The most widely used tube-tube exchanger is the plate and frame heat exchanger, which is a group of formed plates combined on a frame. In order to meet the requirements of different flow rates, heat transfer and temperature, series and parallel lines can be configured in a wide range, but the structural limitations make its use pressure and temperature not high.The second type is the spiral row tube cooler, which is composed of two parallel long plates rolled into a spiral shape and welded at adjacent staggered end surfaces to form a flow channel.Since the channel itself is spiral-shaped and can perform secondary circulation, it can obtain a large heat transfer coefficient under laminar flow conditions and is not easy to scale.The third type is a plate-type heat exchanger. Its structure is constructed by longitudinally welding the flow channels welded together in the shell. Because the flow channels are equipped with gaskets, these plates can withstand greater internal pressure. The film is easy to disassemble, which is convenient for cleaning and inspection.
(1) Pay attention to the harm caused by impurities dissolved in water in ion or molecular state, which is also the main component of heat exchanger fouling. Since this salt is hard and hard crystal, and has a loose structure and low adhesion, it is a fluid when separated from water.
(2) Pay attention to the danger caused by dissolved oxygen, because this is an important factor leading to corrosion of the heat exchanger. Once in contact with the metal surface, local corrosion will occur.
(3) The impurities in the colloidal state are mainly iron compounds, microorganisms, mud and dirt, so they also cause damage to the heat exchanger.