Tube heat exchanger

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The tubular exchanger is currently the most widely used type of heat exchanger in the chemical industry and alcohol production. It is mainly composed of a shell, tube sheet, heat exchange tubes, head, baffle plates, etc. The required materials can be ordinary carbon steel, red copper, or stainless steel. During heat exchange, one fluid enters at the connection pipe of the end cap, flows through the pipes, and exits through the outlet pipe at the other end of the end cap; this is referred to as the tube side ； Another fluid enters through a tube connection on the shell and exits through another tube connection on the shell; this is known as a shell-and-tube heat exchanger. Types: Fixed tube sheet type and shell and tube type. Shell and tube exchangers have a simple and compact structure as well as low manufacturing costs, but the outside of the tubes cannot be mechanically cleaned. In this type of heat exchanger, the tube bundle is connected to the tube sheet, which is welded to both ends of the shell; a top cover is attached to the tube sheet. The top cover and the shell are equipped with fluid inlet and outlet nozzles. Usually, a series of baffles perpendicular to the tube bundle are installed outside the tubes. At the same time, the connections between the tubes and tube sheets and the shell are rigid, while there are fluids at different temperatures inside and outside the tubes. Therefore, when there is a large temperature difference between the tube wall and the shell wall, differences in their thermal expansion lead to significant temperature stress, which can cause the tubes to bend or become loose from the tube sheet, and may even damage the heat exchanger. To overcome thermal stress, a temperature difference compensation device is necessary; generally, when the temperature difference between the tube wall and the shell wall exceeds 50°C, it is advisable for safety reasons that the heat exchanger be equipped with such a compensation device. However, compensating devices (expansion joints) can only be used when the temperature difference between the shell wall and the tube wall is below 60–70°C and the pressure of the fluid in the shell side is not high. Generally, when the shell-side pressure exceeds 0.6 Mpa, the compensation ring becomes too thick and is unable to expand or contract, thereby losing its function of compensating for temperature differences; in such cases, other designs should be considered. In a floating-head heat exchanger, one tube sheet is connected to the shell via flanges, while the other tube sheet is not connected to the shell, allowing the tubes to expand and contract freely as they are heated or cooled. However, a cover is attached to this tube sheet, which is known as the \"floating head,\" and that is why this type of heat exchanger is called a floating-head heat exchanger. Its advantage is that the tube bundle can be pulled out for cleaning ； The tube bundle is constrained by the fixed shell, so when there is a large temperature difference between the two fluids in the heat exchanger, no thermal stress is generated due to the differences in thermal expansion rates between the tube bundle and the shell. Its disadvantages are complex structure and high cost. stuffing box type: In this type of heat exchanger, one end of the tube bundle can expand freely; its structure is simpler than that of the floating head type, and its cost is also lower. However, there is a risk of leakage of the medium in the shell side, and volatile, flammable, explosive, or toxic media should not be handled in the shell side. U-tube type: In a U-tube heat exchanger, each tube is bent into a U shape, with its ends fixed to the same tube sheet; each tube can expand and contract freely, thereby addressing the issue of thermal compensation. The tube bank consists of at least two banks; the tube bundle can be removed for cleaning, and the tubes can expand freely. Its disadvantages are that the inner wall of the tube is difficult to clean, the tubes are hard to replace, and few tubes are arranged on the tube sheet. The advantages are simple structure, light weight, and suitability for high-temperature and high-pressure conditions. Eddy current thermal film: Eddy current thermal film heat exchangers utilize the latest eddy current thermal film heat transfer technology to enhance heat transfer by altering the flow pattern of the fluid. As the fluid passes over the surface of the eddy current tubes, it exerts strong force on the tube surface, thereby improving the heat exchange efficiency. It can reach up to 10,000 W/m2°C. At the same time, this structure provides corrosion resistance, high-temperature resistance, high-pressure resistance, and anti-scaling properties. The fluid channels in other types of heat exchangers have a fixed-direction flow pattern, which causes flow around the surface of the heat exchange tubes and reduces the convective heat transfer coefficient. According to the information provided by the [Heat Exchanger Equipment Promotion Center], the greatest advantage of the eddy current thermal film heat exchanger is the combination of cost-effectiveness and safety. By taking into account the flow relationships between the heat exchange tubes as well as between those tubes and the shell, baffles are no longer used to force turbulence; instead, alternating vortex flows are naturally induced between the tubes, thereby maintaining an appropriate level of oscillation without causing the tubes to rub against each other. The heat exchange tubes have an optimal balance of stiffness and flexibility, preventing them from colliding with each other. This approach not only eliminates the problem of damage caused by collisions between floating coil heat exchangers but also avoids the scaling issue common in conventional shell-and-tube heat exchangers. Performance characteristics of the eddy current thermal film heat exchanger: 1. High efficiency and energy savings; the heat transfer coefficient of this heat exchanger is 6000–8000 W/m2·°C ； 　　2. Made entirely of stainless steel, it has a long service life of over 20 years; in the event of any quality issues with the heat exchanger within 10 years, it will be replaced free of charge ； 　　3. Changing from laminar flow to turbulent flow improves heat transfer efficiency and reduces thermal resistance ； 　　4. Fast heat exchange rate, resistant to high temperatures (400°C) and high pressures (2.5 Mpa); 5. Compact structure, small footprint, light weight, easy to install, and reduces civil engineering costs ； 　　6. Flexible design, comprehensive specifications, strong practicality and relevance, cost-saving ； 　　7. It has a wide range of application conditions, capable of handling high pressures and temperatures as well as heat exchange with various media ； 　　8. Low maintenance costs, easy to operate, long descaling cycle, and convenient cleaning. 　　9. The use of nano-thermal film technology significantly increases the heat transfer coefficient. 　　10. It has a wide range of application fields, and can be widely used in thermoelectricity, factories and mines, petrochemical industry, urban central heating, food and pharmaceuticals, energy electronics, machinery and light industry, and other sectors.