R & Ac Machines_qb

P.A.C. RAMASAMY RAJA POLYTECHNIC COLLEGE, RAJAPALAYAM – 626108. (AUTONOMOUS INSTITUTION) V TERM MECHANICAL ENGINEERING (R & A/C) – ELECTIVE THEORY-I 2471 R & AC MACHINES QUESTION BANK

Prepared by,

G.Kumaraguru, B.E., Lecturer / Mech (R&A/C) department.

Short Answer Questions: UNIT I 1. What is the function of compressor in a refrigeration system? 2. Classify types of refrigerant compressors. 3. Define the following terms relating to a reciprocating compressor: Bore, Stroke, TDC, BDC 4. Define the terms: Positive displacement, Piston Displacement 5. Draw ideal and actual P-V diagram for a reciprocating Compressor. 6. Define the terms: Suction volume, Swept volume. 7. Define: Suction pressure and discharge pressure 8. Define: Clearance volume 9. How will you classify the reciprocating compressor? 10. What is the effect of clearance volume in a reciprocating compressor? 11. Define the terms: Actual volume flow rate, Mass flow rate 12. Define the terms: Refrigeration capacity, Volumetric efficiency, Compression ratio 13. On what factors does the volumetric efficiency of a compressor depend? 14. What is a multi stage compressor? 15. Obtain the conditions for the minimum work required for a two – stage-reciprocating compressor. 16. Describe the effect of suction temperature on the refrigerating capacity and Brake power of a reciprocating compressor. 17. Why a thrust bearing is used in reciprocating compressor? 18. Define Wet and Dry compression 19. Explain the performance of reciprocating compressor under wet compression. 20. Why reciprocating compressor consume high power when compared with other types? 21. Define the principle of roto – dynamic. 22. What are the types of rotary compressor? 23. What are the advantages of rotary compressor? 24. Classify all the centrifugal compressors. 25. What is hermetically sealed compressor? 26. Explain the semi – sealed and permanently sealed compressors. 27. What type of compressors are preferred for the following refrigerants: R-113, R-114, R-12 28. What is lubrication? 29. State the necessity of lubricating a refrigerant compressor. 30. Write any four properties of lubricants. 31. Describe the methods of lubricants.

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32. What is a refrigerant? 33. What are the advantages of scroll compressor? 34. What are the advantages and limitations of screw type compressor? 35. What is mean by clearance factor? 36. Define compressor capacity. 37. In reciprocating compressor clearance volume should be low. Why? 38. What is mean by cylinder heating? 39. What are the advantages of multi stage compression? 40. What are the drawbacks of single stage compression? 41. What are the advantages and limitations of hermetic sealed compressor? 42. Define “Surging”. 43. What is compressor capacity control and why it is necessary? 44. What are the methods used for control the capacity of centrifugal compressor? 45. What are the methods used for control the capacity of reciprocating compressor? 46. Define the process of lubrication. 47. What are the types of pistons used in reciprocating compressor? 48. How do you cool the compressors? 49. How will you find power required to drive a compressor? 50. What are the factors affect the performance of compressors? 51. What are assumptions made in multi stage compression? 52. What are the materials used for making a compressor components? UNIT II 1. What is the function of condenser in refrigeration system? 2. Define the following terms: Condenser capacity, condenser load. 3. Give the main types of condensers in use with specific application of each type. 4. Describe chassis mounted and remote type air-cooled condenser. 5. Discuss economical water flow rate. 6. Discuss water velocity through a water-cooled condenser. 7. Discuss the problem of scale formation in water-cooled condenser. 8. Explain the term: Heat rejection ratio. On what factor does it depend? 9. What are the various factors affecting condenser capacity? 10. What are the advantages and limitations of air-cooled condenser? 11. Define fouling factor. 12. Name the different refrigerants generally used. 13. What are the desirable properties of ideal refrigerant? 14. List the factors considered for the selection of refrigerant for a system. 15. What points are considered in selecting a condenser for a refrigeration system? 16. What are the methods used for removing scales in a condenser tubes? 17. Write sort notes on “rodding” process. 18. Write sort notes on “ Brushing” process. 19. Write sort notes on “Acid pickling”. 20. How will you remove dust and impurities present in water? 21. Why copper tubes are used in a condenser? 22. Why single row condenser is preferred over multi row condenser? 23. List out the types of air-cooled condenser.

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24. Compare natural and forced convection air-cooled condenser. 25. What is the difference between base mounted and remote air-cooled condenser? 26. Define: Counter flow and parallel flow. 27. Why counter flow systems is mostly preferred for water-cooled condenser? 28. What are the advantages of induced draught fan over forced draught fan? 29. What are the points to be considered in designing water circuit? 30. Draw the parallel flow water circuit. 31. Draw the series flow water circuit. 32. Define effectiveness an evaporative condenser. 33. List out the capacities for various water-cooled condensers in tons. 34. Draw a graph: Cost vs. Condenser pressure and also give conclusion. 35. Water-cooled condenser operates at lower condensing temperature than an air-cooled condenser. Why? 36. Where water-cooled condensers are preferred over air-cooled condenser? 37. State the applications of natural convection air-cooled condenser. 38. List out the capacities for various air-cooled condenser in tons. 39. Compare waste water system and recirculated water system. 40. What re the advantages and limitations of evaporative condenser over other? 41. What is the function of eliminator in a evaporative condenser/ 42. Define hard water and soft water. 43. Air is not considered as an economical coolant for using NH3 refrigeration system. Why? 44. State the applications of air-cooled condenser. 45. Where air-cooled condensers are preferred over water-cooled condenser? 46. How the fouling factor is responsible for the proper operation of a condenser? 47. What are the sources of non-condensable gases? 48. What are the effects of non-condensable gases present in the condenser? UNIT III 1. Define the terms: Cooling range, Tower approach, and Heat load 2. Write sort notes on Cooling tower. 3. What factors are considered in designing a cooling tower? 4. How the cooling towers are classified? 5. How the process is done in a cooling tower? 6. Write sort notes on spray ponds. 7. How can the cooling effect be increased in a cooling tower? 8. List out the different types of cooling towers. 9. What are the advantages and limitations of mechanical draft cooling tower? 10. List out the advantages and disadvantages of natural draft cooling tower. 11. What is the difference between cooling tower and spray ponds? 12. How will you find the efficiency of cooling tower? 13. Write the maintenance procedure for a cooling tower. 14. List out the materials used for making a cooling tower. 15. Fogging can be a problem with cooling tower. How is it caused and how is it controlled? 16. How do you filter the cooling water before entering the tower? 17. How do you select the materials for a cooling tower? 18. Define the terms: Evaporator load and fouling rate.

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19. What is the function of evaporator? 20. What are the advantages of flooded evaporator? 21. State the applications of bare tube evaporator? 22. State the applications of wire meshed tube evaporator. 23. State the applications of plate and tube & plate and plate evaporator. 24. State the applications of finned tube evaporator. 25. State the applications of shell and tube & shell and coil evaporator. 26. State the applications of double pipe and Baud lot coolers. 27. What are liquid chillers? 28. Discuss about the evaporator capacity control. 29. Discuss about system balancing. 30. What are natural and forced convection evaporators? 31. What are the factors that affect heat transfer capacity of an evaporator? 32. What is mean by “Slugging”? 33. Write any four applications of flooded type evaporator. 34. What is the function of baffle plate in flooded type evaporator? 35. Explain: direct expansion evaporator. 36. Write sort notes on Frosting and Non – frosting evaporators. 37. What are the advantages and limitations of non-frosting evaporator? 38. Write sort notes on Defrosting evaporator. 39. List out the various methods used for defrosting the evaporator. 40. What are the factors considered to design the evaporator? 41. What is mean by secondary evaporator? 42. What are the advantages of secondary evaporator? 43. Write the applications of fins. 44. What is cooling by evaporation? 45. What problem does lubricating oil causes in the evaporator? 46. What are the factors depend the rate of evaporation of water in cooling tower? 47. Define: Evaporator capacity. 48. What are the environmental impacts crated by cooling tower? 49. How do you find the efficiency of evaporator? 50. List the efficiencies of different cooling systems? UNIT IV 1. What are the functions of expansion devices in R & A/C systems? 2. Name various types of expansion devices. 3. What is a sensing bulb? 4. Differentiate internal equalizing and external equalizing, 5. Compare hand expansion valve and automatic expansion valve. 6. Differentiate automatic expansion valve and thermostatic expansion valve. 7. Compare low side float valve and high side float valve. 8. What is a capillary tube? 9. How does a capillary tube functions as an expansion device? 10. What are the advantages of a capillary tube to use it as an expansion device? 11. What are the disadvantages of a capillary tube to use it as an expansion device? 12. Capillary tube is not used in open system. Why?

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13. What is critical charging? 14. Why critical charging is necessary in systems that are using capillary tube? 15. What are the multi outlet expansion valves and why they are necessary? 16. What is the function of thermostatic expansion valve? 17. What are the problems caused in the operation of thermostatic expansion valve? 18. Write sort notes on dry expansion valve. 19. Write sort notes on float valve. 20. “Distributors” – what are they? 21. Discuss the necessity of distributors in a system. 22. Discuss the location of expansion valve in a system. 23. What is cross charging? 24. What are fans and blowers? 25. Classify all the fans and blowers that are used in R & A/C systems. 26. Mention the places where fans and blowers are used in R & A/C system. 27. Show in a line sketch the possible arrangements of motor with a centrifugal blower. 28. What are the fan classes? 29. What are fan standards? 30. Discuss about testing of fans. 31. How are capacity of fans and blowers controlled? 32. What are sources of fan noise? 33. Define the following terms: Total pressure, Static Pressure, Power, capacity, Efficiency. 34. What are factors to be considered for selecting fan or blower? 35. List out the types of blades in a fan impeller and draw them. 36. What are the advantages and disadvantages of forward curved blades? 37. What are the advantages and disadvantages of backward curved blades? 38. What are the types of axial flow fan? 39. Why axial flow fans never used for duct A/C system? 40. State the applications of propeller fan. 41. Draw the fan characteristics curve. 42. What are the benefits of variable speed motor? 43. What are the advantages of VAV (Variable Air Volume) method? 44. Name any two manufacturers of axial fans, Dual flow fans. 45. What are the data’s required to select a fan for a particular air conditioning installation? 46. What is the limitation of automatic expansion valve? 47. How do you control the idea of superheat condition of the refrigerant leaving the evaporator? 48. Write sort notes on fan laws. 49. “The speed reduction is a more economical method for decreasing the volume than changing the system resistance”. Explain the meaning of the above statement. 50. What is an intermediate valve? UNIT V 1. What are air cleaners and air filters? 2. Explain the use and necessity of air filters? 3. What are various methods of air cleaning? 4. What is mean by air ionization? 5. What is odour? Indicate the sources of odour.

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6. Explain the methods of measuring odour. 7. Describe the factors that are to be considered in selecting an air cleaner. 8. What is an air washer? 9. Discuss the necessity of removal of moisture. 10. Describe various methods of humidification. 11. What is adiabatic air washer? 12. What are the impurities present in the air? 13. What are types of air filters? 14. What are the purposes of dust removal equipments? 15. What are the advantages and disadvantages dry filters? 16. What are the advantages of self-cleaning filter? 17. What are the advantages and disadvantages of electronic filter? 18. What are the advantages and limitations of centrifugal dust collector? 19. How do you find the efficiency of air filters? 20. What are the methods of removing odour? 21. What is the purpose of strainer? 22. What are humidifier and dehumidifier? 23. List out the various methods of humidification. 24. What are the general considerations for the humidification process? 25. List the advantages and disadvantages of steam humidifier. 26. List the advantages and disadvantages of atomizing humidifier. 27. What are the advantages of impact humidifier? 28. Write the capacities of various humidifiers. 29. List the advantages of pan and coil humidifier. 30. Draw a diagram of forced evaporation humidifier. 31. What are the advantages of air washer humidifier? 32. List the methods of dehumidification. 33. What types of cooling coil used in dehumidification? 34. What are the advantages and limitations of refrigerant dehumidifier? 35. What are the advantages and limitations of spray dehumidifier? 36. What is the difference between absorption and adsorption type dehumidifier? 37. List the advantages and disadvantages of adsorption dehumidifier. 38. List the advantages of liquid absorbent dehumidifier. 39. Write sort notes on refrigerant dehumidifier. 40. Why lithium chloride is mostly used in liquid absorbent system? 41. Write sort notes on rotary dehumidification. 42. Name any two manufacturers of steam humidifier, Evaporative humidifier. 43. Name any two manufacturers of electric dehumidifier, heavy-duty dehumidifier. 44. Compare different dehumidification methods. 45. What are the air conditioning processes that can be carried out in an air washer? 46. What are the advantages of gear heat pump dehumidifier? 47. Describe various methods of dehumidification. 48. When will you use “viscosine” in viscous filters? 49. What are the materials used for making a throwaway filters? 50. How do you remove the dust particles by using wet filters? 51. Explain the use of activated carbon (charcoal) for removing gases and odours.

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Essay Type Questions: UNIT I 1. Explain the construction and working principle of single stage reciprocating compressor with a neat sketch. Also represent in P-V diagram. 2. Explain the factors affecting the volumetric efficiency and performance of a reciprocating compressor in detail. 3. Describe construction and working principle of a stationary blade type rotary compressor with a neat sketch. 4. Describe construction and working of vane type rotary compressor with a neat sketch. 5. Describe construction and working of a screw type compressor with neat sketch. 6. Explain the construction and working of a centrifugal compressor with neat sketch. 7. How will select a compressor for a refrigeration and A/C systems? 8. Compare centrifugal and reciprocating compressors. 9. Compare reciprocating and rotary compressors. 10. What is capacity control? Explain the various methods of capacity control used in reciprocating compressor. 11. Explain the construction and working of scroll compressor with a neat sketch. 12. Explain the capacity control of centrifugal compressor. 13. Explain the thermo compressor with a neat sketch. 14. Explain performance characteristics of reciprocating compressor. 15. What are the desirable properties of lubricants? Explain. 16. Compare the performance of reciprocating and centrifugal compressors. 17. Compare Sealed and open type compressors 18. Explain the effects of low suction pressure and high delivery pressure on the volumetric efficiency of a reciprocating compressor. 19. Describe construction and working principle of a rotating blade type rotary compressor with a neat sketch. 20. Explain the working of multi stage air compressor with a neat sketch. UNIT II 1. Classify the condensers and state their function and capacity. 2. Describe shell and tube condenser with a simple sketch. 3. Describe double pipe (Tube in tube) condenser with a neat sketch. 4. Explain natural convection air-cooled condenser. 5. Explain forced convection air-cooled condenser. 6. Describe waste water system used in water-cooled condenser. 7. Describe recirculated water system used in water-cooled condenser. Also mention the problems encountered in this system. 8. Compare air-cooled condenser and water-cooled condenser. 9. Write sort notes on types of refrigerants. 10. Discuss the various factors in detail, affecting condenser capacity. 11. Explain economical water flow rate through the condenser. 12. Discus the effects of non-condensable gases present in a water-cooled condenser. 13. Describe shell and coil condenser with a neat sketch. 14. Describe the evaporative condenser with a neat sketch.

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15. Explain the bare tube condenser with a simple sketch. 16. Explain the plate and plate condenser with a neat sketch. 17. With the help of neat sketch explain finned tube condenser. 18. Describe the wire meshed tube condenser with a neat sketch. 19. Describe the plate and tube condenser with a simple sketch.’ 20. Explain the selection of condenser. 21. Derive the relation for finding the economical water flow rate through a water-cooled condenser. UNIT III 1. Explain the natural draft deck type-cooling tower with a neat sketch. 2. Explain the forced draft-cooling tower with a neat sketch. 3. Explain induced draft cooling tower with a simple sketch. 4. Compare forced and induced draft-cooling towers. 5. What factors are considered in designing a cooling tower? Explain. 6. Write advantages and disadvantages of mechanical draft and natural draft cooling towers. 7. List the types of evaporation and explain it flooded type of evaporator with a neat sketch. 8. Discuss about the natural draft convection evaporator. 9. Explain the deck type spray bond with a neat sketch. 10. Describe the dry expansion (Direct expansion) evaporator with a neat sketch. 11. Describe the baudelot cooler with neat sketch. 12. Explain the atmospheric natural draft spray type-cooling tower with a neat sketch. 13. Explain finned evaporator with a simple sketch.’ 14. Explain plate evaporator with a simple sketch. 15. Describe shell and tube evaporator with a neat sketch. 16. Describe the shell and coil evaporator with a neat sketch. 17. Describe bare tube coil evaporator with a neat sketch. 18. Describe natural convection evaporator with a neat sketch. 19. What are direct and indirect systems? Explain them with suitable examples. 20. Compare base type coil evaporator and finned evaporator. 21. Write briefly a capacity control of evaporator with a neat sketch. UNIT IV 1. State all the expansion devices and mention their applications 2. With a neat sketch explain the construction and working principle of thermostatic expansion valve with internal equalizer. 3. With a neat sketch explain the construction and working principle of thermostatic expansion valve with external equalizer. 4. Describe hand expansion valve with a neat sketch. 5. Describe automatic expansion valve with a help of neat sketch. Why it is called constant pressure expansion valve? 6. Describe low side float valve with a neat sketch. 7. Describe high side float valve with a neat sketch. 8. Compare low side float valve and high side float valve. 9. Describe the installation of externally equalized thermostatic expansion valve along the pilot control solenoid valve. 10. How does a capillary tube function as an expansion device? Explain.

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11. Explain centrifugal fan with a neat sketch. 12. Explain the construction and operation of a vane axial fan with a neat sketch. 13. Explain the construction and operation of a tube axial fan with a neat sketch. 14. Explain the construction and operation of a propeller fan with a neat sketch. 15. Explain the selection procedure for a fan or blower for an air conditioning system. 16. Discuss the operating characteristics of centrifugal fan and draw conclusion from it. 17. Write sort notes on 1) fen in series and 2) fan in parallel. 18. Describe various types of blast from a centrifugal blower. 19. State and explain fan similarity laws. 20. Describe various types of inlets and outlets connected to a blower. 21. What are the advantages of backward blade fan over forward blade fan?

UNIT V 1. What are the different impurities of atmospheric air? Explain the effects of these impurities on human health. 2. Discuss about the various air cleaning methods. 3. With a neat diagram explain air washer humidifier. 4. Describe the process of dehumidification by refrigeration spray type. 5. Explain with a neat sketch of dry filters. 6. Describe the viscous filters with a neat sketch. 7. Describe the wet filters with a neat sketch. 8. Describe the electronic filters with a neat sketch. 9. Describe the centrifugal dust collector with a neat sketch. 10. Explain the steam injection humidifier with a neat sketch. 11. Describe the atomization humidifier with a neat sketch. 12. Describe impact type of humidifier with a simple sketch. 13. With a simple sketch explain the hydraulic separation humidifier. 14. Explain the mechanical separation humidifier with a neat sketch. 15. Write the selection procedure of air filters. 16. Explain the use of activated carbon for removing gases and odours. 17. Explain the heated air type humidifier with a neat sketch. 18. Describe the spray type air humidifier with a neat sketch. 19. Explain spray type dehumidifier with a neat sketch. 20. Discuss about various odour removal methods. 21. Explain heated water humidifier with a simple sketch. 22. Explain capillary humidifier with a neat sketch. 23. Describe liquid adsorbent dehumidifier with a simple sketch. 24. Describe construction and working of gear heat pump dehumidifier. 25. Write the applications of humidifier and dehumidifiers. 26. What is an air washer? What are the various processes in it? Explain the same.

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MODEL QUESTION PAPER CODE NO: ### MAX.MARKS: 75 TIME: 3 HRS

Note: Answer all the questions choosing any TWO divisions from (a) and any ONE from (b) of each question. I

II

III

IV

V

A. 1. What is the effect of clearance volume in a reciprocating compressor? 2. Define the principle of roto – dynamic. 3. What is hermetically sealed compressor?

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B. 1. Explain the construction and working principle of single stage reciprocating compressor With a neat sketch. Also represent in p-v diagram. 2. Compare centrifugal and reciprocating compressors.

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A. 1. What is the function of condenser in refrigeration system? 2. Define fouling factor. 3. Name the different refrigerants generally used.

(4) (4) (4)

B. 1. Describe shell and tube condenser with a simple sketch 2. Explain economical water flow rate through the condenser

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A. 1. What factors are considered in designing a cooling tower? 2. State the applications of bare tube evaporator? 3. What are the factors that affect heat transfer capacity of an evaporator?

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B. 1. List the types of evaporation and explain it flooded type of evaporator with a neat sketch 2. Explain the natural draft deck type-cooling tower with a neat sketch

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A. 1. Name various types of expansion devices. 2. What is a capillary tube? 3. Mention the places where fans and blowers are used in R & A/C system.

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B. 1. With a neat sketch explain the construction and working principle of thermostatic Expansion valve with internal equalizer 2. Explain centrifugal fan with a neat sketch.

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A. 1. Explain the use and necessity of air filters? 2. What is an air washer? 3. Write sort notes on rotary dehumidification.

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B. 1. Describe the electronic filters with a neat sketch. 2. Explain the steam injection humidifier with a neat sketch.

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