# Thermal Engineering 22

Objective Questions and Answer: Thermal Engineering 22

Subject: Thermal Engineering 22

Part 22: Objective questions and answers of Thermal Engineering

Q1. Ratio of indicated H.P. and brake H.P. is known as

a) Mechanical efficiency

b) Volumetric efficiency

c) Isothermal efficiency

Q2. The ratio of work open per cycle to the swept volume in case of compressor is called

a) Compression index

b) Compression ratio

c) Compressor efficiency

d) Mean effective pressure

Q3. Cylinder clearance in a compressor should be

a) As large as possible

b) As small as possible

c) About 50% of swept volume

d) About 100% of swept volume

Q4. Ratio of compression is the ratio of

a) Gauge discharge pressure to the gauge intake pressure

b) Absolute discharge pressure to the ab-solute intake pressure

c) Pressures at discharge and suction cor-responding to same temperature

d) Stroke volume and clearance volume

Q5. Clearance volume in actual reciprocating compressors is essential

a) To accommodate Valves in the cylinder head

b) To provide cushioning effect

c) To attain high volumetric efficiency

d) To provide cushioning effect and also to avoid mechanical bang of piston with cylinder head.

Q6. The net work input required for compressor with increase in clearance volume

a) Increases

b) Decreases

c) Remains same

d) Increases/decreases depending on com-pressor capacity

Q7. Ratio of indicated h.p.to shaft h.p. In known as

a) Compressor efficiency

b) Isothermal efficiency

c) Volumetric efficiency

d) Mechanical efficiency

Q8. Volumetric efficiency is

a) The ratio of stroke volume to clearance volume

b) The ratio of the air actually delivered to the amount of piston displacement

c) Reciprocal of compression ratio

d) Index of compressor performance

Q9. Volumetric efficiency of air compressors is of the order of

a) 20-30%

b) 40-50%

c) 60-70%

d) 70-90%

Q10. Volumetric efficiency of a compressor with clearance volume

a) Increases with increase in compression ratio

b) Decreases with increase in compression ratio

c) In not dependent upon compression ratio

d) May increase/decrease depending on compressor capacity

Q11. Volumetric efficiency of a compressor without clearance volume

a) Increases with increase in compression ratio

b) Decreases with increase in compression ratio

c) Is not dependent upon compression ratio

d) May increase/decrease depending on compressor capacity

Q12. The clearance volume of the air compressor is kept minimum because

a) It allows maximum compression to be achieved

b) It greatly affects volumetric efficiency

c) It results in minimum work

d) It permits isothermal compression

Q13. Euler's equation is applicable for

a) Centrifugal compressor

b) Axial compressor

c) Pumps

d) All of the above

Q14. Out of the following, from where you will prefer to take intake for air compressor

a) From an air conditioned room maintained at 20°C

b) From outside atmosphere at 1°C

c) From coal yard side

d) From a side where cooling tower is located nearby

Q15. Mining industry usually employs following motive power

a) A.C. electric motor

b) Compressed air

c) Petrol engine

d) Diesel engine

a) These are used to dampen pulsations ,

b) These act as reservoir to- take care of sudden demands

c) These increase compressor efficiency

d) These knock out some oil and moisture

Q17. An air receiver is to be placed outside. Should it be placed in

a) Sun

c) Rain

d) Enclosed room

Q18. Which is false statement about multistage compression?

a) Power consumption per unit of air delivered is low

b) Volumetric efficiency is high

c) It is best suited for compression ratios around 7:1

d) The moisture in air is condensed in the intercooler

Q19. In multistage compressor, the isothermal compression is achieved by

a) Employing intercooler

b) By constantly cooling the cylinder

c) By running compressor at very slow speed

d) By insulating the cylinder

Q20. Reciprocating air compressor is best suited for

a) Large quantity of air at high pressure

b) Small quantity of air at high pressure

c) Small quantity of air at low pressure

d) Large quantity of air at low pressure

Part 22: Objective questions and answers of Thermal Engineering