Trapped Air in Water-Glycol Systems – A Guide to Effective Air Removal
Trapped Air in Water-Glycol Systems – A Guide to Effective Air Removal
Water-glycol mixtures are the lifeblood of many critical systems, including heat pumps, solar panels, industrial refrigeration and snow-melt ramps. Their excellent antifreeze properties make them indispensable. However, their greatest strength also creates a significant hidden challenge – a relentless tendency to trap air.
If you're managing a system that relies on a water-glycol mixture, understanding and solving this air problem is crucial for maintaining peak efficiency and preventing damage.
Why Do Water-Glycol Systems Trap Air?
The core issue lies in the fluid's viscosity. Water-glycol mixtures are significantly more viscous than plain water. This thick, syrupy nature is exceptionally good at trapping air bubbles, both large, visible ones and microscopic micro-bubbles. Once trapped, these bubbles cannot easily rise to the surface and escape on their own.
This entrapped air leads to a cascade of problems, including reduced heat transfer efficiency, increased pump strain, corrosion, noisy operation and potential system failure.
How To Remove Trapped Air With Strategic Air Separator Placement
The key to effective air removal is installing an air separator in the correct location. The solubility of gases in water changes with temperature, so it’s optimal to place the separator where the air is most willing to come out of solution.
This principle creates two specific placement rules:
- In Heating Systems – Install the air separator on the outlet side of the heat generator (e.g boiler). Here, the water is at its hottest, causing dissolved gases to break out of solution, making them easy for the separator to capture and vent.
- In Cooling Systems – Install the air separator before the inlet of the chiller. In this case, the water is at its warmest before entering the chiller, which is when the dissolved air is most likely to be released and can be effectively removed.
What Air Separators Should I Use In A Water-Glycol System
Standard, basic air vents may struggle to remove the high volume of micro-bubbles from a water-glycol system. For optimal performance, you require a separator specifically designed for high-efficiency deaeration.
Look for separators that offer:
- High-Efficiency Micro-Bubble Removal – The unit should be specifically designed to target and eliminate the tiny bubbles prevalent in glycol systems.
- A Combination of Separation Methods – The most effective models use a multi-stage process, often combining centrifugal separation with coalescing media.
- Robust Construction – Look for air separators that are compatible with glycol mixtures to ensure long-term reliability and durability.
- Sufficient Flow Rate Capacity – Correctly sized for the flow rate and volume of your specific system.
Altecnic DISCAL Air Separators
A prime example of technology designed to meet the challenges of water-glycol systems is the Altecnic DISCAL range. These air separators are engineered for high performance in both hydronic heating and cooling systems.
Their patented design features a stack of dished plates (discs) that create a large surface area. As the water-glycol mixture flows over these discs, the flow is slowed and agitated, encouraging even the smallest microbubbles to coalesce into larger bubbles that rapidly rise to the top of the unit and are automatically vented.
For optimal performance and longevity of your water-glycol system, proactively removing air is a must. By understanding the fluid's viscous, air-trapping nature and following the crucial rule of placing your air separator at the point of lowest gas solubility, you can ensure your system runs quietly, efficiently and reliably for years to come.
This content was originally published in IDRONICS Issue 1 in December 2020.
FAQs
Why is air a problem in water-glycol systems?
The high viscosity of water-glycol mixtures traps air bubbles and micro-bubbles, preventing their natural escape and leading to inefficiency and damage.
Where should an air separator be placed in a heating system?
Install it near the heat generator outlet, where the water is hottest and the air is least soluble.
Where should an air separator be placed in a cooling system?
Install it before the chiller inlet, where the return water is warmest, allowing for effective air separation.
What is the best type of air separator for a glycol system?
High-efficiency separators that use coalescing technology, such as disc-type separators, are highly recommended for their ability to remove micro-bubbles from viscous fluids.