The tube sheet of evaporator

This is a tube plate of an evaporator. How much is left in the first half of the heat transfer calculation? When calculating the strength, the blank part calculates “ the area of non-pipeline area ” when calculating the strength, it will be obvious when calculating the pvelive part. Sometimes it will be wrong when calculating the strength with sw6. When calculating the strength, I increase the number of tubes more than the actual one. How do you deal with it?
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