MODULE 3

Air Compressor,

Refrigeration and Air-Conditioning

9. Vapour compression Refrigeration cycle

10. Super heat

11. Sub cooling

12. Performance calculations.

13.Working principle of vapour absorption system.

14.Ammonia - water system system

15.Lithium bromide - water system

16.Performance calculation of VARS

17. Cooling load calculations.

18.Concept of RSHF, GSHF, ESHF

19.Air conditioning systems

1. Classification and working principle

of reciprocating air compressor

2. Work of compression with clearance

3. Work of compression without

clearance

4. Volumetric efficiency, Isothermal

efficiency and isentropic efficiency of

reciprocating air compressors.

5. Multistage air compressor

6. Inter cooling

7. Work of multistage air compressor,

8. Various types of rotary compressors

1. CLASSIFICATION AND WORKING

PRINCIPLE OF RECIPROCATING AIR

COMPRESSOR

AIR COMPRESSOR

• An air compressor is a machine to compress the

air to raise its pressure.

• The air compressor sucks air from the

atmosphere, compresses it and then deliver the

same under a high pressure to a storage vessel; it

may be conveyed by the pipe line to the place

where the supply of air compressed air is required.

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

RECIPROCATING AIR COMPRESSOR

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

APPLICATIONS

• Pneumatic drills

• Riveters

• Road drills

• Paint spraying

• Internal combustion engines

• Gas turbine plants

• Jet engines and air motor

• Bessemer converter

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

CLASSIFICATION OF AIR COMPRESSORS

• According to working

Reciprocating compressors

Rotary compressors

• According to the action

Single acting compressors

Double acting compressors

• According to number of stages

Single stage compressors

Multi stage compressors

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

COMPRESSOR CLASSIFICATION

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

TECHNICAL TERMS

• Inlet pressure : It is the absolute pressure of air at

the inlet of a compressor.

• Discharge Pressure : It is the absolute pressure of

air at the outlet of a compressor.

• Pressure Ratio : It is the ratio of discharge pressure

to the inlet pressure .

• Compressor Capacity : It is the volume of air

delivered by the compressor and it expressed in

m3/min or m3/sec.

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

• Free air delivery : It is the actual volume delivered by the compressor when reduced to the normal temperature and pressure condition.

• Swept Volume: It is the volume of air sucked by the compressor during its suction stroke.

• Mean effective pressure : Air pressure on the compressor piston keeps on changing with the movement of the piston in the cylinder. The mean effective pressure of the compressor is equal to the ratio of working done per cycle to the stroke volume.

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

2.WORK OF COMPRESSION WITH

CLEARANCE

WORK OF COMPRESSION WITH CLEARANCE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

3. WORK OF COMPRESSION

WITHOUT CLEARANCE

WORK OF COMPRESSION WITHOUT

CLEARANCE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

WORK OF COMPRESSION WITHOUT

CLEARANCE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

4. VOLUMETRIC EFFICIENCY ,

ISOTHERMAL EFFICIENCY AND

ISENTROPIC EFFICIENCY OF

RECIPROCATING AIR COMPRESSORS

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

COMPRESSION WORK COMPARISON

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

VOLUMETRIC EFFICIENCY

• It is the ratio of the actual volume of free air

delivered to the displacement volume.

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

ISOTHERMAL EFFICIENCY

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

ISENTROPIC EFFICIENCY

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

DRAWBACKS OF SINGLE STAGE AIR

COMPRESSOR • The size of the cylinder will be too large .

• Due to compression , there is a rise in temperature of the air .It is difficult to reject heat from the air in the small time available during compression.

• The temperature of air, at the end of compression ,is too high.

• It may heat up the cylinder head or burn the lubricating oil.

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

MULTI STAGE COMPRESSORS

• In order to over come the above mentioned

difficulties, two or more cylinders are provided in

series with intercooling arrangement between

them. Such an arrangement is known as multistage

compression.

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE

ADVANTAGES OF MULTI STAGE

COMPRESSION

• The work done per Kg of air is reduced in Multistage compression with

intercooling as compared to single stage compression for the same delivery pressure.

• It improves the volumetric efficiency for the given pressure ratio.

• The size of the cylinders may be adjusted to suit the volume and pressure of

the air.

• It reduces the leakage loss considerably.

• It provides effective lubrication because of lower temperature range.

• It reduces the cost of compressor.

A.ABUBAKKAR

DEPARTMENT OF MECHANICAL ENGINEERING ,KONGU ENGINEERING COLLEGE