WHAT YOU BETTER KNOW SHELL AND TUBE HEAT EXCHANGER

 

Types of Shell and tube heat exchanger

Shell and tube heat exchanger is also called tubular heat exchanger. It is a partition type heat exchanger with the wall surface of the tube bundle enclosed in the shell as the heat transfer surface. Shell and tube heat exchanger has simple structure, low cost, wide circulation cross section, and easy to clean scale; but it has low heat transfer coefficient and large area. It can be made of various structural materials (mainly metal materials) and can be used under high temperature and high pressure. It is the most widely used type.

Shell and tube heat exchangers include fixed tube plate steam-water heat exchangers, shell and tube steam-water heat exchangers with expansion joints, floating head steam-water heat exchangers, U-shaped shell and tube steam-water heat exchangers. Corrugated shell and tube steam-water heat exchanger, segmented water-water heat exchanger and other types. The main control parameters of the shell and tube heat exchanger are heating area, hot water flow, heat exchange, heat medium parameters, etc.

Because the temperature of the fluid inside and outside the tube is different in the shell and tube heat exchanger, the temperature of the shell and the tube bundle of the heat exchanger are also different. If the two temperatures are very different, a great thermal stress will be generated in the shell and tube heat exchanger, causing the tube to bend, break, or pull off the tube sheet.

Therefore, when the temperature difference between the tube bundle and the shell exceeds 50°C, appropriate compensation measures must be taken to eliminate or reduce thermal stress. According to the compensation measures adopted, shell and tube heat exchangers can be divided into the following main types:

①The tube sheets at both ends of the tube bundle of the fixed tube sheet heat exchanger are integrated with the shell. The structure is simple, but it is only suitable for heat exchange operations when the temperature difference between the cold and hot fluids is small and the shell side does not require mechanical cleaning. When the temperature difference is slightly larger and the shell side pressure is not too high, an elastic compensation ring can be installed on the shell to reduce thermal stress.

②The tube plate at one end of the tube bundle of the floating head heat exchanger can float freely, which completely eliminates thermal stress; and the entire tube bundle can be drawn out of the shell, which is convenient for mechanical cleaning and maintenance. Floating head heat exchangers are widely used, but the structure is more complicated and the cost is higher.

③ U-shaped tube heat exchanger Each heat exchange tube is bent into a U shape, and both ends are respectively fixed on the upper and lower areas of the same tube plate, and are divided into two compartments with the help of a partition in the tube box. This kind of heat exchanger completely eliminates the thermal stress and has a simpler structure than the floating head type, but the tube side is not easy to clean.

④Eddy ​​current hot film heat exchanger The eddy current hot film heat exchanger adopts the latest eddy current hot film heat transfer technology to increase the heat transfer effect by changing the fluid motion state. When the medium passes through the vortex tube surface, the tube surface is strongly washed to improve the exchange rate Thermal efficiency. The highest can reach 10000W/m2℃.

At the same time, this structure realizes the functions of corrosion resistance, high temperature resistance, high pressure resistance and anti-scaling. The fluid channels of other types of heat exchangers are in the form of fixed-direction flow, which forms a detour on the surface of the heat exchange tube and reduces the convective heat transfer coefficient.

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