A thin film evaporator has a shell with tubes extending through the shell in at least one pass. The shell has a top and a bottom. Process fluid flows through the tubes. A suction from a compressor is applied to the top of the shell at a refrigerant outlet. Refrigerant is introduced into the shell at the bottom and is distributed across the bottom region of the shell. The refrigerant flows up and contacts the tubes, exchanging heat therewith before flowing out of the shell top. Oil in the refrigerant contacts the shell wall and drains into a sump.
