Issue with the guide cylinder on the heat exchanger shell expansion joint
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Recently, I have seen some shell-and-tube heat exchangers with expansion joints on their shells; on the inside of these expansion joints, some have guide tubes welded to them, while others do not. Question: 1. What is the purpose of installing a guide cylinder on the expansion joint? 2. In what situations is a guide cylinder needed, and in what situations can it be omitted? Thank you!
When applied to pipe expansion joints subjected to strong scouring forces, the guide cylinder serves an anti-wear function, protecting the bellows from being scoured by the medium and thus extending the service life of the expansion joint. It also helps to direct the flow within the expansion joint. Additionally, its guiding role prevents the bellows from becoming unstable as the expansion joint accommodates pipe deformation, allowing the expansion joint to achieve its normal service life and functionality. Expansion joints and compensators both require the installation of guide tube devices when handling special pipeline media. The guide cylinder has the following main functions: 1. The guide cylinder serves a guiding role, helping to prevent instability of the bellows caused by pipe deformation. 2. The guide cylinder can reduce the vibrations of the bellows structure caused by high-speed fluids, and serves to protect the bellows. A guide tube needs to be installed inside the bellows expansion joint under the following conditions: 1. When it is necessary to minimize friction losses and ensure smooth flow ； 2. When the medium flow velocity is high, it may cause bellows resonance ； 3. When abrasion is possible ； 4. When the medium temperature is high and it is necessary to reduce the temperature of the bellows metal ； Generally, corrugated expansion joints with a small diameter of DN100 or less do not require a lining guide tube, while those with a diameter of DN100 or more need one. The main function of the lining guide tube is:
Some expansion joints on heat exchanger shells are equipped with guide tubes, while others are not. Is there any standard basis for this in the design process?
Whether to include expansion joints on the heat exchanger is determined during the calculation of the equipment’s strength. As for the flow guide cylinder, its main function is to reduce the inlet flow velocity, prevent high-speed fluid from impacting the heat exchange tubes, and facilitate even distribution of steam. It also ensures uniform heat transfer across each tube, avoids the formation of heat transfer dead zones, and improves the efficiency of heat exchange.
I have compiled information on 10 heat exchangers equipped with expansion joints; in those where fluid flows, the expansion joints come with guide tubes, while those for gas phases do not have such tubes. I’m not sure how to interpret this
The design of expansion joints is related to temperature parameters and pressure. The design of the diversion cylinder is related to the preferences and habits of the designers, as well as internal structural factors. It has little to do with vapor-liquid equilibrium. Let’s conduct a comprehensive analysis based on the drawings.
I suspect that guide cylinder is there to prevent short circuits; in my understanding, guide cylinders should be installed more commonly in gas-phase systems
It’s not clear; all those that use steam have them, while those that use liquids such as cooling water or warm water also have guide cylinders.