Carbon Dioxide (CO2) Flow CalculationsEric W. Forssell – Senior Engineer

NATIONAL FIRE PROTECTION ASSOCIATION RESEARCH FOUNDATION

SUPPRESSION, DETECTION AND SIGNALING RESEARCH AND APPLICATIONS CONFERENCE (SUPDET®2018)

RESEARCH TRIANGLE PARK, NC

SEPTEMBER 14, 2018

SupDet® 2018

IntroductionCarbon Dioxide Fire Suppression Systems

Characteristics:◦ Stored as a liquid under Own Vapor Pressure

◦ High Pressure Systems ◦ Cylinder Pressure: 58.75 bar,abs (853 psia)◦ Density, liquid: 762 kg/m3 (47.6 lb/ft3)◦ Cylinder Fill Density: 680 kg/m3 (42.5 lb/ft3) ◦ Liquid Fill: 81% (Vol) 95% (Mass)

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NFPA 12 Flow Calculation MethodNFPA 12 Annex C Methodology.Methodology Characteristics:◦Single Point Calculation◦Cylinder Pressure: 51.7 bar,abs (750 psia)◦Average Mass Flow-Rate

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NFPA 12 Flow Calculation Method – Pipeline Flow

Q – Average Mass Flow Rate Through Branch [lb/sec]D – Branch Internal Diameter [in]Leqv – Branch Equivalent Length [ft]∆Y – Change in Y factor in Branch ∆Z – Change in Z factor in Branch ρ – Density [lb/ft3]P – Pressure [psia]

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NFPA 12 Flow Calculation Method – Y Factor

0

2,000

4,000

6,000

8,000

10,000

12,000

300 350 400 450 500 550 600 650 700 750

Y Fa

ctor

Pressure (psia)

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NFPA 12 Flow Calculation Method – Z Factor

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

300 350 400 450 500 550 600 650 700 750

Z F

acto

r

Pressure (psia)

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NFPA 12 Flow Calculation Method – Nozzle Orifice Size𝑄𝑄𝑁𝑁𝑁𝑁 = 𝑀𝑀𝑀𝐴𝐴𝑁𝑁𝑁𝑁

QNz – Nozzle Mass Flow Rate [lb/sec]

M” – Nozzle Mass Flux [lb/(sec in2)]

ANz – Nozzle Orifice Area [in2]

0

10

20

30

40

50

60

70

80

90

300 350 400 450 500 550 600 650 700 750

Mas

s Fl

ux (l

b/se

c in

2)Pressure (psia)

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NFPA 12 Flow Calculation Method – Discharge TimeFor a Total Flooding Application

𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 = �𝑀𝑀𝐶𝐶𝐶𝐶𝑇𝑇𝑄𝑄

For a Local Application (Liquid Flow Only)𝑇𝑇𝐿𝐿𝐿𝐿𝐿𝐿 = �𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇

1.4 − 𝑇𝑇𝐿𝐿𝑖𝑖𝐿𝐿𝑇𝑇,𝑣𝑣𝑇𝑇𝑣𝑣

TTotal – Total Discharge Time [sec]

MCyl – Total Mass of Agent [lb]Q – Mass Flow Rate [lb/sec]

TLiq – Liquid Discharge Time [sec]

Tinit,vap – Initial Vapor Discharge Time [sec]

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NFPA 12 Flow Calculation Method – Initial Vapor Discharge Time

𝑇𝑇𝐿𝐿𝑖𝑖𝐿𝐿𝑇𝑇,𝑣𝑣𝑇𝑇𝑣𝑣 = �𝑀𝑀𝑉𝑉𝑇𝑇𝑣𝑣𝑄𝑄 =

𝑀𝑀𝑃𝑃𝐿𝐿𝑣𝑣𝑃𝑃𝐶𝐶𝑃𝑃𝐿𝐿𝑣𝑣𝑃𝑃∆𝑇𝑇𝑇𝑇𝑣𝑣𝑎𝑎𝑄𝑄∆𝐻𝐻𝑉𝑉

MVap – Mass Vaporized in Pipe at Start of Discharge [lb]

MPipe – Mass of Pipe [lb]

CPipe – Specific Heat of the Pipe [Btu/(lb oF)] {for Steel = 0.11 Btu/(lb oF)}

∆Tavg – Temperature Difference between Pipe and Agent [oF] {Assumed to be 10 oF}

∆Hv – Heat of Vaporization for the Agent {64 Btu/lb @60 oF}

Q – Mass Flow Rate [lb/sec]

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CO2 Flow Calculations

Objective:

The objective of this project was to obtain the experimental data to evaluate the veracity of the CO2 design method

Approach:

A series of six tests were performed with the results obtained compared to those predicted with the NFPA 12 Method.

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CO2 Flow Calculations – Test Characteristics

Single Cylinder Discharges

Three Nozzle Configurations

Pipe Volume Ratios: 3% to 75% Discharge times:

◦ Total Discharge Time: [sec]: 30 to 40◦ Liquid Discharge Time [sec]: 18 to 25

Tee Split Ratios:◦ Bull Tees: 50:50 to 80:20◦ Side Tees: 90:10 to 65:35

Constructed of commercially available hardware ifor use in CO2 systems

Cylinders factory/distributer filled

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CO2 Flow Calculations – Test Characteristics

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Limit Description CN01 CN02 CN03 CN04 CN05Value Demonstrated Unit

CylinderInitial Pressure 50.7 bar 50.7 50.7 50.7 50.7 50.7

736 psig 735 735 735 735 735Size 67 L 67 L 67 L 67 L 67 L

Number 1 1 1 1 1Fill Density 0.68 kg/l 0.680 0.680 0.680 0.680 0.680

42.5 lb/ft3 42.5 42.5 42.5 42.5 42.5

Discharge Time (Liquid Flow Time) – NFPA 12 Maximum 85.7 0.0 sMinimum 30.0 18.4 s 21.6 19.6 19.8 18.4 25.7

Discharge Time (SDT) – NFPA12 Maximum 120.0 0.0 sMinimum 42.0 29.7 s 30.4 32.9 31.8 29.7 36.3

Maximum Pipe Volume to Cylinder Volume Ratio 85 76% % 2.8% 75.5% 57.9% 57.4% 2.8%Minimum Pipe Volume Ratio before First Tee see table 1.7% % 1.7% 70.5% 48.2% 48.2% 1.7%Maximum Pipe Volume Ratio After First Tee see table 10% % 1.1% 5.0% 9.7% 9.2% 1.1%

Nozzle Area Ratio of nozzle discharge orifice area to pipe area (based on nominal internal diameters)

Maximum 0.800 0.24 a/A 0.24 0.23 0.23 0.20 0.16Minimum 0.002 0.03 a/A 0.12 0.03 0.03 0.06 0.04

Minimum Nozzle Pressure -NFPA 12NLRO 20.6 28.5 bar 32.4 31.4 29.6 28.5 38.9

299.5 413.0 psig 470.0 455.0 429.0 413.0 565.0

SDT 20.6 28.5 bar 32.4 31.4 29.6 28.5 38.9299.5 413.0 psig 470.0 455.0 429.0 413.0 565.0

Maximum Nozzle Pressure VarianceNLRO N/A 9.2 bar 0.0 5.2 9.2 6.0 1.7

N/A 134.0 psig 0.0 75.0 134.0 87.0 24.0

SDT N/A 9.2 bar 0.0 5.2 9.2 6.0 1.7N/A 134.0 psig 0.0 75.0 134.0 87.0 24.0

Maximum Elevation Change N/A 3.2 m 1.5 1.6 1.6 1.6 1.5N/A 10.3 ft 5.1 5.2 5.2 5.2 5.1

Tee Splits

Bull Tee Standard Orientation

Maximum 50:50 50.0% % 50.0% 34.7%Minimum 5:95 20.8% % 27.1% 34.1% 20.8%

Side Tee Standard Orientation

Maximum 65:35 64.0% % 64.0%Minimum 5:95 89.3% % 89.3% 88.7% 73.0%

CO2 Flow Calculations – Test Layouts

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CO2 Flow Calculations – Test Layouts

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CO2 Flow Calculations – Test Layouts

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CO2 Flow Calculations – Test Layouts

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CO2 Flow Calculations – Test Layouts

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CO2 Flow Calculations – Instrumentation

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Pressure and Temperature Measurements◦ After Flex Hose (Manifold)◦ Before Each Tee◦ Before Each Nozzle◦ After Each Nozzle (Temperature Only)

Agent Mass Delivered◦ Collected in Bags ◦ Bags Back-Flowed through Flow-Meter

CO2 Flow Calculations – Instrumentation

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CO2 Flow Calculations – Discharge Time Determination

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Total Discharge Time◦ Start: Drop in temperature at nozzle after air in pipe

cleared◦ End: <5% remaining in system (cylinders and piping)

◦ Calculated with Peng-Robinson Equation of State and measured pressure and temperature in Manifold

Liquid Flow Time◦ Start: Drop in temperature at nozzle after initial

vapor discharge◦ End: Inflection marking transition from

predominately liquid flow to predominately vapor flow

Total Discharge Time Results Compared to NFPA 12

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System

Nozzle Mass Ave Pressure (SDT) Discharge Time (SDT)

No. Code Exper. Pred. Error Exper. Pred. Error Exper. Pred. Error[kg] [lb] [kg] [lb] [%] [bar] [psig] [bar] [psig] [%] [sec] [sec] [sec]

CN01

1 8.5 21.9 48.2 22.7 50.0 -3.5% 22.1 320.3 32.4 470.0 -31.9%2 6 11.8 26.0 11.3 25.0 4.1% 22.3 322.9 32.4 470.0 -31.3%3 6 11.7 25.7 11.3 25.0 3.0% 22.2 322.5 32.4 470.0 -31.4%

30.8 30.4 0.4

CN02

1 3.5 3.4 7.4 4.9 10.7 -30.9% 21.1 306.3 36.5 530.0 -42.2%2 5.5 11.2 24.7 11.0 24.2 2.3% 19.2 279.2 34.1 494.0 -43.5%3 9.5 30.8 67.9 29.5 65.1 4.2% 16.5 240.0 31.4 455.0 -47.2%

60.6 32.9 27.7

CN03

1 3.5 3.4 7.6 5.1 11.3 -32.6% 23.2 336.5 38.8 563.0 -40.2%2 6.5 15.0 33.0 13.7 30.3 8.8% 19.3 280.5 32.1 465.0 -39.7%3 9.5 27.0 59.4 26.5 58.4 1.7% 15.4 223.3 29.6 429.0 -47.9%

52.2 31.8 20.4

CN3A

1 3.5 3.4 7.5 5.1 11.3 -33.5% 23.4 339.5 38.8 563.0 -39.7%2 6.5 15.2 33.6 13.7 30.3 10.9% 19.5 282.8 32.1 465.0 -39.2%3 9.5 26.7 58.9 26.5 58.4 0.8% 15.5 224.9 29.6 429.0 -47.6%

52.4 31.8 20.6

CN04

1 7 17.6 38.8 16.3 36.0 7.8% 19.1 276.6 34.5 500.0 -44.7%2 5 5.4 11.9 7.8 17.3 -31.1% 17.1 247.7 33.0 479.0 -48.3%3 9 22.4 49.3 21.2 46.7 5.5% 15.4 224.1 28.5 413.0 -45.7%

49.7 29.7 20.0

CN05

1 5.5 15.7 34.5 15.7 34.7 -0.3% 28.8 418.4 40.6 589.0 -29.0%2 3.5 7.1 15.7 6.2 13.6 15.6% 28.1 407.2 39.8 578.0 -29.5%3 7 22.6 49.7 23.5 51.7 -3.9% 28.0 406.9 38.9 565.0 -28.0%

37.1 36.3 0.8

Total Discharge Time Results Compared to NFPA 12

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System

Nozzle Mass Ave Pressure (Liquid Flow Time) Initial Vapor Time Liquid Flow Time

No. Code Exper. Pred. Error Exper. Pred. Error Exper. Pred. Exper. Pred. Error[kg] [lb] [kg] [lb] [%] [bar] [psig] [bar] [psig] [%] [sec] [sec] [sec] [sec] [sec]

CN01

1 8.5 21.9 48.2 22.7 50.0 -3.5% 25.3 366.6 32.4 470.0 -22.0% 0.8 0.132 6 11.8 26.0 11.3 25.0 4.1% 25.5 369.3 32.4 470.0 -21.4% 0.8 0.183 6 11.7 25.7 11.3 25.0 3.0% 25.4 369.0 32.4 470.0 -21.5% 0.8 0.18

21.5 21.6 -0.1

CN02

1 3.5 3.4 7.4 4.9 10.7 -30.9% 26.6 386.2 36.5 530.0 -27.1% 14.5 3.782 5.5 11.2 24.7 11.0 24.2 2.3% 24.6 357.5 34.1 494.0 -27.6% 15.4 4.013 9.5 30.8 67.9 29.5 65.1 4.2% 21.5 311.5 31.4 455.0 -31.5% 15.3 3.82

24.6 19.6 5.0

CN03

1 3.5 3.4 7.6 5.1 11.3 -32.6% 29.0 420.4 38.8 563.0 -25.3% 10.5 3.002 6.5 15.0 33.0 13.7 30.3 8.8% 24.6 356.7 32.1 465.0 -23.3% 11.8 2.983 9.5 27.0 59.4 26.5 58.4 1.7% 20.6 298.5 29.6 429.0 -30.4% 11.5 2.89

22.7 19.8 2.9

CN3A

1 3.5 3.4 7.5 5.1 11.3 -33.5% 29.0 421.1 38.8 563.0 -25.2% 11.2 3.002 6.5 15.2 33.6 13.7 30.3 10.9% 24.7 358.0 32.1 465.0 -23.0% 12.5 2.983 9.5 26.7 58.9 26.5 58.4 0.8% 20.6 299.5 29.6 429.0 -30.2% 12.5 2.89

21.9 19.8 2.1

CN04

1 7 17.6 38.8 16.3 36.0 7.8% 22.4 324.5 34.5 500.0 -35.1% 12.0 2.392 5 5.4 11.9 7.8 17.3 -31.1% 20.3 295.1 33.0 479.0 -38.4% 14.7 3.183 9 22.4 49.3 21.2 46.7 5.5% 18.5 268.2 28.5 413.0 -35.1% 14.1 2.89

22.9 18.4 4.5

CN05

1 5.5 15.7 34.5 15.7 34.7 -0.3% 34.5 500.6 40.6 589.0 -15.0% 0.8 0.182 3.5 7.1 15.7 6.2 13.6 15.6% 33.6 487.9 39.8 578.0 -15.6% 0.8 0.283 7 22.6 49.7 23.5 51.7 -3.9% 33.5 485.4 38.9 565.0 -14.1% 0.8 0.16

24.0 25.7 -1.7

Results Comparison - CN01

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Results Comparison - CN02

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Results Comparison - CN03

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Results Comparison – CN3A

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Results Comparison – CN04

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Results Comparison – CN05

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Results Comparison – Side Tee Splits

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Results Comparison – Bull Tee Splits

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Discussion

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NFPA 12 Method◦ Single Point using Median Cylinder Pressure and Average Flow Rate◦ Same Flow Rate used for Average Flow over Entire Discharge, Liquid Flow (for Local App Systems) and

Initial Vapor Flow

Comparison of NFPA 12 Calculations and Experimental Results◦ Discharge Times

◦ Initial Vapor Discharge Times Under Predicted – Use of Average Flow Rate ◦ Liquid Flow Times Predicted well◦ Total Discharge Times Predicted Well for Small Systems, Poorly for Larger Systems

◦ Pressures◦ Experimental Pressure Much Lower than Predicted

◦ Flow Splits◦ Predicted ok for Bull Tees ◦ Side Tees Predicted Poorly

Discussion

SupDet® 2018

Unknown implications for actual Installed systems◦ Total system discharge test required by NFPA12

Project Summary◦ 6 tests (5 layouts)◦ Single cylinder configurations◦ Discharge times on the Shorter End of the Range

Questions

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Thank you for your attention

Contact:◦ Eric W. Forssell◦ eforssell@jensenHughes.com◦ (410)737-8677 Ext 10219