Micro-channel aluminium tube, also called multi-port extruded (MPE) or flat multi-port tube, is a thin, flat extrusion with a row of small parallel channels for refrigerant or coolant. Brazed to louvred fins and headers, it forms compact all-aluminium condensers, evaporators, heat pumps and battery cooling plates. Metline supplies micro-channel tube to drawing, bare, zinc-coated or flux-coated, in coils or cut lengths, worldwide.
A micro-channel tube looks like a thin flat strip, but inside it carries a row of small ports separated by thin webs. The ports give a large internal surface for the fluid, the webs hold the tube together under pressure, and the flat outer faces give a broad, flat contact for brazed fins. Hydraulic diameters are typically around one millimetre or less, which is where the name comes from.
Micro-channel heat exchangers (MCHX) were first adopted for automotive air-conditioning condensers and are now common in residential and commercial HVAC, heat pumps, chillers, refrigerated transport and electric-vehicle thermal systems. Compared with round-tube plate-fin coils, they hold much less refrigerant, weigh less, take less depth and are made from a single metal, which simplifies recycling and removes galvanic corrosion between tube and fin.
Most micro-channel tube is extruded from rod or billet, then coated and coiled in one continuous line. A folded alternative is made from clad sheet; it uses a different route and is compared in our folded vs extruded micro-channel article. This page covers extruded multi-port tube.
Micro-channel tube is always made to a drawing, because every heat exchanger design has its own port layout. The outer envelope sets fin and header fit; the port geometry sets heat transfer, pressure drop and burst strength. Treat them as two separate sets of requirements.
| Parameter | Typical range | Design effect |
|---|---|---|
| Tube width | About 12 – 32 mm for most HVAC and automotive tubes; wider tubes for special designs | Matches fin depth and header slot |
| Tube height (thickness) | About 1.3 – 2.5 mm | Sets fin contact; usually the most critical tolerance |
| Number of ports | Roughly 8 – 30 or more, depending on width | More ports raise area and strength, and pressure drop |
| Port shape | Rectangular, round, D-shaped or with internal micro-fins | Affects heat transfer and burst resistance |
| Outer wall and web thickness | Typically a few tenths of a millimetre | Set by burst pressure and corrosion allowance |
| Cut length | To coil design; tubes are often cut to length in-line | Length tolerance affects header assembly |
Ranges are indicative of common designs, not supply limits. Wider, ultra-wide and high-pressure tubes (for CO2 / R744 systems) are made to specific designs and need die and burst validation.
The tube alloy must extrude into very thin webs at high speed, survive brazing at about 600 °C and resist corrosion in service. Lean manganese 3102 and commercially pure 1100 or 1050 extrude most easily; long-life alloys add controlled amounts of manganese, copper or zinc to make the tube more noble than the fins and slow pitting.
| Element (wt %) | 3102 | 1100 | 3003 |
|---|---|---|---|
| Silicon (Si) | ≤ 0.40 | Si + Fe ≤ 0.95 | ≤ 0.60 |
| Iron (Fe) | ≤ 0.70 | (see Si) | ≤ 0.70 |
| Copper (Cu) | ≤ 0.10 | 0.05 – 0.20 | 0.05 – 0.20 |
| Manganese (Mn) | 0.05 – 0.40 | ≤ 0.05 | 1.0 – 1.5 |
| Zinc (Zn) | ≤ 0.30 | ≤ 0.10 | ≤ 0.10 |
| Aluminium | Remainder | ≥ 99.00 | Remainder |
A thin layer of zinc is sprayed onto the flat faces in-line, commonly a few g/m² up to about 10 g/m². During brazing it diffuses into the surface, making the outer skin sacrificial, so corrosion spreads sideways rather than through the wall.
A non-corrosive potassium fluoroaluminate flux, sometimes mixed with silicon or filler powder, is applied to the tube. It removes the need to flux the core before brazing and can supply filler metal for tube-to-fin joints.
Uncoated tube for designs where fins and headers carry the filler and the coil is fluxed after assembly, or where the environment is benign.
Because brazing anneals the tube, design strength is the post-braze (O-temper equivalent) strength, not the as-extruded value. Burst pressure, fatigue under pressure cycling and resistance to port collapse should all be checked on brazed samples.
Agree which dimensions are production acceptance limits and which are design targets still being developed, especially for a new die.
When a substitute tube is offered, approve samples on your real brazing line before accepting it. Two tubes with the same envelope can behave very differently in brazing, burst and corrosion if the port layout, alloy or coating differ.
| Factor | Micro-channel (MCHX) | Round-tube plate-fin (RTPF) |
|---|---|---|
| Refrigerant charge | Substantially lower | Higher |
| Weight and depth | Lower | Higher |
| Materials | All aluminium | Copper or aluminium tubes with aluminium fins |
| Air-side pressure drop | Low with louvred fins | Moderate |
| Manufacturing | Brazing furnace; high capital cost | Mechanical expansion; established lines |
| Field repair | Difficult | Easier |
| Evaporator condensate drainage | Needs careful design | Good |
Manufacturers keeping their fin-and-tube lines often move to inner-grooved aluminium tube first; those designing a new compact coil generally choose micro-channel.
Most commonly 3102, 1100 or 1050, which extrude easily into thin webs, plus long-life 3xxx alloys designed to resist pitting. The alloy is chosen together with the fin and header alloys so that the tube stays more noble than the fins.
Zinc sprayed on the flat faces diffuses into the surface during brazing and makes it sacrificial. Corrosion then spreads sideways along the surface instead of pitting through the thin wall, which extends coil life in coastal and polluted air.
Extruded tube is pushed through a die from a single alloy, with ports formed by the die. Folded tube is formed and brazed from clad sheet. Extruded tube dominates HVAC; folded tube is used in some automotive and high-performance designs.
By controlled atmosphere brazing in nitrogen at about 590 – 610 °C with a non-corrosive flux. The Al-Si cladding on fins and headers melts and forms all joints in a single furnace pass.
Yes, with designs made for it: smaller, rounder ports, thicker webs and validated burst performance. Standard HVAC tube is not automatically suitable; ask for a design and burst test on brazed samples.
Yes. Metline supplies micro-channel tube in coils for in-line cutting or as cut lengths, bare or coated, with test records, to customers worldwide.
Send your tube drawing, coating and volumes. We will reply with feasibility, test plan, packing and a delivered price.
