Design calculations for membrane towers

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As the title suggests: Our company currently has film towers in operation. The original designed feed rate was 1 t/h, and we now plan to double that amount. I would like to ask how to conduct the design verification for a membrane tower? Note: The material fed into the thin-film tower contains boiling substances and solid residues; the boiling point of these substances is higher than that of the steam, so operation is required at -80 kPa. I use ASPEN with a flashing module to calculate the heat load. The steam load and the load on the top condenser meet the requirements, and the pipe diameters are also within the design flow velocity range. However, due to the high temperature at the bottom of the tower, the temperature in the flash module remains constant; as a result, the temperature difference between the steam at the bottom of the tower and the material decreases. Since the heat transfer rate is related to this temperature difference, I suspect that the actual steam load does not reflect the actual operating conditions. Moreover, as the feed rate increases, the liquid film condition also causes changes in the K value. How should this be calculated? Or there are relevant design manuals or templates. Production can only increase the feed rate gradually, but I also want to verify this using theory.