State the functions of blow off cock in boiler. 19. State the functions of springs loaded safety valve 20. Define: Capacity of boilers 21. Define: Actual evaporation 22. Define: Factor evaporation 23. Define: equipment evaporation 24. Define: boiler power 25. Write down the formula for mass of actual evaporation? 26. Define: boiler efficiency. 27. What are the objectives of boilers trail? 28. What are the various heat losses in boiler? explain how it is minimized? 29. What are the various factors influencing boilers efficiency? PART-B 1.State the main clauses of Indian boiler act 2. Explain with neat sketch the working of Lamont boiler 3. Explain with line sketch the working of BHEL high pressure boiler 4. Explain with neat sketch the functions location and working of any two boilers mountings 5. Explain with neat sketch the functions locations working of any two boilers accessories 6. A boilers generation 810 kg of steam per hour at 11 bar absolute with 50 C superheat the coal supplied is 90 kg per hour and calorific value is KJ /Kg the feed water temperatures 45 C and specific heat of super heated steam is 2.1 KJ /Kg.calculate a) Actual evaporation

15 b) Equivalent evaporation from and at100 C c) Boiler efficiency d) Boiler power 7. During the test of an oil fired water tube boilers the following data were obtained Steam pressure : 16 bar abs Water evaporation per minute : kg Feed water temperature : 76 c Quality of staem:99%dry Fuel oil fired per minute : 22.45kg Calorific valve of fuel oil: KJ /Kg oil Calculate a) C actual evaporation b) V factor of evaporation c) The Equivalent evaporation from and at 100C d) Boiler efficiency E) Boiler power 8. In an evaporation test on a boiler, the following readings were recorded Size of feed water tank : 5m x2m Initial depth of water:3m Final depth of water:2.25m Amount oil fired:800litres Specific gravity of oil;0.82 Cv of fuel; ;42000kj/kg Boiler water temperature :40.c feed water pressure ;10bar abs quantity of steam : 0.95dry Duration of trail:25min Calculate a) Actual evaporation Equipment evaporation from ands at 100C b) Boiler efficiency

16 c) Boiler power 9. A boiler generation 8.5 kg of steam per kg coal burned at is pressure of 12.5 bar gauge from Feed water having absolute temperature of 350K the efficiency of boiler is 70% and factor of evaporation is 1.17, specific heat of super heated steam is 2.2 KJ /Kg k. UNIT 3 PART-A 1. What are the basic cycles for steam power plant? 2. What is the actual power cycle for steam power plant? 3. Name the processes in Carnot cycle?

17 4. Draw the T-S diagram for Carnot steam power cycle and name the processes 5. Draw the T-S diagram of Rankine cycle and name the processes 6. What Is the purpose of using modified Rankine cycle? 7. Write the formula to determine maximum thermal efficiency of the steam power cycle. 8. What is steam turbine? 9. What is impulse turbine? 10. What is reaction turbine? 11. What is impulse reaction turbine? 12. What is meant by compounding of turbines? 13. Why are the steam turbines compounded? 14. List the type of compounding. 15. Name the important industrial turbines? 16. Why are steam condenser used in steam power plant? 17. List the elements of steam condensing plant. 18. What is jet condenser? 19. What are the types of jet condenser? 20. What is surface condenser? 21. What are the types of surface condensers? 22. What is meant by condensers vacuum? 23. Define :vacuum efficiency 24. Define: condenser efficiency. 25. State Dalton s law of partial pressure PART B 1. Draw the P-V and T-S diagram of modified ranking cycle and indicate various processes

18 2. Explain the working of the following with suitable sketches a)bake pressure turbine b) Exhaust turbine 3. Draw the explain P-V and T-S diagram of Carnot cycle and derive an expression for efficiency of Carnot cycle using steam as working fluid. 4. What is the necessity of compounding? Explain pressure compounding in a steam turbine with a neat sketch. 5. What is meant by special turbine? Explain bleeder turbine with suitable line diagram. Also mention their applications. 6. What is meant by pressure velocity compounding? Explain with a neat sketch. 7. The vacuum in the condenser is 680mm of Hg with barometer readings of 755 mm of Hg. The condenser temperature is 20 C. Find a) corrected vacuum b) Partial pressure of air and steam c) Mass of air per kg of uncondensed steam d) Mass of the air per m 3 of condenser volume. 8. During a trail on steam condenser a vacuum of 685mm of Hg was obtained with a barometer readings of 765 mm of Hg. The temperature of the condenser is 34 c. Correct the vacuum to a standard barometer reading of 760mm of Hg. Also determine the partial pressure of air and steam. Vacuum efficiency, mass of air present per kg of uncondensed stream. 9. Explain the working of condensing plant with line diagram. 10. Explain working of two types jet condenser 11. Explain the working of surface condenser with suitable sketch. 12. Explain the working of evaporative condenser.

19 1. Define : Refrigeration UNIT-4 PART-A 2. What is refrigerator? 3. What is heat pump? 4. Define: COP of refrigerator. 5. Define : COP of heat pump 6. Define: Refrigerating effect 7. Define: capacity of refrigerator 8. Define unit of refrigeration 9. Define: refrigerant

20 10. Define air conditioning 11. Define specific humidity 12. Define relative humidity 13. Define : Dew point temperature 14. Define : Dry bulb depression 15. Define wet bulb depression 16. What is the psychometric chart? 17. What is the sensible cooling? 18. What is the sensible heating? 19. What is humidification? 20. What is de-humidification? 21. Define actual COP. 22. Name the psychometric process employed in summer A/C. 23. Name the psychometric process employed in winter A/C. 24. What are the ideal cycles for air refrigeration system? 25. Give an example for Vapour compression refrigeration system. PART-B 1. Differentiate Vapour compression and Vapour absorption system 2. Explain with line diagram the working of Vapour compression refrigeration system. 3. Explain with line diagram the working of Vapour absorption refrigeration system 4. Describe the working of window type of air conditioning system with a sketch. 5. Describe working of central plant air conditioning system with a sketch 6. With a neat sketch explain the air refrigeration system working on bell- coleman cycle.

21 7. A refrigeration system operates on the reversed carnet cycle. The highest temperature of the refrigeration system is 40 C and the lowest temperature is 10 C. The capacity of the machine is to be 10 tones. Find a) COP b) Heat rejected from the system per hour c) power required for diving of machine. 8. A Carnot refrigerator requires 1.25 KW per ton of refrigeration to maintain the temperature of - 28 c. Find the a) COP b) Temperature at which heat is rejected. 9. An air refrigeration system works on reversed Carnot cycle between the temperature limits of 28 C and 5 C. The capacity of the system is 10 tones. Find a) COP b) Heat rejected from the system per hour. c) Power required for the motor if the overall efficiency is 85%. UNIT -5 PART A 1. What is meant by conventional sources of energy? 2. List the important conventional energy sources. 3. List the important components of hydroelectric power plants 4..list the important components of diesel power plant 5. List the important nuclear fuel 6..list the important fissile fuels used 7. List the important fertile fuels used 8. What is meant by fissile fuel? 9. What is meant by fertile fuel? 10. What is meant by nuclear fission 11. What is meant by nuclear fusion 12. What is chain reactions 13. List the important elements of nuclear fusion 14. List the important components of nuclear power plant 15. Give an example for moderators materials 16. Give an example for control rod materials 17. Give an example for coolant used in nuclear reactor 18. What is the main function of moderator

22 19. What are the functions of control rod? 20. What is the function of coolant in nuclear reactor 21. Write the expansion of PWR 22. Write the expansion of BWR 23. What stands for CANDU? 24. Name the fuel and moderator used in PWR. PART-B 1.Draw the layout of hydroelectric power plant and explain in details 2.With suitable line diagram explain the diesel power plant. State its merits and demerits 3.What are the advantages and disadvantages of hydroelectric power plant 4.What are the merits and demerits of diesel power plant? 5.Draw the layout of nuclear power plant and explain 6. With a neat sketch explain the working of BWR?state its merits and demerits 7.With a neat sketch explain the working of CANDU type reactions.state its merits and demerits 8.Explain nuclear fuel cycle 9.Explain in detail about any three methods of uranium enrichments 10.Discuss in detail about disposal of nuclear wastes 11.Discuss in details about nuclear power plants in India