altitude & temperature ?

Only when you're boiling water or baking a cake !! I did come across a problem with porosity when castings were made during low pressure days but nothing involving HT.
 
sorry to hijack your thread a bit Mark but I have a question for Mete...
Mete, did you find out what the cause of the porosity was? I am very curious because I work in polymer extrusion and we have all sorts of problems under certain atmospheric conditions and I am of course very interested in steel.....
If you do not want to continue the hijack then please send me a pm, my e-mail is in my profile.
Much appreciated Mark and Mete,

thanks,

Mike
 
This was in Syracuse. We were buying castings from a local foundry .Some batches had a very high scrap rate ,that made us and the foundry very unhappy .We looked into every possible variable and after a long search we found ,and verified with the weather bureau, that the bad batches were made during days with low pressure !! Remember that molten metal can contain dissolved gases and how they act can be effected by atmospheric pressure. Actually I wasn't surprised it was just a matter of tracking it down....Norwegians make Krum Kaker which is a thin dough cooked in an iron then formed into a cone.I learned as a kid ,watching my mother make it , to never do it on a rainy low pressure day. They would then be soggy instead of the normal very crisp and fragile !!.....I have a friend who is retired from the plastics business He propably would know about your problem . I'll email you if he can help.
 
This is very a very interesting topic. I lived in Albuquerque for a while (about 1 mile high) and I'm here to tell you it took FOREVER to boil an egg. The water would be boiling and it just wasn't all that hot.

Haven't thought about it too much, but how would it be to run a salt pot up there?
 
I actually read long ago that some guys on an Everest expedidition had a similar problem Joe.
The water was boiling but it was not scalding to the skin, hence, the tea was cold!
They were British of course!

It has to do with the air pressure and lower density of the liquid at higher elevations. Similar reason why water in a car's radiator does not boil because it is under pressure. Science is fantastic!:D
If anyone can add a bit more light to the subject please step in.
Sorry about the hijack again Mark.:foot:

Thanks for the e-mail Mete.

Mike
 
You think Everest is bad, try taking aircraft up to 30k feet. Hyd systems have to be pressurized to keep them from boiling.

It also just occured to me that this also works in reverse when dealing with cold things. If you put something under pressure it drops the freezing point. Such as when your refrigerator freezes your lettuce but your bottle of soda seems just fine, then you open it and it turns instant slushie.
 
The reason water boils at a lower temp at the reduced pressure of higher elevation is that the molecules of water vapor can leave the surface faster, so the water doesn't have to "push" quite as hard to get the vapor moving. As a consequence, the vapor's ability to get pushed away easier means the water will "hold" less energy and results in a lower boiling temp.

Conversely, increase the pressure above the water by keeping it in a pressure cooker and it is harder to "push away" the vapor, so more energy stays in the water, allowing it to get hotter.

The technical description has to do with a concept called "vapor pressure". It is different for every substance and changes with temperature and pressure. Even solids have a vapor pressure as a few atoms/molecules of the material will always be in a gas above it.

Hope that isn't gibberish. Putting this stuff in everyday terms isn't my forte. :o This is that part of chemistry/phyics called "Thermodynamics". If you seek further info, Google "Boyles Law".

Did you know that the reason you don't slide off a chair when you sit on it is because atoms of the seat of your pants actually overlap a bit into the atoms of the chair and vice versa? You are "atomically velcroed" into your seat. That's what makes "friction.":) So, when someone tells you to "get your ass out of that chair", they mean it! :D

back to your regularly scheduled programming.......
 
I can always find some pretty deep stuff on here!!!!!!Cool stuff to think about and see if it can be used to our benefit!
 
'atomically velcroed' don't we have to use the term "nano velcro" ?? Some cookbooks give information on different times to cook at altitude. That's really the time when using a pressure cooker helps. Remember also that we 'clean' steel by vacuum degassing -exposing the molten steel to a vacuum to remove air ,therefore reducing the amount of oxide inclusions.
 
When I used to give cub scouts a tour of my casting shop, I would put a coffee pot of distilled water in the big bell jar. I would tell them that it was a high power,see through microwave,and flip the timer on. The water would boil violently and after 30 seconds the timer would "Ding". I would take the pot out and drink right out of the spout. They all yelled. I would then pour it on my arm. After they were done yelling, I would explain atmospheric pressure, STP, and what low pressure does to the boiling point.Most of the time they would have to put their fingers in the pot to really believe it had not become hot.
Stacy
 
Stacy , excellent demonstration !! We also have sublimation - going directly from solid [ice] to gas [water vapor] !
 
Ok, My turn...

mete, about your mom's Krum Kaker...
Ever year at this time my mom cranks out a ton of that stuff...oh they are real nice when they are fresh and new, but my mom always makes them 3 weeks ahead of time, and then stores them in the freezer.

They end up taisting like wet toast....so wet that the whole point in eating them is lots....(Other than a sugar buzz)

I have always wanted to know what a person could do to keep Krum Kaker in it's fresh state, yet be able to eat them later?

Mete, what would happen if I got my mom one of them kitchen tools that sucks all the air out of a jar?
Would that help?
 
There's no need for a freezer !!! Always do it on a clear sunny day ! when they are thoroughly cooled put them in a tightly sealed tin. We never had any problem keeping them crisp for a long time !!
 
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