A tube bundle is the core, heat-transfer component of a shell and tube heat exchanger. It is a precisely engineered assembly of multiple tubes, held together at both ends by perforated plates called tube sheets, and often supported along their length by baffles. In simple terms, it's the "engine" of the heat exchanger where the actual exchange of thermal energy between two fluids takes place.
1. Tubes: These are the primary heat transfer surface. They can be:
Straight or U-shaped (U-tubes): Straight tubes are fixed at both ends, while U-tubes allow for thermal expansion.
Made from various materials: Such as copper, brass, stainless steel, titanium, or carbon steel, chosen based on the fluid's corrosiveness, pressure, and temperature.
Different sizes and thicknesses: Specified by the required heat transfer area and pressure containment.
Finned: Sometimes they have external fins to increase the surface area for better heat transfer.
2. Tube Sheets: These are thick, round metal plates with precisely drilled holes. The tubes are inserted and secured into these holes. The tube sheet creates a rigid structure and, crucially, acts as a pressure boundary, separating the shell-side fluid from the tube-side fluid.
3. Baffles: These are plates placed inside the shell, along the length of the tube bundle. Their main functions are:
Support the Tubes: Prevent the tubes from sagging and vibrating excessively, which can lead to failure.
Direct Shell-Side Flow: They force the shell-side fluid to flow across the tube bundle in a zig-zag pattern, instead of taking a straight, short path. This cross-flow greatly increases heat transfer efficiency by creating more turbulence.
4. Tie Rods and Spacers: These are used to hold the baffles in their correct positions along the length of the bundle.
5. Channels/End Caps: These are attached to the tube sheets and direct the tube-side fluid into and out of the tubes.
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