The structural design of the heat exchanger is a topic that energy engineers are talking about every day. A common problem faced by design engineers is: dirt, the "external matter" that accumulates in the heat exchanger tubes and hinders heat exchange. How can we minimize the impact of dirt problems?
The rational design and proper installation of the heat exchanger allows it to transfer a certain amount of heat from one liquid medium to another. However, unfortunately, this heat transfer cannot be kept constant: no medium is pure, many can no longer be crystallized, and the accumulated dirt pollutes the inner surface of the heat exchange equipment, which seriously hinders the transfer of heat energy. In order to remove these accumulated dirt, the heat exchange device must be shut down periodically. The problem is: how to minimize dirt.
Reduced fouling by turbulence In a tubularly connected heat exchanger, the built-in wire cleaning device reduces, or prevents, the deposition of dirt inside the pipe simply, efficiently, and at low cost. According to GEA Renzmann & Grünewald. This built-in wire cleaning device can be a spiral wire that can perform different metal strength properties depending on the need for pipe cleaning. It uses the flow energy of the medium being conveyed skillfully when cleaning the dirt inside the pipe. An important feature of this active built-in cleaning system in the heat exchange transfer line of the layered flow medium is that the movement of the wire inside the pipe also significantly promotes the heat exchange capacity of the heat exchanger, according to the manufacturer. Can increase efficiency by 45%.
Plate heat exchangers that can be cleaned in batches Electro-polished descaling methods can also be used in plate heat exchangers. In electropolishing, a thin layer of metal can be removed from the metal surface. The thickness of the removed metal layer can be accurately controlled. Generally, the thickness of each layer is 5 to 50 μm. According to AKK, in the heat exchanger of stainless steel, the thickness of the metal layer removed each time is 25 μm. The advantage of this descaling method is that the electrochemical polishing of the metal surface can reduce the formation of deposits, improve corrosion resistance, and extend the service life of the stainless steel plate. Since the descaling cleaning is performed by the conveyed medium, the flow rate of the plate heat exchanger can also be increased.
When the traditional plate heat exchanger reaches its service life, GEA Ecoflex's free-flow plate heat exchanger is an ideal replacement for its “older generationâ€. The most important feature of the free-flowing plate heat exchanger is that there is a large flow cross-sectional area between the heat exchange plates, and each heat exchange plate has a thick wave shape. The spacing between the individual heat exchange plates can be adjusted by selecting different types of heat exchange plates. The free-flowing plate heat exchanger is suitable for liquid media containing solid particles or containing crystals, as well as pulp-containing or similar viscous media. It guarantees no blockage. According to the manufacturer, the efficiency of the plate heat exchanger is much higher than other types of heat exchange devices.
Alfa Laval has developed an Alfa Cond series of plate heat exchangers that are suitable for heat exchange in low pressure steam condensation in evaporators and distillation systems. Due to the very good heat exchange performance of the device, its volume is also very compact, saving a lot of money in the purchase of low-pressure condensing heat exchange equipment. Compared with the tube condenser, due to the higher velocity of the turbulent flow in the channel, the scale accumulation in the water chamber is significantly reduced. Due to the reverse circulation principle, the gas which cannot be condensed can be well cooled.
Applications of Polymeric Plastics Generally, plastics have poor thermal conductivity and their thermal conductivity is about one-seventh that of steel. However, considering that plastic has self-cleaning properties against the deposition of substances, it can reduce the accumulation and encrustation of dirt, or the original intention of using plastic materials, especially plastics have good resistance to corrosive media, which is also the choice of plastic materials. The main reason for the time.
The heat exchangers produced by Polytetra use polymer plastics such as polytetrafluoroethylene PITE, PFA, polychlorotrifluoroethylene PCTFE and polyvinylidene fluoride PVDF. Its product range is as small as a heat exchanger with a heat dissipation area of ​​only 0.1m2 in the laboratory, and a giant heat sink with a heat dissipation area of ​​100 m2. The company also produces specialty heat exchangers, such as SiC tube heat exchangers. This is a heat exchanger made of silicon carbide, which has good heat exchange performance and resistance to various chemical corrosion. The heat exchanger made of this silicon carbide material also has a very important feature: Excellent pressure resistance at high temperatures and at large temperature differences.
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The block heat exchangers produced by SGL Carbon equipment manufacturer Graphit have attracted great interest due to their flexible performance. They are suitable for heat exchange in corrosive media. The most important features are:
* Integrated form, modular structure.
* Depending on the specific product type, it can be entered from both sides.
* High thermal efficiency at low flow rates.
* Easy to maintain (easy to clean, can be replaced in one piece).
The integrated heat exchanger manufactured by Swep in the Mo- Stahl region has high corrosion resistance and resists the formation of anti-corrosion seams; it is effective against chloride stress crack corrosion. The brazing technology used in the production plant can effectively prevent the intergranular corrosion inside the material. With the integrated heat exchanger of the Swap company in Mo- Stahl, you can safely use the heat exchange device in the corrosive medium. Typical applications for exchangers are those that deal with chlorides.
Mechanical cleaning of pipes
J & W, a subsidiary of Conco Systems, is a well-known heat exchanger pipe cleaning stock service company in the United States. The cleaning equipment used is suitable for all air-cooled heat exchange units. They used a mechanical cleaning method that uses high-pressure water (21 bar) for high-speed (3 to 6 m/s) flushing. In order to remove deposits after agglomeration, the company has developed an ultrasonic cleaning device. Use dry, vibrating air waves to break up dry deposits. The flying object dust generated after crushing is sucked away by the vacuum cleaner and sent to a heat incineration device for burning.