Vapor quality
Water in ammonia systems is not a small problem. It is a hidden performance killer.
Written by: Michael Elstrøm
Most operators assume their ammonia system is clean. In reality, it rarely is.
Water enters during installation, service and operation. And once it is inside the system, it does not distribute evenly – it concentrates where it does the most damage.
Water does not stay where you expect
Ammonia and water mix easily. But inside a refrigeration system, they do not behave uniformly.
The system acts like a distillation process. Water accumulates on the low-pressure side – in evaporators and separators. This means the part of the system that defines performance is also where contamination is highest.
The thermodynamic impact is immediate
When water mixes with ammonia, the evaporation temperature changes.
At the same pressure, contaminated ammonia evaporates at a higher temperature. To maintain the required cooling temperature, the system must reduce pressure, and that forces compressors to work harder.
Even small amounts have a measurable impact: 1% water can reduce capacity by approx. 8%.
Direct performance impact
- Higher evaporation temperature
- Lower suction pressure required
- Increased compressor workload
- Reduced COP
- Reduced cooling capacity
What you do not see is worse
The thermodynamic loss is only part of the problem. Water also changes the chemistry inside the system. When water and air are present, oil oxidizes, acids are formed and the oil properties change.
Oil starts sticking where it should not
Contaminated oil adheres to metal surfaces inside evaporators and heat exchangers. This reduces heat transfer significantly and is difficult to detect in daily operation.
Heat pumps are especially vulnerable
Higher temperatures accelerate chemical reactions, for every 10°C increase, reaction rates roughly double. This makes heat pumps more sensitive to contamination.
You cannot measure it reliably with traditional methods
Manual sampling methods are inconsistent and unreliable. Water is unevenly distributed, leading to different results depending on where samples are taken.
Why measurement fails
- Water is unevenly distributed
- Concentrates at bottom of vessels
- Results vary by sampling point
- Manual methods are inconsistent
The business impact is larger than expected
Water contamination has a direct economic impact. Even small increases in water content reduce efficiency significantly.
Example:
- 1% water → ~93% efficiency
- 3% water → ~86% efficiency
- 10% water → ~77% efficiency
Economic impact
- Up to 20% efficiency loss
- High energy costs
- Short payback time for mitigation
- Often unnoticed losses
Even new systems are affected
New ammonia already contains water, this means performance loss begins from day one.
Control is the only solution
The only effective solution is continuous removal of water and air. Efficient separation and proper monitoring ensure stable performance.
Effective approach
- Continuous air purging
- Efficient water separation
- Monitoring system deviation
- Early detection
- Design for clean operation
This is not maintenance. It is system design.
Water will enter the system.
The question is whether you control it — or let it control your efficiency.
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