Compressors and its applications
-
Upload
taha-malampatti -
Category
Engineering
-
view
98 -
download
4
Transcript of Compressors and its applications
![Page 1: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/1.jpg)
COMPRESSORS
AND
ITS APPLICATIONNAME : TAHA MALAMPATTIWALA
BRANCH : CSE 2ROLL NO. : 14CSE071EN NO. : 14005010052
![Page 2: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/2.jpg)
OBJECTIVES
• Explain the function of the compressor • Discuss the concept of compression ratio• List common compressors found in refrigeration systems• Describe four different methods of compression• Describe the component parts of reciprocating compressors
![Page 3: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/3.jpg)
3
© UNEP 2006
Two Basic Compressor Types
Types of Compressors
Type ofcompressor
![Page 4: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/4.jpg)
FUNCTION OF THE COMPRESSOR
Considered the heart of the refrigeration systems
Compressors are vapor pumpsResponsible for lowering the pressure
on the suction side of the systemResponsible for increasing the
pressure on the discharge side of the system
Suction gas from the evaporator enters the compressor
Refrigerant is discharged to the condenser
![Page 5: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/5.jpg)
COMPARISON OF COMPRESSORS
• Efficiency at full, partial and no load• Noise level• Size• Oil carry-over• Vibration• Maintenance• Capacity• Pressure
![Page 6: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/6.jpg)
COMPRESSION RATIOCompares pumping conditions for
compressorsDefined as the high side pressure divided
by the low side pressureHigh compression ratio can lead to
overheated compressor oilHigh compression ratio leads to reduced
refrigerant flow through the systemReduced refrigerant flow reduces system
capacity
![Page 7: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/7.jpg)
COMPRESSION RATIO EXAMPLESR-12 compressor169 psig high side, 2 psig low side183.7 psia high side, 16.7 psia low side183.7 psia ÷ 16.7 psia = 11:1 compression ratio
R-134a compressor184.6 psig high side, 0.7 in. Hg. vacuum low side
199.3 psia high side, 14.35 psia low side199.3 psia ÷ 14.35 psia = 13.89:1 compression ratio
![Page 8: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/8.jpg)
TWO-STAGE COMPRESSIONLowers the compression ratioUtilizes two compressorsOne compressor discharges into suction of the
otherAlso referred to as compound compressionOften used when the compression ratio of a single
compressor system exceeds 10:1Often used in low-temperature commercial and
industrial storage applications
![Page 9: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/9.jpg)
TWO-STAGE COMPRESSION
FIRST STAGE SECOND STAGE
21 psig 100 psig 169 psig
Suction
Discharge Discharge
Suction
![Page 10: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/10.jpg)
TYPES OF COMPRESSORSReciprocatingFully welded, hermetic compressorsSemi-hermetic compressorsOpen-drive compressorsBelt-driven and direct-drive compressorsScrew compressorsRotary compressorsScroll compressorsCentrifugal compressors
![Page 11: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/11.jpg)
WELDED HERMETIC RECIPROCATING COMPRESSORS
Motor and compressor contained in a welded shell
Cannot be field servicedTypically a “throw-away” compressorConsidered to be a low-side componentCooled by suction gas from the evaporatorLubricated by the splash method
![Page 12: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/12.jpg)
SEMI-HERMETIC COMPRESSORSBolted together, can be field servicedHousing is made of cast ironHas a horizontal crankshaftSmaller compressors are splash lubricatedLarger compressors use pressure
lubrication systemsOften air cooledPiston heads are located at the top of the
compressor
![Page 13: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/13.jpg)
OPEN DRIVE COMPRESSORSCan be direct drive or belt-driven
compressorsMust have a shaft seal to prevent leakageBolted together, can be field servicedBelt-driven compressors have the
compressor and motor shafts parallel to each other
Belt-driven compressors use belts and pulleys
Direct drive compressors have the compressor and motor shafts connected end to end
![Page 14: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/14.jpg)
RECIPROCATING COMPRESSOR COMPONENTSCrankshaftTransfers motor motion to the pistonCreates the back and forth motion of the pistonConnecting rodsConnects the crankshaft to the pistonsPistonsSlide up and down in the cylinderUsed to compress and expand the refrigerant
![Page 15: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/15.jpg)
RECIPROCATING COMPRESSOR COMPONENTS (CONT’D)
Refrigerant cylinder valves (suction)Durable, flexible steelLocated on the bottom of the valve plateOpen when refrigerant is introduced to the pump
Refrigerant cylinder valves (discharge)Durable, flexible steelOpen when refrigerant is discharged from the pump
Located on the top of the valve plate
![Page 16: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/16.jpg)
OTHER COMPRESSOR TYPESScrew compressor Used in large commercial/industrial applicationsUses two matching, tapered gears, and open motor design
Rotary compressorUsed in residential and light commercial applications – primarily in domestic refrigerators
Scroll compressorUses a matched set or scrolls to achieve compressionBecoming more popular for their ability to handle liquid refrigerant without compressor damage
Centrifugal compressorsUsed extensively for air conditioning in large structures
![Page 17: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/17.jpg)
RECIPROCATING COMPRESSOR
• Used for air and refrigerant compression• Works like a bicycle pump: cylinder volume reduces while
pressure increases, with pulsating output• Many configurations available• Single acting when using one side of the piston, and double
acting when using both sides
![Page 18: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/18.jpg)
Suction line Discharge line
Valve plate
Head Discharge valve
Suction valve Piston
Rings
CrankshaftConnecting Rod
![Page 19: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/19.jpg)
RECIPROCATING COMPRESSOR COMPONENTS (CONT’D)
Compressor headHolds the top of the cylinder and its components together
Contains both high and low pressure refrigerantMufflersDesigned to reduce compressor noiseCompressor housingEncases the compressor and sometimes the motor
![Page 20: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/20.jpg)
BELT-DRIVE MECHANISMSMotor pulley is called the drive pulleyCompressor pulley is called the driven
pulleyPulleys can be adjusted to change
compressor speedDrive size x Drive rpm = Driven size x
Driven rpmShafts must be properly alignedPulleys with multiple grooves must used
matched sets of belts
![Page 21: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/21.jpg)
DIRECT-DRIVE COMPRESSOR CHARACTERISTICS
Direct drive compressors turn at the same speed as the motor used
Motor shaft and compressor shaft must be perfectly aligned end to end
Motor shaft and compressor shafts are joined with a flexible coupling
![Page 22: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/22.jpg)
RECIPROCATING COMPRESSOR EFFICIENCY
Determined by initial compressor designFour processes take place during the
compression processExpansion (re-expansion)Suction (Intake)CompressionDischarge
![Page 23: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/23.jpg)
COMPRESSION PROCESS - EXPANSIONPiston is the highest point in the cylinderReferred to as top dead centerBoth the suction and discharge valves are
closedCylinder pressure is equal to discharge
pressureAs the crankshaft continues to turn, the
piston moves down in the cylinderThe volume in the cylinder increasesThe pressure of the refrigerant decreases
![Page 24: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/24.jpg)
Suction valve closed Discharge valve
closed
Piston moving downward in the cylinder
Refrigerant trapped in the
cylinder
Pressure of the refrigerant in the
cylinder is equal to the discharge
pressure
![Page 25: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/25.jpg)
COMPRESSION PROCESS – SUCTIONAs the piston moves down, the pressure
decreasesWhen the cylinder pressure falls below
suction pressure, the suction valve opensThe discharge valve remains in the closed
positionAs the piston continues downward, vapor
from the suction line is pulled into the cylinder
Suction continues until the piston reaches the lowest position in the cylinder (bottom dead center)
At the bottom of the stroke, suction valves close
![Page 26: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/26.jpg)
Suction valve open Discharge valve
closed
Piston moving downward in the cylinder
Pressure of the refrigerant in the
cylinder is equal to the suction pressure
Suction gas pulled into the compression
cylinder
Most of the energy that entering the compressor in the suction cylinder is latent heat.
![Page 27: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/27.jpg)
COMPRESSION PROCESS - COMPRESSION
Piston starts to move upwards in the cylinder
The suction valve closes and the discharge valve remains closed
As the piston moves upwards, the volume in the cylinder decreases
The pressure of the refrigerant increasesCompression continues until the pressure in
the cylinder rises just above discharge pressure
![Page 28: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/28.jpg)
Suction valve closed Discharge valve
closed
Piston moving up in the cylinder
Pressure of the refrigerant in the
cylinder is equal to the suction pressure
Volume is decreasing,
compressing the refrigerant
![Page 29: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/29.jpg)
COMPRESSION PROCESS - DISCHARGE
When the cylinder pressure rises above discharge pressure, the discharge valve opens and the suction valve remains closed
As the piston continues to move upwards, the refrigerant is discharged from the compressor
Discharge continues until the piston reaches top dead center
![Page 30: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/30.jpg)
Suction valve open
Discharge valve closed
Piston moving up in the cylinder
Pressure of the refrigerant in the
cylinder is equal to the discharge
pressure
Discharge gas pushed from the
compression cylinder
What do you think may happen if both of the valves remain closed on an upstroke?
The gas leaving the compressor is very warm.
![Page 31: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/31.jpg)
LIQUID IN THE COMPRESSION CYLINDERIf liquid enters the cylinder, damage
will occurLiquids cannot be compressedLiquid slugging can cause immediate
damage to the compressor components
Common causes of liquid slugging include an overfeeding metering device, poor evaporator air circulation, low heat load, defective evaporator fan motor and a frosted evaporator coil
![Page 32: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/32.jpg)
SYSTEM MAINTENANCE AND COMPRESSOR EFFICIENCY
High suction pressures and low discharge pressures keep the compression ratio low
Dirty evaporators cause suction pressure to drop
Low suction reduces compressor pumping capacity
Dirty condensers increase head pressureCompression ratio is increased by dirty or
blocked condenser and evaporator coils
![Page 33: Compressors and its applications](https://reader034.fdocument.pub/reader034/viewer/2022042706/5883b0791a28ab3b488b6e8b/html5/thumbnails/33.jpg)
THANK YOU