Sparger: design
Sparger: design
(OP)
I'm going to sparge condensate into an atmosferic tank. I designed my piping based on wet steam (condensate in the line flashes)with a max speed of 20 m/s. However the surface area of all the holes of the sparger is smaller than the surface area of the pipe. The velocity of the wet steam through the holes goes up to 80 m/s.
A few questions:
- shouldn't I take the surface area of the sparging holes equal to the surface area of the steampipe? Or is 80 m/s ok (thinking about erosion)? If not, what about backpressure to the flashing condensate?
- can I take the surface area of the holes equal to the surface area of the steampipe or should it always have to be smaller?
- what is maximum hole size, currently i took 4mm, but if the surface area needs to increase, I also need to increase the size of the holes. I want to prevent heavy vibrations
Can anyone give me some advice on this one?
A few questions:
- shouldn't I take the surface area of the sparging holes equal to the surface area of the steampipe? Or is 80 m/s ok (thinking about erosion)? If not, what about backpressure to the flashing condensate?
- can I take the surface area of the holes equal to the surface area of the steampipe or should it always have to be smaller?
- what is maximum hole size, currently i took 4mm, but if the surface area needs to increase, I also need to increase the size of the holes. I want to prevent heavy vibrations
Can anyone give me some advice on this one?





RE: Sparger: design
Don't forget to factor in what the head of tank liquid is vs the steam pressure. Also, if the steam gets shut off - say if the tank temperature setpoint is made - the tank liquid will be drawn back into the steam line by the resulting vacuum. A vacuum breaker will likely be required.
There is a rule of thumb, which is also referred to as the "rule of eights". With an 8 psi differential pressure, a 1/8" diameter hole will pass about 8 lb/hr of steam.
The metric equivalent is: At 1.6 bar, 1.6 mm diameter hole will pass 1.6 kg/hr steam.
RE: Sparger: design
Secondly, what is the reason for putting this condensate into the tank? Are you trying to heat the tank contents? It seems that you are not trying to recover the flash steam because you describe the tank as "atmospheric".
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RE: Sparger: design
In reality, it's probably not that meaningful. Any steam leaving the sparger will condense nearly instantly in the liquid water outside the sparger. The steam INSIDE the sparger will likely be collapsing very rapidly as well. Calculate your heat transfer and exit quality before you really commit to having such a high velocity.
80 m/sec is a lot higher than you want to have for liquid flow in a stainless line. Published guidelines I have seen are closer to 15 m/sec max. Erosion happens at high liquid velocities. Even if the liquid is in the form of droplets.
I'm thinking you might have stable operation of the sparger if it is sloped downward, with larger holes at the end for the water to escape through. If the water begins to build up, then the internal pressure of the sparger would rise as some of the holes have to carry condensate instead of steam. It would find an equilibrium level point. High-velocity droplets could crash straight into a pool of water at the end of the tube, while steam could escape thru the initial holes along the side.
Still keep jets emitted from the sparger a couple of feet fro the vessel wall. Collapsing steam bubbles in condensate is known as cavitation, and that carries its own set of headaches.
RE: Sparger: design
If possible, folks should try to find a copy of "Direct Steam Injection - Heating Liquids With Live Steam" published by Spirax Sarco in the UK. It's literally just a small booklet - 12 pages long. It was one of the Practical Studies series. I have several, but not the whole set. I was given the few I have 25 years ago, by a Spirax rep who was originally from Scotland. I haven't seen them before or since. If it's out of print, the Spirax folks don't mind, I'd be happy to scan & post it.
RE: Sparger: design
I think the answer to your question depends on what fraction of the condensate flashes prior to arriving at the point of exiting through the sparger nozzles.
In any case, wet steam or two phase condensate/steam flow at either 20 or 80 M/sec sounds high to me.
rmw