Cryo sauna | Stirling Cryogenics

Cryo sauna cooling

Trainers have known for years how to cope with athlete injuries through I.C.E.: Immobilization - Cooling - Elevation. The intense, repetitive training and high level competition of some athletes can result in chronic and acute injuries. To cure an injury or to intensify training while shortening recovery time, some athletes are taking that concept to the next level -- whole body cryotherapy by means of cryosaunas which replaces an ice bath with a faster, healthier and completely natural process.

Whole body cold therapy
In a cryo sauna a person is completely exposed to extreme low temperatures (typically -80 to -110°C) for a few minutes as therapeutical treatment. A short stay in the extreme temperature starts body processes that relieve pain and strengthen the body's own immune system. It is proven that the effects of the process improve physical wellbeing and enhance skin condition and beauty.

As the real physical effects start at temperatures below -90°C, the way to efficiently achieve these is by means of cryogenics. Cooling of a cryo sauna can either be:

  • indirect, where cryogenics fluids cool the chamber through heat exchangers, or
  • direct, where the cryogenic fluid is injected directly into the room.
A combination of both methods can be required in certain situations where specific cool down sequences are required. Though in the first method liquid nitrogen is typically used, this is not recommended for the latter since asphyxiation (shortage of oxygen in the air that we breath) is a major hazard. In  these configurations liquid air (with the same nitrogen /oxygen proportions as the air we breath) can be injected directly into the cryo sauna.


Our solutions
Stirling Cryogenics has a whole range of products to support this application: The StirLIN and StirLAIR plants produce cryogenic liquid on-site, close to the cryo sauna. This eliminates the need for complex logistics (trucks) and having huge (cryogenic) storage tanks at site.

Our plants can produce cryogenic fluid for 24 hours per day, 7 days a week, without operators attention, only needing power. As the plants have their own storage tank, the sauna, per treatment, can consume more liquid then the plant can produce. Overnight and in between treatments, the plant will keep running, filling up the buffer tank, preparing for the next therapy session.

Stirling’s liquid air plants produce liquid air which can directly be injected into the chamber, as it has the same amount of oxygen as in normal air (mixture of 21% oxygen and 79% Nitrogen). Therefore the patients in the cryo sauna will be able to breath normally .

In order to prevent oxygen enrichment inside the storage tank (due to difference in density of nitrogen and oxygen) the StirLAIR plants are equipped with the unique AirLock system which prevents segregation of the mixture over time, ensuring a constant and correct mixture (oxygen/nitrogen ratio). Furthermore the plants can be equipped with optional sensors to monitor the oxygen level.
 

More information
Cryo sauna

 
Closed loop re-liquefication:
As applications like cryo sauna's tend to use serious amounts of nitrogen (in case of indirect cooling), it is always useful to evaluate the possibility for a closed loop nitrogen re-liquefication system. In this configuration the nitrogen, is not vented to the atmosphere after it has cooled the chamber but it is fed back to the cryogenic plant in a closed loop.

The vented nitrogen still contains a certain amount of (cooling) energy since only the evaporation energy of nitrogen was used. After evaporation the gas is still very cold (typically at around 100K) when exiting the sauna chamber. This cold gas is directed back into the cryogenic plant and significant efficiency improvements are obtained. As a “rule of thumb” the liquefication capacity of a cryogenerator can double when it can re-liquefy cold gas instead of ambient temperature gas.

Our SPC-1 and SPC-4 cryogenerators can be used and configured for any kind of closed loop, reliquefication system. Furthermore we offer the engineering and associated equipment to make the complete application function as an independent unit. Some issues need to be evaluated carefully and engineered in advance since additional piping is required to transport gas back to the cryogenic plant and control will be more elaborate.

The most important limit of a closed loop design is the cooling capacity of the installed cryogenerator since this determines how much evaporated nitrogen can be reliquefied. If more gas is generated by the application then the cryogenerator can handle, the pressure in the loop will increase and nitrogen gas will be vented to atmosphere and lost.

Example:
If the installed cooling capacity in a loop is 20 l/hr (of cold gas) no more nitrogen is available, not even during a short period.  Especially during the cool down of a cryo sauna or at times when the room is full with users, the required cooling can exceed the installed cooling power, whereas the system can still easily handle the average required cooling power.
For standard cryogenic liquid production plants (StirLIN, StirLAIR) this cooling limit does not exist since during low load and no use periods they create a liquid “buffer” in the storage tank, ready for use during peak loads (peak shaving).

 
Products
For use in applications as described the following Stirling Cryogenics products may be considered: