Heat exchanger tube sheet calculation (examiner’s questions)
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What are the reasons why the thickness of the heat exchanger tube sheet needs to be increased and recalculated? This is an examiner exam question; I’m seeking guidance from experts regarding the answer
It’s definitely necessary. An increase in the thickness of the tube sheet leads to changes in factors such as the flange on the opposite side, the shell sections connected to it, the temperature distribution, and the heat exchange area. Not only does the strength need to be recalculated, but the entire process also needs to be reevaluated.
One more thing: changes in the thickness of the tube sheet may result in changes in the allowable stress...
From a process perspective, the overall design remains unchanged; however, if the tube sheet is thickened, the flow area will also change. Considering more detailed aspects, the area of some dead zones will as well change. In terms of strength, thickening the tube sheet increases the strength; if there is a need for changes, then the strength must be recalculated if resources are to be saved
1. The strength calculation of the tube sheet is related to the stiffness coefficient at the connection between the tube sheet and the shell. As the tube sheet thickens, the stiffness coefficient at the joints increases, affecting the peripheral support condition of the tube sheet ； 2. As the thickness of the tube sheet increases, the support provided by the tubes to the tube sheet decreases under the same conditions ； 3. An increase in the thickness of the tube sheet may lead to an increased unsupported span of the tubes, which in turn affects the calculation results for the tube sheet.
It seems that thickening the tube sheet is not just a matter of increased manufacturing costs
In terms of materials, the allowable stress may vary; where sheets were used in the past, forgings might now need to be considered. From a stress perspective, in the case of a fixed-tube-sheet heat exchanger, the deformation of the tube sheet, the shell, and the heat exchange tubes must be coordinated. If the tube sheet is thickened, its bending resistance increases and deformation decreases.