Each time the fluid passes through the tube bundle in the tube, it is called a tube process, and each time it passes through the shell, it is called a shell side.

In order to increase the speed of the fluid in the tube, an appropriate partition can be placed in the ends of the two ends to divide the entire tube into several groups on average.

In this way, the fluid can pass through the tube bundle multiple times only through a part of the tube at a time, which is called multi-tube.

Similarly, in order to increase the flow rate outside the pipe, a longitudinal baffle can be installed in the casing to allow the fluid to pass through the casing space multiple times, which is called a multi-shell process.

In the shell-and-tube heat exchanger, the temperature of the casing and the bundle are different due to the different fluid temperatures inside and outside the tube. If the temperature difference between the two is very large, there will be a large thermal stress inside the heat exchanger, which may cause the tube to bend, break or loosen from the tube sheet.

Therefore, when the temperature difference between the tube bundle and the casing exceeds 50 °C, appropriate temperature difference compensation measures should be taken to eliminate or reduce the thermal stress.

Compensation method: an expansion ring is attached to the casing or a U-tube heat exchanger and a floating-head heat exchanger are used.

Fixed tube plate heat exchanger

When the temperature difference between the hot and cold fluids is not large, a fixed tube plate heat exchanger can be used. It is simple in structure and low in cost, but it is difficult to clean and is not suitable for fluids with a high degree of fouling and fluids with a large temperature difference. If the temperature difference is not very large, a fixed tube plate heat exchanger with a compensation ring can be used.

Floating head heat exchanger

In the floating head heat exchanger, one end of the tube sheet at both ends can float freely in the axial direction, thereby eliminating thermal stress. Moreover, the entire tube bundle can be withdrawn from the housing for easy cleaning and maintenance. However, the structure is complicated and the cost is high. Such heat exchangers are generally used in the industry.

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