Cryogenics, Part 1

(Industrial applications of cryogenics)

What is cryogenics?

Cryogenics is the study of how to get to low temperatures and of how materials behave when they get there. Besides the familiar temperature scales of Farenheit and Celsius (Centigrade), cryogenicists use other temperature scales, the Kelvin and Rankine temperature scales.

One interesting feature of materials at low temperatures is that the air condenses into a liquid. The two main gases in air are oxygen and nitrogen. Liquid oxygen, "lox" for short, is used in rocket propulsion. Liquid nitrogen is used as a coolant. Helium, which is much rarer than oxygen or nitrogen, is also used as a coolant.

The thermal treatment of metals must certainly be regarded as one of the most important developments of the industrial age. After more than a century, research continues into making metallic components stronger and more wear-resistant.

One of the more modern processes being used to treat metals (as well as other materials) is cryogenic tempering. While the science of heat treatment is well known and widely understood, the principles of cryogenic tempering remain a mystery to most people in industry.

Information regarding this process is full of contradictions and unanswered questions. Until recently, cryogenic tempering was viewed as having little value, due to the often brittle nature of the finished product. It is only since the development of computer modeled cooling and reheat curves that the true benefits of cryogenically treated materials have become available to industry and the general public.

Cryogenics and cryonics are not the same applications

Cryonics is freezing people with the idea that they may be brought back to life in the future. The future is hoped to be an amazing utopian futuristic existence where the sorts of things people died of these days can easily be cured. Of course, the technology is assumed to be good enough to bring people back to life who have been frozen solid in liquid nitrogen for centuries! The idea is in principle not new, and has some similarities in principle to the Ancient Egyptian idea of storing a body by mummification in the hopes that the person will go on to an afterlife.

Sceptics say it's all a bit silly on the basis that it's impossible to restore someone who is dead. It had better be mentioned here that although cryonics is "optimistic immortalism", cryogenics is a serious science dealing with anything that is very cold.

Four Temperature Scales

The most commonly used temperature scale in the US today is the Farenheit scale, abbreviated F. In this scale, water freezes at 32 degrees and boils at 212 degrees. (This only holds strictly when atmospheric pressure equals the average sea level pressure. At high altitudes, water boils at a lower temperature, as anyone who cooks in the mountains knows.)

Another common scale is the Celsius (also called Centigrade) scale. In this scale, water freezes at 0 degrees and boils at 100 degrees.

To convert between Farenheit and Celsius use this formula: Farenheit Temperature = (Celsius Temperature)x(9/5) + 32.

There are also temperature scales in which zero is absolute zero, the lowest possible temperature. (People have gotten close to absolute zero, but have never reached it. According to theory, we never will.) Absolute zero is at -273.15 Celsius, or -459.67 Farenheit.

The Kelvin temperature scale uses the same size degree as Celsius, but has its zero set to absolute zero. To convert from Celsius to Kelvin, add 273.15 to the Celsius reading.

The Rankine temperature scale uses the same size degree as Farenheit, but has its zero set to absolute zero. To convert from Farenheit to Rankine, add 459.67 to the Farenheit reading.

To convert from Kelvin to Rankine, multiply the Kelvin temperature by 9/5.

Here's one example of temperature comparisons: 68 Farenheit is the same as 20 Celsius, 293.15 Kelvin, and 527.67 Rankine.

—Info from the Goddard Space Flight Center.

You may go on to Cryogenics, Part 2 from here.

This link will take you to the main cryo- unit.