Systematic Explanation of Heat Exchanger Design Knowledge (Lecture 1)

Thread Content

The factory has been organizing training on heat exchange knowledge for its technical experts for almost a month now, and I’ve really wanted to share this information with everyone. I originally planned to wait until the training materials were sent to us before sharing them, but it seems that’s no longer possible (the expert who conducted the training was a foreigner who was very protective of the knowledge; only printed copies of the materials were provided, no software). So all I have are the written lecture notes from the training, along with a few notes of my own. I’ll share a little bit of information with everyone each day, which can also serve as a starting point for discussions – I hope we can all improve together. Thermal and structural design ① Design functions and responsibilities ② Basic techniques and knowledge ③ Steps from inquiry to data sheet ④ Steps for evaluating solutions Key points of performance design ① Leak-free operation ② Safety ③ Cost-effectiveness Main aspects considered in performance design: ① Measurements and tolerances ② Surface conditions for sealing and coating ③ Exhaust and drainage systems ④ Demisters ⑤ Safety considerations ⑥ Gaskets ⑦ Standards for semi-finished products Measurements and tolerances ① Primary measurements ② Tolerances ③ Methods for correcting deviations Key measurements for customers: ① Comprehensive measurement of pipe connection positions; ② Comprehensive measurement of saddle positions. It is important to note the term “comprehensive” here – these two dimensions are of primary concern to customers. In our design, we must establish limits regarding these comprehensive measurements to ensure proper installation by the customers. Main performance criteria: Leakage-free flow of liquid from the tube bundle to the housing. Regarding tolerances, the teacher referred to the TEMA standards during the explanation. The corresponding GB standards also have regulations on this. Taking TEMA as an example, the linear tolerances are determined based on length: in the teacher’s example, the tolerance for a spacing of 3.2 inches is ±1/8 inch, while for a spacing of 6.4 inches it is ±1/4 inch. Regarding the dimensions of the pipe fittings, the flange surface of the pipe fitting corresponds to the XZ plane, the centerline of the pipe fitting flange corresponds to the X and Z axes, and the central axis of the pipe fitting corresponds to the Y axis. The required tolerances are as follows: in the XZ plane, the angular tolerance for rotation counterclockwise along the X and Z axes is ±0.15 degrees, while the linear tolerance in the XYZ direction is ±5 mm. In actual design, we can choose tolerances according to standards, or we can use stricter factory-specific standards. Tolerances can be indicated directly on the dimensions or listed in a table attached to the drawings. We have provided drawings that have been converted for a foreign manufacturer; they created a data sheet containing all the dimension tolerances. The tolerances in this data sheet are determined based on the number of decimal places used in the drawing dimensions, and this can serve as a standard template. Methods to correct deviations: ① For the design of large-sized pipes, an insertion method can be used to achieve better positioning, with the pipe inserted inside; the insertion length is generally set at 1/2 inch (based on my experience), but the impact of pressure drop must also be taken into account. ② To ensure the structural strength of the pipes during manufacturing, methods such as welding support strips around the pipes can be employed. ③ Flexible structures: I. Gaskets above and below the pipe bundle; II. Gasket support at the movable ends; III. Adjustment of the height of the slides relative to the pipe bundle. These three structural elements are crucial. That’s all for today’s discussion. You can discuss these three points further, and we’ll continue tomorrow. I hope to see some good ideas from your responses. To facilitate the discussion of key point ③ – Flexible structures: I. Gaskets above and below the pipe bundle; II. Gasket support at the movable ends; III. Adjustment of the height of the slides relative to the pipe bundle – typical structural diagrams are provided here. I’m unable to upload images right now; I’ve sent them to the machinery equipment section for uploading ； Please refer to the structure diagram when discussing these three points to figure out how adjustments can be made in order to correct the deviations that occur during manufacturing. I hope everyone will actively participate in the discussions; we will continue the discussion tomorrow night. Here is the structure diagram: Additionally, I would like to emphasize once again that I hope everyone will engage actively in the discussions and work together to make progress. If no one is enthusiastic, then I won’t be enthusiastic either. By discussing together, it’s possible that even the mistakes made by my instructors might be identified. I hope we can all work together to improve our section. This post was last edited by vivo1314 on 2009-4-7 at 22:59