The document is a study on centrifugal compressors highlighting their introduction, construction, and working principles. It details their operational range, refrigerant capacity, and performance aspects while emphasizing the importance of blade angles and capacity control methods. Various diagrams are provided to illustrate velocity and performance relationships in these compressors.

1. STUDY ON CENTRIFUGAL
COMPRESSOR
1
PRASANTH.M
M.E THERMAL
ENGG

2. 2
CONTENT
• INTRODUCTION
• CONSTRUCTION
• WORKING PRINCIPLE
• ANALYSIS OF CENTRIFUGAL COMPRESSOR
• VELOCITY DIAGRAM
• REFRIGERANT CAPACITY
• CAPACITY CONTROL
• PERFORMANCE ASPECTS
• REFERENCE

3. 3
INTRODUCTION
• Centrifugal compressors are rotary type of
compressors
• It gives high volume flow rate
• They are designed for high capacity applications
• It is available in single stage as well as multistage
• They are operated in wide range of speed

4. 4
Evaporator temperatures : -100◦C to +10◦C
Evaporator pressures : 14 kPa to 700 kPa
Discharge pressure : upto 2000 kPa
Rotational speeds : 1800 to 90,000 RPM
Refrigeration capacity : 300 kW to 30000 kW
OPERATING RANGE

5. 5
CONSTRUCTION

6. 6
WORKING PRINCIPLE
• Continuous conversion of angular momentum of refrigerant vapour
by a high-speed impeller into static pressure
• The refrigerant enters the impeller where it gains momentum and
its static pressure also increases
• The refrigerant flows into a stationary diffuser where pressure drop
is converted into static pressure rise
• The vapour enters the volute casing where further conversion of
velocity into static pressure takes place

7. 7
ANALYSIS OF CENTRIFUGAL
COMPRESSORS
The energy equation of compressor is given by
Neglecting kinetic and potential energy
The heat transfer rate Q is normally negligible, so
the work input is given by

8. 8
VELOCITY DIAGRAM

9. 9
The work input to the impeller is given by
The power input to the compressor depends on the blade angle β
• The blade angle will be less than 90◦ for backward curved blade
• The blade angle is equal to 90◦ for radial blades
• The blade angle will be greater than 90◦ for forward curved
blade.
The tangential velocity is given by

10. 10
REFRIGERANT CAPACITY OF
CENTRIFUGAL COMPRESSOR
The mass flow rate through a centrifugal compressor is given by

11. 11
CAPACITY CONTROL
The capacity of a centrifugal compressor is normally controlled
by
• Adjusting the inlet guide
vanes
• Adjusting the guide vanes of vaned diffusers.
• Varying the compressor speed using
VFD

12. 12
PERFORMANCE ASPECTS
PV DIAGRAM

13. 13
CONDENSING TEMPERATURE vs LOAD

14. 14
EVAPORATOR TEMPERATURE vs
LOAD

15. 15
CONDENSING TEMPERATURE vs COMPRESSOR
POWER

16. 16
SPEED vs REFRIGERATING
EFFECT

17. 17
SPEED vs COMPRESSOR
WORK

18. 18
REFERENCE
• www.nptel.com