用于锅炉热交换器的 ASTM 标准缠绕式 L 型翅片管

KL Type Finned Tube for Heat Exchanger

KL type finned tube is a kind of knurled finned tube. Before winding the fins， knurl patterns on the base tube， or add a blade to the winder， knurl on the base tube， and use the back blade A finned tube made by winding， knurling and winding at the same time.

The KL Type Finned Tube relies on maximum surface contact between the fins and the tube， which is ensured by the tension of the fin strips helically forming around the pre-knurled tube， providing improved bonding and heat transfer. The maximum working temperature of KL Type Finned Tube can reach 250°C， and the maximum working pressure can reach 3.2MPa.

LL Type Finned Tube for Heat Exchanger

Type LL finned tube is a finned tube in which the fin feet are preformed into an LL shape (overlapping LLs) and a strip of aluminum fins or copper fins is applied to the base tube under tension. However， the feet are pre-formed so that one foot overlaps the other， increasing the base tube protection and thermal contact area of ​​the finned tube. LL Type Finned Tube is usually used in steam coils， air pre-heaters.， the maximum operating temperature can reach 180 °C.

The "LL" shaped fin design features interlocking fins that are twisted together to prevent movement and separation. The fins protect the entire tube， the smooth flat fins with "LL" shaped fins perpendicular to the surface of the seamless steel tube tube provide very low resistance to air/gas flow and ensure that fouling is kept to a minimum. The bottom of the fin is in contact with the base tube and provides a complete jacket over the length of the fin. Hence the name applies to applications where corrosion is a factor. This LL Type Finned Tube is often used as a replacement for more expensive extruded fins in corrosive environments.

优势

Transferring heat from a hot fluid into a colder fluid through a tube wall is the reason many of us use finned tubes.

But you may ask， what is the major advantage of using a finned tube? Why can’t you just use a regular tube to make this transfer? Well you can but the rate will be much slower.

如果不使用翅片管，外表面积就不会明显大于内表面积。因此，传热系数最小的流体将决定总传热率。当管内流体的传热系数比管外流体的传热系数大几倍时，通过增大管子的外表面积就可以大大提高整体传热率。

翅片管增加了外表面积。通过安装翅片管，可以提高整体传热率。这就减少了特定应用所需的翅片管总数，从而也缩小了设备的整体尺寸，从长远来看可以降低项目成本。在许多应用案例中，用一根翅片管替代六根或更多根裸管，成本不到原来的 1/3，体积不到原来的 1/4。

在涉及热流体通过管壁向冷流体传热的应用中，需要使用翅片管。通常，在空气热交换器中，其中一种流体是空气或其他气体，空气侧的传热系数会低很多，因此额外的传热表面积或翅片管交换器非常有用。翅片管式换热器的总体流动模式通常是横流，但也可以是平行流或逆流。

翅片管用于增加换热管的有效表面积。此外，当管子外侧的传热系数明显低于内侧的传热系数时，也会使用翅片管。换句话说，热量从液体传递到气体，从蒸汽传递到气体，如蒸汽-空气热交换器和热流体-空气热交换器。

The rate at which such heat transfer can occur depends on three factors – [1] the temperature difference between the two fluids; [2] the heat transfer coefficient between each of the fluids and the tube wall; and [3] the surface area to which each fluid is exposed.