G

Fluid Machineries

Engr. Paul Gerard R. Lasangre Cruz

Table of Contents

Module 4: Performance Characteristics of Pumps 29 Introduction 29

Learning Objectives 29

Lesson 1. Specific Speeds, Head, Flow Rate, and Work Relations 29 Lesson 2. Affinity Laws 33

Assessment Task 4 35

Summary 36

Module 5: Centrifugal Pumps in Series and in Parallel 37

Introduction 37

Learning Objectives 37 Lesson 1. Pumps In Series 38

Lesson 2. Pumps In Parallel 39

Assessment Task 5 43 Summary 43

Reference 43

Module 6: Functions and Types of Compressors 45

Introduction 45 Learning Objectives 45

Lesson 1. Functions of Compressors 45

Lesson 2. Types of Compressors 46

Assessment Task 6 53 Summary 53

Reference 54

29

MODULE 4 Performance Characteristics of Pumps

Introduction

The flow rate (Q) and head (H) are the fluid quantities involved with all hydraulic

devices, while the mechanical quantities associated with the machine itself are power (P),

speed (N), size (D) and efficiency (). The priority put on each of these amounts is different

for different pumps, although they are of equal importance. The output of a pump that runs

at a given speed is the flow rate it delivers, and the head that develops. A plot of head and

flow rate at a given speed therefore forms the fundamental characteristic of a pump's output.

In order to achieve this performance, a power input is required which involves efficiency of

energy transfer. Thus, it is useful to plot also the power P and the efficiency () against Q

(Krishnamurthy, 2015).

Learning Outcomes

At the end of this module, students should be able to:

1. Compute quantities associated to performance of pumps

2. Characterize pumps based on performance

Lesson 1. Specific Speeds, Head, Flow Rate, and Work Relations

The cross section of the liquid direction in the volute of the centrifugal pump is greater

than in the impeller and, in an ideal frictionless pump, the velocity V decrease to the lower one

according to Bernoulli's equation, speed is translated to an increased strain. That is the

pressure source of the centrifugal pump discharge (Krishnamurthy, 2015).

30

Over all efficiency of a pump ( )

= Fluid power output

Power input to the shaft =

gHQ

P

Specific Speed

For English Unit

𝑁𝑠 = 𝑁√𝑄

(𝐻)34

(Francisco, 2014)

where: 𝑁𝑠 = 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑠𝑝𝑒𝑒𝑑 (𝑟𝑝𝑚) 𝑁 = 𝑝𝑢𝑚𝑝 𝑠𝑝𝑒𝑒𝑑 (𝑟𝑝𝑚)

𝐻𝑇 = 𝑇𝑜𝑡𝑎𝑙 ℎ𝑒𝑎𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑢𝑚𝑝 (𝑓𝑡) S= 𝑛𝑜. 𝑜𝑠 𝑠𝑡𝑎𝑔𝑒𝑠

𝐻 = (𝐻𝑇

𝑆) = 𝑝𝑢𝑚𝑝 ℎ𝑒𝑎𝑑 𝑝𝑒𝑟 𝑠𝑡𝑎𝑔𝑒 (𝑓𝑡)) 𝑄 = 𝑝𝑢𝑚𝑝 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 (𝑔𝑝𝑚)

For SI Unit

𝑁𝑠 = (51.65523641) 𝑁√𝑄

(𝐻)34

(Francisco, 2014)

where: 𝑁𝑠 = 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑠𝑝𝑒𝑒𝑑 (𝑟𝑝𝑚) 𝑁 = 𝑝𝑢𝑚𝑝 𝑠𝑝𝑒𝑒𝑑 (𝑟𝑝𝑚)

𝐻𝑇 = 𝑇𝑜𝑡𝑎𝑙 ℎ𝑒𝑎𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑢𝑚𝑝 (𝑚) S= 𝑛𝑜. 𝑜𝑠 𝑠𝑡𝑎𝑔𝑒𝑠

𝐻 = (𝐻𝑇

𝑆) = 𝑝𝑢𝑚𝑝 ℎ𝑒𝑎𝑑 𝑝𝑒𝑟 𝑠𝑡𝑎𝑔𝑒 (𝑚)) 𝑄 = 𝑝𝑢𝑚𝑝 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 (

𝑚3

𝑠))

Table 4.1 Specific Speed and Pump Impeller Types (Neutrium, 2013)

Impeller Type

Ns Metric units*

Ns US units**

Nd Dimensionless

Do

Di Characteristics

Radial Flow 500 -

1,700 800 - 2,800 0.3 - 1.0 > 2

Low flow, high

head

Francis Vane 1,700 - 4,000

2,800 - 6,500

1.0 - 2.4 1.5 - 2

Mixed Flow 4,000 - 9,000

6,500 - 15,000

2.4 - 5.4 < 1.5

Axial Flow > 9,000 > 15,000 > 5.4 1 High flow, low

head

* Metric units - rpm, L/s, m

** US units - rpm, USgpm, ft

31

In pump selection, it should be noted that for metric specific speeds less than 1000, a

multi-stage pump should be considered while for metric specific speeds less than 500, a

positive displacement pump should be considered (Neutrium, 2013).

Specific speeds are used to (Francisco, 2014):

1. Classify pumps: a) Radial; b) Francis; c) Mixed Flow; or d) Propeller or axial

2. Determine pump efficiency

Sample 1. Determine the specific speed s of the following single-stage pumps and specify

the type of pump to be used (Francisco, 2014)

Table 4.2. Pump Characteristics for Selection

PUMP N (rpm) Q H

A 1150 4000 gpm 105 ft

B 885 0.76 m3/s 4.572 m

Sol’n:

a. For pump A,

𝑁𝑠 = 𝑁√𝑄

(𝐻)34

= 1150√4000

(105)34

𝑁𝑠 = 2217 𝑟𝑝𝑚 Refer to Table 4.1 Radial Flow (800 - 2,800)

32

b. For pump B,

𝑁𝑠 = (51.65523641)𝑁√𝑄

(𝐻)34

= (51.65523641)885√0.76

(4.572)34

𝑁𝑠 = = 12746 𝑟𝑝𝑚 Refer to Table 4.1 Axial Flow (> 9,000 metric)

Sample 2. A 4-stage pump delivers 2000 gpm against a net pressure rise of 720 psi. What

is the specific speed if it rotates 2050 rpm (Francisco, 2014)?

Given: S = 4 (4-stage pump system)

Q = 2000 gpm

P = 720 psi (net pressure rise)

N = 2050 rpm

Req’d: 𝑁𝑠 = ?

Sol’n: p = gH = 𝐻𝑇

𝐻𝑇 = 𝑝

=

720 psi (144 𝑖𝑛2

𝑓𝑡2)

62.4lb

𝑓𝑡3

=21600

13 𝑓𝑡

𝐻 = (𝐻𝑇

𝑆) = (

2160013

4) =

5400

13 𝑓𝑡

𝑁𝑠 = 𝑁√𝑄

(𝐻)34

= 2050√2000

(5400

13)

34

= 996.3939 𝑟𝑝𝑚

33

Lesson 2. Affinity Laws

A. For constant impeller diameter (D=c) with variation in impeller speed

1. if the speed of the impeller is increased from N1 to N2 rpm, the flow rate will increase

from Q1 to Q2 as per the given formula (Krishnamurthy, 2015):

𝑄1

𝑄2 =

𝑁1

𝑁2

2. The head developed(H) will be proportional to the square of the quantity discharged

and diameter of impeller, so that (Krishnamurthy, 2015):

𝐻1

𝐻2 =

𝑄12

𝑄22 =

𝑁12

𝑁22

3. The brake power (P) varies as the cube of head (H), flow rate (Q), and Diameter of

impeller (D), therefore (Krishnamurthy, 2015):

𝑃1

𝑃2 =

𝑄13

𝑄23 =

𝑁13

𝑁23

B. Variation of Impeller diameter without changing speed

1. Capacity of the Pump varies with impeller diameter (Francisco, 2014)

𝑄1

𝑄2 =

𝐷1

𝐷2

2. Head varies with square of impeller diameter (Francisco, 2014)

𝐻1

𝐻2 =

𝐷12

𝐷22

3. Brake power varies with cube of impeller diameter (Francisco, 2014)

𝑃1

𝑃2 =

𝐻1

𝐻2=

𝑄13

𝑄23 =

𝐷13

𝐷23

34

Sample Problem. A centrifugal pump was designed for a 1800 rpm operation and a head of

60.9 m has a capacity of 189.3 l/s (lps) with a power of 130.6 kW. What effect will a speed

reduction to 1200 rpm have on the head, capacity and power input of the pimp? What will be

the changes in these variables if the impeller diameter is reduced from 304. 8 mm to 254 mm

while the speed is constant at 1800 rpm?

Given:

H1 = 60.9 m

Q1 = 189.3 lps

P1 = 130.6 kW

N1 = 1800 rpm

D1 = 304.8 mm

N2 = 1200 rpm

D2 = 254 mm

Req’d: a. For D = c, find Q2, H2 and P2

b. For N = c, find Q2, H2 and P2

Sol’n:

a. for D = c (constant), N1 = 1800 rpm, N2 = 1200 rpm, Q1 = 189.3 lps

𝑄2 = 𝑄1𝑁2

𝑁1= 189.3 lps

1200 rpm,

1800 rpm,=

631

5𝑜𝑟 126.2 𝑙𝑝𝑠

𝐻2 = 𝐻1𝑁2

2

𝑁12 = (60.9 m)

(1200 rpm)2

(1800 rpm)2 =406

15 𝑚 𝑜𝑟 27.0667 𝑚

𝑃2 = 𝑃1 𝑁2

3

𝑁13 = 130.6 kW

(1200 rpm)3

(1800 rpm)3 =5224

135 kW or 38.6963 kW

35

1. Determine the specific speed s of the following single-stage pumps and

specify the type of pump to be used

Table 1 Pump Characteristics for Selection

PUMP N (rpm) Q H

A 1300 3870 gpm 132 ft

B 924 0.862 m3/s 5.335 m

C 720 2200 gpm 132 ft

D 625 0.092 m3/s 4.32 m

E 844 7000 gpm 110 ft

2. A 6-stage pump delivers 3500 gpm against a net pressure rise of 680 psi.

What is the specific speed if it rotates 2050 rpm ?

b. for N = c (constant) with variation in impeller diameter

𝑃1

𝑃2 =

𝐻1

𝐻2=

𝑄13

𝑄23 =

𝐷13

𝐷23

𝑄2 = 𝑄1𝐷2

𝐷1 = (189.3 lps) (

254 mm304.8 mm

) = 631

4 𝑙𝑝𝑠 𝑜𝑟 157.75 𝑙𝑝𝑠

𝐻2 = 𝐻1𝐷2

2

𝐷12 = (60.9 m) (

254 mm

304.8 mm)

2

=1015

24 𝑚 𝑜𝑟 42.29817 𝑚

𝑃2 = 𝑃1 𝐷2

3

𝐷13 = 130.6 kW (

254 mm304.8 mm

)3

= 16325

216 kW or 75.5787 kW

Assessment Task 4

Express answers in fraction or in 4 decimal places as in samples

36

3. A centrifugal pump was designed for a 1940 rpm operation and a head of 63.4 m

has a capacity of 201.2 l/s (lps) with a power of 135. kW. What effect will a speed

reduction to 1200 rpm have on the head, capacity and power input of the pimp?

What will be the changes in these variables if the impeller diameter is reduced from

332.5 mm to 275 mm while the speed is constant at 1940 rpm?

Summary

Pumps often work by translating electrical power to motion. A pump output can be

calculated using key analytical models; flow rate, head, impeller speed and diameter and

efficiency.

References

EnggCylopedia. (n.d.) Pump Performance Curves. Retrieved from:

https://www.enggcyclopedia.com/2011/09/pump-performance-curves/

Engineering ToolBox, (2004). System Curve and Pump Performance Curve. [online] Available

at: https://www.engineeringtoolbox.com/pump-system-curves-d_635.html [15 August

2020].

Francisco, Jose R. (2014). Lecture Notes in Industrial Plant Design.

Krishnamurthy, V.P. (2015). A Course Material on CE 6451 FLUID MECHANICS AND

MACHINERY. http://www.sasurieengg.com/e-course-material/MECH/II-

Year%20Sem%203/CE6451Fluid%20Mechanics%20and%20Machinery(FMM)with%20Q

B.pdf

Whitesides, Randall W. (2012). Basic Pump Parameters and the Affinity Laws. PDH Online

PDH Center. Retrieved from: https://www.pdhonline.com/courses/m125/m125content.pdf

37

MODULE 5 Centrifugal Pumps in Series and in Parallel

Introduction

The operating conditions needed for a system are often beyond the scope of a single,

regular pump. Instead of buying a heavy-duty pump that could be much more than you need,

consider using device design techniques to combine basic pump efficiency that adds up to

the necessary requirements (Ballun, 2015).

Learning Outcomes

At the end of this module, students should be able to:

1. Identify Pumps in Series; and

2. Compute head, capacity and power of pumps in series;

Lesson 1. Centrifugal Pumps in Series

Putting centrifugal pumps in series, or connecting them along a single line, will allow

you to add the head together from each and meet your high, low-flow system requirements.

This is because, as the continuous flow moves through each pipe, the fluid pressure increases

just like how a multi-stage pipe operates. The head would still be applied on the combined

pump curve for two separate pumps, but the curve would most likely have a piecemeal

discontinuity (Ballun, 2015).

38

Figure 1.1. Pumps in Series (CheCalc, n.d.)

Pump handles the same flow rate in series arrangement but the total head provided

by the pump combination will be additive. Since each pump produces a head H corresponding

to a flow Q, the total head formed when connected in series is HT = H1 + H2, where H1, H2 are

the heads produced by the pump in series at the typical flow rate Q (CheCalc, n.d.).

As the system pressure develops, remember to consider downstream pump and seal

pressure ratings to prevent damage to the equipment (Ballun, 2015).

Figure 1.2. Schematic Diagram of Pumps in Series (Ballun, 2015)

P1

P2

Pump 1

Pump 2 H1

H2 HT

HT

39

Figure 1.3 Two Equal-Sized Pumps Connected in Series (Ballun, 2015)

Lesson 2. Pumps in Parallel

The flow rates, with pumps in parallel, are additive with a common head. The QT flow

rate is divided between Q1 and Q2 for the inlet. At the corresponding power, each pump

develops the same head H. At capacity Q1, the first pump thus produces the same head H as

the second pump at capacity Q2 (CheCalc, n.d.).

40

Figure 1.4. Two Equal-Sized Pumps Connected in Parallel (Ballun, 2015)

For two pumps of equal specifications such as head and flow

P2

H1 = H2 = HT

P1

H2

H1

QT = Q1 + Q2

41

Sample Problems:

1. Two pumps operate in series. The first pump has a head of 3.5 m and the next pump has

a head of 5 m and both has a flow rate of 3 m3/min. Find the total head of the two pumps

and what is the final flow?

Given:

H1 = 3.5 m Q1 = 3 m3 / min

H2 = 5 m Q2 = 3 m3 / min

Req’d: HT & QT

Sol’n: HT = H1 + H2 = 3.5 m + 5 m = 8.5 m

QT = Q1 = Q2 = 3 m3 / min

2. Three pumps operate in series. The first pump has a head of 2.95 m, the second has a

head of 4.23 and the last pump has a head of 5.64 m. The flow rate of the pumps is 4.36

m3/min. Find the total head and flow of the system.

Given:

H1 = 2.95 m Q1 = 4.36 m3 / min

H2 = 4.23 m Q2 = 4.36 m3 / min H3 = 5.64 m Q3 = 4.36 m3 / min

Req’d: HT & QT

Sol’n: HT = H1 + H2 + H3 = 2.95 m + 4.23 m + 5.64 m = 12.82 m

QT = Q1 = Q2 = Q3 = 4.36 m3 / min

3. Two pumps operate in parallel. Both pumps have a head of 3.47 m and the flow rate of

the first pumps is 2.44 m3/min and the second pump flows at 3.58 m3/min. Find the total

head and flow of the system.

42

Given:

H1 = 3.47 m Q1 = 2.44 m3 / min

H2 = 3.47 m Q2 = 3.58 m3 / min

Req’d: HT & QT

Sol’n: HT = H1 = H2 = 3.47 m

QT = Q1 + Q2 = 2.44 + 3.58 = 6.02 m3 / min

4. Three pumps operate in parallel. Both pumps have a head of 4.23 m and the flow rate of

the first pumps is 3.26 m3/min the second pump flows at 3.21 m3/min and the third pump

has a flow rate of 2.78 m3/min. Find the total head and flow of the system.

Given:

H1 = 4.23 m Q1 = 3.26 m3 / min

H2 = 4.23 m Q2 = 3.21 m3 / min H1 = 4.23 m Q1 = 2.78 m3 / min

Req’d: HT & QT

Sol’n: HT = H1 = H2 = H3 = 4.23 m

QT = Q1 + Q2 + Q3 = 3.26 + 3.21 + 2.78 = 9.25 m3 / min

43

Assessment Task 5

Summary

Pumps are placed either in series or in parallel depending upon the need of the

application of these pumps.

Answers are hand written (ENGINEERING LETTERING) on a bond paper.

1. Two pumps operate in series. The first pump has a head of 6.25 m and the next pump

has a head of 5.75 m and both has a flow rate of 5.3 m3/min. Find the total head of the

two pumps and what is the final flow?

2. Two pumps operate in parallel. Both pumps have a head of 24.57 ft and the flow rate

of the first pumps is 26.78 ft3/s and the second pump flows at 2.42 m3/min. Find the

total head (m) and flow (m3/min) of the system.

3. Three pumps operate in parallel. Both pumps have a head of 28.37 ft and the flow rate

of the first pumps is 2.96 m3/min the second pump flows at 45.32 ft3/min and the third

pump has a flow rate of 3.28 m3/min. Find the total head (ft) and flow (ft3/min) of the

system.

44

References

Ballun, Jorie. (2015 Jan 22). How To Operate Centrifugal Pumps In Series Or Parallel.

Retrieved from: https://blog.craneengineering.net/operating-centrifugal-pumps-in-

series-or-parallel

CheCalc. (n.d.). Pump Operation Series & Parallel Retrieved from:

https://blog.craneengineering.net/operating-centrifugal-pumps-in-series-or-parallel

45

MODULE 6 Functions & Types of Compressors

Introduction

In a range of compressible fluids, or gases, compressors are mechanical devices used

to raise pressure, the most common of which is air. Compressors are used to supply shop or

instrument air in the industry; to power air instruments, paint sprayers, and abrasive blast

equipment; to phase change coolants for air conditioning and cooling; to propel gas through

pipelines; etc. (Thomas, n.d.).

Learning Outcomes

At the end of this module, students should be able to:

1. Differentiate the functions of compressors;

2. Determine the different types of compressors; and

Lesson 1. Functions of Compressors

Functions

Compressor is a device which is used to increase the pressure of air from low

pressure to high pressure by using some external energy. Some of the basic functions of a

compressor are (Sarkar, n.d.):

46

For filling the air in tube of vehicles

In automobile service station to clean vehicles.

For spray painting in paint industries.

In vehicle to operate air brakes.

For cleaning workshop machines.

For supercharging of an IC engines.

For operation of pneumatic tools i.e. rock drills, vibrators

etc.

Lesson 2. Types of Compressor

Compressors may be represented in a variety of different ways, but are typically

classified into categories based on the practical method used to produce compressed air or

gas. We outline and present the common types of compressor in the sections below (Thomas,

n.d.).

1. Piston/Reciprocating Compressors

In order to compress gas inside a cylinder (or cylinders), piston compressors or

reciprocating compressors depend on the reciprocating motion of one or more pistons to

discharge it into high pressure receiving tanks via valves. The tank and compressor are, in

many cases, installed as a so-called bundled unit in a typical frame or skid. Although the key

use of piston compressors is to provide compressed air as an energy source, piston

compressors are also used for natural gas transmission by pipeline operators. In general,

piston compressors are selected according to the required pressure (psi) and flow rate (scfm).

Compressed air in the 90-110 psi range with volumes varying from 30 to 2500 cfm is provided

by a standard plant-air system; these ranges are normally achievable by commercial, off-the-

shelf units. Farm-air systems can be dimensioned around a single unit or can be centered on

several smaller units that are spread all over the farm (Thomas, n.d.).

47

Figure 2.1. Reciprocating Compressor (Bright Hub Engineering, 2009)

2. Diaphragm Compressors

The diaphragm compressor uses a motor-mounted concentric, a very specialized

reciprocating design that oscillates a flexible disc that expands and contracts the compression

chamber volume in turn. The drive is sealed from the process fluid by the flexible disc, almost

like a diaphragm pump, and therefore there is no chance of lubricant coming into contact with

any gas. As in many laboratory and medical settings, diaphragm air compressors are relatively

low capacity machines that have applications where very clean air is needed (Thomas, n.d.).

48

Figure 2.2. Diaphragm Compressor (Sivaranjith, 2019)

3. Helical Screw Compressors

Rotary compressor machines known for their ability to work on a 100 percent duty

cycle are helical-screw compressors, making them good choices for trailer-able applications

such as construction or road building. These units pull gas in at the drive end using geared,

meshing male and female rotors, compress it as the rotors form a cell and the gas axially

travels its length, and discharge the compressed gas at the non-drive end of the compressor

casing through a discharge port. Owing to decreased vibration, the rotary screw compressor

operation makes it quieter than a reciprocating compressor. The discharge air is free of

pulsations, another benefit of the screw compressor over piston forms. These units can be

lubricated with oil or water, or they can be built to produce air that is oil-free. The demands of

critical oil-free service can be met by these designs (Thomas, n.d.).

49

Figure 2.3. Helical Screw Compressor (Medium, n.d.)

4. Sliding Vane Compressors

A sliding-vane compressor relies on a series of rotor-mounted vanes that sweep an

eccentric cavity along the inside wall. The vanes decrease the amount of space they are

sweeping past by rotating from the suction side to the discharge side of the eccentric cavity,

compressing the gas trapped within the space. On an oil film that forms on the wall of the

eccentric cavity, the vanes glide along, creating a seal. In order to provide oil-free air, sliding-

vane compressors cannot be made, but they are capable of providing pulsation-free

compressed air. Due to the use of bushings rather than bearings and their comparatively slow-

speed activity compared to screw compressors, they often forgive pollutants in their

environments. They are relatively quiet, secure, and capable of 100 % duty cycle service. In

air-compressor applications, some sources say that rotary vane compressors have been

largely overtaken by screw compressors (Thomas, n.d.).

50

Figure 2.4. Helical Screw Compressor (Enggcyclopedia, n.d.)

5. Scroll Compressors

As the orbiting spirals trace the route of the fixed spirals, scroll air compressors use

stationary and orbiting spirals that decrease the volume of space between them. Gas intake

occurs at the outer edge of the scrolls, and in the core, the compressed gas discharge takes

place.

Figure 2.5. Helical Screw Compressor (Thomas, n.d.)

51

No lubricating oil is necessary because the scrolls do not touch, rendering the

compressor intrinsically oil-free. However, since no oil is used to extract compression heat as

it is for other designs, there are very restricted capacities for scroll compressors. They are

also used in low-end air compressors and in compressors for home air conditioning (Thomas,

n.d.).

6. Rotary Lobe Compressors

High-volume, low-pressure machines that are more properly known as blowers are

rotary-lobe compressors (Thomas, n.d.). Two mating lobe-type rotors mounted in a case are

shown in the rotary lobe type. At near clearance, the lobes are gear guided, but without metal-

to - metal contact. The suction to the unit is placed where there is the largest cavity made by

the lobes. The cavity size is decreased as the lobes rotate, allowing the vapor inside to

compress. The compression continues until it enters the discharge outlet, at which point the

vapor escapes at a higher pressure from the compressor (Inst Tools, n.d.)

Figure 2.6. Helical Screw Compressor (Inst Tools, n.d.)

Lobes

52

7. Centrifugal Compressors

To create an increase in pressure, centrifugal compressors rely on high-speed pump-like

impellers to impart velocity to gases. They are primarily used in high-volume applications such

as industrial refrigeration systems in the region of 100 + hp and in large processing plants

where they can get as high as 20,000 hp and produce volumes in the region of 200,000 cfm.

Centrifugal compressors, almost similar in design to centrifugal pumps, increase the gas

velocity by tossing it outward through the motion of a rotating impeller. In a casing volute,

where its velocity slows and its pressure increases, the gas expands (Thomas, n.d.).

There are lower compression ratios for centrifugal compressors than for displacement

compressors, but they handle vast gas volumes. To boost the compression ratio, many

centrifugal compressors use multiple phases. The gas normally passes between stages via

intercoolers in these multi-stage compressors (Thomas, n.d.).

Figure 2.7. Centifugal Compressor (Mech4study, 2017)

53

Answers are hand written (ENGINEERING LETTERING) on a bond paper.

1. Draw and label the types of compressors.

2. Complete the table below

Type of Compressor Description Advantages/Disadvantages

1

2..

3.

4.

5.

6.

7.

Assessment Task 6

Summary

Compressors are designed differently according to its function and

application. This provides a basic understanding of compressor varieties,

power options, selection considerations, applications, and industrial uses.

54

References

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https://www.brighthubengineering.com/hvac/51688-principle-of-working-of-

refrigeration-reciprocating-compressors/

Davis, John. (2014). Rotary Screw Air Compressor Features and Advantages. Retrieved

from: https://medium.com/@johnd/rotary-screw-air-compressor-features-and-

advantages-42f82660436c

Enggcyclopedia. (n. d.). Compressors. Retrieved from:

https://www.enggcyclopedia.com/2011/05/compressors/

Inst Tools. (n.d.) Rotary Compressors. Retrieved from:

https://instrumentationtools.com/rotary-compressors/

Mech4study. (2017). Centrifugal Compressor: Principle, Construction, Working, Types,

Advantages, Disadvantages with its Application. Retrieved from:

https://www.mech4study.com/2017/11/centrifugal-compressor.html

Sivaranjith. (2019). What is the Diaphragm compressor? Retrieved from:

https://automationforum.in/t/what-is-diaphragm-compressor-how-it-works/5787

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https://www.thomasnet.com/articles/machinery-tools-supplies/understanding-

compressors/ October 15, 2020.