Cryogenics and low-temperature refrigeration have taken the world by storm in recent years. Produce is commonly sprayed with liquid nitrogen to preserve foods without threat to human consumption. Gases, like natural gas, can be frozen into a compact liquid state and transported efficiently. Cryogenic liquids are used in diagnostic imaging like MRIs. Even the International Space Shuttle utilizes cryogenics!
Can’t Have One Without the Other
These incredible applications are made possible through the use of cryogenics as well as insulation. After all, it wouldn’t be much use to freeze something to these extreme temperatures if the holding vessel couldn’t maintain the required conditions. Cryogenic insulation, unlike more moderate forms of temperature control, goes beyond saving money on utility bills. It is a necessary component of a controlled and effective cryogenic system.
Vacuum Insulation
Sir James Dewar developed the vacuum flask, also known as the dewar, back in 1892. At the time, the implications of this invention were to keep liquids hot or cold. In fact, the Thermos company patented this technology to develop and sell their ever-popular thermoses to hundreds of thousands of coffee-lovers the world over. Aside from its personal applications, this style of flask is still the prime insulating technology of cryogenics to this day. At its most basic, the dewar is a closed space formed out of glass, metal, or sometimes composite materials that are evacuated with a pump. As the inner walls get colder, gaseous molecules stick to them, thus maintaining the low pressure within the space.
Additional Firepower
Depending on the application, if radiant heat transfer poses a threat, solid materials may be introduced to the vacuum. A number of substances can be used, such as expanded perlite and silica aerogel. Whatever the material, its duty is to shield radiant heat from transferring between the outer and inner walls of the vacuum space.
Industrial Process Cooling Applications
As well-used as dewar flasks are, they are not the only insulation system used to protect cryogenic systems. In short-term storage or transfer applications, a handful of alternatives can be implemented. In non-food industrial process cooling applications, polyisocyanurate (PIR) foam insulation and cellular glass insulation are the most common. Regardless of material or system, however, all insulations used in cryogenic applications must make use of a high-quality continuous vapour retarder. You can learn more about condensation on insulation here.
- PIR Insulation. This rigid foam can work effectively in temperatures as low as -196℃. It boasts low thermal conductivity, meaning that it performs well, even with thinner layers than other comparable materials.
- Cellular Glass. Also rigid, cellular glass insulation can perform in astounding temperatures near -268°C. That being said, its thermal conductivity is higher than PIR insulation and will need to be installed thicker to have the same effectiveness.
If your industrial facility utilizes cryogenic processes, you know how important using the right insulation materials is! For expert advice, installation, and maintenance for your cryogenic insulation system, contact our team at Westcal Insulation today!
