The materials of construction for a Dry Fluid Cooler are critical for its performance, longevity, and suitability for a specific environment and fluid. They are selected to balance corrosion resistance, heat transfer efficiency, mechanical strength, and cost.
Here is a breakdown of the common materials used for key components:
1. Heat Exchanger Coils (The Core Component)
This is the most important part, and material choice depends heavily on the process fluid and ambient environment.
| Material | Typical Use Case | Advantages | Disadvantages |
| Aluminum Fins / Copper Tubes | Standard Application: Cooling water, water-glycol mixtures, and other non-corrosive fluids in standard atmospheres. | Excellent Heat Transfer: Copper and aluminum are among the best thermal conductors. Cost-Effective: Good balance of performance and price. Lightweight. | Vulnerable to Corrosion: Copper tubes can be corroded by ammonia, sulphides, and acidic conditions. Aluminum fins are susceptible to pitting in coastal or heavily industrial atmospheres. |
| Stainless Steel Tubes (e.g., 304, 316L) / Aluminum Fins | Corrosive Fluids or Environments: Cooling corrosive fluids (e.g., some oils, acids, seawater in coils). 316L is used for highly corrosive coastal or chemical plant atmospheres (chloride resistance). | Superior Corrosion Resistance: Especially 316L SS. High Strength: Withstands higher pressures. Long Lifecycle in harsh conditions. | Higher Cost: Significantly more expensive than copper. Lower Heat Transfer: Stainless steel is a poorer conductor than copper, which may require a larger coil surface area for the same duty. |
| Carbon Steel Tubes | Specialized Applications: High-pressure applications with non-corrosive fluids (e.g., compressor intercooling, lube oil). Almost always used with galvanized steel fins. | High Mechanical Strength: Can withstand very high internal pressures. Lower Material Cost. | Very Prone to Corrosion: Requires protective coatings or specific fluid treatment. Not suitable for water or moist environments without protection. Poor Heat Conductor. |
| Cupronickel (e.g., 90/10, 70/30) | Marine & Coastal Applications: Excellent for resisting corrosion from saltwater spray and brackish water as the process fluid. | Exceptional Corrosion Resistance in marine environments. Erosion Resistance against sand/silt in water. Biofouling Resistance. | Very High Cost. Heat transfer is lower than copper but better than stainless steel. |
Note on Fins: Fins are almost always made of aluminum due to its excellent malleability, light weight, and great thermal conductivity. For corrosive environments, they can be coated or made from a more exotic alloy, but this is rare due to cost.
2. Casing / Frame
The structure that houses the coils, fans, and other components.
- Galvanized Steel (G90 or higher): The industry standard. Zinc coating provides a sacrificial layer that protects the underlying steel from rust. Durable and cost-effective for most environments.
- Aluminum: Used in highly corrosive environments (e.g., chemical plants, coastal areas) where even galvanized steel may corrode. More expensive but offers excellent corrosion resistance without needing paint.
- Stainless Steel (304 or 316): Used for the most aggressive environments or where hygiene is a priority (e.g., food, pharmaceutical industries). This is a premium, high-cost option.
- Paint/Coating: Galvanized frames are often painted with a polyester or epoxy powder coat for additional aesthetic and corrosion protection. Common colors are ANSI 61 (Light Gray) or RAL codes specified by the customer.
3. Fans
- Blades: Typically made from aluminum (good balance of strength, weight, and corrosion resistance) or fiberglass-reinforced plastic (FRP) (excellent corrosion resistance, especially in chemical fume environments).
- Hubs: Typically cast aluminum or ductile iron (galvanized or coated for protection).
4. Tanks & Headers
These distribute the fluid from the pipes into the many tubes of the coil.
- Carbon Steel with Internal Epoxy Lining: Common for standard applications. The coating prevents corrosion from the fluid inside.
- Stainless Steel: Used for corrosive fluids or where high purity is required. A more robust and maintenance-free option.
5. Other Components
- Drip Pans (if applicable): Usually stainless steel (304) to withstand constant moisture and prevent rust
- Fasteners (Bolts, Nuts, Screws): Hot-dip galvanized steel or stainless steel to prevent galvanic corrosion and seizing.
- Supports & Legs: Galvanized steel or painted carbon steel.
Material Selection Guide Based on Environment
| Environment | Recommended Coil Material | Recommended Casing Material | Key Consideration |
| Standard Inland | Copper Tubes / Aluminum Fins | Galvanized Steel (painted) | Cost-effectiveness |
| Coastal / Marine | Cupronickel Tubes / Al Fins or 316L SS Tubes / Al Fins | Aluminum or 304 SS | Chloride-induced corrosion |
| Heavy Industrial | 316L SS Tubes / Al Fins | Aluminum or 304 SS | Resistance to acidic fumes (SOx, NOx) |
| High-Pressure Duty | Carbon Steel Tubes / Galvanized Steel Fins | Galvanized Steel | Mechanical strength, non-corrosive fluid |
| Food & Pharmaceutical | 316L SS Tubes / Al Fins (or SS fins) | 304 or 316 SS | Hygiene, c |