Welcome to Very Cool Stuff: Air, Water, and Cryogenics. Air is not nothing, water is a very unusual substance, and cryogenics means cold. Cryogenics is NOT freezing bodies.
Although mostly hidden from our daily scene, Cryogenics is part of all modern life and industry. Cryogenics can do two practical engineering things for us.
Thing 1: Store a lot of energy in a small space. This energy density is why we use cryogenic propellants to get into space. The future of transportation on the Earth includes fuels such as LNG and LH2 for cars, trucks, and buses.
Thing 2: Use the low temperature to do something useful. These include many things which we don't even see that are very important to life. Examples: freezing foods, medical imaging machines (MRI), superconducting power devices, cryosurgery, biological storage, manufacture of computer chips, and on and on.
ü Check the superconducting magnetic bearing and add some liquid...but don’t say anything about it....build some intrigue.
As we see, cryogenics makes modern life possible and gives many more possibilities for the future. And everything about it goes back to energy. That’s why our theme is Energy Efficient Cryogenics.
II. How Cold is Cold?
ü Use temperature sensor to check room temperature and ice water.
ü Use vacuum chamber to boil water. Get volunteer to stick fingers in it. R U Crazee?
Liquid nitrogen (LN2): -321°F or 77 K (Note: Nitrogen turns to solid at 63 K). For our purposes here, we can consider liquid nitrogen to be about like liquid air (air is 78% nitrogen).
Much colder is liquid hydrogen at 20 K and liquid helium at 4 K. Absolute zero is close but yet far away.
Solid matter going from energy 1 to energy 2.
ü Quench stainless steel nut in the Dog Dish and listen for the crescendo at the end! Then dip super cold nut in water a few times and set out on table.
ü Quench a couple of hot dogs.
Safety talk: Three general hazards in cryogenics: over-pressurization, oxygen deficiency, and cold burns (frostbite). There’s no substitute for knowing what you’re doing. In everyday life we all do some potentially hazardous things, like boiling water on the stove top or pumping gasoline, but they are done safely by design, training, and experience.
Touching boiling water versus boiling nitrogen: what is the difference? The technical term is: film boiling effect (or Liedenfrost effect).
ü Hammer test old penny (pre-1982) versus new penny. What is the difference?
ü Test rubber hose or racquet ball.
ü Test bungee cord made into a spring.
ü Quench a banana or some flowers [always last].
ü Blow up some balloons.
ü Put balloons into bucket.
ü Blow up long skinny latex balloon. Put end of balloon into Dog Dish.
Look closely, and we can see liquefied air inside the balloon. There is a 700X expansion from liquid to vapor.
Vacuum is important and is really another world. There are vacuum containers built on the Earth and there is the vacuum of space. Vacuum is not nothing either, but it is a lot about nearly nothing! It helps us to preserve the cold.
If we wanted to keep a pan of water inside a pizza oven (a real commercial one at 600 degF), how would we do that? The temperature difference is over 500 degrees! Keeping liquid hydrogen as a liquid is the same problem: the temperature difference is over 500 degrees, the other direction. We do that! One way is with high vacuum and multilayer insulation (MLI).
ü Half-inflated balloon goes big.
ü Marshmallow man! Spacewalk and all going well until problem with the airlock....Oops!
Cryogenics is about cold and harnessing the cold to do many important things. Because cryogenics is about temperature, it’s all about energy. Nobody knows what energy is, but whatever it is, it’s important and we don't want to waste it.
ü Fuji film cap Pop off.
Thank you for your attention. I hope you enjoyed it. Remember, cryogenics is all about energy and energy sustains all life.