Shell and tube heat exchanger consist of the shell, heat pipe bundle, tube board, baffle (baffle) and tube boxes and other components. Shell is mostly cylindrical, equipped with a tube bundle inside, the tube bundle ends fixed on the
The two fluids, hot and cold, one that flows in the tube and is called the tube-path fluid and the other that flows outside the tube, is called the shell-side fluid. In order to increase the heat transfer coefficient of the fluid outside the tube, several baffles are usually installed in the housing.
The baffle can improve the fluid velocity of the shell and force the fluid to flow through the tube several times in accordance with the specified distance to enhance the turbulence degree of the fluid. Heat exchange tubes in the tube plate can be arranged equilateral triangle or square.
The equilateral triangle is arranged more compactly, the degree of fluid turbulence is higher and the heat transfer coefficient is larger. The square arrangement is convenient for external cleaning and is suitable for the fluid with easy
Shell and tube heat exchanger main control parameters for the heating area, hot water flow, heat exchange, heat medium parameters and ect.
Each pass of the fluid through the tube bundle is called a tube pass; once passed through the shell, it is called a shell pass. The picture shows the simplest single-shell single tube heat exchanger, referred to as 1-1 type heat exchanger.
In order to improve the fluid velocity in the tube, a partition plate can be arranged in both ends of the tube box to divide all the tubes into several groups. In this way the fluid passes through only a portion of the tube at a time, thus
traversing the tube bundle multiple times, which is called multi-tube routing.
Similarly, in order to increase the flow rate outside the tube, a longitudinal baffle may also be installed in the housing, forcing the fluid to pass through the housing space several times, referred to as multi-hull. Multi-tube and
multi-shell process can be used in conjunction.
Shell and tube heat exchanger due to the the difference of fluid temperature inside and outside , so the heat exchanger shell and tube bundle's temperature is also different.
If the temperature difference between the two is very large, the heat exchanger will have a lot of heat stress, resulting in pipe bending, fracture, or pulled off from the tube plate.
Therefore, when the temperature difference between the tube bundle and the shell exceeds 50 ℃, appropriate compensation measures should 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 Fixed tube-sheet exchanger at the ends of the heat exchanger tube are combined with the shell body, which is simple in structure, but only applicable to the temperature difference of the cold and hot fluid, and the heat transfer operation of the shell is not required for mechanical cleaning.When the temperature difference is slightly larger and the shell pressure is not too high, the elastic compensation ring can be installed on the shell to reduce the thermal stress.
② Floating tube heat exchanger tubes at one end of the tube plate can float freely, completely eliminating the thermal stress; and the entire tube bundle can be drawn from the shell, easy to mechanical cleaning and maintenance. Floating head heat exchanger is widely used, but the structure is more complex and costly.
③ U-tube heat exchanger tubes are bent into each tube to U-shaped, the two ends were fixed in the same tube plate up and down the two areas, with the help of the partition inside the tube box into the import and export of two rooms.
This heat exchanger completely eliminates the thermal stress, the structure is simpler than the floating head, but the pipe is not easy to clean.
(4) Eddy current hot film heat exchanger eddy current hot film heat exchanger using the latest eddy current film heat transfer technology, by changing the fluid movement to increase the heat transfer effect, when the medium through the
vortex tube surface, the strong erosion of the pipe surface, thereby enhancing the exchange thermal efficiency. Up to 10000W / m2 ℃. At the same time this structure to achieve a corrosion-resistant, high temperature, high pressure,
anti-scaling function. The fluid channel of other types of heat exchangers is a fixed directional flow, and the flow is formed on the surface of the heat transfer tube, and the convective heat transfer coefficient decreases.