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July 22, 2021
Heat exchanger is widely used in chemical industry, petroleum industry, electric power industry, food industry and many other industries. It accounts for about 40% of the equipment investment in petrochemical plants. It is a key chemical equipment. At the same time, the rational use of heat energy is of great significance to reduce product costs, environmental protection, energy conservation and emission reduction.
Heat exchanger is the common equipment of chemical workers, but as a senior chemical worker, do you really understand heat exchanger?
Why called heat exchanger?
Heat exchanger is a kind of equipment to transfer heat energy from one fluid to another. In the simplest heat exchanger, hot fluid and cold fluid are directly mixed together; The more common heat exchanger is that the heat and cold fluids are separated by the partition in the heat exchanger. Due to the temperature difference between the hot fluid and the cold fluid on both sides, the heat exchange will be formed, that is, the heat balance of junior high school physics. The heat of high-temperature objects is always transferred to low-temperature objects. In this way, the heat on the hot side is exchanged to the cold side. Sometimes we also call the heat exchanger.
Heat exchanger Classification:
According to the heat transfer mode can be divided into: inter wall heat exchanger, regenerative heat exchanger, hybrid heat exchanger.
According to the use can be divided into: heater, cooler, condenser, evaporator, reboiler, etc.
According to the structure can be divided into: shell and tube heat exchanger, plate heat exchanger. What we often talk about in chemical industry is the two kinds of equipment classified by structure.
What is the difference between plate heat exchanger and shell and tube ?
Shell and tube heat exchanger
Shell and tube heat exchanger is the most typical inter wall heat exchanger. It has a long history of application in industry and is still widely used in today's chemical plants.
Shell and tube heat exchanger is mainly composed of shell, tube bundle, tube sheet and head. The shell is mostly round, with parallel tube bundle inside, and both ends of the tube bundle are fixed on the tube sheet.
There are two kinds of fluid in the shell and tube heat exchanger, one is flowing in the tube, and its stroke is called tube side; One kind flows outside the tube, and its stroke is called shell side. The wall of the tube bundle is the heat transfer surface.
In order to improve the heat transfer coefficient of the fluid outside the tube, a certain number of transverse baffles are usually installed in the shell.
In shell and tube heat exchanger, the temperature of shell and tube bundle is different due to the difference of fluid temperature inside and outside the tube. If the temperature difference between the two is large, there will be great thermal stress in the heat exchanger, which may make the tube bend, fracture or loose from the tube sheet. Therefore, when the temperature difference between tube bundle and shell exceeds 50 ° C, appropriate temperature difference compensation measures should be taken to eliminate or reduce the thermal stress.
Plate heat exchanger
Plate heat exchanger was initially used in food industry, and gradually extended to chemical industry and other industries in the 1950s. It is an efficient and compact heat exchange equipment.
The conventional plate heat exchanger is composed of a group of rectangular thin metal heat transfer plates, which are clamped and assembled on the support with a frame. The edges of the two adjacent plates are lined with gaskets to compress, and the four corners of the plates are provided with round holes to form fluid channels.
In addition, in different chemical process applications, there are all welded plate heat exchanger, spiral plate heat exchanger, plate and shell heat exchanger