The primary differences between the various types of evaporators are the way in which the heat exchanger and vapor body are connected together and their physical relationship to each other.The most common evaporators fall into three types: rising film, falling film, and forced circulation flash.Rising filmThe drawing (right) shows a typical rising film evaporator. The heat exchanger is mounted vertically and the evaporator liquid flows upward through the tubes. Water in the evaporator liquid boils as the liquid rises. This boiling action helps force liquid up and out of the tubes.The liquid and vapor leave the heat exchanger together and enter the vapor body. A

fter vapor separation, the evaporator liquid flows from the vapor body through the circulating pump to the heat exchanger.