Connection type between the tubes and the tube sheet of a falling film evaporator
Thread Content
I would like to ask everyone: 1. In a typical falling film evaporator, how are the heat exchange tubes connected to the tube sheet? Is it by welding, expansion bonding, or a combination of both? 2. If expansion jointing is used, what is the level of sealing performance, especially under negative pressure? 3. Since a liquid distribution device is required, conventional ones consist of a small sleeve that extends into the heat exchange tube; if welding is used, could the welded area of the heat exchange tube become deformed, thereby affecting the liquid distribution via the sleeve?
Those who know the answer could please give some guidance
We have designed for situations where the pipeline pressure is low, with vacuum conditions. At this time, a combination of strength welding and expansion bonding can be used, provided that the protrusion length of the heat exchange tubes from the upper tube sheet does not exceed 0.5 mm; it is best to keep them as short as possible to prevent the accumulation of liquid. When the pressure in the tube side is high, since the diameter of the heat exchange tubes used for falling film evaporation is generally large, their wall thickness is relatively thick as well. If high-strength welding is employed, the height of the weld corner must meet certain requirements; consequently, the tube sheet needs to pass strength checks, and its thickness becomes very large. Even the use of expansion joints may not be sufficient in such cases. Therefore, a connection structure combining strength expansion and seal welding can be chosen. This approach helps to avoid the situation where, in accordance with standard requirements, the height of the weld corner between the heat exchange tubes and the tube sheet is too large; in the absence of external weld corners, this can lead to difficulties in welding as well as an increased amount of welding work required.