There are analyzed the heatmasstransfer processes, performing in equipment of one of possible sea water desalination systems, acting with solar heating source usage. The circulation in system air is humidized by the sea water, then it is heated in solar heater and enters in a dehumidizator — condenser, which is cooled by sea water in flow. A desalinated condensate is directed to fresh water consumer. There is considered in detail a process of condensation of system from moistened steam — air mixture in a heat exchanger — dehumidizator of plate type.