Views: 0 Author: Site Editor Publish Time: 2026-09-30 Origin: Site
An ammonia (NH3, R717) evaporator coil must be built in stainless steel or aluminium tube. Copper and copper alloys — including brass and cupronickel — are not compatible with ammonia: in the presence of even small amounts of moisture, ammonia attacks copper rapidly, and the coil fails. CSTHEATEXCHANGER manufactures ammonia evaporators and ammonia air coolers with stainless steel tubes (316L for food-grade duty), aluminium or stainless fins, and galvanized or stainless casings, for cold storage, blast freezing, processing plants and large commercial refrigeration. If a supplier offers you a copper-tube coil for an ammonia system, the coil is wrong for the refrigerant.
Factor | Effect |
|---|---|
Chemical attack | Ammonia in the presence of moisture corrodes copper and copper alloys (copper, brass, bronze, cupronickel); the metal is dissolved and the tube wall thins |
Moisture is never zero | Industrial ammonia systems always carry some water; the reaction does not need much |
Stress corrosion cracking | Copper alloys under stress in ammonia atmospheres crack — a known failure mechanism |
System contamination | Dissolved copper deposits elsewhere in the plant |
Codes and practice | Industrial refrigeration standards exclude copper-bearing materials from ammonia-wetted parts |
This is why every component in an ammonia plant that the refrigerant touches — evaporators, condensers, vessels, piping, valves — is carbon steel, stainless steel or aluminium.
Both are correct for ammonia; the choice is driven by hygiene, cost and mechanical requirements.
Criterion | Stainless steel tube (304 / 316L) | Aluminium tube |
|---|---|---|
Ammonia compatibility | Excellent | Excellent |
Food-grade / washdown | Preferred — 316L resists cleaning chemicals and chlorides | Acceptable with care; softer and more easily damaged by aggressive cleaning |
Mechanical strength | High — thinner wall for the same pressure; robust in blast freezers | Lower — thicker wall; lighter unit |
Weight | Heavier | Lighter |
Heat transfer | Lower conductivity than aluminium, offset by thin wall | Good |
Cost | Higher | Lower |
Fin bonding | Mechanical expansion or brazing to Al/SS fins | Aluminium fin on aluminium tube — single metal, good galvanic balance |
Typical CSTHEATEXCHANGER use | Food processing, IQF, spiral freezers, blast freezers, any washdown environment | Large cold stores without washdown where weight and cost dominate |
From our Ammonia Evaporator, Stainless Steel Evaporator and Blast Freezer Unit Cooler pages:
Capacity range: 9.8 kW to 122 kW per unit in the standard ammonia evaporator range (capacity figures stated for R404A-equivalent rating); larger industrial units to drawing.
Tube material options: stainless steel, aluminium — and, for other refrigerants only, copper, Cu-Ni, brass, titanium. For ammonia we specify stainless or aluminium.
Tube diameters: 5, 7, 7.94, 9.52, 11.5, 12, 12.7, 15, 15.8, 20 and 25 mm; smooth, thick-walled, grooved or super-grooved; multi-circuit connection.
Stainless evaporator coil: small-diameter spiral SS316L tube for high efficiency.
Fins: aluminium, coated aluminium, stainless steel, titanium or hot-dip carbon steel; 0.1–2 mm; wave, flat or louvred; E-coating, aluminium epoxy or hydrophilic coating.
Casing: aluminium-zinc coated plate, electrostatic powder-coated plate or 304 stainless steel plate.
Fans: external-rotor motors, high efficiency and low power; totally enclosed.
Drain pan: double-wall insulated.
Design: direct oil return and counter-current circuiting; suited to pumped-liquid (overfeed) ammonia as well as DX; hot-gas defrost provisions.
Applications: blast freezers, blast chillers, processing facilities, cold stores, carcass chilling, refrigerated ship holds — designed for energy efficiency, food safety and reliability in extreme applications.
Food contact area or washdown? → Stainless steel 316L tubes, stainless or coated fins, 304 stainless casing.
Blast freezer or IQF with mechanical knocks and ice loading? → Stainless steel.
Large dry cold store, weight on a long ceiling span, tight budget? → Aluminium tube and fin.
Chlorides or cleaning chemicals in the air? → 316L stainless, including fins if severe.
Pumped-liquid ammonia at high recirculation rate? → Either; stainless preferred for pressure margin.
We state the chosen material and the reason on the drawing we send for approval.
No. Moisture is never zero in an industrial ammonia plant, and copper alloys also suffer stress corrosion cracking in ammonia. Use stainless steel or aluminium.
304 is fine for ammonia itself. 316L is chosen where chlorides, food acids or cleaning chemicals attack the outside of the coil — which is most food plants.
Yes, when wall thickness and fin bonding are designed correctly. They are lighter and cheaper; stainless is preferred where washdown or mechanical robustness matters.
Aluminium or coated aluminium for most duties; stainless steel fins for the most aggressive environments.
The evaporators must be replaced with stainless or aluminium units; we build them to the existing mounting and footprint where possible.
Send CSTHEATEXCHANGER your room temperature, cooling load, ammonia feed method (DX or pumped), hygiene requirements and mounting details. We will specify stainless steel or aluminium with the reason, size the evaporator and return a drawing for approval.
Email: info@cstheatexchanger.com
International business: +86 0519 8878 2189
Website: https://www.cstheatexchanger.com/
CSTHEATEXCHANGER — ammonia evaporators in the metals ammonia allows.
