We prepared a series of articles to help readers better asses the challenges and the current state of the refrigeration industry. Through this series of articles, we aim to present our advantages over standard technologies and approaches and explore the benefits to the end customers.
This article is dedicated to the presence of oil in refrigeration systems.
Comparison with oil management in vapour compression systems
Our refrigeration machines don’t use oil for the operation which is one of the benefits in comparison with standard vapour compression. In the vapour compression refrigeration oil plays a key role in the whole system to ensure:
- Proper lubrication of all moving parts in the compressor
- Prevent overheating due to friction
- Ensure air tightness for some types of compressors (scroll, vane…)
Oil is essential for vapour refrigeration systems, though not all of the oil is present in the compressor itself (about 50 %). It’s important to know that oil as a lubricant is present in every part of the system where it has a purpose and where also it can cause several problems.
Inconveniences in the badly designed or badly operated systems:
- In case of low oil level in the compressor critical mechanical breakdowns may occur together with irreversible damage and increase of overheating.
- Wrongly designed heat exchangers or piping can cause „oil traps“ and contribute to low oil levels (or even excess of oil). This trapped oil can cause inefficient lubrication and friction, or slugging of the compressor. (highly increase chance of damage).
- Bad oil circulation and oil slugs also can reduce inner heat transfer surface in the heat exchangers and thus decrease overall system efficiency and capability.
- Poor system operation with low refrigerant velocity (or too high), mainly during gaseous stage, can lead to bad oil circulation.
- Oil also affects physical and thermodynamic properties of refrigerant. We have to say, that if the system is designed well, it can even slightly improve these properties, but on the other hand due to degradation of the oil, refills, contamination, etc. properties of oil and refrigerant detoriate over time.
- Especially during operation in ULT applications, changes in thermodynamic properties of the oil may lead to accumulation of the oil and further reduction of the whole system cooling efficiency due to further reduction of heat transfer capacity of heat exchangers.
- To prevent risks mentioned above a lot of additional costs for components needed for proper oil management (Oil separator, oil receiver, level regulator, valves, oil filter, sigh glass, etc.)
MIRAI Cold – the Oil FREE solution
In our home base, Mirai Intex, we have developed our own Air foil bearings which eliminate the need for complex oil management systems. Such a change is beneficial to the consumer due to their extended life cycle, reduced operating costs and improved reliability, as well as other advantages which we explore in more detail below.
How is this possible?
The main reason is the use of AIR-bearings in our refrigeration machines. Compression of refrigerant (air) is done by our turbo module where compressor and expander are situated on the same shaft and equipped by air bearings. Our precise manufacturing and use of air bearings allows the shaft to rotate freely without oil and without any friction due to “air pillow”.
Oil free system advantages:
- No need for refills, retrofits and oil change.
- Zero risk of dangerous waste oil disposal during maintenance.
- Fewer unreliable components in comparison with vapor system.
- No need for leak checks and contamination risks.
- Without mechanical breakdown possibility due to low oil level.
- Non – toxic, non-flammable solution.
We have an ambitious goal to revolutionize the refrigeration industry in favour of climate protection and that is why we believe that the implementation of our solutions is the right path for this growing industry.
Stay tuned for more articles regarding common challenges in the refrigeration industry and how we approach them.