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steam pipe distributor

steam pipe distributor

(OP)
Hi to all, I would like to simulate in cfd (ansys discovery live) a steam pipe distributor, but i have difficulty to set boundary conditions. This pipe connect a control steam valve with a pressurized tank.
I know pressure of steam feed and mass flow; i want to calculate mass flow, velocity and pressure drop in each exit point. Can you help me how to set up the simulation?

Second question: do you know a method to hand calculate minimum diameter of exit points? Do I have only consider speed of steam as a limit? Thank you very much for any advice.

RE: steam pipe distributor

First of all you need to decide about inlet BC.

If you provide inlet pressure, you can not provide the flow as it will be determined by calculation. If you provide the flow, the inlet pressure will be calculated.

Secondly, for calculating flows through different outlets you need to provide full flow geometry of different outlet lines and the pressures at end points (BCs).

Regarding minimum diameters you should calculate from allowable velocities through steam pipelines (depending on steam conditions (superheated/saturated) as a starting point. You can change the diameters (within limits) if the flow values are going higher or lower than the requirement.

Engineers, think what we have done to the environment !

RE: steam pipe distributor

(OP)
thanks for the quick response Goutam; i don't understand why i can't provide flow and pressure at the inlet as it is normally done. They should be indipendent parameters, or am I missing something? Maybe you mean velocity+ pressure or velocity+steam flow as the couple of inlet BC?

RE: steam pipe distributor

I am afraid they are not independent ! If you provide the flow, pressure is determined by calculation. If you provide the pressure flow is calculated.

Engineers, think what we have done to the environment !

RE: steam pipe distributor

You must somehow establish two of three parameters for every pipe; Inlet pressure, outlet pressure, or flow rate. The unknown variables may then be calculated. Initially you can size outlets by dividing flow rate by an established a maximum velocity.

If distances between outlets are made short enough, so that the pressure drops between the header's outlets are essentially negligible and the pressure drops in all outlet pipelines are equal, than the flows into each outlet will also be equal, so to determine outlet flow you can simply divide your header flow rate by the number of outlets. That requires that the header diameter is large enough to minimize velocity disturbance. Try a header diameter equal to 2 to 4 times the largest outlet diameter.

RE: steam pipe distributor

There are chapters in books about sparger design. There are fairly standard guidelines for this.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: steam pipe distributor

In real applications there also exists a developed pipe length downstream of the individual nozzles, an outlet collection header, and possibly heat transfer, gravity effects, phase changes, and variations in pipe geometry. The presssures at the inlet of the inlet header and at the outlet of the outlet header are given, and the flow for each individual nozzle is then calculated. In the case of large supercritical steam generators ( boilers), there can be over 100 nozzles per header/ manmifold combination, and perhaps 10 header/manifolds in parallel, with over 1000 total nozzles / tube in the furnace enclosure.Rather than calculate each nozzle/tube, a statistical analysis is computed, with an output representing the average tube and the worst tube ( 2 standard deviations in all handicapping parameters) , and all 1000 tube are designed to be adequate for the "worst case", since it only takes the failure of one tube to cause the outage of a \$2 billion USD power plant.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

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