Abstarct: In many cases, the supply of drinking water in a high volume is faced with a lot of problems. Therefore, it is very necessary to build a small or medium scale desalination plant in the range of one to one hundred cubic meters per day. One of the best methods for small-scale water desalination is the use of multi-effect distillation. In this method, water evaporates in the evaporator in the vacuum chamber at a temperature below its boiling point, and in the condenser the steam from evaporation is converted into fresh water. Since these devices have been designed and built for large scale (more than 1000 cubic meters per day) so far, we face a lack of information for optimal design on a small scale (1 to 100 cubic meters per day) and also the most important point is heat transfer coefficient estimation. Therefore, to design a MED system, it is necessary to know the heat transfer coefficient (falling film) in different working conditions. Therefore, for small-scale MED design (which is the focus of the present study) requires a detailed experimental study on falling film converters with the possibility of changing sensitive parameters.