Titanium and titanium alloys
Titanium finned tube is a type of heat exchange device material. In order to improve the heat transfer efficiency of titanium tubes, fins are usually machined on the surface of the titanium heat exchange tube to increase the outer surface area (or inner surface area) of the heat exchange tube, thereby achieving the goal of improving heat transfer efficiency.
1、 Performance indicators of titanium finned tubes
As a heat exchange element, titanium finned tubes work in high-temperature flue gas conditions for a long time. For example, finned tubes used in boiler heat exchangers are used in harsh environments, with high temperature and pressure, and are in a corrosive atmosphere. This requires finned tubes to have high performance indicators, usually including the following points:
1) Anti corrosion performance
2) Anti wear performance
3) Low contact resistance
4) High Stability
5) Ability to prevent dust accumulation
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2、 The processing technology of titanium finned tubes
3-roll oblique rolling integral spiral finned tube
The production principle of a 3-roll oblique rolling integral spiral finned tube is as follows: a core rod is lined inside the smooth tube, and driven by the rotation of the rolling blade. The titanium tube is processed into fins on its outer surface through the hole cavity composed of the rolling groove and the core head. The finned tubes produced by this method have a high heat transfer efficiency as the base tube and outer fins are an organic whole, so there is no problem of contact thermal resistance loss. Compared with the welding method, the 3-roll oblique rolling method has the advantages of high production efficiency, low raw material consumption, and high heat exchange rate of the produced finned tubes.
At present, the 3-roll oblique rolling technology for integral spiral finned tubes has been successfully applied to titanium low finned tubes; At present, titanium finned tubes are commonly seen in the market as low finned tubes, while integral high finned tubes are mostly made of materials such as aluminum and copper, and are generally formed by cold rolling.
3、 Performance advantages of titanium finned tubes
The heat exchanger made of titanium finned pipes has the characteristics of resistance to seawater corrosion and acid corrosion. The superior heat transfer capability of titanium finned tubes, combined with high-density and low fin design, can reduce the size of heat exchangers and improve their performance. Seawater is an inexhaustible source of cooling water for offshore petrochemical facilities. When selecting the material of the heat exchanger, it is necessary to understand the corrosiveness of seawater to it. Under the action of seawater, copper nickel alloy pipes or carbon steel pipes will gradually corrode, while titanium finned pipes have unique properties such as high strength, excellent corrosion resistance, and long-lasting resistance to seawater erosion.
Under the same thermal load conditions, titanium finned tubes possess both the superior physical properties of titanium materials and the high heat transfer capacity of finned tubes. Its length is only half that of a regular bare tube. This technology can be applied to equipment modification and manufacturing conditions of new equipment.
At the same investment as ordinary pipes, heat exchangers made of titanium low finned tubes have smaller dimensions, lower maintenance costs, and can improve the working condition of the heat exchanger and extend its service life. Due to its passivity to seawater, titanium material can resist erosion, corrosion, scaling, and rusting. Compared with materials that are prone to corrosion, titanium finned pipes can effectively prevent scaling on the tube side. The surface of titanium metal will form a tough oxide film (mainly TiO2). When it is mechanically damaged, it can form a new oxide film in an oxidizing environment. This tough and smooth film enables the titanium tube to increase the flow rate of seawater on the tube side, while also resisting impact, turbulence, erosion/cavitation, and physical damage, as well as preventing pitting corrosion by chloride ions and crevice corrosion caused by seawater bacteria.
The strength to weight ratio of titanium material is large, which reduces the thickness of the pipe wall and greatly saves raw materials. To achieve better heat exchange function, the inner diameter of the finned tube should be smaller to allow for a higher speed and a larger amount of seawater to pass through (as long as a higher pressure drop is allowed in the application). The magnitude of the pressure drop can be limited by the appropriate design of the inner diameter and length of the finned tube.
The overall high-density low finned tube has a fin height of 0 022-0.032 inches, with a fin density of 30-40 fins per inch. Compared to the bare tube, the surface area of the outer side of the finned tube cooled by seawater increases by three times. In areas where bare tubes waste heat transfer potential on the tube side, a larger surface area can balance heat exchange between the shell side and the tube side.
Increasing the heat transfer area on the shell side can reduce the length of the heat exchange tube by half. Other benefits of having a larger surface area on low finned tubes are:
(1) Reduce the pressure on the shell side of the heat exchanger to half of the bare tube.
(2) Reduce the size of the heat exchanger by 50%.
(3) Can reduce the number of required heat exchangers.
In situations where equipment spacing is very important, smaller heat exchangers can adapt to smaller intervals. Small intervals can reduce the layout size, making inspection and maintenance easier to operate.
In addition to reducing the tube bundle by half, thinner fins are better. Titanium fins enhance the strength of the tube, providing greater flattening, pressure, and resistance to damage during installation and transportation. Experiments have confirmed that non finned sections with thicker fin areas have greater resistance to pitting and flattening. Similarly, the internal blasting pressure is relatively high.
4、 Work and maintenance of titanium finned tubes
Titanium finned tubes can reduce the tendency of scaling on the shell side. When cooling crude oil or gasoline with a tendency to scale, the fouling rate of finned tubes is relatively slow and has a tendency to self clean. The deposited impurities and rust debris will not uniformly adhere to the surface of the fins. If rust is generated, it is easy to break and remove using traditional cleaning methods. If there are some very sticky impurities that may adhere to the fins, the time required to remove them is only about one tenth of that of the bare tube.
5、 Order instructions for titanium finned tubes
1. Clarify the material grade
2. Clarify specification drawings
3. Clarify the operating conditions
4. Payment settlement or weighing settlement
5. The processing cycle shall be based on the quoted construction period
If you have any questions about the above details, please contact Manager Su at 15353005227 (same WeChat account)
