What materials are used in heat exchanger tubes

Core requirements for heat exchanger pipe materials
The pipe materials of heat exchangers must meet the following key properties:

1. Thermal conductivity: Efficient heat transfer, usually requiring a thermal conductivity of ≥200 W/(m·K) (such as aluminum alloy).

2. Corrosion resistance: Resistant to humid air or acidic exhaust gas corrosion, the corrosion resistance life of stainless steel (such as 304 stainless steel) can reach more than 20 years.

3. Sealing: Prevent air leakage, the interface sealing of plastic pipes (such as PVC) is better than that of metal.

4. Cost and weight: In the civil field, priority is given to lightweight (such as PP material density 0.9 g/cm³) and low cost (the unit price of aluminum alloy pipes is about 50 yuan/meter).

The material selection of heat exchanger tubes needs to be determined comprehensively based on the working temperature, pressure, corrosion environment and economy, and is mainly divided into the following three systems:

Metal materials (mainstream applications)
‌1. Stainless steel series‌
‌Austenitic stainless steel‌:
‌304/304L‌: used in conventional corrosive environments (such as weak acids, water vapor), applicable temperature ≤400℃.
‌316L‌: Add molybdenum (2%–3%) to improve chloride corrosion resistance, suitable for seawater cooling, chemical media and other environments.
‌Duplex stainless steel‌: such as S32205, which has both high strength and resistance to chloride ion stress corrosion, and is used for heat exchangers in high-salt environments.
‌2. Copper alloy series‌
‌Phosphorus deoxidized copper (such as HSn70-1B): high thermal conductivity (380W/m·K), suitable for civil heat exchangers (such as air conditioners, water heaters), but weak corrosion resistance.
‌Copper-nickel alloy‌: resistant to seawater corrosion, used in ships and seawater desalination equipment.
‌3. Carbon steel and alloy steel‌
‌20G carbon steel‌: low cost, used in low pressure, non-corrosive conditions (temperature ≤450℃).
‌Chromium-molybdenum alloy steel (such as 15CrMoG): temperature resistance of 540℃, suitable for high pressure and high temperature heat exchangers.
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Non-metallic and special materials (extreme conditions)
‌1. Fluoroplastic‌
‌Polytetrafluoroethylene (PTFE/F4):
Resistant to strong acids and alkalis (aqua regia, hydrofluoric acid), applicable temperature –250℃~260℃.
Sintered into capillary bundles (φ3–10mm) through powder metallurgy, used for heat exchange of corrosive media in chemical and electroplating industries.
‌FEP‌: temperature resistance of 200℃, easy to weld, can replace PTFE.
‌2. Ceramic materials‌
‌Silicon carbide (SiC):
Temperature resistance of 1600℃, strong thermal shock resistance (withstands 1000℃ rapid cooling and heating cycles).
Applied to high-temperature and strong corrosion scenarios such as polysilicon production and molten salt heat exchange.
‌3. Other non-metallic materials‌
‌Graphite: Resistant to hydrochloric acid corrosion, good thermal conductivity, used in sulfuric acid industry.
‌Polypropylene (PP)/Polyethylene (PE): Low cost, used in low-pressure corrosion environments ≤100℃.

Enhanced heat transfer structural materials

 Key Guidelines for Selection