Heat exchanger - Tubular

Because the temperature of the fluid inside and outside the tube is different, the temperature of the shell and tube bundle of the heat exchanger are also different. If the two temperatures differ greatly, great thermal stress will be generated in the heat exchanger, resulting in bending, fracture or pulling off from the tubesheet. Therefore, when the temperature difference between the tube bundle and the shell exceeds 50 ℃, appropriate compensation measures shall be taken to eliminate or reduce the thermal stress. According to the compensation measures adopted, shell and tube heat exchangers can be divided into the following main types:

① The tubesheets at both ends of the tube bundle of the fixed tubesheet heat exchanger are connected with the shell as a whole. The structure is simple, but it is only applicable to the heat exchange operation when the temperature difference between cold and hot fluids is small and the shell side does not need mechanical cleaning. When the temperature difference is slightly large and the shell side pressure is not too high, an elastic compensation ring can be installed on the shell to reduce the thermal stress.

② The tubesheet at one end of the floating head heat exchanger tube bundle can float freely, completely eliminating the thermal stress; And the whole tube bundle can be extracted from the shell, which is convenient for mechanical cleaning and maintenance. Floating head heat exchanger is widely used, but its structure is complex and its cost is high.

③ Each heat exchange tube of the U-shaped tubular heat exchanger is bent into a U shape, and both ends are respectively fixed in the upper and lower areas of the same tubesheet. With the help of the partition plate in the tube box, it is divided into inlet and outlet chambers. The 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.

④ Vortex hot film heat exchanger vortex hot film heat exchanger adopts vortex 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, it strongly washes the tube surface, so as to improve the heat transfer efficiency. Zui 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 channel of other types of heat exchangers is in the form of fixed direction flow, which forms a flow around the surface of the heat exchange tube and reduces the convective heat transfer coefficient.