air compressors refrigeration cycles refrigeration plant nozzles steam turbines - One Line Questions

1. In a reciprocating compressor, the clearance volume significantly affects the volumetric efficiency. What is the typical range for clearance volume as a percentage of the stroke volume? — 1% to 5%
2. What is the primary difference between a nozzle and a diffuser? — A nozzle increases velocity and decreases pressure; a diffuser decreases velocity and increases pressure.
3. In a steam turbine, the expansion of steam occurs across: — Both stationary and rotating blade rows
4. The efficiency of a nozzle is defined as the ratio of: — Actual kinetic energy at exit to isentropic kinetic energy at exit
5. The volumetric efficiency of a reciprocating compressor is defined as the ratio of: — Actual volume of air delivered to the swept volume
6. The term 'isentropic efficiency' of a compressor refers to the ratio of: — Actual work input to isentropic work input
7. What is the critical pressure ratio for air expanding from stagnation conditions to sonic velocity at the throat of a nozzle? — Approximately 0.528
8. Which refrigeration cycle is considered the ideal vapor-compression cycle? — Vapor-compression cycle with saturated vapor at compressor inlet and saturated liquid at condenser outlet
9. Which component in a refrigeration plant is responsible for removing heat from the cooled space? — Evaporator
10. In a vapor-compression cycle, the heat rejected in the condenser is equal to: — Enthalpy of vapor refrigerant leaving condenser - Enthalpy of vapor refrigerant entering evaporator
11. In a steam turbine, blade speed is crucial. For maximum efficiency in an impulse turbine, the blade speed should ideally be: — Half the steam jet velocity
12. Which problem is most likely to occur in the later stages of a steam turbine operating with wet steam? — Erosion of blades
13. The Coefficient of Performance (COP) for a refrigeration system is defined as: — Heat absorbed from the cold reservoir / Work input
14. The Bell-Coleman cycle, also known as the air refrigeration cycle, is best suited for applications requiring: — Cooling with a non-condensable fluid
15. What is the primary advantage of using a Curtis turbine (a type of velocity-compounded impulse turbine)? — Low blade speeds required, reducing centrifugal forces
16. A rotary vane compressor utilizes vanes that slide in and out of slots in a rotor. What is the main advantage of this type of compressor? — Compact size and low noise levels
17. What is the main cause of 'th trusting' in steam turbine blades? — Centrifugal forces
18. Which type of steam turbine is typically used for high-power generation in thermal power plants? — Multi-stage turbine
19. A nozzle is a device designed to: — Decrease the pressure of a fluid by increasing its velocity
20. The 'flash gas' in a refrigeration system causes: — Reduced compressor efficiency
21. What is the effect of increasing the compression ratio in a reciprocating compressor, assuming constant stroke volume and speed? — Decreased volumetric efficiency
22. The theoretical COP of a vapor-compression refrigeration cycle can be increased by: — Decreasing the evaporator pressure
23. Which factor has the most significant impact on reducing the work of compression in a multi-stage compressor with intercooling? — Increasing the number of stages
24. In a vapor-compression refrigeration cycle, the expansion valve (or capillary tube) is responsible for: — Cooling the refrigerant to a lower temperature and pressure
25. Which of the following is a characteristic of a 'supercritical' fluid in the context of refrigeration? — It exists above its critical temperature and critical pressure.
26. Which statement about R-744 (Carbon Dioxide) as a refrigerant is correct? — It operates in a transcritical cycle at typical conditions.
27. In a converging-diverging nozzle, if the back pressure is equal to the pressure at the exit of the diverging section under choked conditions, what is the Mach number at the exit? — Greater than 1
28. What is the main disadvantage of using a single-stage impulse turbine for high-pressure applications? — High blade speeds required, leading to mechanical stress
29. What is the primary energy conversion occurring in the nozzle of a steam turbine? — Thermal energy to kinetic energy
30. A centrifugal compressor is characterized by: — Continuous flow with no moving valves
31. A reaction turbine is characterized by: — Pressure drop occurring in both stationary and moving blades
32. The efficiency of a steam turbine is generally higher for which type of turbine? — Multi-stage impulse-reaction turbine
33. Which refrigerant is commonly used in domestic refrigerators and has a high COP but is flammable? — R-600a (Isobutane)
34. Which of the following refrigerants has the highest Ozone Depletion Potential (ODP)? — R-22
35. Which type of compressor uses a rotating impeller to impart velocity to the fluid, which is then converted to pressure energy in a diffuser? — Centrifugal compressor
36. Which type of rotary compressor is known for its high volumetric efficiency and ability to handle large volumes of air or gas? — Rotary screw compressor
37. In a vapor-compression cycle, the refrigerant enters the compressor as: — Superheated vapor
38. Which type of steam turbine uses multiple stages of nozzles and rotors to extract energy from the steam progressively? — Multi-stage turbine
39. In an isentropic nozzle, the velocity of the steam increases as it passes through. What happens to the temperature and pressure of the steam? — Temperature and pressure decrease
40. For a converging nozzle, the maximum mass flow rate occurs when: — The back pressure is equal to or below the critical pressure
41. Choked flow in a nozzle occurs when: — The Mach number at the throat reaches unity
42. In a centrifugal compressor, the pressure rise is achieved by: — The centrifugal force acting on the fluid
43. In a de Laval nozzle (converging-diverging), if the back pressure is reduced below the pressure corresponding to the Mach number at the exit, what happens to the flow? — The flow remains choked at the throat and expands further in the diverging section
44. For a converging-diverging nozzle, what is the condition at the throat for supersonic flow to exist in the diverging section? — The Mach number at the throat must be unity (M=1)
45. What is the 'degree of reaction' in a steam turbine? — The ratio of enthalpy drop in the moving blades to the total enthalpy drop
46. What is the purpose of a muffler in an air compressor system? — To reduce the noise level of the compressed air
47. What is the purpose of compounding in a steam turbine? — To increase the efficiency by reducing blade speed
48. What is the primary function of an intercooler in a multi-stage reciprocating compressor? — To reduce the work done per unit mass of air compressed
49. What is the primary function of the nozzle in a steam turbine? — To convert the thermal energy of steam into kinetic energy
50. What is the primary purpose of a receiver in a refrigeration plant? — To ensure a liquid supply to the expansion device
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