Compressors+Pumps

8/9/2019 Compressors+Pumps

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Pumps, Compressors, Fans,

Ejectors and Expanders

Chapter 20

ChEN 4253 Design Ierr! "# $ing


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Pumps

% &o'es (i)uid, Creates Pressure * +apor u-es

% Causes Ca'itations

% Erodes Impe--er

* .o-ids Erode Impe--er % Pump !pes

* Centri/uga-

* Positi'e Disp-acement% Piston

% diaphragm

% Pump Poer 1 P 1 rae 6de-i'ered7 6horse7 poer/rom motor


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Centri/uga- Pumps

% Two Basic Requirements for Trouble-

Free Operation of Centrifugal Pumps

* no ca'itation o/ the pump occurs throughout

the road operating range

* a certain minimum continuous /-o is a-a!s

maintained during operation

% Pump around -oops


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$educed F-os

% 8n/a'ora-e conditions hich ma! occurseparate-! or simu-taneous-! hen the pump isoperated at reduced /-os

% Cases o/ hea'! -eaages /rom the casing, sea-, and stu//ingox

% De/-ection and shearing o/ sha/ts

% .ei9ure o/ pump interna-s

% C-ose to-erances erosion

% .eparation ca'itation

% Product )ua-it! degradation

% Excessi'e h!drau-ic thrust

% Premature earing /ai-ures


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Centri/uga- Pump

E-ectric &otor


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Centri/uga- Pump

E-ectric

&otor


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Centri/uga- Pump

% Con'erts

inetic

energ! to

pressure

energ!


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Impe--ers


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Con'erts :inetic Energ! to

Pressure Energ!


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Different Types of Pump Head

% ota- .tatic ;ead < ota- head hen the pump is not running% ota- D!namic ;ead 6ota- .!stem ;ead7 < ota- head hen the

pump is running% .tatic .uction ;ead < ;ead on the suction side, ith pump o//, i/ the

head is higher than the pump impe--er% .tatic .uction (i/t < ;ead on the suction side, ith pump o//, i/ the

head is -oer than the pump impe--er% .tatic Discharge ;ead < ;ead on discharge side o/ pump ith the

pump o//% D!namic .uction ;ead=(i/t < ;ead on suction side o/ pump ith

pump on% D!namic Discharge ;ead < ;ead on discharge side o/ pump ith

pump on


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Pump ;ead

% he head o/ a pump can e expressed in metricunits as>

% head = (p2 - p1 )/(ρg) + (v 2 2 - v 12 )/(2g) + (z 2 -z 1 )

% where% h = total head developed (m)% p2 = pressure at outlet (N/m2 )

% p1 = pressure at inlet (N/m2 )

% ρ = density of liuid (!g/m")% g = a##eleration of gravity ($%&1) m/s2

% v 2 = velo#ity at the outlet (m/s)

http://www.engineeringtoolbox.com/pump-energy-equation-d_631.htmlhttp://www.engineeringtoolbox.com/pump-energy-equation-d_631.html


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Pump E//icienc!

% Centri/uga- Pump


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Pump Performance Cures

Resistance


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Pump Design .ca-ing

% Pump Flow rate% !2 " !? # $%D2#&2'(%D?#&?')

% Pump Head% H2 " H? # $%D2#&2'(%D?#&?')2

% Pump Bra*e Horse Power% BHP2 " BHP? # $%D2#&2'(%D?#&?')3

* D 1 Impe--er Diameter

* N 1 speci/ic speed


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Net Positi'e .uction ;ead


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$e)uired, NP.;$

"s the -i)uid passes /rom the pump suction to the e!e o/ the impe--er, the 'e-ocit!

increases and the pressure decreases# here are a-so pressure -osses due to

shoc and turu-ence as the -i)uid stries the impe--er# he centri/uga- /orce o/ the

impe--er 'anes /urther increases the 'e-ocit! and decreases the pressure o/ the-i)uid# he NP.; required is the positi'e head 6aso-ute pressure7 re)uired at the

pump suction to o'ercome these pressure drops in the pump and maintain the

-i)uid ao'e its 'apor pressure#


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"'ai-a-e, NPSH A

Net Positi'e .uction ;ead +ailable is a /unction o/ the s!stem in hich the

pump operates# It is the excess pressure o/ the -i)uid in /eet aso-ute o'er its 'apor

pressure as it arri'es at the pump suction, to e sure that the pump se-ected does

not ca'itate#

;ead to Feed Pump .ucoo-ing e/ore Pump

o o'ercome suction head

;ead

Designed

into

Insta--ation

;A

Coo- a /e Degreeso o'ercome suction head


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Piston Pumps


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Bear Pumps


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(oe Pumps

% /ood app-ications,

ecause the!

hand-e so-ids

ithout damagingthe pump#

% Partic-e si9e

pumped can e

much -arger inthese pumps than

in other PD t!pes


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.cre Pump


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Centri/uga-

Pump


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Positi'e Disp-acement Pumps

% Piston Pumps

% Bear Pumps

* (oe Pumps

% Diaphragm Pumps * he -oer the speed o/ a PD

pump, the -oer the NP.;$#


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Pump Costs

% Cost ased upon .i9e Factor

* Centri/uga- Pump

% .1;?=2

* Bear Pump

% .1

* Piston Pump

% .1 Poer 6rae7

% &ust cost E-ectric &otor a-so% .1Pc1PC=&


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Compressors

% !pes * Centri/uga- * thers

% Piston% (oed% .cre

*&ethods o/ Ca-cu-ation in .imu-ators% Po-!tropic, P+


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Positi'e Disp-acement Compressor

http>==#cit!


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Centri/uga- Compressors

% $otors

% .tators

% Get

Engine

Design


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Piston Compressor


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Expander

% $e'erse o/ Compressor % (et /-o produce sha/t or% !pes

* Centri/uga- * Positi'e Disp-acement

% Piston% (oed% .cre

* &ethods o/ Ca-cu-ation in .imu-ators% Po-!tropic, P+


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Fans and -oers

% !pes * Centri/uga- 6?03


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Choice to Increase Pressure

% ;euristic 34 * 8se a Fan

% "tm to ?#4H psig

* 8se a -oer % 30 psig

* Compressor 6or staged s!stem7% J 30 psig

% ;euristic 34 < Numer o/ .tages * 8p to a Compression ratio 4 /or each stage

% Kith intercoo-er eteen stages 6P12 psi7

* E)ua- ;p /or each stage 6e)ua- compression ratio7

P d i +


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Producing +acuum

.team Ejector


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Producing +acuum

% !pes * Ejector < ad'antage 1 -arge 'o-umetric /-o rate

% &u-ti


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Ejector% Produces +acuum

% Pro'ides (o Pressures /orDisti--ation Co-umns

% F-uid 6P L Psat7 * .team

% /or suction pressure e-o ?00 maraso-ute, more than one ejector i-- eused, ith condensors eteen theejector stages

* "ir

* Kater

% Co--ects Partic-es in Bas .tream * +enturi .cruer

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Compressors+Pumps