[Principle of heat exchanger]What is the principle of heat exchanger? How does heat exchanger work?
The working principle of heat exchanger is simple It is the transfer of heat from an object on one side to an object on the other side through thermal conduction. However, according to the different types of heat exchangers, the specific working principles and usage methods are also different. For example, the air heat exchanger is mainly used for air heating in the drying system, and it is the main equipment in the hot air device.
The working principle of the heat exchanger is: the relative flow direction of the fluid in the heat exchanger generally has two kinds of co-current and counter-current. In co-current flow, the temperature difference between the two fluids at the inlet is the largest and gradually decreases along the heat transfer surface. In countercurrent flow, the temperature difference distribution between the two fluids along the heat transfer surface is relatively uniform.
Under the condition of constant inlet and outlet temperatures of cold and hot fluids, when both fluids have no phase change, the average temperature difference in countercurrent flow is the largest and the smallest in cocurrent flow. Under the condition of completing the same amount of heat transfer, the use of countercurrent can increase the average temperature difference and reduce the heat transfer area of the heat exchanger; if the heat transfer area remains unchanged, the consumption of heating or cooling fluid can be reduced when countercurrent is used. The former can save equipment costs, while the latter can save operating costs, so countercurrent heat transfer should be used as much as possible in design or production.
Shell and tube heat exchangers can be divided into the following three types according to different stress compensation methods:
1, fixed heat exchange Tube plate heat exchanger
The fixed tube plate heat exchanger is the simplest shell and tube heat exchanger. The tube plates at both ends of the heat transfer tube bundle are directly connected to the shell. A stress compensation ring is installed on the shell, which can reduce the thermal stress when the temperature difference inside the fixed tube plate heat exchanger is large. The thermal stress compensation of the fixed tube sheet heat exchanger is small, and it cannot adapt to the work with a large temperature difference.
2, floating head heat exchanger
The floating head heat exchanger is the most widely used shell and tube heat exchanger. A broad one, its stress relief principle is to release the tube sheet of a section of the heat transfer tube bundle and let it float freely in a certain space to eliminate thermal stress. The heat transfer tube bundle of the floating head heat exchanger can be extracted from the shell, which is convenient for cleaning and maintenance, but due to the complex structure, the price of the floating head heat exchanger is relatively high.
3,Utube heat exchanger
The heat transfer tube bundle of the U-shaped tube heat exchanger is a U-shaped curved heat exchanger. Outlet in two parts, while completely eliminating the effect of thermal stress on the tube bundle. The U-tube heat exchanger has a simple structure and is easy to use, but it is difficult to disassemble and clean.
