【Weekly Topic】Discussion on the advantages and disadvantages of double-pass shell-and-tube heat exchangers, January 13, 2016 ~ January 20, 2016?
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To increase the popularity of the heat exchange section, a 【Weekly Topic】 activity is organized there; this helps to foster an active atmosphere for technical exchanges while also providing members with certain financial rewards. 【Weekly Topic】Besides inheriting the advantages and disadvantages of floating-head and fixed-tube-sheet shell-and-tube heat exchangers, what other notable advantages and disadvantages does the double-pass shell-and-tube heat exchanger have? We hope everyone will share their opinions; we will give points and encouragement based on the quality of the content. Thank you all for your support.
The advantage is that the use of two shell passes allows for cost savings, an increase in the flow rate within the shell passes, and improved heat exchange efficiency； The drawback is that the shell-side sealing plate must be well-designed and possess good elasticity; otherwise, it will cause a short circuit in the shell-side fluid, severely affecting the heat exchange efficiency.
Advantages of fixed-tube-sheet heat exchangers: simple structure, easy to manufacture; they have the smallest shell inner diameter under the same tube bundle conditions, and it is convenient to divide the tube side into sections. Disadvantages: The shell side cannot be mechanically cleaned, and it is difficult to inspect the shell side. When there are no temperature difference compensation elements between the shell and the tubes, significant temperature difference stresses are generated; therefore, expansion joints or bellows and other compensation elements must be used when the temperature difference is large in order to reduce these stresses. Advantages of floating-head heat exchangers: they do not generate thermal stress, the floating head can be removed, and the tube bundle is easy to pull out or insert, facilitating maintenance and cleaning. Disadvantages: The structure is relatively complex, and it is difficult to check the sealing condition of the floating head cover during operation.
By using a double shell pass, one shell can function as equivalent to two smaller shells, which reduces the investment required for shells. At the same time, it enables the equipment to be larger in size, thereby saving on costs.
Compared with single-pass heat exchangers, double-pass heat exchangers offer advantages such as higher heat exchange efficiency, less space requirement, lower weight, and reduced investment costs. The key issues that need to be addressed in the design are: the sealing, stiffness, and installation of the partition in the double-pass heat exchanger ； There is also the concentricity of the double-shell heat exchanger shell.
1. Shell-and-tube heat exchangers are suitable for use as heaters, coolers, condensers, evaporators in various operating conditions, as well as for multi-medium heat exchange. However, in situations where pressure and temperature are not high, other types of heat exchangers are generally used, as they offer a more compact design. 2. Split-plate heat exchangers can be used for heaters, coolers, condensers, oil coolers, and water-to-water heat exchangers, with operating temperatures not exceeding 150 degrees and pressures not exceeding 1.6 MPa. It has a high heat transfer coefficient and a small volume. 3. Brazed plate heat exchangers are used for condensers, evaporators, oil coolers, oil heaters, and gas coolers, where the operating temperature does not exceed 250 degrees and the pressure does not exceed 3.5 MPa.
By using a double shell pass, one shell can function as equivalent to two smaller shells, which reduces the investment required for shells. At the same time, it enables the equipment to be larger in size, thereby saving on costs.
1. Improve heat transfer efficiency. 2. Considering fluid scaling and coking, it is also necessary for the fluid on the shell side of the heat exchanger to have a certain flow rate. In double-pass heat exchangers, the heat transfer coefficient of the outer surface of the heat transfer tubes is often the determining factor for heat transfer, as it is easier to achieve multi-pass flow in the tube side structure, thereby increasing the flow rate.
1. Shell-and-tube heat exchanger with pure counterflow heat transfer. 2. For a double-pass shell-and-tube heat exchanger, the fluid in the shell side requires only a low flow velocity to reach turbulence, thereby increasing the convective heat transfer coefficient of the fluid in that side. 3. Since its pressure drop is much higher than that of heat exchangers with the same heat exchange area, it is less commonly used in applications where strict requirements are placed on pressure drop.
I have one here; the sealing part leaks frequently, and it’s difficult to fix – it can only be kept working until maintenance is done.
I have one here; the sealing part leaks frequently, and it’s difficult to fix – it can only be kept working until maintenance is done.