october 20 newsletter 2015files.ctctcdn.com/5e1fd810201/c7683ba7-58cd-4cac-a... · cfd modeling...

Newsletter

October 20

2015 [Type the abstract of the document here. The abstract is typically a short

summary of the contents of the document. Type the abstract of the document

here. The abstract is typically a short summary of the contents of the

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Chapter Officer: Board of Governors: Newsletter Committee: Kinan Fahs – President Ghassan Trabolsi – RP Chair Hassan Sultan - Chair

Fady Abu Jamra – President Elect Mostafa Hariri – SA Chair Kinan Fahs - Member

Salah Nezar – Vice President Ali Ibrahim – CTTC Chair Mostafa Hariri - Member Seenu Pillai – Treasurer Mutassim Al Ghadir – GGAC Chair

Tony Khoury – Secretary Chinna Kannan

Diwakar N. Lal Mohamed El Sayed

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INSIDE THIS ISSUE

Newsletter Chair Message………………………………………………………………… 2

Article - CFD Predictions of Pressure Loss in Duct Fittings……………………………… 3

ASHRAE News…………………………………………………………………………… 10

Photos Gallery…………………………………………………………………………….. 11

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NEWSLETTER CHAIR MESSAGE

I had the privilege of travelling to Istanbul for the ASHRAE Regional at Large CRC-2015 as the Student

Activities Regional Vice Chair & part of Qatar Oryx Chapter delegation.

The relationship between ASHRAE & Turkey dates back couple of years but our friends in the Turkish

Chapter did their best to provide a successful CRC full with technical presentations and very remarkable

social events at the Bosphorus.

Dear ASHRAE members at Qatar Oryx Chapter, I would like to share with you and to address about the

importance of the CRC.

Members who are attending the Chapter’s Regional Conference (CRC) can get experience where these

conferences provide an excellent opportunity to:

1. Meet with Board Members in the region.

2. Interact and network with other ASHRAE members in the region.

3. Attend seminars and technical presentations presented by ASHRAE distinguished lecturers and

HVAC industry leaders.

4. Communicate and interact with HVAC manufacturers and stakeholders of the country where the

CRC is taking place.

5. Practice and experience the ASHRAE business and election meeting.

6. Attend to share the election of the Region officers and leaders for the next term.

7. Enjoy the special social events and the well planned activities.

8. Practice and explore about the HVAC industries and news at the CRC country.

9. Attend the training session for student activities, CCT, GR, RP & MP.

10. Chance of building the leadership from the CRC program.

These are some of the benefits and many more you should see with your participation in the CRC.

Hassan Sultan

Former President

ASHRAE Qatar Oryx Chapter

ASHRAE RAL SA, RVC

E&IEC Organizing Committee Chair

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ARTICLE

Computational Fluid Dynamics (CFD) Predictions of Pressure Loss in Duct Fittings

By: Dr. Ahmad Sleiti, Ph.D., P.E., CEM

[email protected]

INTRODUCTION

This paper reports on a systematic study to establish whether CFD techniques are capable of obtaining

pressure drop predictions in elbows that are accurate to within 15% of experimental loss coefficients. A

test program was initiated to measure the friction factor in a straight duct, and the loss coefficient of both

a single five-gore elbow and two close-coupled five-gore elbows. This paper presents results from tests

conducted on ducts/fittings having a nominal diameter of 203 mm (8 in.). Likewise a comparison of CFD

turbulence models in predicting pressure drop for each of the configurations was performed. This was

achieved by conducting a critical comparison between turbulence models, including k-ε, k-ω and the

Reynolds Stress Model (RSM) to establish their capabilities and limitations in predicting such flows.

TEST PROGRAM

An experimental apparatus was constructed to measure the friction factor in a straight duct, and the loss

coefficient of both a single five-gore elbow and two close-coupled five-gore elbows. The measurements

of pressure drop and volumetric flow rate through the ductwork and fittings were performed in

accordance with ASHRAE Standard 120-2008. The elbow pressure loss experiments were preceded by a

series of tests designed to evaluate the friction factor of straight ducts.

CFD MODELING

Computational fluid dynamics is employed to predict the pressure loss in straight duct, in single elbow

and in close-coupled five gore elbow (Z-configuration and U-configuration). The numerical solution

method used to solve Navier-Stokes equations is the finite volume method. A control-volume-based

technique is used to convert the governing equations to algebraic equations that can be solved

numerically.

Turbulence Models

The Navier-Stokes equations are non-linear partial differential equations that cannot be solved

analytically, except a few special cases. Consequently, for most cases, numerical solution is needed to

solve the NS-equations. Direct Numerical Simulations (DNS’s) and Large Eddy Simulations (LES’s) are

mailto:[email protected]

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the most accurate but they require large computational resources. Reynolds Averaged Navier Stokes

(RANS) turbulence models although are affected by numerical and physical approximations still they

perform reasonably accurate, require less computational resources and they are widely used for industrial

applications. Thus, in this paper RANS turbulence models are used.

Grid Generation and Boundary Conditions

The performance of turbulence models is evaluated by comparing the CFD predictions of each model to

experimental measurements in straight duct, single elbow, Z-configuration duct and U-configuration duct.

The numerical grid for the studied duct geometries is shown by Figure 1.

CFD RESULTS

1. Straight Duct

Figure 2 shows a comparison between experimental friction factor and 3 CFD k-e turbulence models with

wall roughness. Results in Figure 2 are summarized as follows:

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CFD RNG k-e for e/D = 0.009 rough duct: RNG k-e turbulence model was used with 60 x 200 grid size

and standard wall functions to compare friction factor of rough duct to experimental and Moody diagram

friction factor. Results show that the error in friction factor prediction using RNG k-e CFD model ranges

from 6% to more than 17%.

CFD Realizable k-e for e/D = 0.009 rough duct: Realizable k-e turbulence model was used with 60 x

200 grid size and standard wall functions to compare friction factor of rough duct to experimental and

Moody diagram friction factor. Results show that the error in friction factor prediction using Realizable k-

e CFD model ranges from 10% to more than 21%.

Figure 3 shows a comparison between experimental friction factor and 2 CFD k-w turbulence models

with wall roughness. Results in Figure 3 are summarized as follows:

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CFD Standard k-w for e/D = 0.009 rough duct: Standard k-w turbulence model was used with 60 x 200

grid size and standard wall functions to compare friction factor of rough duct to experimental and Moody

diagram friction factor. Results show that the error in friction factor prediction using Standard k-w CFD

model ranges from 2 % (for high Re) to more than 13% (for low Re).

CFD SST k-w for e/D = 0.009 rough duct: SST k-w turbulence model was used with 60 x 200 grid size

and standard wall functions to compare friction factor of rough duct to experimental and Moody diagram

friction factor. Results show that the error in friction factor prediction using SST k-w CFD model ranges

from 6 % (for high Re) to more than 18% (for low Re).

Figure 4 shows a comparison between experimental friction factor and RSM turbulence model with wall

roughness. Results in Figure 4 are summarized as follows:

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CFD RSM for e/D = 0.009 rough duct: RSM turbulence model was used with 60 x 200 grid size and

standard wall functions to compare friction factor of rough duct to experimental and Moody diagram

friction factor. Results show that the error in friction factor prediction using RSM CFD model ranges

from 13 % to more than 22% .

2. Single Elbow

Figure 5 shows a comparison between experimental loss coefficient and CFD k-e turbulence model

predictions for single elbow. Results in Figure 5 are summarized as follows:

CFD Standard k-e for e/D = 0.009 rough duct: A standard k-e turbulence model was used with grid

size of 60 x 200 in the entrance region, 60 x 22 in the curve region and 60 x 160 in the exit region and

with standard wall functions to compare friction factor of rough duct to experimental loss coefficient.

Results show that the error in CFD predictions using Standard k-e ranges from 5% to more than 18%.

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CFD Standard k-w for e/D = 0.009 rough duct: A standard k-w turbulence model was used with grid

size of 60 x 200 in the entrance region, 60 x 22 in the curve region and 60 x 160 in the exit region and


Results show that the error in CFD predictions using Standard k-w ranges from 9% to more than 19%.

CFD RSM for e/D = 0.009 rough duct: RSM turbulence model was used with grid size of 60 x 200 in

the entrance region, 60 x 22 in the curve region and 60 x 160 in the exit region and with standard wall

functions to compare friction factor of rough duct to experimental loss coefficient. Results show that the

error in CFD predictions using RSM turbulence model ranges from 4% to 16%, which are more accurate

than k-w and k-e turbulence models

3. Double Elbow Loss Coefficient: Z-Configuration with Lint = 2.52 m (8.28 ft)

Figure 6 shows a comparison between experimental loss coefficient and CFD turbulence model prediction

for the Z-Configuration with Lint = 2.52 m (8.28 ft). Results in Figure 6 are summarized as follows:

CFD Standard k-e for e/D = 0.009 rough duct: A standard k-e turbulence model was used with grid

size of 60 x 200 in the entrance region, 60 x 22 in the curve regions and 60 x 160 in the exit region and

0

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0 50 100 150 200 250 300 350

Tota

l Pre

ssur

e Los

s (Pa

)

Velocity Pressure (Pa)

ExperimentalData

CFD k-e

CFD k-w

CFD RSM

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Results show that the error in CFD predictions using Standard k-e ranges from 0.1% to more than 18%.

CFD Standard k-w for e/D = 0.009 rough duct: A standard k-w turbulence model was used with grid

size of 60 x 200 in the entrance region, 60 x 22 in the curve regions and 60 x 160 in the exit region and


Results show that the error in CFD predictions using Standard k-w ranges from 7% to more than 24%.

CFD RSM for e/D = 0.009 rough duct: RSM turbulence model was used with grid size of 60 x 200 in

the entrance region, 60 x 22 in the curve regions and 60 x 160 in the exit region and with standard wall

functions to compare friction factor of rough duct to experimental loss coefficient. Results show that the

error in CFD predictions using Standard k-e ranges from 0.4% to more than 15%, which are more

accurate than k-w and k-e turbulence models.

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0 50 100 150 200 250 300 350 400 450 500

Tota

l Pre

ssur

e Lo

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a)

Velocity Pressure (Pa)

Experimental Data

CFD k-e

CFD k-w

Experimental Data

CFD k-e

CFD k-w

CFD RSM

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ASHRAE NEWS

MANAGE ENERGY EFFECTIVELY Sustained energy management is the quickest,

cheapest, cleanest way to expand the world’s energy supplies and to reduce

greenhouse gas emissions. Learn the strategies for ensuring that energy

management efforts don’t fall short of their potentials. This online course, part of

the 2015 Fall Online Series, will take place October 12, 1:00 – 4:00 EDT. This

course is a part of the ASHRAE Career Enhancement Curriculum Program.

GEOTHERMAL HVAC The 2015 edition of Geothermal Heating and Cooling:

Design of Ground-Source Heat Pump Systems is a complete revision. This is an essential

guide for HVAC design engineers, design-build contractors, GSHP subcontractors, and

energy/construction managers, building owners and architects. The book provides

insights into characteristics of high-quality engineering firms and key information that

should be provided by design firms owners competing for GSHP projects and owners

evaluating them.

HVAC TRAINING IN DUBAI ASHRAE is offering its popular Level I and

Level II HVAC Design training on November 15–19, 2015 in Dubai. Reserve your seat

today to attend both courses to gain real-world knowledge; you can put to immediate

use. HVAC Design: Level I – Essentials provides the fundamental and technical

aspects of HVAC design in commercial buildings. HVAC Design: Level II –

Applications provides advanced instruction on HVAC system designs. Accelerate your

transformation into a more effective member of your design, construction or facilities

maintenance team, whether you are new to the field or an experienced engineer

.

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ASHRAE Photos Gallery

Innovative Cooling Solutions with “Indirect Evaporative Cooling”

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K 12 Training for Lebanese School

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CRC Turkish (2 - 4.10.2015)

october 20 newsletter 2015files.ctctcdn.com/5e1fd810201/c7683ba7-58cd-4cac-a... · cfd modeling...

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