Comparison of Experimental and Analytical Substation … · Who we are 3 • Tony Pribble •...

Comparison of Experimental and Analytical Substation Bus 

Temperatures

Presented by: Joe Goldenburg, Tony Pribble

IEEE PES Scottsdale, AZ May, 2018

1

Who we are• Joe Goldenburg• Leads GA Tech NEETRAC’s 

Mechanical Section• BME GA Tech• MSOR GA Tech• Licensed Engineer, Georgia• 26 years experience• Chair ANSI C119.0 OH Connectors• Member ASTM B01 OH Conductors• Member Overhead Lines 

Committee

2

Who we are3

• Tony Pribble• Research Engineer –

NEETRAC Lab• BSME Iowa State 

University• MSE‐MS Georgia Tech – In 

progress• EIT

NEETRAC Overview

• Non-profit, 37 member industry consortium at Georgia Tech– 37 Members – Utilities and Manufacturers– Represent ~65% of US + Canadian electric customers

• Provide third‐party testing and application research services.

4

Electrical SectionMechanical Section

NEETRAC Overview5

Agenda1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

6

Agenda7

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

History of the Project

• In 2012, NEETRAC members funded a project to develop a bus ampacity software package.– Automates IEEE 605 with some slight modifications. 

• CFD simulations were run to determine the steady state bus temperature.– Predicted values from 605 were used to verify the results.

• CFD and 605 didn’t match in some cases.– 605 made several simplistic assumptions not made in CFD.

• A wind tunnel was built and experimental data collected.

8

History of the Project

• The temperature differences were confirmed in experiments. 

• NEETRAC members requested we share the data with the 605 committee.

• This presentation is meant to inform the committee of available data and resources.

9

Agenda

1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

10

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

Steady‐State Heat Transfer

Qresistance

Qsun

Qconvection

Qradiation

Steady‐State Heat Transfer

Qresistance

Qsun

Qconvection

Qradiation

Ignore

Ignore

Forced Convection13

Tw

Tair, Vair QcIf Tair < Tw

Convection Coefficient [w/m2K]

Forced Convection14

Tw

Tair, VairQc1

h is different

Tw

Tair, Vair

Qc2

Forced Convection

The convection coefficient, h, is affected by:• Geometry• Fluid properties• Fluid velocity

15

Forced Convection

• How is h determined?• The Nusselt number is a dimensionless quantity used to find h.

16

Convection Coefficient

Characteristic Length

Thermal Conductivity of the Fluid

Forced Convection

Experiments have shown a relationship between the Nusselt, Reynolds, and Prandtl numbers to find h.

17

Fluid Velocity Characteristic Length

Kinematic Viscosity

Prandtl –Typically taken as 0.7 for air

Forced Convection18

Flat Plate Nusselt Correlation

Tw

Tair, Vair QcIf Tair < Tw

Forced Convection19

Tw

Tair, Vair

Qc

Round Body Nusselt Correlation

Steady‐State Heat Transfer

Qresistance

Qsun

Qconvection

Qradiation

Ignore

Radiation21

T

Tsur Qr

Emissivity Stefan-Boltzmann Constant

Radiation is the emission of energy through EM waves; In substations, this happens at infrared wavelengths.

Steady‐State Heat Transfer

Qresistance

Qconvection

Qradiation

Agenda

1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

23

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

Heat Transfer Solution MethodsThree methods to solve the steady‐state heat transfer problem.

• IEEE 605• Experimental• CFD/FEA

24

CFD/FEA Experimental

IEEE 605

IEEE 605 Calculation

IEEE 605 uses the Nusselt correlation for a flat plate to find h.– All bus geometries (except round) are broken into a series of horizontal flat plates. 

– Disregards orientation

25

Nusselt correlation for a flat plate

IEEE 605 Calculation

AB

CD

Flow Direction

Flow Direction

=++

A C

B

D

IEEE 605 Calculation

A

B

C

D

+

++A C

B

D=

Flow Direction

IEEE 605 Calculation28

AB

CD

A

B D

C

IEEE 605 Calculation29

Round Body Nusselt Correlation

IEEE 605 Calculation30

Flow Direction

++

++

IEEE 605 Calculation31

These regions are approximated by free (natural) convection

IEEE 605 Calculation32

++

Force Convection

+

+Natural Convection – Horizontal Surfaces

+ +Notice these are all downward facing surfaces.

Agenda

1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

33

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

Δ(Qres ‐ Qconv)

Δ T4

Δ Qrad

Steady‐State Heat Transfer

Qresistance

Qconvection

Qradiation

I2RΔT

ΔR

ΔI2R

TΔT

Δ air prop.

Δh

T4

CFD Simulation35

Flow Direction

CFD Simulation36

Fluid Velocity

Bus Temperature

CFD Simulation37

Swirling & Recirculation

CFD Simulation38

Un-even heat flux

Agenda

1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

39

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

Experimental40

Wind Tunnel Anatomy

Flow Straightener

Compression Zone

Sample Chamber

Bus

Expansion Zone

Wind Tunnel Anatomy

Expansion Zone

Sample Chamber

Fan

Experimental

• We assume:– Heat conduction from the bus is negligible.– Surface‐to‐surface radiation model.– Input air flow is uniformly laminar.

• Wind tunnel data and CFD results are compared for agreement. – This helps us check our assumptions and verify the results.

43

Experimental44

Geometry Wind Speed Targets

Temperature Targets

0.61 m/s

70 C110 C140 C190 C

1 m/s

70 C110 C140 C190 C

2 m/s

70 C110 C140 C190 C

Rectangular Horizontal

Experimental45

Geometry Wind Speed Targets

Temperature Targets

0.61 m/s

70 C90 C120 C160 C

1 m/s

60 C90 C120 C140 C

2 m/s

50 C90 C110 C140 C

Rectangular Vertical

Experimental46

Geometry Wind Speed Targets

Temperature Targets

0.61 m/s

80 C100 C120 C140 C

1 m/s

70 C90 C120 C140 C

2 m/s70 C120 C140 C

UAB Closed

Experimental47

Geometry Wind Speed Targets

Temperature Targets

0.61 m/s90 C120 C140 C

1 m/s 90 C120 C140 C

2 m/s90 C120 C140 C

UAB Open

Experimental48

Geometry Wind Speed Targets

Temperature Targets

0.61 m/s90 C120 C140 C

1 m/s 90 C120 C140 C

2 m/s90 C120 C140 C

IWBC

In Progress

Agenda

1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

49

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

Results• On the proceeding slides, the steady state bus temperature is displayed by method (605, CFD, Experimental)

• Experiments were run first. From these runs, input current was recorded. This current was then used in CFD & 605 to determine the bus temperature.

• Nussult correlations were developed from this data.

50

1 21 086420

200

1 75

1 50

1 25

1 00

75

50

Case

Tem

pera

ture

(C)

CFDExperimentalIEEE 605

Method

Horizontal Rectangular Results51

0.6 m/s 1 m/s 2 m/s

*Each point represents the steady state temperature determined by the respective method

22 C difference between 605 & exp.

1 21 086420

1 75

1 50

1 25

1 00

75

50

Case

Tem

pera

ture

(C)

CFDExperimentalIEEE 605

Method

Vertical Rectangular Results52

0.6 m/s 1 m/s 2 m/s

17 C difference between 605 & exp.

1 21 086420

1 50

1 40

1 30

1 20

1 1 0

1 00

90

80

70

60

Case

Tem

pera

ture

(C)

CFDExperimentalIEEE 605

Method

UAB Closed Results53

0.6 m/s 1 m/s 2 m/s31 C difference between 605 & exp.

9876543210

1 50

1 40

1 30

1 20

1 1 0

1 00

90

80

70

60

Case

Tem

pera

ture

(C)

CFDExperimentalIEEE 605

Method

UAB Open Results54

0.6 m/s 1 m/s 2 m/s

33 C difference between 605 & exp.

IWBC Results

In progress

55

Experimental Results

• For vertical rectangular, IEEE 605 is conservative.– Translates to lost ampacity

• For horizontal rectangular, closed UAB, open UAB, and IWBC IEEE 605 is aggressive.– Predicts lower steady‐state temperature  than found in experiments

56

Survey 

• NEETRAC sent out a survey to determine the popularity of each style bus.

57

Total Number of Substations

(3 Responses)

58

Average Percentage of Bus Used

(3 Responses)

59

Flat Plate Correlation

• Advantages of flat plate correlations:– Can be built up to approximate complex geometries

– Inexpensive – Computationally simplistic

• Disadvantages of flat plate correlations:– Inaccurate, upwards of 20% error

60

Whole Body Correlation61

• Advantages of whole body correlations– More accurate– Computationally less complex (one formula)

• Disadvantages of whole body correlations– Only good for specific geometry, orientation, and Reynolds number range.

• Given the limited number of geometries, NEETRAC recommends using whole body correlations, as is currently done with round.

9.59.08.58.07.5

4.4

4.2

4.0

3.8

3.6

3.4

3.2

3.0

S 0.0572904R-Sq 97.7%R-Sq(adj) 97.6%

Ln(Re)

ln(N

u/Pr

^0.

33)

Regression95% CI

Rectangular - Horizontalln(Nu/Pr^0.33) = - 1 .834 + 0.6553 Ln(Re)

Correlations62

exp.

9.59.08.58.07.5

4.75

4.50

4.25

4.00

3.75

3.50

S 0.0982542R-Sq 90.8%R-Sq(adj) 90.4%

Ln(Re)

ln(N

u/Pr

^0.

33)

Regression95% CI

Rectangular - Verticalln(Nu/Pr^0.33) = - 0.5852 + 0.5504 Ln(Re)

Correlations63

Correlations64

9.259.008.758.508.258.007.757.50

4.25

4.00

3.75

3.50

3.25

3.00

S 0.0641 092R-Sq 97.4%R-Sq(adj) 97.3%

Ln(Re)

ln(N

u/Pr

^0.

33)

Regression95% CI

UAB Closedln(Nu/Pr^0.33) = - 2.354 + 0.71 21 Ln(Re)

9.08.58.07.5

4.00

3.75

3.50

3.25

3.00

2.75

2.50

S 0.0729692R-Sq 96.9%R-Sq(adj) 96.7%

Ln(Re)

ln(N

u/Pr

^0.

33)

Regression95% CI

UAB - Openln(Nu/Pr^0.33) = - 2.523 + 0.71 54 Ln(Re)

Correlations65

Correlations

In progress

66

Agenda

1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

67

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

Recommendations

• IEEE 605 move to whole body correlations.• NEETRAC member have agreed to provide our data to the substation committee.

• NEETRAC members have funded our participation in the next revision of 605.

68

Questions?

69

Agenda

1. History of the project2. Heat transfer refresher

– Convection – Radiation

3. Three methods– 605– CFD– Experiments

70

4. How 605 works5. How CFD works6. How the experiments work7. Results8. Discussion / question9. Lessons learned

Radiation

• The below equation assumes radiation from the body is lost to the surroundings.

• This is not always the case.

71

Radiation72

How much radiation is “seen” by the other surface is determined by it’s view factor.

Radiation

• The view‐factor is the percentage of energy emitted by one surface that irradiates another.

• This is known as a Surface‐to‐Surface model.• Modern day simulation software can calculate view factors for complex geometries.– Not available during the creation of 605

73

Radiation74

Changing ε from 0.3 to 0.5 results in about 10oC change (As determined in CFD simulations)