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Common Problems and Treatment Methods of Heat Exchanger Unit



Heat exchanger units often appear problems and deal with the treatment method, some common problems may often be ignored. It is very common and easy to be ignored in the operation of plate heat exchanger units, and the treatment methods are summarized, which has certain reference significance for the designers and users of plate heat exchanger units. Shell and tube heat exchanger shell and tube heat exchanger is also called tube heat exchanger. Is enclosed in the shell tube bundle wall as the heat transfer surface of the recuperator heat exchanger. This kind of heat exchanger is simple in structure, reliable in operation, can be made of various structural materials, can be used under high temperature and high pressure, and is a widely used type at present. The structure is composed of shell, heat transfer tube bundle, tube sheet, baffle plate and tube box. The shell is mostly cylindrical, with a tube bundle inside, and the two ends of the tube bundle are fixed on the tube plate. Heat exchange of two kinds of fluid, a flow in the tube, called the tube side fluid; another kind of flow in the tube, called the shell side fluid. In order to improve the heat transfer coefficient of the fluid outside the tube, several baffles are usually installed in the shell. The baffle can increase the fluid velocity on the shell side, forcing the fluid to pass through the tube bundle several times laterally according to the specified distance, and enhancing the degree of fluid turbulence. The heat exchange tubes may be arranged in an equilateral triangle or square on the tube sheet. The equilateral triangle arrangement is compact, the turbulence degree of the fluid outside the tube is high, and the heat transfer coefficient is large; the square arrangement is convenient for cleaning outside the tube and is suitable for fluids that are easy to scale. Each time the fluid passes through the tube bundle is called a tube pass; each time it passes through the shell is called a shell pass. The diagram shows a very simple single shell pass single tube pass heat exchanger, referred to as 1-1 heat exchanger. In order to increase the velocity of the fluid in the tube, partitions can be set in the tube box at both ends, and all the tubes can be divided into several groups. In this way, the fluid only passes through part of the tubes at a time, so it goes back and forth many times in the tube bundle, which is called multi-tube pass. Similarly, in order to increase the flow rate outside the tube, longitudinal baffles can also be installed in the shell to force the fluid to pass through the shell space multiple times, which is called multi-shell pass. Multi-tube side and multi-shell side can be used together. Type Because the temperature of the fluid inside and outside the tube is different, the temperature of the shell and tube bundle of the heat exchanger is also different. If the two temperatures are very different, a large thermal stress will be generated in the heat exchanger, causing the tube to bend, break, or pull off the tube sheet. Therefore, when the temperature difference between the tube bundle and the shell exceeds 50 ℃, appropriate compensation measures should be taken to eliminate or reduce the thermal stress.