By Bruce I. Nelson, P.E., President
Evaporator Coils for Food Processing
Introduction
The control of pathogens in food processing facilities plays an important part in ensuring the safety of our food supply. Among other requirements, the USDA mandates that equipment is carefully cleaned to remove soil and then sanitized to disinfect surfaces. Often these two processes involve chemicals which, if not selected and applied properly, have the potential to corrode and damage the metal surfaces of evaporator coils. This technical bulletin discusses sources of corrosion, corrosion resistance of various metals used in evaporator coils, and makes recommendations regarding the selection of coil construction and accompanying cleaning and sanitizing chemicals appropriate for the operating environment.
Evaporator Construction
Industrial evaporator coils can be manufactured by Colmac Coil with a number of different tube and fin materials to match the requirements of the working fluid (refrigerant), the operating environment, and the project’s first cost requirements.
Tube Materials:
- Aluminum (3003)
- Copper (not suitable for ammonia)
- Stainless Steel (304L, 316L)
- Carbon Steel – Hot Dip Galvanized after fabricating
Fin Materials:
- Aluminum (1100, 8006, AlMg2.5)
- Epoxy Coated Aluminum
- Copper
- Anti-Microbial Alloy
- Stainless Steel (304L, 316L)
- Carbon Steel – Hot Dip Galvanized after fabricating
Available Combinations (Tube/Fin):
- Aluminum / Aluminum
- Stainless Steel / Aluminum
- Stainless Steel / Epoxy Coated Aluminum
- Copper / Aluminum
- Copper / Epoxy Coated Aluminum
- Copper / Copper
- Stainless Steel / Anti-Microbial
- Stainless Steel / Stainless Steel
- Carbon Steel / Carbon Steel - Hot Dip Galvanized after fabricating
In general, the listings above show materials and combinations in order of increasing first cost with aluminum being the lowest cost material. Aluminum is also the lightest metal of those listed and is more thermally conductive than any of the metals shown except copper.
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