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Waste heat recovery heat exchangers are mainly used to recover waste heat generated by waste gas, waste water, steam, etc. in industrial production, and transfer heat to other media (such as water, air, etc.) through heat exchange technology to achieve energy saving and emission reduction. Its structure mainly includes various forms such as tube type, plate type, heat pipe, etc.
1. Purpose of waste heat recovery heat exchanger
(I) Industrial field
In industrial production, a large amount of heat energy is often wasted in the form of waste gas, waste water, etc. For example, high-temperature waste gas from steel plants, clinker cooling process in cement plants, and reaction waste heat in chemical production all contain considerable heat. Waste heat recovery heat exchangers can recover this waste heat and transfer the heat to the medium that needs to be heated, such as preheating raw materials in the production process, heating domestic water, or heating the factory.
(II) Energy industry
In thermal power plants, boiler rooms and other places, a large amount of steam condensation process will release heat. If this waste heat is not recycled, it will be lost in the environment. Waste heat recovery heat exchangers can transfer steam condensation heat to other media, such as heating circulating water in the heating system, expanding the heating area, improving the heating capacity of thermal power plants, and making better use of energy.
For some new energy fields, such as solar thermal power stations, when the medium heated by solar energy completes the power generation task, it still carries a certain amount of heat. The waste heat recovery heat exchanger can collect this part of the heat and use it for other auxiliary production links or surrounding life heat, further tapping the utilization value of solar energy resources and improving the comprehensive benefits of the entire energy system.
Cangzhou Datang Steel Pipe Co., Ltd.’s main products are: industrial heat exchange equipment, finned tube heat exchangers, air preheaters, steam heaters, flue gas waste heat recovery equipment, etc.
2. Structure of waste heat recovery heat exchanger
(I) Tubular heat exchanger
Tubular waste heat recovery heat exchanger is a more common type of structure, which is mainly composed of tube bundles, tube sheets, shells and other components. The tube bundle is the core part, which is composed of many metal tubes. The hot medium flows in the tube, and the cold medium flows in the shell outside the tube. The heat is conducted through the tube wall to achieve heat exchange.
The tube sheet is used to fix the tube bundle and separate the tube bundle from the shell to ensure that the two media flow along the set path. The shell plays the role of containing and protecting the internal tube bundle, and also guides the cold medium to flow around the tube bundle reasonably to form a good thermal convection environment. According to different application scenarios, tubular heat exchangers can also be subdivided into fixed tube sheet type, floating head type, U-tube type, etc. They have their own characteristics in dealing with thermal expansion and contraction, easy cleaning and maintenance, etc.
(II) Plate heat exchanger
The plate type waste heat recovery heat exchanger is composed of a series of corrugated metal plates, which are sealed by sealing gaskets to form many narrow channels. The hot medium and the cold medium flow in opposite directions in adjacent channels, and the heat is transferred through thin metal plates.
This structure makes the heat transfer efficiency of the plate heat exchanger extremely high, because the corrugated shape of the plate increases the surface area, and the heat exchange distance between the two media is very short. At the same time, its structure is compact, occupies a small area, is easy to install and disassemble, and is suitable for application scenarios with limited space but high requirements for heat exchange efficiency. However, its sealing requirements are high. Once there is a problem with the sealing gasket, it is easy to cause medium leakage, affecting the normal operation of the heat exchanger.
(III) Heat pipe heat exchanger
The core component of the heat pipe heat exchanger is the heat pipe, which is usually filled with working medium (such as ammonia, water, etc.). It is a component with high thermal conductivity.
The heat pipe consists of three parts: evaporation section, condensation section and insulation section. In the waste heat recovery application, the high-temperature waste heat medium causes the working medium in the evaporation section of the heat pipe to absorb heat and evaporate. The steam flows along the inside of the heat pipe to the condensation section, where it releases heat to the cold medium and recondenses into liquid. The liquid then returns to the evaporation section through capillary action, etc., and the cycle repeats to achieve efficient heat transfer from the high-temperature side to the low-temperature side.
