Steam Flow Rate

One usually measures flowrate rather than calculating it. The method depends upon the installation, about which this forum knows nothing.

You also need to know the boiler leakage rate, but this might be considered in the same category as blow-down, even if it is a steam leak. Of course a steam leak will reduce process efficiency in a very significant way. A tight ship (boiler) is next to godliness in these industries.

Boiler blow-down can be intermittent, or it can be continuous, or it can be a Universal Pressure Boiler, or a supercritical boiler, in which case all of the feedwater is converted to steam, once through, there is no blow-down possible, as there is no boiler drum, only tubing coils.

One can get a crude handle on feedwater flow (and hence steam flow) in such cases merely by knowing the operating point(s) of the boiler-feedwater pump, and the pump curve data. Beyond that, steam flow measurement is not all that difficult, and no different than measureing any other gas (as long as you are dealing with dry steam). Two phase flow measurement is quite complicated. Three phase flow measurement is virtually impossible without some instrumental data on the relative contributions of each phase.

There phases? You're not going to have ice in that line, Mildred!

Maybe Plasma.

I was thinking about situations where dirt, water, and air (or steam) might be flowing simultaneously.

Whatever you calculate you might have it wrong because you already admit that you don't know how to.

Now if you measure it you have a better chance of being wrong. So why not measure it?

Hint: try to find out mass flow then you can at least use your pressure and temperature data.

Hint2: Check this: "Steam tables"

It depends!

You can in theory have any flowrate that you like. However it depends on the velocity and pressure drop limitations of the system.

The practical limit for velocity would be sonic flow but this is to be avoided except for relief and blowdown lines (and even for them its best avoided generally)

The pressure drop limit is 12kg/cm2 over an unspecified length but as the pressure falls the physical properties change and so the calculation becomes unstable and unwieldy.

Steam distribution networks have limits on velocity / pressure drop to 'optimise' the balance between making lines as small (and cheap) as possible but still having them deliver usable steam.

As a rule of thumb for a dry gas . superheated steam something in the range 10 - 50 m/s or 0.1 - 0.4 bar/100m pressure drop

Assuming 100mm NB as 100mm internal diameter (id) -4" Schedule 40 pipe which would probably be ok for this service is 102.3mm id

A = 0.0082m2 => A * 50 * 3600 = 1480m3/hr for 50m/s

Taking your pressure as a gauge pressure 12 barg 400C

Density = 4.27 kg/m3

Mass Flow 6300kg/hr

Various calculation tools as noted above will give answers but typically you will have to provide a pressure drop as bar/100m for the flow in the pipe or the pressure drop through a flowmeter.

It all depends on the reasons for the question. I really like the answer that the flow you get out of the boiler is the flow in minus any blowdown!