The analysis of the samples in the transition zone shows that there are no dense microcracks on the whole connection boundary. Therefore, the pneumatic spraying method can promote the interaction between the surface and the matrix to form branch boundaries, and can promote the penetration of powder particles into the matrix, which shows that the adhesion strength is high, and there is physical contact and metal chain formation. Therefore, pneumatic spraying can be used not only for molding, but also for fixing the fins manufactured by ordinary methods on the surface of heat exchange tubes, and also for supplementing and strengthening the bottom of ordinary fins. It can be predicted that pneumatic spraying method will be widely used to produce compact and efficient heat exchangers. In shell-and-tube heat exchangers, the shell side is usually a weak link. Usually, the common arch baffle will cause a tortuous flow channel system (tortuous flow channel), which will lead to a large dead angle and a relatively high backmixing. These dead corners will aggravate the scaling on the shell side, which is unfavorable to the heat transfer efficiency. Backmixing can also distort and reduce the average temperature difference. Therefore, the arch baffle will reduce the net heat transfer compared with plug flow. Shell-and-tube heat exchangers with superior bow baffles are difficult to meet the requirements of high thermal efficiency, so they are often replaced by other types of heat exchangers (such as compact plate heat exchangers). Improving the geometry of ordinary baffles is the first step to develop shell side. Although measures such as sealing strip and additional baffle are adopted to improve the performance of heat exchanger, the main shortcomings of ordinary baffle design still exist.
Therefore, the United States put forward a new scheme, that is, it is suggested to adopt spiral baffles. The advanced design has been confirmed by the results of fluid dynamics research and heat transfer test, and has been patented. This structure overcomes the main shortcomings of ordinary baffles. The design principle of spiral baffles is very simple: a special plate with circular section is installed in the "quasi-spiral baffle system", each baffle accounts for a quarter of the cross section of the shell side of the heat exchanger, and its inclination angle is towards the axis of the heat exchanger, that is, it keeps an inclination angle with the axis of the heat exchanger. The peripheries of adjacent baffles are connected and form a continuous spiral shape with the excircle. The baffles overlap axially, and if you want to reduce the span of the support tube, you can also get a double helix design. The spiral baffle structure can meet a wide range of process conditions. This design has great flexibility, and the best spiral angle can be selected according to different working conditions. Overlapping baffle or double spiral baffle structure can be selected respectively. A flat tube heat exchanger, usually called twisted tube heat exchanger, has been developed by Alares Company in Sweden. The Brown Company in Houston, USA, made improvements. The manufacturing process of spiral flat tube includes two processes: "flattening" and "hot twisting" The improved twisted tube heat exchanger is as simple as the traditional shell-and-tube heat exchanger, but there are many exciting progress. It has achieved the following technical and economic benefits: improving heat transfer, reducing scaling, real countercurrent, reducing cost, no vibration, saving space and no baffle elements.
Due to the unique structure of the tube, the tube side and shell side are in spiral motion at the same time, which promotes the degree of turbulence. The total heat transfer coefficient of the heat exchanger is 40% higher than that of the conventional heat exchanger, and the pressure drop is almost equal. When assembling heat exchanger, spiral flat tube and smooth tube can also be mixed. The heat exchanger is manufactured in strict accordance with asme standards. This kind of heat exchanger can be used to replace all shell-and-tube heat exchangers and traditional equipment. The best value that can be obtained by ordinary shell-and-tube heat exchanger and plate-and-frame heat transfer equipment can be obtained. It is estimated that it has broad application prospects in chemical industry and petrochemical industry. spiral plate heat exchanger
spiral plate heat exchanger
The heat transfer element is a heat exchanger composed of spiral plates.
Spiral plate heat exchanger is an efficient heat exchange equipment, which is suitable for steam-steam, steam-liquid and liquid-liquid heat transfer. Suitable for chemical industry, petroleum, solvent, medicine, food, light industry, textile, metallurgy, steel rolling, coking and other industries. According to the structural form, it can be divided into non-detachable spiral plate heat exchangers (type ⅰ) and detachable spiral plate heat exchangers (types ⅱ and ⅲ).
Structure and performance of spiral plate heat exchanger
1. The equipment consists of two coils, forming two uniform spiral channels. The two heat transfer media can flow in full countercurrent, which greatly enhances the heat transfer effect. Even two kinds of medium with small temperature difference can achieve ideal heat transfer effect.
2. The nozzle on the shell adopts tangential structure, and the local resistance is small. Because the curvature of the spiral channel is uniform, the liquid flowing in the equipment has no big turning point, and the total resistance is small, so the design flow can be improved and it has high heat transfer capacity.
3. The end face of spiral channel of type I non-removable spiral plate heat exchanger is sealed by welding, which has good sealing performance.
4. The structural principle of Type II detachable spiral plate heat exchanger is basically the same as that of non-detachable heat exchanger, but it can be disassembled and cleaned in one channel, which is especially suitable for heat exchange of viscous and precipitated liquids.
5. The structural principle of type Ⅲ detachable spiral plate heat exchanger is basically the same as that of non-detachable heat exchanger, but its two channels can be disassembled and cleaned, and its application range is wide.
6. When a single device cannot meet the use requirements, multiple devices can be used in combination, but the following requirements must be met when combining: parallel combination, series combination, and the same distance between devices and channels. Mixed combination: one in parallel and one in series.