CHAPTER-4 SOURCE MODELS for Chemical Industries.pptx

Source Model

1. CHAPTER-4 SOURCE MODELS source models 1 12-08-2024

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4. Introduction to Source Models Source models are constructed from fundamental or empirical equations representing the physicochemical processes occurring during the release of materials. source models 4 12-08-2024

5. source models 5 12-08-2024 physical state of the material affects the release mechanism

6. flow of liquid through a hole, flow of liquid through a hole in a tank, flow of liquids through pipes, flow of vapor through holes, flow of gases through pipes, flashing liquids, and liquid pool evaporation or boiling. source models 6 12-08-2024

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9. 12-08-2024 source models 9 The frictional losses in the leak are approximated by a constant discharge coefficient

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12. Flow of Liquid through a Hole in a Tank 12-08-2024 source models 12

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17. 12-08-2024 source models 17 The time t e , for the vessel to empty to the level of the leak

18. Flow of Liquids through Pipes 12-08-2024 source models 18

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22. 12-08-2024 source models 22 Colebrook equation for turbulent flow for fully turbulent flow

23. For smooth pipes 12-08-2024 source models 23 For smooth pipe with a Reynolds number less than 100,000 the following Blasius approximation to

24. 12-08-2024 source models 24 f over the entire range of Reynolds numbers

25. Flow of Vapor through Holes For flowing liquids the kinetic energy changes are frequently negligible and the physical properties (particularly the density) are constant. For flowing gases and vapours these assumptions are valid only for small pressure changes (P 1 /P 2 < 2) and low velocities (<0.3 times the speed of sound in gas) Throttling releases: the gas issues through a small crack with large frictional losses Free expansion releases: most of the pressure energy is converted to kinetic energy; the assumption of isentropic behaviour is usually valid. 12-08-2024 source models 25

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29. 12-08-2024 source models 29 For downstream pressures less than P choked the following statements are valid: The velocity of the fluid at the throat of the leak is the velocity of sound at the prevailing conditions, and the velocity and mass flow rate cannot be increased further by reducing the downstream pressure; they are independent of the downstream conditions. This type of flow is called choked, critical, or sonic flow

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31. Flow of Gases through Pipes adiabatic and isothermal behaviour The adiabatic case corresponds to rapid vapor flow through an insulated pipe. The isothermal case corresponds to flow through an insulated pipe maintained at a constant temperature. 12-08-2024 source models 31

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33. Adiabatic Flows 12-08-2024 source models 33

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41. lsothermal Flows 12-08-2024 source models 41

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48. Flashing Liquids 12-08-2024 source models 48

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50. 12-08-2024 source models 50 If the fluid path length through the release is greater than 10 cm (through a pipe or thick walled container), equilibrium flashing conditions are achieved and the flow is choked.

51. 12-08-2024 source models 51 For liquids stored at their saturation vapor pressure

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55. Liquid Pool Evaporation or Boiling 12-08-2024 source models 55

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58. PROBLEMS 12-08-2024 source models 58 1 A 0.20-in hole develops in a pipeline containing toluene. The pressure in the pipeline at the point of the leak is 100 psig. Determine the leakage rate. The specific gravity of toluene is 0.866. 2 A 100-ft-long horizontal pipeline transporting benzene develops a leak 43 ft from the high-pressure end. The diameter of the leak is estimated to be 0.1 in. At the time, the upstream pressure in the pipeline is 50 psig and the downstream pressure is 40 psig. Estimate the mass flow rate of benzene through the leak. The specific gravity of benzene is 0.8794. 3 The morning inspection of the tank farm finds a leak in the turpentine tank. The leak is repaired. An investigation finds that the leak was 0.1 in in diameter and 7 ft above the tank bottom. Records show that the turpentine level in the tank was 17.3 ft before the leak occurred and 13.0 ft after the leak was repaired. The tank diameter is 15 ft. Determine (a) the total amount of turpentine spilled, (b) the maximum spill rate, and (c) the total time the leak was active. The density of turpentine at these conditions is 55 lb /ft 3 .

59. 12-08-2024 source models 59 4 The TLV-TWA for hydrogen sulphide gas is 10 ppm. Hydrogen sulphide gas is stored in a tank at 100 psig and 80°F. Estimate the diameter of a hole in the tank leading to a local hydrogen sulphide concentration equal to the TLV. The local ventilation rate is 2000 ft 3 /min and is deemed average. The ambient pressure is 1 atm. 5 Water is pumped through a 1-in schedule 40 pipe (internal diameter = 1.049 in) at 400 gal/hr. If the pressure at one point in the pipe is 103 psig and a small leak develops 22 ft downstream, compute the fluid pressure at the leak. The pipe section is horizontal and without fittings or valves. For water at these conditions the viscosity is 1.0 centipoise and the density is 62.4 lb /ft 3 . 6 A laboratory apparatus uses nitrogen at 250 psig. The nitrogen is supplied from a cylinder, through a regulator, to the apparatus through 15 ft of 0.25-in (internal diameter) drawn copper tubing. If the tubing separates from the apparatus, estimate the flow of nitrogen from the tubing. The nitrogen in the tank is at 75°F.

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