injecting superheated water into chamber

Question

injecting superheated water into chamber

slowoldguy (Automotive)

(OP)

24 May 21 21:30

We are injecting 230 deg C water at 275 atm into a small chamber with air at about 30 atm at about 500 deg C. Our thinking is that the water should be instantly turning to steam when leaving the injector nozzle. We expected to see a large increase in pressure due to the vaporization and expansion, but this does not appear to be the case. Does anyone else have experience with this? Could the vaporization of the water into steam be taking energy from the chamber and lowering the temp and pressure?

horacio Torres (Chemical) · Answer 1 · 2021-05-24 22:41:18

Calculate by energy balance and you will see the thermodynamics behavior,,, the water flow and the steam mass into the camber will fix the final temperature

LittleInch (Petroleum) · Answer 2 · 2021-05-25 09:19:11

slowoldguy.

How much do you know about steam?

At 30 bar (atm is not normally used) the saturated steam temperature (boiling point if you like) is a fraction more than 230 Deg C. This means when you inject your hot water into the chamber what you'll have is still hot water. The air at 500C has a very small fraction of energy compared to the water so will add very little to the water temperature.

Even if you were at a little higher temperature, you still need a certain amount of energy to convert the liquid water to steam. This lowers the temperature of the water / steam, possibly preventing its conversion to steam or resulting in a low amount of steam.

If you want instant explosive steam generation you will need to either increase the water temperature to maybe 260 or 275C or lower the chamber pressure to maybe 25 bar.

Saturated steam tables are your friend.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

saplanti (Mechanical) · Answer 3 · 2021-05-25 12:15:44

As described you need to follow thermodynamic tables, and do your balance calculation with mass flow rates.

EdStainless (Materials) · Answer 4 · 2021-05-25 13:32:30

And if you lower the chamber press then when you inject hot water as soon as it reaches saturation pressure you again will have hot water. Unless the chamber vents to hold the lower pressure this process will stop.

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

slowoldguy (Automotive) · Answer 5 · 2021-05-26 16:51:33

Thanks everyone for the useful info. As Little Inch observed, I don't know much about steam, so this is just the info I was looking for. Pretty amazing how these forums work. I will start looking at steam tables and thermodynamic tables and doing some calculating.

LittleInch (Petroleum) · Answer 6 · 2021-05-26 17:18:22

Well it's good you're not trying to do this in your back garden...Or at least I hope you're not.

Steam is a very well know substance and is quite an amazing substance as is water. It can be very powerful and lead to enormous pressures and if it escapes from where it is supposed to be can very easily kill and maim. Be VERY careful. you're talking about some pretty high pressures and temperatures here.

Oh and because of that it is often highly regulated and illegal to operate without the correct certification, testing and protective devices.

We're happy to help around here, but generally won't like it if you seem to be way out of your depth.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

MortenA (Petroleum) · Answer 7 · 2021-05-27 14:22:39

With regards to the steam table: checalc.com has an excellent one.

With regards to the warning: It require that you know your thermodynamics and are carefull.

With regards to regulation: If you are in the EU you may or may not be under PED. It may still be dangerous but not illegal....

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injecting superheated water into chamber