refrigeration qb

Jpi-refqb2006 page 1

P.A.C. RAMASAMY RAJA POLYTECHNIC COLLEGE, RAJAPALA YAM – 626 108.

(AUTONOMOUS INSTITUTION) V TERM MECHANICAL(R & A/C) - 2451 REFRIGERATION

QUESTION BANK

Prepared by, J.Ilangumaran, B.E., P.G.D.C.A.,

Senior Lecturer / Mech(R&A/C) Department.

Short Answer Questions: UNIT I

1. Define Gauge Pressure, Absolute Pressure, Specific Volume and Density 2. Define Internal Energy, Specific Weight, Specific Heat and Heat 3. Define Temperature, Sensible Heat, Latent Heat and Saturated Liquid 4. Define Saturated Vapour, Superheated Liquid, Superheated Vapour and Sub-cooled liquid 5. Define Enthalpy, Entropy, Second Law of thermodynamics and Reversible process 6. Define Irreversible Process, Constant volume process, Constant pressure process and

Isothermal process 7. Define Adiabatic process, Polytropic process, Refrigerating effect and Refrigerating capacity 8. Define Refrigeration, COP, TR and Ice Refrigeration 9. Differentiate direct and indirect cooling ice refrigeration methods 10. State any four applications of liquid gases in refrigeration 11. List the names of any four liquid gases that are used in refrigeration 12. What is a heat pump? 13. Compare the refrigerator with the heat pump 14. What is the working principle of evaporative refrigeration? 15. Explain the working principle of an air refrigerator 16. How will you achieve refrigeration by throttling of the gas? 17. State the principle of operation of the Steam jet refrigeration system 18. State any four advantages of the Steam jet refrigeration system 19. What are the limitations of the Steam jet refrigeration system? 20. What is a cold plate cooling system? 21. State the applications of the spray cooling system 22. What is a relative COP? 23. Define the Energy Performance Ratio (EPR) 24. What is the Energy Efficiency Ratio (EER)? 25. Draw the reversed Carnot cycle 26. Explain the temperature limitations of the Carnot cycle for refrigeration 27. What will be the maximum possible COP of a reversed Carnot cycle? 28. Draw the line sketch of a Bell Coleman air refrigerator 29. Write notes on the actual analysis of Bell Coleman cycle 30. List any four advantages of Air Refrigeration System 31. List any four disadvantages of Air Refrigeration System 32. State the necessity for cooling an Aero plane 33. List any four advantages of Air Refrigeration System for Aero plane 34. List any four factors that are to be considered in selecting the refrigeration system for Aero

plane 35. Draw the line sketch of simple evaporative cooling system 36. Draw the line sketch of Boot strap cooling system


37. What is a regenerative cooling system? 38. What is a reduced ambient type cooling system? 39. Explain the working principle of a Vapour Absorption Refrigeration System? 40. List the parts of a NH3 absorption system 41. List any four desired properties of an ideal absorbent 42. What is a three fluids absorption system? 43. What is the COP of the Vapour absorption refrigeration system? 44. Draw the line sketch of the lithium bromide Vapour absorption refrigeration system 45. What is aqua ammonia? 46. List any four advantages of Vapour absorption refrigeration system 47. State the working principle of a Steam jet refrigeration system 48. How will you determine the mass of steam required per TR at the given temperature? 49. List any four advantages of Steam jet refrigeration system 50. Write a short notes on water as refrigerant

UNIT II

1. State working principle of the Vapour Compression Refrigeration System 2. Draw the line sketch of a Vapour Compression Refrigeration System 3. Draw the p-h diagram of the Vapour Compression Refrigeration System 4. What is called as the dryness fraction of the vapour? 5. What is a p-h chart? 6. What is a t-s chart? 7. How will you get COP from a t-s chart? 8. Draw the t-s diagram of the Vapour Compression Refrigeration System 9. Show the effect of under-cooling of the refrigerant in the condenser in p-h and t-s diagrams 10. Draw the p-h and t-s diagrams for the Vapour Compression Refrigeration System with wet

compression 11. Draw the p-h and t-s diagrams for the Vapour Compression Refrigeration System with Dry

compression 12. Draw the p-h and t-s diagrams for the Vapour Compression Refrigeration System with

superheated compression 13. Draw the p-h and t-s diagrams for the Vapour Compression Refrigeration System with the

condition that the vapour is dry at suction 14. Draw the p-h and t-s diagrams for the Vapour Compression Refrigeration System with the

condition that the vapour is superheated at the suction 15. Draw the p-h and t-s diagrams for the Vapour Compression Refrigeration System with the

condition that the vapour is superheated at the suction and the liquid is sub-cooled before expansion

16. What is wet compression? 17. What is dry compression? 18. List any four sources of superheating 19. List any advantages of Vapour Compression Refrigeration System 20. What are the effects of foreign materials if any present in the refrigerant, on the performance of

the cycle? 21. What will be the effects of pressure losses due to friction in the performance of a Vapour

Compression Refrigeration System cycle? 22. What is a refrigerating capacity? 23. What is an inter-cooler? 24. What will be the theoretical power required to drive the theoretical Vapour Compression

Refrigeration System cycle? 25. What is a flash chamber? 26. How will you sub-cool the liquid refrigerant by using vapour refrigerant?


27. What is the sub-cooling of liquid refrigerant by using external cooling source? 28. How the process of sub-cooling is done with liquid refrigerant? 29. What is an evaporator booster? 30. What is an optimum inter-stage pressure for two stage refrigeration system? 31. Define single load systems 32. What do you mean by compound compression? 33. Define multi-load systems 34. What is the use of a back pressure valve? 35. Compare any four points between wet and dry compression 36. Compare any four points between Vapour Compression Refrigeration System and Vapour

absorption refrigeration system 37. Compare any four points between Vapour Compression Refrigeration System and Air

Refrigeration System 38. “The value of COP of a Vapour Compression Refrigeration System is always more than one”.

Explain why? 39. Define the operating pressure range of a Vapour Compression Refrigeration System 40. Why the COP of a Vapour Compression Refrigeration System is quite high as compared to Air

Refrigeration System? 41. How the highest temperature occur after compression during the Vapour Compression

Refrigeration System cycle? 42. How an actual Vapour Compression Refrigeration System cycle differs from a theoretical

Vapour Compression Refrigeration System cycle? 43. Why in practice a throttle valve is in Vapour Compression Refrigeration System rather than an

expansion cylinder to reduce the pressure between condenser and evaporator? 44. How would you detect whether a refrigerator is under-charged or over-charged? 45. What are the methods to prevent a foreign material in a Vapour Compression Refrigeration

System? 46. State all four assumptions that are made in calculating the COP of a Vapour Compression

Refrigeration System UNIT III

1. What is a refrigerant? 2. Classify all the refrigerants 3. What are halocarbon compounds? 4. What are azeotropes? 5. What are hydrocarbons? 6. List the names and chemical formula for any four popular refrigerants 7. State any four thermodynamic properties of refrigerants 8. State any four safe working properties of refrigerants 9. List any four physical properties of refrigerants 10. Explain briefly about the refrigerant and oil relationship 11. List any four important properties of Ammonia 12. State any four important properties of R134a 13. List the normal requirements for the refrigerants that are used for low temperature 14. Why is the refrigerant R12 phased out? 15. How does R502 replace R22 and many other refrigerants? 16. Write short notes on refrigerant nomenclature 17. What are cryogenic refrigerants? 18. What are secondary refrigerants? 19. State any four properties of anti-freeze solutions 20. How will you select the refrigerant? 21. List any four properties of good refrigeration oil


22. Define dielectric strength and oxidation stability of refrigeration oil 23. Write the chemical name and chemical formula for R134a 24. List any four important properties of R22 25. What are GWP and ODP? 26. State any four applications of ODS 27. Explain briefly about the chain reaction by CFCs in depleting ozone layer 28. What happens if ozone layer is damaged? 29. What do you mean by global warming? 30. What are the alternatives to CFCs? 31. State any four advantages of HFCs and HFC blends 32. State any four important properties of polyol ester oil 33. List any four issues with the alternate refrigerant R134a 34. Write short notes on the handling precautions of HFC-134a 35. State any four units that are used for measuring pressure 36. Define gauge pressure and absolute pressure 37. What is a Bourdon tube gauge? 38. How is a U tube manometer used for measuring pressure? 39. Name any four temperature detectors 40. What are RTD and thermocouple? 41. Draw the line sketch of a bridge circuit for the measurement of temperature 42. Differentiate balanced and unbalanced bridge circuits 43. Draw the block diagram of a temperature detection circuit 44. List any four pressure detectors 45. What is the use of the strain gauge? 46. What are resistance type transducers? 47. Write short notes on level detectors 48. What is the use of the head flow meter? 49. What is a venturi tube? 50. Write short notes on displacement flow meters 51. State the working principle of ultrasonic flow equipment 52. What is the use of position indicators?

UNIT IV

1. What is cryogenics? 2. Write a brief history on the production of low temperature 3. State any four limitations of Vapour Compression Refrigeration System for the production of

low temperature 4. What is a multistage refrigeration system? 5. List any four advantages of multistage refrigeration system 6. Write any four limitations of the multistage refrigeration system 7. Draw the line sketch of a three stage cascade system 8. What is the optimum inter-stage temperature for a cascade system? 9. List any four advantages of three stage cascade system 10. State any four advantages of using dry ice 11. What are the three methods of manufacture of dry ice? 12. Define joule Thomson effect 13. What is a triple point? 14. How is the air liquefied? 15. Draw the line diagram of the Linde system 16. Compare any two points between Linde and Claud systems 17. How is the liquefaction of H2 different in two respects from liquefaction of N2 and O2? 18. List any four important properties of liquid He


19. List any four applications of low temperature 20. Define superconductivity 21. Explain briefly about expansion fitting 22. Define super-fluidity 23. Define cryosurgery 24. List any four important properties of liquid N2 25. State any four advantages of using cryogenic liquids in space research 26. Write short notes on low temperature insulation 27. What is a reflective insulation? 28. What are evacuated powders? 29. Name the four common types of rigid foams 30. Define super-insulation 31. Explain multilayer insulation 32. Write short notes on the hazards due to the properties of cryogenic liquids 33. What is frostbite? 34. What is a cold-burn? 35. Explain briefly about the methods used for separating liquid O2 and N2 from air 36. How is the Helium liquefied? 37. Draw the p-h diagram for a three stage cascade system 38. Draw the cycle on p-h diagram for the production of solid CO2 39. Draw the line diagram of the Claude system 40. State any four biomedical applications of cryogenic liquids 41. Define Hypothermia 42. What is an inversion temperature? 43. How does the inversion temperature affect the liquefaction of gases? 44. Describe briefly the phenomena observed at temperature close to absolute zero 45. How do you determine the temperature in the region very close to absolute zero? 46. List any four instruments that are used in the measurement of Cryogenic temperature 47. Write down the expression for finding the COP of the two stage cascade system 48. State the reasons for using solid CO2 despite of its high manufacturing cost 49. What are overlap temperature and intermediate temperature? 50. Write down the working principle of production of low temperature by adiabatic

demagnetization UNIT V

1. Explain the working principle of Thermo Electric Refrigeration System 2. Define Seebeck effect 3. Define Peltier effect 4. State the assumptions that are made in analyzing the Thermo Electric Refrigeration System 5. Write notes on the materials used for Thermo Electric Refrigeration System 6. What are the required properties of the Thermo Electric materials? 7. Define Thomson effect 8. Explain the Seebeck and Peltier effects in semi-conductors 9. State any four advantages of Thermo Electric Refrigeration System 10. What are the applications of Thermo Electric Refrigeration System? 11. What is a vortex tube? 12. Draw the line sketch showing the components of a vortex tube 13. Explain briefly about the working principle of a vortex tube 14. List any four advantages of vortex tube 15. List any three applications of vortex tube 16. What are the various types of vortex vortex tube?


17. Write down the simple theory of refrigerant mixture 18. State any four desirable properties of the refrigerant mixture 19. List the applications of the refrigerant mixture 20. What is a multi evaporator system? 21. List any four outstanding features of refrigerant mixtures 22. List any four advantages of refrigerant mixtures 23. What are the disadvantages of mixture refrigerants? 24. State the principle of magnetic cooling 25. Explain briefly about pulse tube refrigeration 26. What do you understand by non-azeotropic mixture? 27. What is the necessity of defrosting? 28. Explain manual defrosting 29. Draw the line diagram of automatic periodic defrosting 30. Explain briefly about the solid absorbent system 31. State the advantages of water defrosting system 32. Draw the arrangement of water defrosting method for an industrial installation 33. What is “defrosting by reversing cycle”? 34. Describe briefly about automatic hot gas defrosting 35. Draw the line sketch of thermo-bank defrosting 36. What is meant by automatic hot gas defrosting? 37. State the advantages of electric defrosting 38. Draw the line diagram of electric air switch defrost system 39. Explain briefly about the two units system 40. Describe briefly about multiple evaporators defrosting 41. What is the reason for frost formation? 42. What effect does frost have on cooling coil? 43. Compare any four points between automatic hot gas defrosting and Thermo-bank defrosting 44. Explain why the thermo-bank defrosting method is preferred for industrial refrigeration 45. What factors are considered in selecting a particular type of defrosting method? 46. Differentiate frosting and defrosting evaporators 47. Explain briefly about pressure control defrost method 48. Describe briefly about temperature control defrost method 49. List any four methods of defrosting 50. Compare simple hot gas and automatic hot gas defrosting methods

Essay Type Questions: UNIT I

1. Explain the six different thermodynamic processes which occur in the cycle of a closed system 2. Describe the construction and working of direct and indirect ice refrigeration methods with line

sketches 3. Explain the construction and working of evaporative refrigeration with a line sketch 4. Describe the process of refrigeration by throttling of gas using a temperature-pressure chart 5. Explain the construction and working of Vapour Compression Refrigeration System with a

neat sketch 6. Describe the cold plate cooling system and spray cooling system of refrigeration by liquid

gases 7. Describe the construction and working of engine, refrigerator and heat pump with neat

sketches 8. Explain the construction and working of Carnot and reversed Carnot cycles using p-v and t-s

diagrams


9. Describe the construction and working of Bell-coleman air refrigerator using neat sketches 10. List the advantages and disadvantages of air refrigeration system 11. Explain the factors that are to be considered in selecting a refrigeration system for aeroplane 12. Describe the construction and working of Boot-strap and Boot-strap evaporative type air cycle

refrigeration systems with neat sketches 13. Explain the construction and working of regenerative cooling system with a neat sketch 14. Explain the construction and working of practical ammonia vapour absorption system with a

neat sketch 15. Derive the COP for a Vapour absorption refrigeration system 16. Describe the construction and working of the Vapour absorption domestic Electrolux

refrigerator with a neat sketch 17. Explain the construction and working of Lithium Bromide Vapour absorption refrigeration

system with a neat sketch 18. Make an analysis of ammonia Vapour absorption refrigeration system 19. List all the advantages of Vapour absorption refrigeration system over Vapour Compression

Refrigeration System 20. Explain the construction and working of Steam jet refrigeration system with a neat sketch 21. Describe the construction and working of the steam ejector of Steam jet refrigeration system

with a neat sketch 22. State all the advantages, limitations and applications of the Steam jet refrigeration system 23. Describe the construction and working of Steam jet refrigeration system that is used for

supplying drinking water and indirect cooling with a neat sketch 24. Make an analysis of the combined Carnot engine the Steam jet refrigeration system cycles

using p-v and t-s diagrams 25. Compare Vapour absorption refrigeration system with Steam jet refrigeration system

UNIT II

1. Explain the construction and working of the Vapour Compression Refrigeration System using p-h and t-s diagrams

2. Make an analysis of Vapour Compression Refrigeration System and derive the equation for finding COP

3. How will you find the COP of the Vapour Compression Refrigeration System using t-s chart? Explain in detail

4. Represent the six different possible cycles of Vapour Compression Refrigeration System on p-h diagrams

5. Compare wet and dry compression 6. Explain the effects of under-cooling and superheating with p-h and t-s diagrams 7. List the effects of foreign material if present along with the refrigerant on the performance of

the Vapour Compression Refrigeration System cycle 8. Explain the effects of suction and discharge pressures on the performance of the Vapour

Compression Refrigeration System cycle 9. Write down the step-by-step procedure to find the refrigerating effect, work of compression,

COP, weight of refrigerant required and power required to drive the system when the vapour refrigerant is dry and saturated while leaving the evaporator

10. Write down the step-by-step procedure to find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system when the refrigerant is dry and saturated at the end of compression

11. Write down the step-by-step procedure to find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system when the refrigerant is not saturated at the end of compression and having dryness fraction


12. Write down the step-by-step procedure to find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system when the vapour refrigerant is not saturated at the inlet of compressor and superheated at the end of compression

13. Write down the step-by-step procedure to find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system when the vapour refrigerant is dry and saturated at the end of compression and the liquid refrigerant is sub-cooled after condensation

14. A refrigeration system using R134a operates between the evaporator temperature of -10 oC and the condenser temperature of 30 oC. The vapour is dry and saturated at the end of evaporation. Find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system

15. A refrigeration system using R22a operates between the evaporator temperature of -15 oC and the condenser temperature of 35 oC. The vapour is dry and saturated at the end of compression. Find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system

16. A cold storage system using NH3 operates between the evaporator temperature of -20 oC and the condenser temperature of 30 oC. The vapour is not saturated at the end of compression and having a dryness fraction of 0.16. Find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system

17. A refrigeration plant using R134a operates between the evaporator temperature of -5 oC and the condenser temperature of 30 oC. The vapour is not saturated at the inlet of compressor and superheated by 3 oC at the end of compression. Find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system

18. A refrigeration system using R134a operates between the evaporator temperature of -10 oC and the condenser temperature of 30 oC. The vapour is dry and saturated at the end of compression and sub-cooled by 4 oC after condensation. Find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system

Note

a. The above problems from 14 to 18 may also be asked by giving the operating pressure range for the most commonly used refrigerants with different possible conditions of the refrigerant.

b. Use of standard refrigerant tables and charts are permitted

19. Explain any three methods of improving COP 20. Explain the optimum inter-stage pressure for two stage refrigeration system 21. Describe the construction and working of single evaporator with multi-expansion valves and

flash chambers with neat sketches 22. Explain the compound compression with water intercooler and single expansion valve with a

neat sketch 23. Describe the construction and working of compound compression with flash intercooler and

single expansion along the flow line evaporator with a neat sketch 24. Explain the construction and working of any two types of multi-load systems with single

compressor 25. Describe the construction and working of any two types of multiple evaporator and multiple

compressor systems UNIT III

1. Explain about the classification of the different groups of refrigerants 2. Explain the desirable thermodynamic, safe-working, physical and other properties of primary

refrigerants 3. State and explain the important properties of refrigerants NH3, CO2, R12 and SO2


4. State and explain the important properties of refrigerants R134a, R22, R502 and R11 5. List the applications of Freon group of refrigerants 6. Explain about the refrigerant nomenclature using a suitable example 7. Write notes on secondary refrigerants and antifreeze solutions 8. Why the naphthalene based oils are more suitable for refrigeration purposes? Explain 9. Explain in detail about the environmental impact of CFCs and HCFCs 10. Describe the procedure of retrofitting of CFC-12 appliances with HFC-134a 11. Explain the international and national scenario for ODS phase out 12. Describe the construction and working of RTD and Thermocouple temperature detectors with

neat sketches 13. Explain the construction and working of bellows type and Bourdon type pressure detectors

with neat sketches 14. Describe the construction and working of resistance type and inductance type transducers with

neat sketches 15. Explain the gauge glass method of level detection with necessary sketches 16. Describe the construction and working of Ball float and Chain float methods of level detection

using neat sketches 17. Describe the construction and working of head flow meter and venture tube meter with neat

sketches 18. Explain the construction and working of Rota meter and displacement flow meter with neat

sketches 19. Describe the construction and working of hot wire anemometer ultrasonic flow equipment with

neat sketches 20. Explain the construction and working of differential flow detection with a block diagram 21. Describe the construction and working of “synchro” equipment and limit switch with neat

sketches 22. Describe the construction and working of LVDT with a neat sketch 23. Explain the construction and working of open loop and closed loop control systems with neat

sketches 24. Describe the functions of various elements of an automatic control 25. Explain the feed back control system with a block diagram 26. Explain the lubricant oil cooler temperature control with an equivalent block diagram 27. Explain in detail about all the four modes of automatic control 28. Explain the construction and working of proportional plus rate control system with neat

sketches 29. Describe the construction and working of hydraulic and pneumatic actuators with neat sketches 30. Explain the construction and working of electric solenoid and electric motor actuators with

neat sketches UNIT IV

1. List and explain the limitations of Vapour Compression Refrigeration System for the production of low temperature

2. Describe the construction and working of compound compression system with inter-cooling and sub-cooling with liquid refrigerant itself with neat sketches

3. Explain the construction and working of the three stage cascade system with a line sketch and represent the cycles in p-h diagram

4. Describe the three methods that are used to find the optimum inter-stage temperature for cascade system

5. Explain all the three methods of manufacture of dry ice with neat sketches 6. Describe the construction and working of Linde system of liquefaction of air with a neat sketch 7. Explain the construction and working of Claude system of liquefaction of air with a neat sketch


8. Describe the process of liquefaction of H2 with a line sketch 9. Explain the process of liquefaction of He with a line sketch 10. State and explain any seven applications of low temperature(cryogenics) 11. Describe any four types of low temperature insulation and insulating materials 12. Explain in detail about the hazards that are formed due to the properties of cryogenic liquids 13. List out the difficulties that are encountered in the production of low temperature with the help

of a single stage or multistage Vapour Compression Systems 14. Explain the p-t and p-h diagrams for CO2 in detail 15. Explain the production of low temperature by adiabatic demagnetization of a paramagnetic salt 16. Write down the history and development of cryogenics 17. Write down the general and health effect properties of liquid O2 and H2 18. Write down the general and health effect properties of liquid N2 and Argon 19. Write down the general and health effect properties of liquid He and LNG(methane) 20. Explain the general safety requirements that are becoming necessary due to the properties of

liquid CO2, O2, H2 and He 21. Describe the applications of liquid N2 and He 22. Describe the applications of liquid O2 and H2 23. Explain in detail about the cold treatment and shrink fitting of metals 24. Explain the methods of preservation of seed “germplasm” using liquid N2 25. List the effects of cryoprotectants

UNIT V

1. Write down the history and development of Thermo Electric Refrigeration System 2. Explain Seebeck, Peltier and Thomson effects with necessary sketches 3. Make an analysis of Thermo Electric Refrigeration System 4. List the advantages, disadvantages and applications of Thermo Electric Refrigeration System 5. Describe the construction, working and phenomenon of energy transfer of Vortex tube 6. State the advantages and also explain any seven applications Vortex tube 7. Explain the simple theory of refrigerant mixture 8. Explain the applications of mixture refrigerants in the process of refrigeration 9. Explain the applications of mixture refrigerants in multi-evaporator refrigeration system 10. State the advantages and disadvantages of mixture refrigerants 11. Explain the principle of magnetic cooling in detail 12. Describe the construction and working of a pulse tube with a schematic line diagram 13. Explain the construction and working of the pressure operated and temperature operated

automatic periodic defrosting methods with neat sketches 14. Explain the construction and working of the solid absorbent system of defrosting with a line

sketch 15. Describe the construction and working of the water defrosting method for industrial installation

with a neat sketch 16. Explain the construction and working of automatic hot gas defrosting method which is

employing re-evaporator coil with a neat sketch 17. Describe the construction and working of thermo bank defrost system with a neat sketch 18. Describe the construction and working of electric defrosting methods with neat sketches 19. Describe the construction and working of electric air switch defrosting method with a neat

sketch 20. Explain the method of defrosting using two outdoor units 21. Explain the construction and working of multiple evaporators defrosting 22. Compare automatic hot gas and thermo bank defrosting methods 23. Compare solid absorbent and water defrosting methods 24. Compare electric and electric air switch defrosting methods 25. Write down the factors that are to be considered in selecting a defrosting method


MODEL QUESTION PAPER CODE NO: ###

TIME: 3 HRS MAX MARKS: 75 NOTE:

1. Answer all the questions by selecting TWO questions from “a” part and ONE question from “b” part of each question

2. Use of standard refrigerant tables and charts are permitted

1 a i) Define Refrigeration, COP, TR and Ice Refrigeration [4] ii) List the names of any four liquid gases that are used in refrigeration [4] iii)What is a heat pump? [4] b i) Describe the process of refrigeration by throttling of gas using a temperature-pressure chart [7] ii) Explain the construction and working of Vapour Compression Refrigeration System with a neat sketch [7] 2 a i) How will you get COP from a t-s chart? [4] ii) Draw the t-s diagram of the Vapour Compression Refrigeration System [4] iii)Show the effect of under-cooling of the refrigerant in the condenser in p-h and t-s diagrams [4] b.i) Write down the step-by-step procedure to find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system when the vapour refrigerant is dry and saturated at the end of compression and the liquid refrigerant is sub-cooled after condensation [7] ii)A refrigeration system using R134a operates between the evaporator temperature of -10 oC and the condenser temperature of 30 oC. The vapour is dry and saturated at the end of evaporation. Find the refrigerating effect, work of compression, COP, weight of refrigerant required and power required to drive the system [7] 3 a i) Why is the refrigerant R12 phased out? [4] ii) How does R502 replace R22 and many other refrigerants? [4] iii)Write short notes on refrigerant nomenclature [4] b i) Write notes on secondary refrigerants and antifreeze solutions [7] ii)Why the naphthalene based oils are more suitable for refrigeration purposes? Explain [7] 4 a i) What is the optimum inter-stage temperature for a cascade system? [4] ii) List any four advantages of three stage cascade system [4]

iii)State any four advantages of using dry ice [4] b i) List out the difficulties that are encountered in the production of low temperature with the help of a single stage or multistage Vapour Compression Systems [7] ii)Explain the p-t and p-h diagrams for CO2 in detail [7] 5 a i) What is a multi evaporator system? [4] ii) Write notes on the materials used for Thermo Electric Refrigeration System [4] iii)Draw the line diagram of automatic periodic defrosting [4] b i) Describe the construction and working of a pulse tube with a schematic line diagram [7] ii)Explain the construction and working of the pressure operated and temperature operated automatic periodic defrosting methods with neat sketches [7]

refrigeration qb

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