DIERS Benchmarks

Two-phase Flashing  Flow

DIERS performed series of benchmark test on several relief calculations to include nozzles and piping. 

There were 17 different relief cases that were investigated such as, vapor flow, two-phase flashing flow, hybrid flow, frozen flow, churn-turbulent, and bubbly flow.  Within the categories of two-phase flashing flow, hybrid flow, and frozen flow were added low viscosity, medium viscosity, high viscosity, and very high viscosity cases. 

The purpose of the benchmarks was to compare different computer programs results to determine consistency and identify errors or limitation of different methods.  Several individuals participated in the benchmarks and their results were published in an article by Harold Fisher and Shawn P. Adair, entitled, "Benchmarking Two-phase Flow Through Safety Relief Valves and Pipe.  Download

The physical property and vessel data for these cases are list below.

Vessel data

Volume                                                                                             1595 gals.  

Diameter                                                                                          5.25 ft.            

Height                                                                                               9.85 ft.     Initial fill ratio   0.85

Relief  valve  4 P 6

Orifice area                                                                                    6.38 in2        

Set Pressure                                                                                   52.55 psig      

Flowing Pressure                                                                          72.5 psia  

Discharge coeff. (Kd)                                                                   0.91

Inlet line

Square cut entrance                                                                   K = 0.5      

internal diameter                                                                           4.026 in2    

Horizontal length                                                                          (0)  

Vertical height                                                                               6.0 ft.  

Full port valve                                                                                K = 0.12

Discharge line  

Intern diameter                                                                        6.065 in2    

Horizontal length                                                                                                1.0 ft.  

St. 90 o elbow                                                                                K= 0.30    

Vertical height                                                                              7.0 feet

Physical Properties (from steam tables and physical property database or flash calculation)

                                                                                   Stagnation                                Ambient

Pressure (psia)                                                          72.5                                            14.7

Temperature (oF)                                                      304.5                                           212

X(quality)                                                                                    as specified

viscosity liquid (cp)                                                 0.18                                             0.28

viscosity of gas (cp)                                               0.014                                          0.012

specific volume liquid(ft3/lb.)                              0.01751                                     0.01672

specific volume of gas (ft3/lb)                             6.0024                                         27.1

heat of vaporization(Btu/lb)                                905.1                                           970.3

heat capacity(Btu/lb-0F)                                        1.0306                                        1.0056

heat capacity ratio                                                1.324