AHM SHISHIR ATHLE Blowers and Compressors.pdf

8/18/2019 AHM SHISHIR ATHLE Blowers and Compressors.pdf

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Sudnya Industrial Services Pvt.Ltd., Pune

Energy Conservation in Fans,Blowers and Compressors


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Vacuum Pump, Fan, Blower or

Compressor?

How can we distinguish between thesemachines?

Vacuum Pump:Draws gases/ vapours from a system to make itspressure lower than its surroundings

27-Feb-14 Sudnya Industrial Services Pvt. Ltd., Pune 2

Moves gases/ vapours such that the difference in totalpressure is a few hundred mm WG

Blower:When the ∆∆∆∆P is > few hundred mm WG but < 2 kg f /cm 2

Compressor:When the ∆∆∆∆P is > 2 kg f /cm 2


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Types of Fans and BlowersCentrifugal

Forward Curved BladesBackward Curved BladesRadial Blades

Aerofoil Blades


Tube Axial

Vane AxialPropeller

Lobe Type (Roots Blowers)Single-StageMulti-Stage


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Fan (& Pump) Equation

Rotation

u2

Volute (Discharge)

2 n H

d Q nQ

∝∝∝∝

∝∝∝∝

∝∝∝∝

u H uQ

∝∝∝∝

∝∝∝∝

2


u1

Eye (Inlet)

3

3

2

d P

n P

H Q P d H

∝∝∝∝

∝∝∝∝

××××∝∝∝∝

∝∝∝∝

nu ∝∝∝∝


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System Flow Rate

35.00

40.00

45.00

50.00

1460 rpm 1095 rpm 730 rpm No Static Head 10 m Static Head 15 m Static Head


0.00

5.00

10.00

15.00

20.00

25.00

.

0 20 40 60 80 100 120 140

Flow Rate m3/h

H e a d m


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Friction LossesFanning equation forPressure drop inStraight PipesLoss in Fittings

Values of K are

c

2

p g2

u

D

Lf 4P =∆

2u⋅


tabulated inHandbooks

Since ∆∆∆∆P ∝∝∝∝ u 2 , therelationship betweenthese quantities is aparabolic curve

cf

g2


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Fan Efficiencies at different

Speeds



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Static Head vs Fan Efficiency in

Variable Speed Control



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Reading the Curves



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Flow Control Methods

Throttling by a valve

By-passing by a valve


Parallel running of Pumps

Variable speed control of the pump

On-off control of the pump


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Throttle Control



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Throttling Increases Resistance

in the System



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By-Passing



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On-Off Control



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Variable Speed Control



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Fans in Parallel


Pumps1 and 2


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Fans in Series


Pumps1 and 2


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Variable Speed Control of Fans

Pays



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Consider Variable Speed Control

when...the fan is a part of the control system. the fan output varies.



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Power Consumption of a Fan

η ρ g H QP ***=


H Qk P **=when η is constant


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Relative Power Consumption



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Energy Consumption of a Fanis the Power multiplied by the Time

P


t


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Duty Cycle Curve


QQQ min50maxm 61

32

61

FlowMedian Q ++=


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Energy Use Calculated by the

Median Flow Method

Qmax = 300 l/sQ50 = 250 l/sQmin = 81 l/s

∗

(= Energy Consumption in Variable Speed Control)


l/s204l/s636m

=++=

and the equivalent power is 42 kW.

The total energy isW = 42 kW*5000 h = 210 MWh


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Reading the Power Consumed

by a Fan

Duty point of a fan:

Nominalx Throttle controlx Variable speed control


Power consumption ofthe fan in variable speedcontrol


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Segmented Duty Cycle



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Comparison based on Energy

ConsumptionTime Flow Throttle

ControlVariable Speed

Control

1480 rpm

% h % l/s kW MWh rpm kW MWh


40 2000 90 270 75 150 1400 64 128

30 1500 62 186 71 107 1180 35 53

30 1500 32 96 65 98 920 24 36

Compared to throttle control variable speed controlsaves energy 355 - 217 MWh = 138 MWh


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Variable Speed Control Saves

Energy

Cost saving =


saved energy*energy price137 MWh * Rs.3700/MWh = Rs. 5.07 lakhs/year

For Variable Speed AC Drives

the Payback Period would beless than Two Years


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Types of CompressorsPositive Displacement

ReciprocatingLobe typeScrewScroll


KinematicCentrifugal

Axial Flow

LubricatedNon-Lubricated


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Screw Compressor



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Volumetric Efficiency Volumetric Efficiency is the ratio of Volume of Gas delivered to the displacedvolume



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Power Drawn dp

p dW Power

P

P∫ ∫ ∆

==2

1 ρ k pV n =

−

−⋅⋅⋅⋅=

−

11

1

1

21

0

0

0γ

γ

γ

γ

η p p

T q

T p

K Power A

Adiabatic Compression


Isothermal Compression

⋅=

1

20

0

1 ln p p

qT RT

K Power Aη

−

−<

=

−

11

ln

1

1

2

2

2γ

γ

γ

γ

p p

p p

X For n > 1 and p 2 > p1


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K A

K A = 0.004363 0.001 98066.5

p 0 , p 1 , p 2 lb f /in 2 Pa = N/m 2 kg f /cm 2


T1 , T 2 °R °K °K

q 0 ft 3 / min m 3 /secm 3 /sec

P h. p. kW kW


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Factors affecting Energy UseTackle each of the factors in the equation

Factor Units Change by Energy usechanged by


p 2 /p 1 kg f /cm 2 1 6 – 10%T1 °K 4 1%

q 0 m 3 /sec 1% 1%

X °K 5 2.1%


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Measures: Compression RatioClean filters regularlyReduce Process Operating PressureConsider two sets of numbers

1,2,4,8: AM = 3.75 GM = 2.821,3,9,27,81: AM = 24.2 GM = 9


s suggests t at a ser es o compressors av ngCompression ratios < p 2 /p 1 of one largecompressor will have a lower energy usageHence, multi-stage compression

Implicit assumption: each stage startscompression at the same temperatureCompression Ratios for each stage are equal


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MeasuresCool intake from outside compressor room

Reduce leakagesMaintain compressor



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ModulationBlow off

By-passi.e. re-circulate from exhaust to suction “Unload” individual cylinders


Inlet Guide Vane Control for CentrifugalCompressorsBlade angle control for Axial flow

Compressors Variable Speed Drives


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Reduce VolumeReduce Leakages

Reduce UsageFlow nozzles



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TestingCapacity

Time to pump up the pressure of a receiver of known

volume to a given pressureUse of flow nozzles

Leakages


Close all valves at the points of usePump up the receiver to a desired pressureNote the time/s taken for the pressure to drop to a lowerpressure/s

U L

L

T T T LeakRate+

=


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Drying and FiltrationFilter air only if the application demands it

DryersRefrigerant DryersLimitation on the Dew Point temperatures that can


Dessicant DryingPurge dryer using compressed air

Highest operating costs though capital costs are lowWaste a lot of compressed air

Heat of Compression DryersMost expensive, but most efficient


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GeneralReceiver

Volume: about 1 min. generation capacityLocate near large loads

Install drains and traps at intervals


Avoid misuseUse only where necessaryCheck periodically for leakages


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Contact Us

Sudnya Industrial Services Pvt. Ltd.5 Raj Apartments,28 Pushpak, Park, Aundh,


Pune – 411 007Tel: +91 20 3291 2316

Mobile: +91 98224 07214E-mail: [email protected]

Documents

AHM SHISHIR ATHLE Blowers and Compressors.pdf