Design of falling film evaporators

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According to the design of evaporators described in textbooks on chemical engineering principles, the equal pressure difference method is used; the area of each stage is determined through initial calculations. The textbooks state that for the sake of ease in manufacturing, installation, storage, and operation, it is common to make the heat transfer areas of each stage equal. To achieve roughly equal areas, the temperature differences across each stage are reallocated, and then the heat transfer areas are calculated again. Question: Is it appropriate to keep the temperature difference across each stage constant when the heat transfer areas are made essentially equal here? Do we need to do the accounting? In the calculations in the book, only the overall heat transfer coefficient needs to be verified; if the overall heat transfer coefficient is appropriate, are then all other parameters also appropriate? In the design of falling film evaporators, steam is used for heating; the steam flows through the shell side while the liquid flows through the tube side. So how should the flow velocity of the liquid, or the minimum wetting volume, or the minimum liquid flow rate be determined? Knowing this is necessary to calculate the size of the falling film circulation pump.