Tube bundle in heat exchanger is one of the most widely used heat exchangers in chemical and alcohol production.It is mainly composed of shell, tube plate, heat transfer tube, sealing head and baffle baffle.The materials required can be made of ordinary carbon steel, copper, or stainless steel.In the heat exchange processing, a fluid is entered by the connecting tube of the sealing head and flows out of the outlet pipe at the other end of the sealing head.This is called the tube path.The other fluid is entered by the shell's take-over and flows out from the other receiver on the shell, which is called the shell path.
There are many types of tube bundle in heat exchanger, the current widely used classification method is based on its temperature differential compensation structure, mainly including the following:
1.Fixed tube plate heat exchanger:
The structure of this kind of heat exchanger is simple, compact and cheap, but it can't clean the tube by mechanery.The tube bundles of this heat exchanger are connected to the tube plate. The tube plates are welded to the ends of the shell respectively, and the top cover is connected with the tube.The top cover and shell is equipped with a fluid inlet and outlet connection.A series of baffles that are usually perpendicular to the tube.At the same time, the
connection between the tube and the shell is rigid, and the inner tube is a fluid of two different temperatures.Therefore, when the tube wall and the shell wall temperature difference is bigger,the tube will bends or the tube will drop from the tube plate and even destroys the heat exchanger due to the difference in thermal expansion of the them, the great temperature difference stresses.
Must have temperature compensation device in order to overcome the temperature stress, generally in the tube wall and the shell wall temperature is 50 ℃ above, for safety, heat exchanger should have temperature compensation device.
But compensation device (inflation) can only be used on the shell wall and pipe wall temperature falls below 60 ~ 70 ℃ and the situation of the shell side fluid pressure is not high.When the pressure of normal shell is over 0.6mpa, due to the over-thickness of the compensation ring, it is difficult to scale and lose the effect of temperature compensation. Other structures should be considered.
2.Floating head heat exchanger:
A piece of tube plate heat exchanger with flange connected to the shell, another piece of tube plate is not connected to the shell, so that the pipe can free expansion when heated and cold, but connect a lid on the tube plate, called a "floating", so this kind of heat exchanger is called floating-head type heat exchanger.The advantage is that the tube can be pulled out for cleaning;when the temperature difference between the two heat exchanger media is large, the
temperature difference stress will not be generated due to the different thermal expansion of the tube bundle and the shell.Its disadvantages are complex structure and high cost.
3.Stuffing box heat exchanger:
This kind of heat exchanger is free to expand at one end, and the structure is simpler than the floating head, and the cost is lower than the floating head.However, there is a possibility of leakage in the medium of the shell, which
should not deal with volatile, inflammable, explosive and poisonous media.
4.U-tube heat exchanger:
U-tube heat exchanger, each tube is bent into a U shape, and the two ends are fixed on the same tube plate. Each pipe can be flexibly scaled to solve the heat compensation problem.The tube is at least two, and the tube can be removed and cleaned, and the pipe can expand freely.The defect is the difficulty of cleaning the inner wall of the tube, the difficulty in replacing the pipe, and the few tubes arranged on the tube plate.The advantages are simple structure, light weight and suitable for high temperature and high pressure conditions.