radial flow fan test

By abnet mengesh (ADDIS ABABA UNIVERSTIY INSTITUTE OF TECHNOLOGY 2015)

Radial flow fan test

Objective:

The main objectives of this lab>

To measure the total pressure drop with respect to flow rate To measure static pressure drop with respect to flow rate. To know the parameters that affects the operation capacity and efficiency of

the fan. And determine which parameters are the most determinant for the flow fan.

Theory

A radial flow fan comprising an impeller where the direction of the entry air flow is vertical to the direction of the exit air flow

A centrifugal fan is a mechanical device for moving air or other gases. These fans increase the speed of air stream with the rotating impellers. They use the kinetic energy of the impellers or the rotating blade to increase the pressure of the air/gas stream which in turn moves them against the resistance caused by ducts, dampers and other components. Centrifugal fans accelerate air radially, changing the direction (typically by 90°) of the airflow. They are sturdy, quiet, reliable, and capable of operating over a wide range of conditions.

Centrifugal fans are constant displacement devices or constant volume devices, meaning that, at a constant fan speed, a centrifugal fan will pump a constant volume of air rather than a constant mass. This means that the air velocity in a system is fixed even though mass flow rate through the fan is not.

The centrifugal fan is one of the most widely used fans. Centrifugal fans are by far the most prevalent type of fan used in the HVAC industry today. They are usually cheaper than axial fans and simpler in construction. It is used in transporting gas or materials and in ventilation system for buildings. They are also used commonly in central heating/cooling systems. They are also well-suited for industrial processes and air pollution control systems.

It has a fan wheel composed of a number of fan blades, or ribs, mounted around a hub. As shown in the figure, the hub turns on a driveshaft that passes through the fan housing. The gas enters from the side of the fan wheel, turns 90 degrees and accelerates due to centrifugal force as it flows over the fan blades and exits the fan housing.

1


Main parts of a centrifugal fan are:

Fan housing Impellers Inlet and outlet ducts Drive shaft Drive mechanism

Principles of operation

The centrifugal fan uses the centrifugal power generated from the rotation of impellers to increase the kinetic energy of air/gases. When the impellers rotate, the gas near the impellers is thrown-off from the impellers due to the centrifugal force and then moves into the fan casing. As a result, the kinetic energy of gas is converted to pressure because of system resistance offered by the casing and duct. The gas is then guided to the exit via outlet ducts. After the gas is thrown-off, the gas pressure in the middle region of the impellers decreases. The gas from the impeller eye rushes in to normalize this pressure. This cycle repeats and therefore the gas can be continuously transferred.

Apparatus and materials used

Data

DimNozzle position

Turn 1 3 5 7 9 11 13 15 17 19

wattmeter

α 25 27 28 31.5 35 39 41 43 46 48

Voltage V 450 450 450 450 450 450 450 450 450 450current A 2.7 2.8 2.9 3 3.05 3.12 3.15 3.20 3.25 3.3Speed n rpm 280

02800

2800

2800

2800

2800

2800

2800

2800

2800

∆ pvent mmw 40 130 270 410 610 830 103 120 138 151

2


c 0 0 0 0∆ pfan mmw

c930 890 885 880 860 840 790 740 680 610

Bf=603mmHg

T=210C

B =Bf-T/8

C =20;

Power=C/2*αw

SFven=1

SFfav= (808.3/0.787)*(inch/250)

AD=0.1452m

A0=34.77m

1, Calculation

value Dim

1 Nozzle position

Turn

1 3 5 7 9 11 13 15 17 19

2 wattmeter α 25 27 28 31.5 35 39 41 43 46 483 Voltage V 450 450 450 450 450 450 450 450 450 4504 current A 2.7 2.8 2.9 3 3.05 3.12 3.15 3.2 3.25 3.35 Speed n rp

m2800

2800

2800

2800

2800

2800

2800

2800

2800

2800

6 ∆ pvent mmwc

40 130 270 410 610 830 1030

1200

1380

1510

7 ∆ pfan mmwc

930 890 885 880 860 840 790 740 680 610

8 Nactive=(C/

2)*α

W 250 270 280 315 350 390 410 430 460 480

9 Napparent=V*A VA 121 126 130 135 137 140 141 144 146 148

3


5 0 5 0 2.5 4 7.5 0 2.5 510

cosφ=Nactive/Napparant

- 0.206

0.2143

0.2146

0.23 0.255

0.278

0.2892

0.299

0.315

0.323

11

n=n(rpm)/60

1/s 46.67

46.67

46.67

46.67

46.67

46.67

46.67

46.67

46.67

46.67

12ω=2πn 1/s 293.

067293.067

293.067

293.067

293.067

293.067

293.067

293.067

293.067

293.067

13

U1=r1*ω m/s

20.632

20.632

20.632

20.632

20.632

20.632

20.632

20.632

20.632

20.632

14

U2=r2*ω m/s

23.6 23.6 23.6 23.6 23.6 23.6 23.6 23.6 23.6 23.6

15

U22=(r2ω)2 m

2/s2556.38

556.38

556.38

556.38

556.38

556.38

556.38

556.38

556.38

556.38

16

A0u1=34.77*(r1ω)

m3/s

717.375

717.375

717.375

717.375

717.375

717.375

717.375

717.375

717.375

717.375

17

U13=(r1ω)3 m

3/s38782.062

8782.062

8782.062

8782.062

8782.062

8782.062

8782.062

8782.062

8782.062

8782.062

18

A0u1

3=34.77*(r1ω)3

m5/s3

305372

305372

305372

305372

305372

305372

305372

305372

305372

305372

19

(ρ/2)* A0u1

3=0.45* A0u1

3

Kg/m.s3

137417.23

137417.23

137417.23

137417.23

137417.23

137417.23

137417.23

137417.23

137417.23

137417.23

20∆pven/20*0.8*0.5

mmwc

0.8 2.6 5.4 8.2 12.2 16.6 20.6 24 27.6 30.2

21∆pven=g*pvent

=9.81*’20’Kg/ms2

7.85 25.506

52.974

80.442

119.88

162.85

202.09

235.44

270.76

296.3

22∆pven/(ρ /2)

m2/s2

17.44

56.68

117.7082

178.76

266.4

361.89

449.09

523.2

601.63

658.44

23√ ∆pven/ρ m/

s4.177

7.529

10.852

13.37

16.322

19.023

21.2 22.9 24.53

25.66

24α A 0√∆pven/ρ=V

m/s

0.027564

0.0497

0.07161

0.08823

0.10771

0.125533

0.1349

0.15114

0.162

0.1693

25∆Pfan=s ʄfan*∆P*

fan

mm

18.6 17.8 17.7 17.6 17.2 16.8 15.8 14.8 13.6 12.2

4


wc26∆Pfan=g∆Pfan

Kg/ms2

182.47

174.62

173.64

172.66

168.723

164.81

155 145.19

133.42

119.682

27

Ystat=∆Pfan/ρ

m2/s2

202.744

194.02

192.93

191.84

187.5

183.122

172.22

161.32

148.244

133

28

CD=V/AD m/s

1.8981

3.423

4.932

6.07645

7.41804

8.6455

9.635

10.4091

11.157

11.66

29

Ydyn=CD2/2 m

2/s21.8014

5.86 12.162

18.462

27.514

37.282

46.42

54.175

62.24

67.98

30

Y= Ydyn+ Ystat

m2/s2

204.55

199.88

205.092

210.302

215.014

220.404

218.64

215.5

210.5

201

31

Neff=VYρ w 5.0744

8.94063

13.22

16.7 20.843

24.9012

27.53

29.314

30.691

30.63

32Ƞtot= Neff/ Nactive

- 0.0203

0.0331

0.04721

0.05302

0.06 0.064

0.06715

0.0682

0.06672

0.064

33

φ=V/ A0u1 10^-5

3.8423

6.93 9.982

11.472400

15.0145

17.5 18.805

21.07

22.582

23.6

34

Ψ=2Y/u22 - 0.36

760.3593

0.369

0.378

0.3865

0.39614

0.93 0.38733

0.37834

0.3613

35

μtot=2Nact/ρ A0u1

310^-3

1.82 1.965

2.04 2.3 2.547

2.84 2.984

3.13 3.35 3.5

2,plots

A, calculation and graph

φ 10^-5

3.8423

6.93 9.983 11.4724

15.0145

17.5 18.805

21.07

22.582

23.6

cosφ

0.206 0.2143

0.2146

0.23 0.255 0.278

0.2892

0.299

0.315 0.323

Nacti w 250 270 280 315 350 390 410 430 460 480

Cosφ Vs Nactive graph

5


0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34250

300

350

400

450

500

cos@

Nac

tive

B

φ 10^-5

3.8423 6.93 9.983 11.4724

15.0145

17.5 18.805

21.07 22.582

23.6

V m/s

0.027564

0.0497

0.07161

0.08823

0.10771

0.125533

0.1349

0.15114

0.162

0.1693

x mm 1 3 5 7 9 11 13 15 17 19cosφ

- 0.206 0.2143

0.2146

0.23 0.255 0.278

0.2892

0.299

0.315 0.323

Vx

m/s

0.00568

0.0107

0.0154

0.0203

0.0275

0.035 0.039 0.0452 0.051

0.055

6


0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.0550

2

4

6

8

10

12

14

16

18

20

Vx(m/s)

x(m

m)

Vx Vs x graph

C

φ 10^-5

3.8423 6.93 9.983 11.4724

15.0145

17.5 18.805

21.07 22.582

23.6

V m/s 0.027564

0.0497

0.07161

0.08823

0.10771

0.125533

0.1349

0.15114

0.162

0.1693

x mm 1 3 5 7 9 11 13 15 17 19cosφ

- 0.206 0.2143

0.2146

0.23 0.255 0.278

0.2892

0.299

0.315 0.323

Vx

m/s 0.00568

0.0107

0.0154

0.0203

0.0275

0.035 0.039 0.0452 0.051

0.055

7


Yx

m2/s2

42.14 42.8343

44.013

48.37 54.83 61.3 63.2307

64.435 66.308

64.923

Y m2/s2

204.55 199.88

205.092

210.302

215.014

220.404

218.64

215.5 210.5

201

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.05540

45

50

55

60

65

70

Vx(m/s)

Yx

Vx Vs Yx graph

D

Vx m/s

0.00568

0.0107

0.0154

0.0203

0.0275

0.035

0.039

0.0452

0.051

0.055

Nactive

w 250 270 280 315 350 390 410 430 460 480

8


0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055250

300

350

400

450

500

Vx(m/s)

Nact

ive(

w)Vx Vs Nctv graph

E

Vx m/s

0.00568

0.0107

0.0154

0.0203

0.0275

0.035

0.039 0.0452

0.051 0.055

Ƞtot

- 0.0203

0.0331

0.04721

0.05302

0.06 0.064

0.06715

0.0682

0.06672

0.064

9


V x v s Ƞtot graph

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.0550.02

0.025

0.03

0.035

0.04

0.045

0.05

0.055

0.06

0.065

0.07

Vx

tota

l effi

cien

cy

F

φ vs. Ψ graph

10


0 5 10 15 20 250.355

0.36

0.365

0.37

0.375

0.38

0.385

0.39

0.395

0.4

G

φ vs. v graph

11


0 5 10 15 20 250.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

H

φ vs.Ƞtot graph

12


0 5 10 15 20 250

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Conclusion and discussion

The centrifugal fan performance tables provide the fan RPM and power requirements for the given CFM and static pressure at standard air density. When the centrifugal fan performance is not at standard conditions, the performance must be converted to standard conditions before entering the performance tables. Centrifugal fans rated by the Air

13

http://en.wikipedia.org/wiki/Air_Movement_and_Control_Association


Movement and Control Association are tested in laboratories with test setups that simulate installations that are typical for that type of fan. Usually they are tested and rated as one of four standard installation types as designated in AMCA Standard 210.

AMCA Standard 210 defines uniform methods for conducting laboratory tests on housed fans to determine airflow rate, pressure, power and efficiency, at a given speed of rotation. The purpose of AMCA Standard 210 is to define exact procedures and conditions of fan testing so that ratings provided by various manufacturers are on the same basis and may be compared. For this reason, fans must be rated in standardized SCFM.

Generally from calculation and graphs we observed the fooling points:

From graph A, the cosine of the Angele and Native slightly has direct relation (.i.e. when cosine of the angle increases and also power requirement also increases.). In our design of the fan we must consider this relation,(we should compromise the speed and power requirement).

From graph B, the nozzle position and the speed of the motor has direct relation. From graph C, at lower speed there is low amount of specific energy is needed, and

then sharply increases and at higher speed the specific energy start to decrease. From graph D, Nactive and the speed of the motor has direct relation. As the speed

increases and also the power requirement increase. From graph E, generally as speed increases efficiency increases and after reaching

maximum efficiency point it start to decrease as speed increases. From graph H, at very low angle the total efficiency also low, but a little increscent of

the angle increase the total efficiency very sharply and then a little incensement of angle decreases the total efficiency very sharply. Here we observed that the angle of rotation is the greater factor that affects the total efficiency of our flow fan, so when we design the fan we must consider the angle of rotation greatly.

14

http://en.wikipedia.org/wiki/Air_Movement_and_Control_Association

radial flow fan test

Documents