2010-2-2** Question—Essay Question—(Prize for participation)
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Question: What are the advantages and disadvantages of double-shell and tube heat exchangers compared to single-shell and tube heat exchangers? This question was provided by member feiyun2010; please keep an eye on it from the person who submitted it. The purpose of this* topic is to help everyone review some basic theoretical knowledge, gain new insights by reviewing what has been learned before, discuss and gain a deeper understanding of standards or specifications, as well as address specific issues encountered in practice. This enables us to learn together and improve together; we welcome all friends to participate actively. If you have good *questions, you can also provide them to us; we will give certain rewards to those who provide them. For more details, please refer to the top post in the heat exchange section titled “Special Thread for Collecting Questions on Heat Exchange Zone Technology”, with the link: http://bbs.hcbbs.com/thread-526242-1-1.html. Note: 1. For fill-in-the-blank, multiple-choice, true/false, and essay questions, please reply in hidden format (for specific methods of hiding replies, see http://bbs.hcbbs.com/viewthread.php?tid=492556&highlight=%D2%FE%B2%D8). Rewards will be given to those who reply correctly; those who do not use hidden formatting or revise their replies will not receive any rewards. Please cooperate actively. 2. For multiple accounts under the same IP, only the first response counting as participation is valid.
In a double-tube-sheet heat exchanger, there is one tube sheet at the end of the heat exchange tubes; this is known as the outer tube sheet. It also serves as the flange of the equipment, connecting to both the heat exchange tubes and the tube box flanges. Near the end of the heat exchange tubes, there is another tube sheet, known as the inner tube sheet, which is connected to both the heat exchange tubes and the shell side. There is a certain distance between the outer tube sheet and the inner tube sheet, which are connected by harf joints to form a pressure-free isolation chamber. The characteristic of the double tube sheet structure is that two tube sheets completely separate the fluids in the tube side from those in the shell side. On the back of each outer tube sheet, there are 2 symmetric discharge holes that communicate with the isolation chamber. There are 12 tie rod screw holes on the back side of the inner tube sheet 2 (the surface welded to the shell). The outer tube sheet 1 and the inner tube sheet 1 form the first set of double tube sheets, while the outer tube sheet 2 and the inner tube sheet 2 form the second set of double tube sheets. In a single-tube-sheet heat exchanger, the tube sheet at each end is composed of one tube sheet. The advantage of a double tube sheet is that, in the event of a leak at the tube sheet, the media do not mix with each other. To prevent accidents or other issues that may occur as a result of the mixing of the two media. Single tube sheets are inexpensive and easy to manufacture
The leakage points of heat exchangers include gasket leakage at the connection between the end cover and the tube sheet, leakage at the end cover, leakage at the ends of the cooling tubes, and corrosion-induced leakage in the middle sections of the cooling tubes. Leakage at the gasket between the end cover and the tube sheet, as well as leakage from the end cover itself, can be controlled by using high-quality materials, increasing thickness, and raising the bolt tension. Corrosion-induced leakage at the ends of the cooling tubes, as well as corrosion-induced leakage in the middle sections of these tubes, cannot be prevented over time as the heat exchanger continues to operate. It is therefore impossible to ensure that there is no corrosion-induced leakage at either the ends or the middle parts of the cooling tubes, meaning that the possibility of such leakage always exists, and the absolute safety and reliability of the heat exchanger cannot be guaranteed. In a heat exchanger with a single cooling tube and a single tube sheet, the cooling medium and the medium to be cooled are separated only by the wall of that single cooling tube. If the cooling tube ruptures, the two media will mix together; such a mixed mixture, once it enters other equipment, can cause damage to those devices, and in severe cases, it can even lead to the destruction of the equipment. In addition, some media are high-pressure and toxic fluids; in the event of a leak, they can cause environmental pollution and even pose a threat to human safety. In light of this situation, it is very important to develop double-cooling-tube, double-shell heat exchangers that meet requirements for absolute reliability.
The advantage of a double-tube-sheet heat exchanger over a single-tube-sheet heat exchanger is its ability to effectively prevent mixing of the fluids in the two flow paths. For example, when the shell side has high pressure and is non-corrosive, while the tube side has low pressure and is exposed to corrosive substances, a double-tube-sheet design can be used, with a thick tube sheet made of carbon steel for the shell side and a thin tube sheet made of stainless steel for the tube side, thereby saving stainless steel material； The disadvantage is its complex structure, which makes manufacturing difficult and increases production costs.
The leakage probability between the tube side and shell side of a double-shell-and-tube heat exchanger is much lower； The stress condition is better. Structurally, the double-shell-and-tube heat exchanger adopts a fixed-shell design, and the tube bundle cannot be removed for cleaning.
It is used in applications with high sealing requirements, and its processing difficulty and precision are higher than those required for single-tube-sheet heat exchangers.
The leakage points of heat exchangers include gasket leakage at the connection between the end cover and the tube sheet, leakage at the end cover, leakage at the ends of the cooling tubes, and corrosion-induced leakage in the middle sections of the cooling tubes. Leakage at the gasket between the end cover and the tube sheet, as well as leakage from the end cover itself, can be controlled by using high-quality materials, increasing thickness, and raising the bolt tension. Corrosion-induced leakage at the ends of the cooling tubes, as well as corrosion-induced leakage in the middle sections of these tubes, cannot be prevented over time as the heat exchanger continues to operate. It is therefore impossible to ensure that there is no corrosion-induced leakage at either the ends or the middle parts of the cooling tubes, meaning that the possibility of such leakage always exists, and the absolute safety and reliability of the heat exchanger cannot be guaranteed. In a heat exchanger with a single cooling tube and a single tube sheet, the cooling medium and the medium to be cooled are separated from each other only by the wall of that single cooling tube. If the cooling tube ruptures, the two media will mix together; such a mixed mixture, once it enters other equipment, can cause damage to those devices, and in severe cases, it can even lead to the destruction of the equipment. In addition, some media are high-pressure and toxic fluids; in the event of a leak, they can cause environmental pollution and even pose a threat to human safety. The double-cooling-tube double-shell-and-plate heat exchanger boasts absolute reliability, and this is its advantage.
Compared to single-tube-sheet heat exchangers, double-tube-sheet heat exchangers have a much lower probability of leakage between the tube side and the shell side； The stress condition is better. Structurally, the double-shell and tube heat exchanger adopts a fixed-shell design, and the tube bundle cannot be removed for cleaning.
The advantage of a double-shell-and-tube heat exchanger over a single-shell-and-tube heat exchanger is its ability to effectively prevent mixing of the materials between the two flow paths; the disadvantages are its complex structure, greater manufacturing difficulty, and higher processing costs.
Double-shell and plate heat exchangers and single-shell and plate heat exchangers were compared in terms of structure, application, manufacturing, etc. Compared to single-tube-sheet heat exchangers, double-tube-sheet heat exchangers have a much lower probability of leakage between the tube side and the shell side ； The stress condition is better. Structurally, the double-shell-and-tube heat exchanger adopts a fixed-shell design, and the tube bundle cannot be removed for cleaning. Practical use has shown that double-sheet plate heat exchangers manufactured using the mechanical expansion tube method can meet the operational requirements.
Compared to single-tube-sheet heat exchangers, double-tube-sheet heat exchangers have a much lower probability of leakage between the tube side and the shell side； The stress condition is better. Disadvantage: Structurally, double-sheet plate heat exchangers use a fixed-sheet plate design, preventing the tube bundle from being removed for cleaning ； At the same time, the manufacturing process is more complex, and the production costs are higher.