These days we get condenser (heat exchangers) made of copper & Stainless-steel. Both having distinct advantages & use cases. Selection of material depends upon Heat exchange efficiency & Corrosion resistance.
Heat Exchange Efficiency:
The advantages and disadvantages of the two in terms of heat exchange efficiency and corrosion resistance. Heat transfer requires the thermal conductivity of the material.
The thermal conductivity of copper is 400W/mK.
The thermal conductivity of stainless steel is 16.2W/mK.
The thermal conductivity of the two is quite different. Copper tubing has better thermal conductivity than stainless steel coils. Although the wall thickness can be reduced enhance the thermal conductivity of stainless-steel coils, but stainless-steel coils still cannot reach the thermal conductivity of copper coils.
Corrosion resistance:
In terms of corrosion resistance, Copper coils will scale in areas with poor water quality. However, in areas with better water quality or where water is pre-treated scaling on the surface of copper pipes basically does not occur. Copper cannot be used if PH of water is below 7 pH or acidic in nature since it will react with copper ions & corrade it.
The surface of the stainless-steel coil is coated with a layer of chromium oxide film. The corrosion resistance is strong, but the chromium oxide film comes from the nickel-chromium alloy. Nickel has the worst corrosion resistance to chloride ions. Municipal tap water is usually disinfected with chlorine when the chloride ion content of tap water is high, Stainless-steel will also corrode to a certain extent. Water below chlorine content of 25 ppm or less is suitable for Stainless-steel condenser.