carbon dioxide (co 2) flow calculations eric w. forssell
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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)
SupDet® 2018
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]
SupDet® 2018
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.
SupDet® 2018
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
SupDet® 2018
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
SupDet® 2018
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
SupDet® 2018
Thank you for your attention
Contact:◦ Eric W. Forssell◦ eforssell@jensenHughes.com◦ (410)737-8677 Ext 10219
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