Liquid nitrogen (LN2) and liquid helium (LHe) are both cryogenic coolants that exist at extremely low temperatures. Although they share some similarities, they serve very different purposes across science and industry. This article explores what sets these two apart in properties and applications.
Key differences
| Property | Liquid Nitrogen | Liquid Helium |
|---|---|---|
| Boiling Point | -196°C (-320°F) | -269°C (-452°F) |
| Cost | Relatively low | High |
| Applications | Food, medical, industrial | Scientific, medical imaging |
| Special Property | Inert, easy to store | Superfluid at low temps |
What are cryogenic fluids?
Cryogenic fluids are liquids with a boiling point below minus 130 degrees Fahrenheit (90 degrees Celsius). These fluids are used in research and scientific applications to provide extremely low temperatures.
What is liquid nitrogen?
Liquid nitrogen is nitrogen gas cooled to -196°C (-320°F), at which point it turns from a gas into a liquid. It is widely used because it is relatively inexpensive and easy to produce through cryogenic distillation of ambient air.
Common uses of liquid nitrogen include:
- Food preservation: Flash-freezing and packaging.
- Medical applications: Cryotherapy and cryopreservation, biobanking, drug development.
- Industrial processes: Cooling, shrink-fitting, and creating inert environments.
- Scientific research: Cryogenics and sample storage, low-temperature physics.
What is liquid helium?
Liquid helium is helium cooled to -269°C (-452°F), just 4 degrees above absolute zero, making it the coldest liquid on Earth. It is unique because it remains a liquid even near absolute zero and exhibits superfluidity, meaning it can flow without friction with zero viscosity.
Common uses of liquid helium include:
- MRI machines: Cooling superconducting magnets.
- Particle physics: Maintaining ultra-low temperatures for experiments.
- Quantum research: Studying superconductivity and quantum states.
Which one does my application need?
Whether your application is better off by using liquid nitrogen or liquid helium depends on several factors, and commonly comes down to temperature requirements and cost considerations.
Choose liquid nitrogen for applications that:
- Need cooling around -196°C
- Are cryopreserving/freezing materials
- Are in need of a cost-effective, widely available cryogen
- Need robust industrial cooling.
Choose liquid helium if you:
- Must reach temperatures near absolute zero
- Are operating in quantum computing or advanced research in physics
- Are able to secure liquid helium supply.
Conclusion
Both liquids are essential in modern science and technology, but their roles differ significantly. Liquid nitrogen is the driver of cryogenics and many industrial processes, while liquid helium is the key to unlocking quantum phenomena and other research.
Liquid nitrogen is widely available as a safe, practical choice, especially with a generator placed on-site for uninterrupted supply. Since helium is extracted as a by-product of natural gas production, liquid helium is scarcer and more expensive compared to nitrogen.