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Can anybody explain the science behind this?

Sunday, September 17, 2017   By: P I [1983] 3 Stars
Can anybody explain the science behind this technology? At least what I can understand that this is not water jet ejector. I am curious to understand how the discharge is at higher pressure than both the inlets.

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Monday, September 18, 2017   By: Murphy [21] 4 Stars
This has been discussed before and they are called a boiler feedwater ejector or something like that. These have been used on firetube boilers up to the 1960s. They were standard equipment as a back up source when the feedwater pump was not available. Anyhow they use the heat of the steam to expand the water volume which increases the pressure above the steam pressure, so the trick is getting the right proportions with properly shaped venturi. Sure that explanation is not real fancy, but for most is works.

I have attached a cross section of a sketch and this one has a throttle valve with handle so the boiler water level can be controlled.


Click on picture for full size view or to view PDF!

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Tuesday, September 19, 2017   By: Murphy [21] 4 Stars
I should have also said these ejectors was a must on steam locomotives, firetube of course, and that is how the handle evolved, but on stationary boilers the handle was eventually removed and the feedwater ejector was throttled by the steam hand valve.

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Tuesday, September 19, 2017   By: P I [1983] 3 Stars
No, This is not an ejector. In ejectors, there are two fluids at different pressure level and the exhaust will be something in between depending on terms and conditions. Whereas in this case, the exhaust pressure is higher than both the input. A big difference.

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Tuesday, September 19, 2017   By: Murphy [21] 4 Stars
Oh, excuse me for not using the right term, for I should have said feedwater INJECTOR and not ejector. So, INJECTOR it is.

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Tuesday, September 19, 2017   By: P I [1983] 3 Stars
In commercially available injectors at present, do the exhaust be at higher pressure than both steam and water input? I dont think so. I also dont know any injector where steam is mixed with water to get a higher pressure exhaust.

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Tuesday, September 19, 2017   By: Murphy [21] 4 Stars
Of course the discharge or exhaust pressure is higher, otherwise how would the boiler feedwater get into the boiler. So, we are using the boiler drum saturated steam pressure as an input and we have to put the lower pressurized feedwater into the boiler drum at a higher pressure than the steam drum pressure. So, yeah it works and has for many years or at least as long a steam locomotives were around.

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Wednesday, September 20, 2017   By: P I [1983] 3 Stars
I think you are again making a mistake. In Boiler injectors, the pressure of the injected water is higher than the pressure inside the Boiler and as far as I know, steam isnt mixed with water in an injector. It has been done in steam jet ejectors, but in that case the steam pressure is sufficiently high.

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Saturday, September 23, 2017   By: Jim Watts [764] 5 Stars
Murphy is not making a mistake.
The water and the motive steam are both travelling in the same space and enter the boiler as feed water.

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Wednesday, September 27, 2017   By: P I [1983] 3 Stars
In that case, I want to know just one thing. How can the exhaust pressure be higher than both the inputs.

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Wednesday, September 27, 2017   By: Jim Watts [764] 5 Stars
Water hammer

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Wednesday, September 27, 2017   By: P I [1983] 3 Stars
Can you give another example of water hammer where the exhaust is higher than both inputs?

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Thursday, September 28, 2017   By: Jim Watts [764] 5 Stars
This process is converting velocity to pressure by sudden velocity reduction.
I mentioned water hammer because it is the same process and pressure developed is almost always above supply pressure.

The pressure is higher at the outlet because the density has increased .

A feedwater injector works whether you like it or not. But they are not upscalable.
And are tricky to adjust because they only just work.

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Thursday, September 28, 2017   By: P I [1983] 3 Stars
Can pressure and density of steam alone can be raised in this way? If yes, how much would be the upper level?

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Friday, September 29, 2017   By: Jim Watts [764] 5 Stars
No, the steam pressure cannot be increased in this way because it is compressible.
You dont get a steam compressor that easy.
All the steam powering the injector must condense at the outlet.
The second outlet called overflow is there to allow the ratio of water and steam to be optimised and the velocity established before the flow can be established to the boiler.

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Saturday, September 30, 2017   By: P I [1983] 3 Stars
Seems that water is necessary. Can you tell me how much water at what pressure is needed to compress steam at 2.536 kPa pressure @ 1 kg/sec to 1 barA?

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Sunday, October 01, 2017   By: Jim Watts [764] 5 Stars
The question is totally unanswerable and beyond the context of this thread.

We are talking about raising the pressure of cold water by using steam and raising it to a pressure above the source of the steam. This by increasing the water to a high velocity and then converting its momentum back to pressure.

Steam compression by magic is your department.

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Sunday, October 01, 2017   By: P I [1983] 3 Stars
This system too is compression of steam indirectly as the steam is first being absorbed in water and then its pressure raised to higher level. It seems to me that by this process, the Latent Heat of Vaporisation of the steam remains intact.

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Sunday, October 01, 2017   By: Jim Watts [764] 5 Stars
That is correct, and it just needs a boiler to get it back out of the water.
We may be onto something here.

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Monday, October 02, 2017   By: P I [1983] 3 Stars
Can you tell me how much water is necessary for 1 kg steam at 2.536 kPa pressure?

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Monday, October 02, 2017   By: Jim Watts [764] 5 Stars
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Monday, October 02, 2017   By: P I [1983] 3 Stars
You mean just 1 kg water is enough to raise the pressure of 1 kg steam? If yes, then whats the pressure level of the water?

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Monday, October 02, 2017   By: Jim Watts [764] 5 Stars
1Kg of water is necessary to make 1Kg of steam. You just add heat and confine the volume to raise the pressure.

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Monday, October 02, 2017   By: P I [1983] 3 Stars
Actually, what I have asked for is how to raise pressure of 1 kg steam at 2.536 kPa to 1 bar BY WATER HAMMER METHOD to around 1 barA. Not how to make steam by heating water.

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Tuesday, October 03, 2017   By: Jim Watts [764] 5 Stars
Try going back to your question where I first answered No and read the remaining thread a few times to see where we went wrong.

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Tuesday, October 03, 2017   By: P I [1983] 3 Stars
We havent gone wrong any where. What I have understood from you postings is that the steam is being absorbed by the water. What I want to do is to absorb the steam at 2.536 kPa pressure into water by water hammer method and then raise the pressure. I want to do this because you have said before that the Latent Heat of Vaporisation of steam has been conserved by this way. To be more precise, I want to dissolve the steam into water by preserving its LHV and then raising the pressure of water. I hope its clear enough.

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Wednesday, October 04, 2017   By: Jim Watts [764] 5 Stars
Unfortunately your fixation on wanting to compress steam leads to strange concepts like preserving steam LHV in water no doubt with the hope that somehow after compression you can flash it out again. For this you need to know how much water is required to compress it and you have asked that.

The reality is, this process is a water compressor not a steam compressor.

The energy in the steam is used to mechanically increase the velocity of water which must be in a ratio such that all of the steam used in propulsion is Condensed into Water Not dissolved.
The water is therefore required to be cold enough for this to happen without the amount of water being more than the steam can propel to the required speed.

When the water is at the higher pressure it has gained temperature but the heat of the steam is not all there because of work done.

There is no scope to use it as a steam compressor that is what the boiler is for.

Here is a link which gives a very good explanation of the process and may answer your next question I hope. http://tinyurl.com/y6vq2pg5

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Tuesday, October 31, 2017   By: Talmor [2174] 1 Stars
spray water with garden hose and pinch the end with your finger.. you increase the pressure and at the same time reduce the flow.
Dont get confused between the law of conservation of energy and this one... there is no law of conservation of pressure.
Outlet pressure can be higher than inlet pressure if you change flow rate or density.

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Published on steamforum.com


High Sulfite Residual
By: Ross. [390]

First, I want to say that large amounts of Sodium Sulfite NaSO3 becomes a contaminate because it will produce foaming and other problems, but foaming is the primary problem.

Your 500-psi Water Tube Boiler is seems to have reasonable level of residual Sodium Sulfite NaSO3 remaining in the boiler water. Nice pH too.

Your 300-psi Waste Heat Recovery Boiler has twice what I would expect for Sodium Sulfite NaSO3 at ranging 80-ppm to 100-ppm. pH is good so you are getting a good yield.

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