Why aluminium tubes instead of copper for air conditioning?
Systems manufacturers used copper for automotive heat transfer tubing until they understood aluminium was superior as a material. HVAC & Refrigeration systems are not the same, but aluminium tubing is replacing copper for many of the same reasons.
The conversion of copper tubing to aluminium tubing in the automotive industry was completed decades ago. Now you find only all-aluminium heat exchanger units in the industry.
Aluminium tubes for HVAC systems
HVAC & Refrigeration systems are not the same. But aluminium is becoming the tube material of choice in HVAC applications, too. Why?
- It is less expensive than copper
- It is far more abundant than copper
- It is lighter than copper
- It is recyclable
You obtain a lighter heat exchanger when you use aluminium for both tubes and fins, as opposed to copper tube and aluminium fin solutions. An all-aluminium system improves the galvanic balance of the materials, giving better corrosion resistance and less heat transfer performance degradation during its service.
You also get more design flexibility with aluminium, and recycling is easier.
Many people are familiar with how easily copper conducts heat. Although it is true that the thermal conductivity of aluminium is half that of copper, in a heat exchanger, the difference in this property is entirely negligible for heat transfer performance. The reason is the fact that heat exchanger performance is dominated by the airside interface conductivity, so the actual, measure performance difference between copper and aluminium heat exchangers is limited.
Aluminium immune to formicary corrosion
One more important point that favors aluminium tubing is its immunity to formicary corrosion.
Formicary corrosion is caused by a chemical reaction requiring oxygen, water and an organic acid, induced by common lubricating oils. It is a type of premature failure with copper in air conditioning units. It has been a long-standing problem with copper tubing for HVAC & Refrigeration application.
Formicary corrosion only occurs in copper-based alloys. Aluminium is immune to it. Consequently, replacing copper with aluminium creates a dual benefit of lower initial raw material costs and a reduction of warranty costs, since it is estimated that 10 percent of indoor heat exchangers fail prematurely due to formicary corrosion.
Fact-based HVAC & Refrigeration decisions
The scientific reasoning for replacing copper tubing with aluminium stands on its own.
The hard part of replacing copper with aluminium is in the mindset of the people and is to actually make the switch. My advice is to examine the technical evidence and make the change, because the more experience you have, the better your chances of staying ahead with your own product solutions.