Hacker News Reader

HNHacker News

Top New Best Ask Show Jobs

Comment by Eisenstein | Hacker News Reader

Parent Full thread

Eisenstein·

> But if we want it to be steam, isn't that a bad thing?

Not if we want the steam to be hotter.

> Don't we want a nice big safety margin between our active steam temperature and the temperature it condenses?

Water is in one of three states: liquid, gas, solid. It has to be one of those. Where does the margin come from?

View on HN

You're phrasing that like you're unaware you can keep heating stean after boiling it. Steam can be 100C at 1atm, it can be 125C at 1atm, it can be 500C at 1atm.

The autoclave does not superheat steam.

Okay. Now we're back at the original unanswered question, which is why it's doing it that way.

Is the pressure helping directly? Why not use a heater; is dangerous levels of pressure easier than an extra heating element?

When you raise the pressure the boiling point of water increases which makes steam which is hotter than 100C. This is not 'superheated' because it is still at the boiling point (which is raised by pressure). This will condense on things inside the autoclave and dump the its heat into the thing killing anything on it. If you superheat the steam it is just as effective as air, which is to say not very. If you want to know more than that, you need to ask someone else, because that's about the extent of my knowledge.

Okay so the answer to my first question of "if we want it to be steam" is "not particularly, letting it condense is good".

It took some roundabouts but we got there. Thanks for the information.

Reply on news.ycombinator.com