Shell and Tube Heat Exchanger

Shell and Tube Heat Exchanger

Tubular heat exchangers are widely used in chemical and alcohol production. They are primarily composed of a shell, tube plates, heat exchange tubes, end caps, and baffle plates. The materials used can be carbon steel, copper, or stainless steel. During heat exchange, one fluid enters through the connecting pipe at the end cap, flows through the tubes, and exits through the outlet pipe at the other end of the end cap, which is known as the tube side; the other fluid enters through a connection on the shell and exits through another connection on the shell, referred to as the shell side.
 
Structural Description
Shell-and-tube heat exchangers are structurally simple, compact, and cost-effective, but they cannot be mechanically cleaned on the outside. The tube bundles are mounted on tube plates, which are welded to the ends of the shell. A top cover is connected to these plates, and both the top cover and shell are equipped with fluid inlet and outlet connections. Typically, a series of vertical baffles perpendicular to the tube bundles are installed outside the tubes. Moreover, the connections between the tubes, tube plates, and the shell are rigid, while the fluids inside and outside the tubes are at different temperatures. Consequently, when there is a significant temperature difference between the tube wall and the shell wall, the differing thermal expansions of the two materials create a substantial temperature difference stress. This can lead to tube twisting, bending, or even loosening from the tube plates, and in extreme cases, damage to the heat exchanger.
To overcome thermal stress due to temperature differences, a temperature compensation device is necessary. Generally, when the temperature difference between the tube wall and the shell wall exceeds 50°C, for safety reasons, the heat exchanger should be equipped with a temperature compensation device. However, the compensation device (expansion joint) can only be used when the temperature difference between the shell wall and the tube wall is below 60-70°C and the shell side fluid pressure is not high. Normally, when the shell side pressure exceeds 0.6Mpa, due to the excessively thick compensation circle, it becomes difficult to expand or contract, thereby losing the temperature compensation effect, alternative structures should be considered.