Copper tube Vs Stainless Steel Evaporative Condenser coil
Copper Tube Coils
- Thermal Conductivity: Excellent. Copper transfers heat much more efficiently than stainless steel, leading to a more compact and potentially more efficient condenser.
- Corrosion Resistance: Good general resistance to corrosion from clean water. However, it is vulnerable to specific threats:
- Ammonia (NH₃): Copper is attacked by ammonia and is not suitable for ammonia refrigeration systems.
- Sulphates & Specific Chemicals: Can be susceptible to pitting corrosion in water with high sulphate concentrations or other contaminants.
- Strength & Pressure: Lower mechanical strength compared to stainless steel. May have lower maximum working pressure ratings.
- Cost: Lower initial cost. Generally more economical upfront.
- Repairability: Easier to repair in the field by soldering or brazing.
- Typical Use: The standard choice for halocarbon refrigerant systems (e.g., R134a, R410A, R507) where water quality is well-controlled.
Stainless Steel Coils
- Thermal Conductivity: Poor. Stainless steel has significantly lower thermal conductivity (~1/25th that of copper). This often requires a larger coil surface area to achieve the same heat transfer, making the unit larger and heavier.
- Corrosion Resistance: Superior. Highly resistant to a wide range of corrosive elements. This is its primary advantage.
Ammonia (NH₃):Ideal choice. Essential for ammonia refrigeration systems
- Poor Water Quality: Resists pitting and corrosion from chlorides, sulphates, and aggressive water chemistries far better than copper.
- Marine/Coastal Environments: Excellent resistance to salt-laden air.
- Strength & Pressure: Higher mechanical strength and yield pressure. Can withstand higher operating pressures.
- Cost: Higher initial cost. Significantly more expensive material and often more complex to manufacture.
- Repairability: Difficult to repair in the field; often requires specialized welding techniques.
- Typical Use: Mandatory for ammonia systems. Also chosen for halocarbon systems located in corrosive environments (coastal, industrial) or where water treatment cannot be reliably maintained.
Selection Summary
| Factor | Copper Tube Coil | Stainless Steel Coil |
| Heat Transfer | Winner (More Efficient) | Poorer (Larger coil required) |
| Corrosion Resistance | Good (but vulnerable to NH₃ & sulphates) | Winner (Superior, especially for NH₃) |
| Cost | Winner (Lower Initial Cost) | Higher Initial Cost |
| Refrigerant | Halocarbons (e.g., R134a, R410A) | Ammonia (NH₃), Halocarbons in harsh conditions |
| Environment | Standard environments | Harsh, coastal, or industrial environments |
Rule of Thumb:
- Use Copper for standard halocarbon systems with good water quality. It’s the cost-effective, high-performance choice.
- Use Stainless Steel for ammonia systems or any application where corrosion is a primary concern. It’s the durable, long-life choice for harsh conditions.