Flashing flow

Choked and unchoked flow situations arise in pipes and nozzles in the same fashion for homogeneous equihbrium flashing flow as for gas flow. For nozzle flow from stagnation pressure po to exit pressure pi, the mass flux is given by... 

With flashes carried out along the appropriate thermodynamic paths, the formalism of Eqs. (6-139) through (6-143) applies to all homogeneous equihbrium compressible flows, including, for example, flashing flow, ideal gas flow, and nonideal gas flow. Equation (6-118), for example, is a special case of Eq. (6-141) where the quahty x = and the vapor phase is a perfect gas. 

FIG. 26-70 Accuracy in HEM predictions for slightly to moderately siibcooled flashing flow. Comparison with data for water by Sozzi and Sutherland (1975) also ASME Symposium on Non-Equilibrium Two-Phase Flows (1975) (Nozzle type 2). 

Figure 12-34. Correotion faotor versus L/D for two-phase flashing flow through pipes. (Source J. C. Leung and M. A. Grolmes, The Discharge of Two-Phase Flashing Flow in a Horizontal Duct," AlChE Journal, 33(3), p. 524, 1987.)...

Fauske [32] represented a nomograph for tempered reaetions as shown in Figure 12-35. This aeeounts for turbulent flashing flow and requires information about the rate of temperature rise at the relief set pressure. This approaeh also aeeounts for vapor disengagement and frietional effeets ineluding laminar and turbulent flow eonditions. For turbulent flow, the vent area is... 

The PHI-TEC or VSP bench scale apparatus can be employed to determine information about the self-heat rate and vapor disengagement when this is not readily available. Additionally, the VSP equipment can be used for flashing flow characteristics using a special bottom vented test cell. Here, the flowrate, Gq (kg/sm ), is measured... 

Huff, J. F., 1985, Multiphase Flashing Flow in Pressure Relief Systems, Plant Operations, 4, 191-199. 

Regarding two pliase flow, pressurized liquid above its noniial boiling point will start to flash when released to aUiiospheric pressure, and two pliase flow will result. Two-pliase flow is also likely to occur from depressurization of tlie vapor space above a volatile liquid, especially if the liquid is viscous (e.g., greater tlian 500 cP) or has a tendency to foam. Fauske and Epstein liave provided tlie following practical calculation guidelines for two-phase flashing flows. The discharge of subcooled or saturated liquids is described by... 

First K. E. and J. E. Huff, Design Chaits for Two-Phase Flashing Flow in Emergency Pressure Relief Systems, Plant Operations Progress, Vol. 8, No. 1, 1989, p. 40. 

F auske, H. K., Flashing Flows Some Practical Guidelines for Emergency Releases, Plant/Operations Progress, 4 (3), 132-134, July 1985. 

Fauske, H. K., Turbulent and Laminar Flashing Flow Considerations, Paper Presented at the 4th International Symposium on Multi-phase Flow, Miami Beach, FL, December 15-17, 1986. 

Leung, J. C. and Nazario, F. N., Two-Phase Flashing Flow Methods and Comparisons, Journal Loss Prevention Process Industries, (3), 253-260, April 1990. 

Leung, J. C. and Epstein, M., The Discharge of Two-Phase Flashing Flow from an Inclined Duct, Trans., ASME—jemr-nal of Heat Transfer 112 (2), 224-228, May 1990. 

Pressure drop, chart, 102, 103, 111 Computer aided drafting, 17 Condensate, flashing flow, 135-142, 147 Charts, 142, 143 Control valve pressure drop, 90 Calculations, 90-96 Cost estimates, plant, 45-49 Accounting, 48... 

In 1972 a paper on venting by Huff 2J documented concerns that many designers suspected that to truly be safe the vent sizing of many systems should be based on assuming two-phase flashing flow in the vent system. A two-phase flow vent method developed by Huff was compared with Boyle s all-liquid method, and values from the FIA chart in Figure 2. It can be seen that under many conditions, previous methods were not... 

Case 1 Flashing in Orifice, Two-Phase Flashing Flow in Pipe... 

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