What is an Embedded Finned Tube
Embedded finned tubes are also known as G-type finned tubes, which are a common heat-transfer component of a heat exchanger. They are manufactured by machining a spiral groove into a base tube, then embedding an aluminum or copper strip and securing it through a compression process. They offer excellent heat-transfer performance and structural stability; their applications cover air coolers, heat exchangers, and boiler economizers.
How Is Embedded Finned Tube Produced
Fin Preprocessing
Metal strips are preprocessed into fin materials using a punch press and specialized dies. The operator shall control press pressure and stroke to ensure dimensional accuracy and surface flatness. The height of burrs on the fin edges is kept below 0.1 mm to prevent loose fitting and damage to the base tube during fin embedding.
Grooving
To fabricate the groove, a mechanical cutting blade is used to cut into the surface of a rotating base tube. The groove depth typically ranges from 0.25 mm to 0.50 mm. The grooving precision directly affects the next step—fin embedding tightness.
Fin Embedding
While rotating the base tube, a pre-processed metal strip (typically aluminum 1060/1100 or copper) is wound and embedded into the pre-machined groove. It is important to maintain constant tension during the embedding process to achieve an even depth of fin root embedding.
Mechanical Locking
As the fin is embedded, the displaced part of the base tube during the grooving process is pressed back into position by a trailing pressure roller, which means the base of the fin is locked mechanically.
The finished embedded fin tube will be cleaned and tested, including degreasing and cleaning, and inspection and checking the fin embedding (pull-out resistance), and the uniformity of the fin pitch must be inspected.
Flexible Material Options for Base Tube and Fin
Same as other fin tubes, base tube material options are carbon steel, stainless steel, copper, alloy, titanium; fin materials are aluminum (economical with good thermal conductivity), copper (high heat transfer efficiency), or stainless steel (high-temperature resistance).
Customers can have a customized design of base tube and fins to produce embedded finned tubes for their specific applications at AGICO.
Feature: An embedded fin tube offers enhanced heat transfer efficiency with a stable mechanical bond between fin and the base tube; it can offer good corrosion resistance and long service life when using copper and stainless steel materials. AGICO always offers you cost-effective fin tube solutions to save your investment.
Embedded Finned Tubes vs Wrapped Finned Tubes
Embedded and wrapped finned tubes (L-type/LL-type/KL-type) are the 2 most common fin tube types used in industrial heat exchangers. As the name implies, their different bonding methods of the fin have a major impact on the final applications over working temperature and other performance metrics. Here are the details:
- Working Temperature Resistance
Embedded (G-type) Fin Tube: Its fin is “locked” into a groove; the bonding structure does not loosen due to thermal expansion at high temperatures. Embedded fin tubes’ working temperatures can reach 400°C–450°C.
Wrapped (L-type) Fin Tube: Fin bonding is realized by welding at the tube ends. When high temperatures cause thermal expansion, it creats a gap between the fin and the base tube. It has a relatively smaller working temperature range below 130°C–150°C. - Heat Transfer Efficiency
Embedded (G-type): It has high and stable heat transfer efficiency due to its stable bonding structure; because the contact area doesn’t change, its operating performance remains stable during long-term operation.
Wrapped (L-type) Fin Tube: High initial efficiency but reduces over time. With long-term use or temperature fluctuations, the fin part will loosen slightly, reducing the contact area and leading to low heat transfer performance. - Corrosion Resistance
Embedded (G-type) Fin Tube: Although metal backfilling offers a solid structure of the fin tube, the root of the groove is still very easily rusted.
Wrapped (L/LL-type) Fin Tube: The wrapped fin tube has no damaged base tube, so it offers better corrosion resistance. The LL-type fin tube features a fin foot that completely covers and overlaps the base tube, creating a “protective layer” that effectively avoids atmospheric corrosion. - Cost and Maintenance
Embedded Fin Tube: Its manufacturing cost is higher for slower processing speeds while offering a long service life and low maintenance costs.
Wrapped-type (L-shaped) Fin Tube: It has a low manufacturing cost; this type of fin tube is suitable for medium-to-low-temperature environments. When used under extreme operating conditions, it is required to be frequently replaced.
How to Select – Embedded Fin Tube or Wrapped Fin Tube
The key to selecting a finned tube type is its working temperature; embedded fin tubes are suitable for medium temperatures exceeding 150°C, while wrapped fin tubes are designed for temperatures below 120°C. Besides temperature, check the following instructions as a guide for choosing fin tube:
Choose Embedded (G-type)
- The equipment is subject to severe thermal shock and high operating temperatures (up to 400°C).
- Long-term stability of heat transfer performance is critical.
- The operating environment is harsh, involving high pressures or mechanical vibrations.
Choose Wrapped (L/LL-type) fins:
- Initial investment cost (unit cost) is a primary concern.
- The environment is highly corrosive but the operating temperature is relatively low (below 150°C).
- Applications involve standard commercial HVAC or light industrial heat recovery.
