23407077 Fans Blowers Compressors (1)

7/31/2019 23407077 Fans Blowers Compressors (1)

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FARRUKH SHAHZADDEPARTMENT OF CHEMCIAL ENGG.University of Engg &Tech. PESHAWARPAKISTAN.


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OUTLINEINTRODUCTION FANS

AND BLOWERSCOMPRESSORSDYNAMIC TYPE COMPRESSORSPOSITIVE DISPLACEMENT COMPRRS CONCLUSIONS


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Major Factors During SelectionHead

or Pressure Rise Flow Rate Temperature Limitations Consumption of Power Cost


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The pressure rise which is the main difference between fans, compressors and blowers can be stated as follows: P(psig) Fans 2 Blowers 2-10 Compressors >10


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FANS & BLOWERS


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FANSThey

are the air displacement systems moving air continuously to moderate pressures Due to little change in pressure of air in fans, air is considered to be incompressible They can have pressure rise up to 2 psig.


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The characteristics of fans can be classified as;The

volumetric flowrate of the gas displaced by the fan is directly proportional with the fan speed The static pressure varies with the square of the fan speed Thepower consumed varies with the cube of the fan speed


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FANS

Axial

Centrifugal

Tube

Vane

Radial Forward Backward Air Foil Blade Curved Curved


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AXIAL FANSGas moves parallel to the axis of rotation There are two types of axial fans; -Tube axial fans - Vane axial fans


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Tube

axial fans are used for wide range of volumes at medium pressure In vane axial fans there is air guide vane on the discharge side and the air flow pattern is astraight line hence improvement in efficiency and reducement in turbulance is observed


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CENTRIFUGAL FANSGas

stream moves perpendicular to the axis of rotation They are classified as; radial blade, forward curved, backward curved and air foil

wheel


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RADIAL BLADE CENTRIFUGAL FANSThey

are used for pneumatic transportation and exhausting process gas in high resistance systems With relatively low capacity, they can achive high static pressure They can develop high pressures with high speeds Blades clean themselves They arenot used for ventilating purposes


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FORWARD CURVED CENTRIFUGAL FANSThey

discharge higher volume of air at slower fan speeds They operate with a moderateamount of noise They require little space They are used for clean gases


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BACKWARD CURVED CENTRIFUGAL FANSThey

develop much of their energy directly as pressure They develop less velocity heads by operating at medium speeds Small variations in system volume result in small variations in air pressure


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AIR FOIL CENTRIFUGAL FANSThey

are backward curved centrifugal fans with an air foil cross section They can operate more silently since air forms no turbulance while flowing through the wheels


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BLOWERSBlowers

are used for supplying low pressure air up to between 2-10 psig. They consist oftwo parallel shaft rotors They may have 2 4 lobes The rotating shaft in the con

stitution of the blower traps some gas The compression of the gas in the bloweris negligible


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They are used for; - Pneumatic transportation of particulate material - Water and waste treatment - Providing moderate vacuum


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COMPRESSORSCOMPRESSOR

Dynamic

Positive Displacement

Centrifugal Type

Axial Type

Reciprocating

Rotary


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CENTRIFUGAL DYNAMIC TYPE COMPRESSORSThere

is flow of air in radial direction They are the most popular type of compressorssince they are simple and have maintainance free designs They are used for widevariety of services which are; cooling and drying, compressing gas or steam, su

pplying combustion air to furnaces, agitation and aeration


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The advantages of centrifugal compressors can be classified as;-

They are more efficient than reciprocating ones They provide high flowrates Theyare compact, less site area They need lower maintainance requirements They are

tolerant to liquid carry


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The disadvantages of centrifugal compressors can be classified as; They have lower capacity - They have lower efficiency at low flow rates-


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AXIAL COMPRESSORSThey

have blades having air foil structure pushes air in axial direction They have high speed and they are large volume compressors They have low head


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Blades

of axial compressors have airfoil structure and decrease in diameter There is astationary phase between each row, redirecting the flow and accompolishing a level of conversion of velocity to pressure There is a pressure increase in each row


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The advantages of axial compressors; They have higher efficiency - They have higher capacity (flow rate) - They are in smaller size-


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The disadvantages of axial compressors;-

They limited operating range They are more subjected to corrosion They are subjected to deposits They have higher capital costs They have lower heads


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Combined Axial and Radial Compressor Applications

They have flow rates ranging from 50,000 to 690,000m3/hr They have pressure ratio ranging from 5.8 to 12.5


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Multistage Integrally Geared Compressor Applications

Flow rate ranging from 1,000 to 500,000m3/hr Having pressure upto 100 bar


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Single Stage Centrifugal Compressor Application

Flow rate is 500,000m3/hr and having compression ratio 3 with discharge pressure80bar


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Pipeline Compressor Applications

This is the natural gas compressor for pipeline transportation having pressure ratio ranging from 1.05 to 1.5, shaft speed ranging from 3,000 to 13,500 rpm anddischarge pressure ranging from 80 to 125 bar


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Axial Flow Compressor Applications

This is used in catalyst regeneration plant having flow rate ranging from 50,000to 1,400,000m3/hr having pressure ratio ranging from 1.9 to 6.5


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POSITIVE DISPLACEMENT COMPRESSORSPositive Displacement Compressors

Reciprocating Compressors

Rotary Compressors


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RECIPROCATING COMPRESSORSThey

are the oldest type of compressors They have higher maintainance costs and lowercapacity than dynamic compressors They are widely used in industry They have cy

linders which are equipped with suction and delivery valves Compression cycle iscomposed of 3 cycles which are intake, compression and discharge


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They

intake gas by the help of cylinders The pistons motion is reversed and the gas which taken in is compressed The gas is expelled during the delivery stroke


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In -

multistage reciprocating compressors;

The gas is compressed to an intermediate pressure - The other cylinders raise the pressure to the end pressure - There also exist intercoolers


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The

two rotating components confine a volume of gas The volume of the pocket decreases in rotation so pressure increases


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The

rotary compressors have high range of capacity and compression ratio The rotarycompressors are classified as; Lobed, Helical Screw, Sliding Vane


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HELICAL SCREW COMPRESSORSThere

are mainly two screws which are called male and female The gas is compressed between the lobes of the screw and move along the axis to an outlet port


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These

units can be; oil flooded and dry The contamination of oil is prevented by dry compressors Oil flooded units are used in refrigeration systems and plant air service


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SLIDING VANE COMPRESSORSThe

gas trapped between the vanes and it is compressed as the compartment moves around the casing


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CONCLUSIONSThe

fans have wide range of flowrate The material selection is important during manufacturing fans The blowers have low power and pressure applications The blower is less efficient method of compression


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CONCLUSIONSWhen

centrifugals are run at lower flow rates the efficiencies decrease The centrifugals are tolerant to liquid carry The liquid with the gas can cause erosion and severe damage in centrifugals In axial equipment, high compression efficiency isobserved The axial equipment is applied for high flow andlow discharge pressures


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CONCLUSIONS

The reciprocating systems are applicable for low flow rate of high pressure ratio The oil contamination is important in reciprocating systems The reciprocatingsystems have higher maintainance cost The reciprocating systems are not suited to dirty gasses The process gases that are taken in should be clean and dry in axial equipments The reciprocating systems are not tolerate liquid droplets in thesuction flow


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CONCLUSIONSThe

screw compressor have higher initial cost than reciprocating compressors for thesame duty The sliding vane compressors have low pressure applications The slidi

ng vane compressors operate at low speeds The noise level of the sliding vane compressors is low


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23407077 Fans Blowers Compressors (1)

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