Numerical Investigation of the Performance of an ACC Presenter: RA Engelbrecht

Academic Mentor: Prof. S.J. van der Spuy

Industrial Mentor: AF Du Preez

Date: 11/12 July 2016

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Outline

• Project Background

• Model Implementation & Validation

• Future/Planned Research

• Recirculation at periphery fans

• Effects of buildings

• Effects on fan volume flow and performance

Fan Flow Effects

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• Separation Effects

Study Objectives

• Objectives

• Implement axial flow fan and A frame heat exchanger model

• Validate Models

• Determine operating points

• Model 30 fan ACC bank with different fan configurations and different environmental effects

• Outcomes

• Determine effect of environmental conditions on performance of ACC through power requirements

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Axial Flow Fan Model

• Actuator Disk Model (ADM) developed by Thiart and von Backström (1993)

• Implemented in Open source Field Operation and Manipulation (OpenFOAM) software package

• Blade element theory

• Uniform disk grid spacing

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Axial Flow Fan Model

• Actuator Disk Model was chosen for:

Accurate flow representation downstream of fan

Power can be measured

OpenFOAM implementation

• Two fans used in this study

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Fan

Designation

Fan Diameter

(m)

Hub-to-tip

Ratio

No. of Blades

A Fan 9.145 0.153 8

B2 Fan (small) 1.542 0.4 8

ADM Validation

• BS848 Type-A test facility at Stellenbosch

• Computational Domain

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ADM Validation

• Performance Characteristics

• Static Pressure vs. Flow Rate

8

-10

40

90

140

190

240

290

340

390

440

490

0 5 10 15 20 25

Sta

tic

Pre

ss

ure

[P

a]

Volumetric Flow Rate [m3/s]

ADM Analysis

Experimental

B2-Fan: 8 bladed

Diameter: dF = 1.542 m

Blade Angle (chord line): cr = 31o

Density: a = 1.2 kg/m3

Speed: N = 750 rpm

ADM Validation

• Performance Characteristics

• Power vs. Flow Rate

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0

1000

2000

3000

4000

5000

6000

0 5 10 15 20 25

Po

we

r [W

]

Volumetric Flow Rate [m3/s]

ADM Analysis

Experimental

B2-Fan: 8 bladed

Diameter: dF = 1.542 m

Blade Angle (chord line): cr = 31o

Density: a = 1.2 kg/m3

Speed: N = 750 rpm

ADM Validation

• Performance Characteristics

• Static Efficiency vs. Flow Rate

10

-10

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25

Sta

tic

Eff

icie

nc

y [

%]

Volumetric Flow Rate [m3/s]

ADM Analysis

Experimental

B2-Fan: 8 bladed

Diameter: dF = 1.542 m

Blade Angle (chord line): cr = 31o

Density: a = 1.2 kg/m3

Speed: N = 750 rpm

Heat Exchanger Model

• Heat Exchanger Models

• Elliptical, double row finned tubes

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Designation Loss Parameter Heat Transfer (1st Row) Heat Transfer (2nd Row)

Finned

Elliptical Tube

Khe = 4464.831Ry-0.439275 Ny(1) = 583.8307Ry0.4031 Ny(2) = 1277.72Ry0.3806

• Pressure Drop

• One Dimensional Draft Equation without fan pressure recovery term

𝑝𝑎1 − 𝑝𝑎7 ≈ 𝐾𝑡𝑠1

2𝜌𝑎1

𝑚𝑎

𝑛𝑏𝐴𝑓𝑟

2

+ 𝐾𝑢𝑝 + 𝐾𝑑𝑜1

2𝜌𝑎3

𝑚𝑎

𝐴𝑒

2 + 𝐾𝜃𝑡

1

2𝜌𝑎56

𝑚𝑎

𝑛𝑏𝐴𝑓𝑟

2

• Flow Conditioning

• Darcy-Forccheimer Porous Medium

𝐹𝑖 = − 𝐶𝑖1

2𝜌 𝑣 𝑣𝑖 +

𝜇𝑖

𝛼𝑣𝑖

• Heat Transfer

• 𝛆-NTU

𝑄(𝑖) = 𝑚𝑎𝑐𝑝𝑎 𝑇𝑎𝑜 𝑖 − 𝑇𝑎𝑖 𝑖 = 𝑒 𝑖 𝑚𝑎𝑐𝑝𝑎(𝑇𝑠 − 𝑇𝑎𝑖 𝑖 )

Heat Exchanger Model

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Heat Exchanger Model Validation

• Heat Transfer

• Pressure Drop

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315

319

323

327

331

335

0 200 400 600 800 1000

Ou

tlet

Tem

pera

ture

[K

]

Volumetric Flow Rate [m3/s]

Analytical Solution

Numerical Results

0

100

200

300

400

500

600

0 200 400 600 800 1000

Pre

ssu

re D

rop

[P

a]

Volumetric Flow Rate [m3/s]

Analytical Solution

Numerical Results

Heat Exchanger Model Validation

• Flow Conditioning

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• Computational Domain

• Operating Point

Operating Point

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Fan Designation Analytical (m3/s) Numerical (m3/s) Power (W)

A Fan

631.1685

620.193 207 814

B2 Fan 625.923 203 281

Operating Point

• A Fan

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• B2 Fan

30 Fan ACC Bank

• Generic ACC with B2 Fans for validation

• Validation will be done by comparing the volumetric effectiveness to previous literature

𝑉𝑒𝑓𝑓 = 𝑉/𝑉𝑖𝑑

• Different fan configurations will be tested under differing environmental conditions to determine the effect on power output of the bank

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Thank you