What is an All-Aluminium Fin and Tube Heat Exchanger?

What is an All-Aluminium Fin and Tube Heat Exchanger?

As the name implies, it's a heat exchanger where both the tubes (through which the refrigerant or fluid flows) and the fins (which increase the surface area for air contact) are made entirely from aluminium.

This is in contrast to the more traditional design, which uses copper tubes with aluminium fins (Cu-Al). The structure typically involves:

Tubes: Aluminium tubes arranged in rows and columns. The refrigerant flows inside these tubes.

Fins: Thin, corrugated aluminium sheets that are mechanically or hydraulically expanded onto the tubes to ensure good thermal contact.

Headers: Aluminium distributors at the ends of the tubes that distribute the refrigerant evenly into the circuit.

Key Advantages of All-Aluminium Design

Lightweight: Aluminium has a density about one-third that of copper. This makes the entire heat exchanger significantly lighter, which is crucial for applications like automotive HVAC, aerospace, and portable air conditioners, reducing overall system weight.

Superior Corrosion Resistance in Specific Environments:

No Galvanic Corrosion: In a Cu-Al heat exchanger, copper and aluminium are dissimilar metals. In the presence of an electrolyte (like moisture with dissolved salts), galvanic corrosion can occur, where the aluminium fins corrode aggressively. An all-aluminium design eliminates this problem entirely.

Resistance to Ammonia (R717): Aluminium is highly resistant to corrosion from ammonia, a natural and efficient refrigerant. This makes all-aluminium heat exchangers the standard choice for industrial refrigeration and heat pumps using ammonia.

Higher Potential for Heat Transfer Efficiency:

Modern manufacturing techniques like extruded microchannel tubes (see below) create a much larger internal and external surface area for heat transfer compared to traditional round tubes.

The all-aluminium construction allows for improved brazing processes that create a monolithic, highly efficient unit.

Lower Material Cost: Aluminium is generally less expensive than copper on a per-kilogram basis. While the design might use more aluminium to achieve the same strength, the overall raw material cost is often lower.

Compatibility with New Refrigerants: As the industry shifts towards more environmentally friendly but potentially more corrosive refrigerants (like R32 and R454B), aluminium's corrosion properties can offer better long-term reliability.