Double H HH Finned Tube for Boilers Economizer

What is an HH-type finned tube/Double H-type finned tube?

An HH-type finned tube, also known as a rectangular finned tube, is a special type of H-shaped finned tube consisting of two tubes. It is formed by symmetrically welding two steel plates to the tube wall along a central arc to create fins. The front ends of the fins are shaped like double “H,” hence the name HH-type finned tube. HH-type finned tubes are highly effective in recovering waste heat from power plant boilers, industrial boilers, industrial kilns, and marine power plants.

H/HH Type Fin Tube Specifications

Material Combinations

• ‌Fin Material‌:

  • C.S. (most common grade: Q235B)
  • S.S. (most common grades: AISI 304, 316, 409, 410, 321, 347, 2205)
  • A.S. (most common grade: 12 CrIMoV)

• ‌Tube Material‌:

  • C.S. (most common grade: A106 Gr.B)
  • S.S. (most common grades: TP304, 316, 321, 347)
  • A.S. (most common grades: T/P5, 9, 11, 22, 91)

Applied Temperature

• 300°C

Double H Finned Tube Production

The production method for HH-type finned tubes is basically the same. The fins, formed by stamping and shearing steel plates, are manually coded and placed into an automatic unloading hopper. A feeding cylinder automatically unloads the fins. Simultaneously, the two steel tubes are transported to the welding position, where a horizontal pushing cylinder drives the electrode clamping mechanism to achieve automatic welding. The electrode clamping mechanism is a key component of the welding machine. Both electrodes are equipped with material receiving and pneumatic positioning mechanisms. Driven radially by the hydraulic cylinder, the fins automatically enter the welding position for clamping and welding, achieving welding between the fins and the steel pipe on both sides. After welding, the clamping mechanism is released, the finned tube is manually removed, and the steel pipe moves forward. Parallel automatic welding of the steel pipe and fins effectively meets the quality and efficiency requirements of finned tube welding.

Advantages of HH-type finned tubes:

1. Employing a new finned tube welding process, the fin welding area uses a multi-serrated contact, resulting in a strong weld, uniform weld shape, smooth surface, no slag inclusions or porosity, and a penetration depth of 97%.

2. The multi-serrated welding position effectively reduces the local stiffness of the finned tube, thereby reducing the amount of compressive plastic deformation during welding, lowering the longitudinal residual tensile stress near the weld, and significantly reducing the residual compressive stress in the plate far from the weld, thus significantly reducing the wavy deformation of the plate.

3. With a weld penetration of 97%, the weld surface is uniform and smooth, free of weld beads. The expanded heating surface improves the heat transfer coefficient.

4. The extended heating surface unit has a self-cleaning function, which can reduce carbon buildup, blockage, and wear on the heating surface. In particular, it reduces wear, ensuring a reasonable service life for the heating surface.

Applications of Double H Finned Tubes

1. Boiler and Heat Exchanger Components:

Double H finned tubes are widely used in utility and industrial boilers due to their excellent heat transfer performance. Double H finned tubes maximize the heated surface area, thereby improving heat transfer efficiency. In heat exchangers, double H finned tubes are key components for promoting efficient heat transfer between two fluids. Their unique design gives them a higher heat transfer coefficient and stronger resistance to thermal stress.

2. Marine Propulsion Systems:

In marine propulsion systems, double H finned tubes are used for heat recovery and efficiency enhancement. They help capture and utilize waste heat, converting it into usable energy, thereby improving the overall efficiency of the marine propulsion system. The compact design of double-H finned tubes gives them an advantage in space-constrained marine applications. They provide efficient heat transfer even in confined spaces, making them ideal for marine engines and other small machinery.

3. Power Plants and Industrial Process Equipment:

In coal-fired power plants, double-H finned tubes are used in air preheaters and economizers. They help preheat combustion air and recover heat from flue gas, thereby improving thermal efficiency and reducing emissions. In various industrial processes, double-H finned tubes are used for heating and cooling. They can withstand high temperatures and pressures and have high heat transfer efficiency, making them suitable for furnaces, ovens, dryers, and other industrial equipment.

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