Function and application of graphite heat exchanger

2020-12-15173

        What is the main function of graphite heat exchanger? As for graphite heat exchanger, its function and use are closely related, so let's check it together.

        Graphite heat exchanger is widely used. The radiator used in daily life, condenser in steam turbine and oil cooler on space rocket are all graphite heat exchangers. It is also widely used in the chemical, petroleum, power and atomic energy industries. Its main function is to ensure the specific temperature required by the medium in the process, and it is also one of the main equipment to improve energy utilization.

        Graphite heat exchanger can be a separate equipment, such as heater, cooler and condenser; it can also be an integral part of processing equipment, such as heat exchanger in ammonia converter.

        Due to the limitations of manufacturing technology and scientific level, the early heat exchanger can only use simple structure, and the heat transfer area is small, large, bulky and bulky, such as coiled heat exchanger. With the development of manufacturing technology, shell and tube heat exchanger is gradually formed. It not only has larger heat transfer area per unit volume, but also has better heat transfer effect. For a long time, it has been a typical heat exchanger in I industry.

        The mixed heat exchanger is a kind of heat exchanger which can exchange heat through direct contact and mixing cold and hot fluids, also known as contact heat exchanger. After the two fluids mix and exchange heat, the graphite heat exchanger needs to be separated in time. This kind of heat exchanger is suitable for heat exchange between gas and liquid. For example, in cooling towers used in chemical plants and power plants, hot water is sprayed from the top to the bottom, while cold air is drawn from the bottom to the top, on the water film surface of the filler or on the surface of the container. Water droplets and water droplets, hot water and cold air contact each other to exchange heat. Hot water is cooled, cold air is heated, and then separated in time by the density difference between the two fluids.

        The regenerative heat exchanger is a kind of heat exchanger which uses the cold and hot fluid to flow through the surface of the heat storage body (valuable material) alternately to exchange heat, such as the preheated air storage room under the coke oven. This kind of heat exchanger is mainly used to recover and utilize the heat of high temperature waste gas. Similar equipment used to recover cold air is called cold storage, which is mainly used in air separation equipment.

        The cold and hot fluid of the separated heat exchanger is separated by the solid partition plate, and the heat exchange is carried out through the baffle plate. Therefore, it is also called surface heat exchanger. This type of heat exchanger is widely used.

        According to the structure of heat transfer surface, wall heat exchanger can be divided into tube type, plate type and other types. Tube heat exchanger takes the surface of tube as the heat transfer surface, including coil heat exchanger, double tube heat exchanger and shell and tube heat exchanger. Plate heat exchanger uses plate surface as heat transfer surface, including other types of heat exchanger, such as spiral plate heat exchanger, plate fin heat exchanger, plate shell heat exchanger and umbrella plate heat exchanger, which are special requirements designed to meet specific conditions. For example, scraper type heat exchanger, rotary plate heat exchanger and air cooler.

        The relative flow direction of fluid in heat exchanger usually has two types: forward flow and reverse flow. When the fluid flows forward, the temperature difference between the two fluids at the inlet is larger and decreases gradually along the heat transfer surface until the temperature difference at the outlet is small. In countercurrent, the temperature difference between the two fluids along the heat transfer surface is more uniform.

        Under the same heat transfer conditions, the use of counter current will increase the average temperature difference. The heat transfer area of the heat exchanger is reduced; if the heat transfer area remains unchanged, the consumption of heating or cooling fluid can be reduced when counter current is used. The former can save the equipment cost, while the latter can save the operation cost. Therefore, countercurrent heat transfer should be used as much as possible in design or production.

        When one or two of the cold and hot fluids undergo phase transition (boiling or condensation), the temperature of the fluid itself remains unchanged because only the latent heat of vaporization is released or absorbed during the phase transition process. Therefore, if the inlet and outlet temperatures of the fluid are equal, the temperature difference between the two fluids is independent of the choice of the flow direction of the fluid. In addition to downstream flow and countercurrent flow, there are also flow directions, such as cross flow and kink flow.