Shell-and-tube heat exchangers, also known as shell-and-tube heat exchangers, are suitable for processes such as condensation, heating, reboiling, and waste heat recovery. Due to its fast structure, high reliability, strong adaptability, wide application range and other advantages, it is widely used in the industrial field. Especially under high temperature and high pressure conditions, shell and tube heat exchangers have incomparable advantages over other types of heat exchangers. Only when the flow rate is small, the pressure and temperature are low, especially when the fluid is corrosive to carbon steel or its viscosity is high, the
Plate Heat Exchanger is preferred. If the flow rate is small, but the pressure or temperature is high, the casing heat exchanger should be preferred.
What type of heat exchanger is used for specific working conditions requires comprehensive analysis. The basic structure types of commonly used shell and tube heat exchangers are:
(1) Fixed tube-sheet heat exchanger: The heat exchange tube bundle is fixed on several plates, and the plates are welded to both ends of the shell. The tubes, plates, and shell are all rigidly connected.
When the temperature difference between the fluids on both sides of the pipe wall is higher than 50°C, in order to reduce or eliminate the thermal stress caused by the temperature difference, a temperature difference compensation device, such as an expansion joint, must be installed. The fixed tube-sheet heat exchanger has simple structure and low cost, and there are many styles of tubes to choose from. However, the shell side is not easy to clean, so it is not suitable for heat exchange between dirty or corrosive fluids. It is only suitable for processes with small temperature difference, low shell side pressure, not serious shell fouling, and can be cleaned by chemical methods. condition.
(2)
Floating Head Heat Exchanger: one end of the tube plate is fixed to the shell, and the other end of the tube plate can float freely in the shell.
The shell and heat exchange tubes of this heat exchanger are free from thermal expansion, and there is no temperature difference stress between the shell and the heat exchange tubes. In order to facilitate maintenance and cleaning of the floating head, it is often designed as a detachable structure. It is necessary to test the sealing of the floating head during installation, otherwise it is impossible to know whether there is leakage in the internal floating head during operation. Although it has a wide range of applications, its structure is complex and its manufacturing cost is high.
(3) U-shaped tube heat exchanger: the tube bundle is in the shape of a "U" character, and both ends are fixed on the same
Tube Sheet. The tube bundle is separated from the shell, and there is no other mechanism, so there is no need to consider temperature difference compensation.
The "U" type tube heat exchanger has a simple structure, and the tube bundle can be pulled out for easy cleaning, but it is difficult to clean inside the tube, so the fluid flowing through the tube bundle must be a medium that is not easy to scale and easy to clean. Due to the gaps between the tube bundles, the shell side medium is easy to flow through the short circuit, which has a bad effect on the heat transfer effect. Moreover, the "U"-shaped tubes cannot be pulled out for replacement. If one of them is damaged, the other tubes will be damaged at an accelerated rate, which will greatly reduce the heat transfer efficiency of the entire heat exchange tube bundle.
(4) Stuffing box heat exchanger: The floating head of the heat exchanger and the shell are sealed with a stuffing box. There are three structural types: the stuffing box is set at the end of the floating head, set at the tube plate, and stuffing box outside the shell.
In addition to the characteristics of the floating head heat exchanger, this type of heat exchanger also avoids the disadvantages of the
Fixed Tube Sheet type, and is easy to repair and clean.
Please inquire us if necessary.
December 27, 2022
