The invention relates to a falling film evaporator, which is fitted with a liquid distributor which is divided into segments, such that it is possible to charge only a limited number of evaporator tubes with liquid and the evaporator can be operated in an optimum manner even with a partial load. The invention also relates to a method for operating said falling film evaporator, the aim of which is to transfer heat, which is released when a gas-vapor mixture is condensed, to a liquid which is to be evaporated at least partially. It would be useful to use said falling film evaporator thus fitted in heat recuperation systems such as those used in the production of 1,2 dichloroethane.