Thermal Engineering 24

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Objective Questions and Answer: Thermal Engineering 24

Subject: Thermal Engineering 24

Part 24: Objective questions and answers of Thermal Engineering


Q1. More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than

a) 2 kg/cm^2

b) 6 kg/cm^2

c) 10 kg/cm^2

d) 14.7 kg/cm^2


Q2. The advantage of multistage compression over single stage compression is

a) Lower power consumption per unit of air delivered

b) Higher volumetric efficiency

c) Decreased discharge temperature

d) All of the above.


Q3. Pick up the wrong statement about advantages of multistage compression

a) Better lubrication is possible advantages of multistage

b) More loss of air due to leakage past the cylinder

c) Mechanical balance is better

d) Air can be cooled perfectly in between


Q4. As the value of index '«' is decreased, the volumetric efficiency will

a) Increase

b) Decrease

c) Remain unaffected

d) May increase/decrease depending on compressor clearance


Q5. The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called

a) Slip factor

b) Velocity factor

c) Velocity coefficient

d) Blade effectiveness


Q6. Losses in a centrifugal compressor are due to

a) Inlet losses

b) Impeller channel losses

c) Diffuser losses

d) All of the above


Q7. The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature

a) 0.10%

b) 0.50%

c) 1%

d) 5%


Q8. The indicated work per unit mass of air delivered is

a) Directly proportional to clearance volume

b) Greatly affected by clearance volume

c) Not affected by clearance volume

d) Inversely proportional to clearance volume


Q9. The blades of gas turbine are made of

a) Mild steel

b) Stainless steel

c) Carbon steel

d) High nickel alloy


Q10. Which is false statement about advantages of multistage compressor in comparison to single stage compressor?

a) Less power requirement

a) Better mechanical balance

b) Less loss of air due to leakage past the cylinder

c) Lower volumetric efficiency.


Q11. The ratio of isentropic work to Euler work is known as

a) Pressure coefficient

b) Work coefficient

c) Polytropic reaction

d) Slip factor


Q12. The criterion of the thermodynamic efficiency for rotary compressor is

a) Isentropic compression

b) Isothermal compression

c) Polytropic compression

d) Any one of the above


Q13. For supplying intermittent small quantity of air at high pressure, following compressor

is best suited

a) Centrifugal

b) Reciprocating

c) Axial

d) Screw


Q14. For minimum work in multistage compression, assuming same index of compression in all stages

a) Work done in first stage should be more

b) Work done in subsequent stages should increase

c) Work done in subsequent stages should decrease

d) Work done in all stages should be equal


Q15. For a two stage compressor* if index of compression for higher stage is greater than index of compression for lower stage, then the optimum pressure as compared to ideal case will

a) Increase

b) Decrease

c) Remain unaffected

d) Other factors control it


Q16. Diffuser in a compressor is used to

a) Increase velocity

b) Make the flow stream-line

c) Convert pressure energy into kinetic energy

d) Convert kinetic energy into pressure energy


Q17. The ratio of isentropic work to euler's work is known as

a) Compressor efficiency

b) Isentropic efficiency

c) Euler's efficiency

d) Pressure coefficient


Q18. The thermodynamic efficiency of rotary compressor is based on

a) Isothermal compression

b) Adiabatic compression

c) Isentropic compression

d) Polytropic compression


Q19. Phenomenon of choking in compressor means

a) No flow of air

b) Fixed mass flow rate regardless of pressure ratio

c) Reducing mass flow rate with increase in pressure ratio

d) Increased inclination of chord with air steam


Q20. The maximum compression ratio in an actual single stage axial flow compressor is of the order of

a) 01:01.2

b) 1:02

c) 1:05

d) 1:10


Part 24: Objective questions and answers of Thermal Engineering


Q1. Answer: a

Q2. Answer: d

Q3. Answer: b

Q4. Answer: b

Q5. Answer: a

Q6. Answer: d

Q7. Answer: c

Q8. Answer: c

Q9. Answer: d

Q10. Answer: d

Q11. Answer: a

Q12. Answer: a

Q13. Answer: b

Q14. Answer: d

Q15. Answer: a

Q16. Answer: d

Q17. Answer: d

Q18. Answer: b

Q19. Answer: b

Q20. Answer:

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