The new heat exchanger technology reprinted abroad
Read the number：(2786) Time：2014/3/9 11:26:09
The new heat exchanger technology reprinted abroad
Foreign market survey showed that the heat exchanger shell and tube heat exchangers 64%. Although the competitiveness of various plate heat exchanger on the rise, but the shell and tube heat exchangers will dominate. With the development of power, petrochemical industry, the device continues toward high temperature, high pressure, large-scale direction. The heat exchanger in the structure, there are many new developments. Now it features several new heat exchanger as outlined below:
A pneumatic spray finned tube heat exchanger
Proposed a sophisticated method of Russia, i.e. pneumatic spraying, to improve the performance of the fin surface. Its essence is the use of high-speed fluid containing particles of cold or slightly warm to the fin surface spray powder particles. This method not only can be sprayed with the metal alloy and the ceramic coating can (metal ceramic composites) to obtain various surface properties.
In practice, typically the bottom surface of the contact resistance of the fin is one factor limiting the fin tube installation. To assess the finned tube heat exchanger elements studied. Test was adopted in ac-fin surface coating of aluminum, and alumina added 24a white electric stove. The obtained experimental data collated, you can evaluate the underside of the fin contact resistance.
The study of the fin efficiency and calculation data for comparison, the conclusion is: no substantial impact efficiency contact resistance pneumatic spray the underside of the fins. To confirm this, but also on the base (tube) and surface (fin) transition zone were metallurgical structure analysis.
The transition zone specimen analysis showed that all the rigor of micro-cracks on the entire length of the border connections. Therefore, promoting the formation of branched pneumatic spray boundary surface interacting with the base, to facilitate penetration of the powder particles to the substrate, which shows a high adhesion strength, and physical contact is formed of metal chains.
Thus not only can be used for pneumatic spraying molding, can also be used for manufacturing the conventional method will be fixed on the surface of the fin tube heat exchanger, can also be used to supplement the ordinary reinforcement of the bottom surface of the fin. It can be expected in a compact and efficient pneumatic spraying production of heat exchangers, will be widely used.
Second, the helical baffle heat exchanger
In shell and tube heat exchangers, shell is usually a weak link. Usually normal segmental baffles can cause tortuous flow channel system (z-shaped flow channel), this will result in a larger dead and a relatively high backmixing. These dead shell can cause increased fouling of heat transfer efficiency disadvantage. Backmixing also make the average temperature distortion and out. As a consequence, compared with piston flow, segmental baffles will reduce net heat. Superior segmental baffle shell and tube heat exchanger efficiency is difficult to meet the requirements, it is often replaced by other types of heat exchangers (such as compact plate heat exchanger).
Ordinary baffle geometry improvements, is the first step in the development of the shell. Although the introduction of such seals and additional partial transition flow plate and take other measures to improve the performance of the heat exchanger, but the main drawback of the ordinary baffle design still exists.
To this end, the United States proposed a new plan, which proposes using a spiral baffle. This design has been confirmed by the advanced nature of fluid dynamics and heat transfer research results, this design has been patented. The main disadvantage of this structure to overcome the ordinary baffle.
Helical baffle design principle is simple: the special panel mounted circular cross-section, "intends helical baffle system", each baffle heat exchanger shell accounts for a quarter of the cross section, its inclination toward the axis of the heat exchanger, which maintained a tilt axis of the heat exchanger. Surrounding the adjacent baffle phase, with a continuous spiral outer office. Axially overlapping baffles, support tubes To narrow span, double spiral design can be obtained.
Helical baffle structure to meet the relatively wide process conditions. This design has a great deal of flexibility for different operating conditions, select the best helix angle; may overlap each case selected baffle or baffles double helix structure.
Third, the new twist tube heat exchangers
Swedish alares developed a flat tube heat exchanger, often referred to twist tube heat exchanger. Houston Brown company made improvements. Flat spiral pipe manufacturing process includes a "flattening" and "hot twist" the two processes. The improved twist tube heat exchangers with traditional shell and tube heat exchangers as simple, but there are a lot of exciting progress, it gained economic techniques are as follows: the improved heat transfer, reduced fouling, true countercurrent reduce the cost, no vibration, saves space, no baffle element.
Due to the unique structure makes the tube and the tube shell in a spiral motion while promoting the degree of turbulence. The overall heat transfer coefficient of 40% compared to conventional heat exchangers, and pressure drop is almost equal. Flat spiral tube may also be mixed with the light pipe heat exchanger when assembling manner.
The heat exchanger manufactured in strict accordance with asme standards. Any use of the shell and tube heat exchangers and can be used to replace traditional devices such heat exchangers. It can get the best value of the ordinary shell and tube heat exchangers and plate and frame heat transfer equipment acquired. Estimates have broad application prospects in the chemical, petrochemical industry.
Fourth, non-reinforced pipe brazing wire around the spiral heat exchanger
Wire wound on the tube as the ribs (fins) of the spiral heat exchanger (ta), usually by welding the wire fixed on the tube. However, this method has a number of effects on the quality of the entire apparatus, as will brazing heat from the "net" a large part of the surface of the tube and the wire. More importantly, because the solder can cause rapid aging and broken machinery and equipment clogging, followed earlier reported loss.
Russian manufacturers recommend a new approach tendons around the wire tube that produced by mechanical contact with the wire tension during winding and on the pipe to fix ribs. This method can facilitate the use of continuous nature (ie wire securely fixed on the pipe, over the cross section of the tube without pressing) to obtain brazing, so do the just cut off the metal wire can be considered as representing the brazing more popular approach. However, if the use of wire as ribs (fins) to increase the heat transfer area, and only when the effective heat transfer surface non-brazed ribs not less than brazed connection, it should be more emphasis on this method.
Tests showed that when the wire is in linear contact with the tube, the maximum effective heat transfer surface, but this time the wire will slide along the tube. So the key is to select the best contact width, that is, when the wire around the tube deformation traces width. Thus, the effective heat transfer surface than the non-brazing Brazing large.
