Mass Split of Two-Phase-Flow

Transcription

1 Mass Split of Two-Phase-Flow The split of two-phase-flow at horizontal side-t-junctions in unbalanced pipe systems for clean extinguishing agents Speaker: Gudrun Fay Minimax

2 Content 1. Applications of clean extinguishing agents 2. Characteristics of two-phase flow 3. Experimental Setup and Data Collection 4. Comparison of results 5. Verification 6. Conclusions 2

3 Applications of clean agent systems Clean agents have many advantages Protection of sensitive electronic equipment Safe extinguishing concentrations below LOAL Very small agent storage volume 3

4 Applications of clean agent systems but they have some properties that cause challenges for designers: To extinguish a fire the fluid has to change from a liquid into a vapor. Boiling pressure at 70 F is near (HFC227ea) or even lower (FK ) ambient conditions (16 psi / 1 bar). The agent must leave the system with high velocity and obstructions near the nozzles have to be avoided. The system has to be pressurized with nitrogen. The mixture of agent and nitrogen creates two-phase flow with changing gas content in the pipe system. Modeling the hydraulic system is made complex by the two-phase flow. 4

5 Characteristics of two-phase flow Specific properties of two-phase flow Liquid-gas separation at low speed Differing flow pattern at horizontal and vertical pipes bubbles Increasing gas content with decreasing pressure Unequal split of liquid and gas at side-t-junctions flow direction bubble 5

6 Characteristics of two-phase flow Side-T 90 with water/air flow top view v 1 = kg/s Gas content x1: 0.21 % x3: 0.55 % p 1 = 14.8 bar D 1 =D 2 =D 3 =38 mm (Hwang, 1988) 6

7 Experimental Setup Test Arrangement for Side-T modeling Feeding 40 l container pipe and with straight 48 kg pipe: extinguishing 1 ½ agent (fill 90 density side = pipe: 1.2 kg/l) ½ Mass 610 psi split (42 from bar) 10% fill pressure to 35% into 70 F the (21 C) side container pipe temperature Mass flow feeding pipe 4.8 kg/s 64 F 75 F (18 C 24 C) ambient Straight pipe temperature flow divided equally by a bullhead-t ends in two identical nozzles 7

8 Experimental Setup Experimental setup Pressure transducer at the top of the container (in the nitrogen blanket) Pressure measurement at the start of the pipe system (behind valve) Pressure measurement at all nozzle 8

9 Experimental Setup Preparing the container Welded sockets at the top for pressure and temperature measurement Construction to shake filled container in a horizontal position Temperature is adjusted manually with a gas burner 9

10 Experimental Setup Data collection Socket for pressure transducer at the top of container (nitrogen blanket) Sockets for pressure transducer and thermocouple behind the hose and direction valve Sockets for pressure and temperature before each nozzle 10

11 Experimental Setup Agent collection at discharge Better First try 11

12 Experimental Setup Agent Collection at discharge 250 l bin, collected agent is weighed on a platform scale Plastic bag to collect drops and lead agent into the bin Metal can with 250 mm diameter around the nozzles to stop horizontal flying droplets 12

13 Comparison of Results Discharge at side nozzle Nozzle orifices: 10%: 4.1 mm 15%: 5.1 mm 20%: 6.1 mm 25%: 7.0 mm 30%: 7.8 mm 35%: 8.7 mm 13

14 Comparison of Results Discharge at side nozzle Nozzle orifices: 10%: 4.1 mm 15%: 5.1 mm 20%: 6.1 mm 25%: 7.0 mm 30%: 7.8 mm 35%: 8.7 mm 14

15 Comparison of Results Discharge at side nozzle Nozzle orifices: 10%: 4.1 mm 15%: 5.1 mm 20%: 6.1 mm 25%: 7.0 mm 30%: 7.8 mm 35%: 8.7 mm 15

16 Comparison of Results Discharge at side nozzle Nozzle orifices: 10%: 4.1 mm 15%: 5.1 mm 20%: 6.1 mm 25%: 7.0 mm 30%: 7.8 mm 35%: 8.7 mm 16

17 Verification Verification Tests Various container sizes: 40 l to 180 l Variable fill pressure: 360 psi, 610 psi, 725 psi Variable fill density: 0.4 to 1.2 Different pipe systems: pipe diameter ½ to 2 17

18 Verification - Test 1 Filling pressure 610 psi (42 bar) Container size Filling amount Fill density 100 l kg 1.2 kg/l 18

19 Verification - Test 1 Nozzle 5 Nozzles Exp kg kg Calc kg kg Dev. 3.1 % -0.2 % 19

20 Verification - Test 2 Filling pressure 610 psi (42 bar) Container size Filling amount Fill density 80 l 62,0 kg 0.78 kg/l 20

21 Verification - Test 2 Nozzle 5 Nozzles Exp. 6.5 kg 53.8 kg Calc. 6.1 kg 54.5 kg Dev % 1.3 % 21

22 Verification - Test 3 Filling pressure Container size 610 psi (42 bar) 80 l Filling amount 75,0 kg Fill density 0.94 kg/l 22

23 Verification - Test 3 Nozzle 5 Nozzles Exp kg 50.2 kg Calc kg 48.5 kg Dev. 8.0 % -3.5 % 23

24 Verification - Test 4 Filling pressure Container size 360 psi (25 bar) 40 l Filling amount 45,6 kg Fill density 1.14 kg/l 24

25 Verification - Test 4 Nozzle 5 Nozzles Exp kg kg Calc kg kg Dev % 1.5 % 25

26 Verification Summary of Results Summary of verification tests Deviation of side-flow at verification tests Test No. Mass split Deviation 10% 1 10 % -6.6 % 2 14 % 3.1 % 3 34 % 8.0 % Deviation of the side flow 5% 0% -5% 4 35 % -3.4 % -10% 0% 10% 20% 30% 40% mass split 26

27 Conclusions Result of tests: Deviation in discharge is below 10 % at all test cases Conclusions: The model is valid for mass splits from 10% to 35% to the side. The model does not depend from the parameters of the feeding container. It is suitable for typical pipe dimensions of clean agent systems. It gives opportunities in the individual design of unbalanced pipe system. 27