The design flows and Pressure drops through the evaporators are as follows.

10m2 Light Lube Evaporator
We are looking for a friction pressure drop of 20 psig with a flow of 165 GPM. The 2 shells are piped in series so the full flow goes through both shells and the pressure drop is 10 psi in each shell. This is just the friction pressure drop. Pressure drop due to elevation is already taken into account in my sizing.

7.5m2 Heavy Lube Evaporator
We are looking for a friction pressure drop of 20 psig with a flow of 125 GPM. The 2 shells are piped in series so the full flow goes through both shells and the pressure drop is 10 psi in each shell. This is just the friction pressure drop. Pressure drop due to elevation is already taken into account in my sizing.