WHAT ARE CRYOGENICS?

As a carrier of cryogenic liquids, our team needs to understand what we are transporting. Cryogenics is “the production of and behavior of materials at very low temperatures” (GasLab.com). When materials are manipulated to reach extremely low temperatures, their chemical properties change. Cryogenic scientists look at how the materials act when they change from a gaseous form to a liquid state. The experimentation and studies as a result of these scientists have led to great advances in technology and industries, but also in the understanding of the behaviors of different materials in our world.

Now to discuss the scientific aspect a little more. We all know that matter has molecules that contain energy. So these particles are always moving and at very fast speeds. The movement of the molecules produces heat, and the faster the movement, the higher the temperature. But when these moving molecules reach a temperature low enough to slow their movement, the materials change from a gaseous state to a liquid state. But just how low are these temperatures? GasLab states that “cryogenic temperatures range much lower; from -150°C to -273°C. The temperature -273° C is the absolute lowest that can be achieved”. In Fahrenheit, that’s -254°F to -459°F.

THE SCIENCE BEHIND CRYOGENICS

To be correct, cryogenics is not typically measured in Celsius or Fahrenheit. If you remember back in high school, the third system for measuring temperatures is in Kelvin (K). Named after Baron Kelvin “who believed that at very low temperatures a new scale was needed that was not measured by the material state change of water” (GasLab.com), which is what we use to determine Celsius and Fahrenheit. 0 Kelvin is in theory the lowest possible temperature, meaning there are no negative temperatures in this system. So for example, the boiling point of water is 212°F (100°C) which is 373.15 Kelvin. The absolute lowest temperature (absolute zero)  for water is -460°F (-273°C) or 0 Kelvin (K). Absolute zero means that these molecules are in their lowest possible energy state.

Since typical thermometers use mercury or alcohol to measure Celsius or Fahrenheit, their properties can’t reach such low temperatures, so they are useless in cryogenics. The way cryogenic temperatures are measured is with a platinum resistance thermometer which shows electrical resistance rather than temperature. This method usually is very accurate up until about 20 K. After that point, other devices like doped germanium accurately measure as far down as 1 K and below.

METHODS OF PRODUCING CRYOGENIC TEMPERATURES

There are four main processes for creating cryogenic liquids: heat conduction, evaporative cooling, cooling by rapid expansion, and adiabatic demagnetization.

HEAT CONDUCTION

Heat Conduction is probably the most familiar with the average person. When something hot comes into contact with something cold, the heat passes from the hotter object to the colder object, which is Conduction. A way to create cryogenic temperatures with this method is by taking the sample and putting it in direct contact with a cryogenic fluid or by putting it in an atmosphere that is cool by cryogenic refrigeration. The sample is cooling by conducting heat to its cooler surroundings.

EVAPORATIVE COOLING

Evaporative Cooling occurs because when materials are in a liquid form, they have less energy than their gaseous form. To explain this a little better, say you have a puddle of water. The surface of the water will evaporate faster than the particles on the bottom. When these evaporated particles leave, it makes the puddle’s temperature drop since it lost energy. This is exactly what scientists do for cryogenic liquids. They encourage the process of evaporation by pumping away the atoms as they evaporate to get the material to the correct temperature. Once the temperature is achieved, the pumping continues, but the process is slowed down.

COOLING BY RAPID EXPANSION

This one is interesting. This method is used to cool a gas to a liquid by quickly expanding its volume and thus dropping its temperature. This is called the Joule-Thompson effect. A small valve with a small opening is used for this. What happens is a high pressure gas drops very suddenly when passing through the valve. For a more detailed explanation, read here.

ADIABATIC DEMAGNETIZATION

The last involves the use of “paramagnetic salts” to absorb heat. Paramagnetic salt is basically a collection of tiny magnets and when they are all together, are not magnetic. But as soon as an electromagnet is near, they repel from the magnetic field of the electromagnet making them align in a certain way (lattice pattern most often). The goal of this is to decrease the entropy of the system (Science Encyclopedia).

HISTORY OF CRYOGENICS

The Greek word Kyros (meaning cold or frost) and the abbreviated English suffix -genics (meaning to generate) come together to form the word cryogenics. The word was first used by Professor Kamerlingh Onnes from the Netherlands in 1894 to “describe the art and science of producing much lower temperatures”(National Institute of Standards and Technology). The original use of the term was for the liquefaction of permanent gases. As cryogenics have become more advanced, the term is now used in reference for temperatures below approximately -150° C.

The first breakthrough for the cryogenics industry was in 1877 when Rasul Pictet and Louis Caillet liquefied oxygen for the first time. Soon afterwards, Liquid Nitrogen was achieved and this sparked a competition amongst scientists all over the world to see who could lower the temperature of matter to absolute zero.

In 1898, James DeWar liquefied Hydrogen at 20 K which made people start to think about how to handle and and store gases at these temperatures. This is where Dewar flasks were invented, which are still used today. Finally, the last major breakthrough in the cryogenics industry was in 1908 when Heike Kamerlingh Onnes liquefied Helium at 3.2 K. Since then, there have been small advancements, but no one has ever reached absolute zero.

WHAT ARE CRYOGENICS USED FOR?

People may not realize just the reach that cryogenics has on our everyday lives. Cryogenics are in our household appliances and hygiene supplies, to the aerospace technology field. Cryogenics are used in cryosurgery, cryoelectronics, and cryobiology. All of these involve extreme frozen temperatures to understand how cryogenics plays a role on living organisms and other elements.

Food preservation is a very common use of cryogenics, where liquid nitrogen is sprayed on the food to help it absorb the heat in the produce. This means that food can be preserved for extended amounts of time without any chemical threat to humans. Cryotherapy and cryonics are other areas where cryogenic fluids play a major role. They can be used as healing methods or even a form of human preservation, but this is still an uncertain practice.

Lastly is that cryogenics allows for the transportation of gases that are typically not liquefied. Liquifying gases into their cryogenic form allows for easier and cheaper forms of transport. Gases such as Helium, Argon, Oxygen, Nitrogen and Ammonia all take up a large surface area when in their gaseous state, so cryotechnology allows these to be compacted to be transported across the country. If you want to read about the more specific uses, GasLab goes into further detail.

HOW DO YOU DELIVER CRYOGENIC LIQUIDS?

Here at LGT, we specialize in the transportation of industrial gases like those mentioned above. Our services reach all across the United States, partnering with industry leaders in Cryogenic Liquids. To be able to transport cryogenic liquids, top-of-the-line equipment is necessary to create and distribute these materials. There are a few methods for storing and transporting cryogenic liquids, like the Dewar flasks but also such things like Liquid Cylinders that Cryogenics Companies use. Specialty Cryogenic Tanks are what cryogenics drivers and companies use to deliver these liquids. They pump the liquids into specialty cryogenic trailers (CO2, Oxygen, and so forth) that have the capabilities to keep the fluids stable and in their liquid state.

SPECIALTY CRYOGENIC TRAILERS

Cryogenic tanks vary, but essentially they all have the same function: maintain the correct atmospheric conditions to transport the liquids. Each of the Specialty Cryogenic Trailers have three layers. There is the outer vessel, the annular space, and the inner vessel. The annular layer is the key aspect to maintaining the interior atmosphere. The annular layer is a vacuum layer that acts as the barrier between heat from the exterior from reaching the pressurized liquid on the interior. If heat were to enter the trailers, the liquids would become unstable and ruin the material. So how does it work? For heat to pass through to the interior, it must have matter to interact with but since it’s a vacuum, there is no matter for heat to pass through.

The interior layer has its own form of a barrier. Newer cryogenic trailers have an insulated interior layer wrapped with a special material called Super Insulation. It was developed by NASA for thermal insulation of Liquid Hydrogen and Helium (NASA). This barrier acts as a reinforcement to the metal interior to keep heat out. Older cryogenic trailers used Perlite, which is volcanic rock used as another form of insulation.

Along with insulation, cryogenic tanks are pressurized. Each trailer has different specs for pressure levels to maintain, but generally the pressure inside the tank creates a back pressure. This pressure is a force that pushes on the liquid inside the trailer to stabilize and limit its movement. Most of the cryogenic liquids don’t require extreme pressures once inside the trailer, except for CO2, but this extra step acts as a safety precaution to prevent sloshing. Handling and transporting cryogenics comes with its own dangers as well.

CRYOGENICS AS A WHOLE

Cryogenics is a very complex and ever advancing science. Testing and learning the boundaries of the world around us is what it’s all about from providing life-saving remedies to launching people into space. It spans across entire industries and is in our everyday lives in more ways than we think.