The research focuses on water desalination by distillation process under condition of vacuum pressure. The distillation unit was elevated over the ground surface then water was sucked from it. The water was boiled at temperatures below (100)oC as a result of reaching the absolute pressure to the vapor pressure values of water at these temperatures. The distillation unit was elevated at (6.27-7.15-8.25)m over ground surface, so that the absolute pressures exerted were (37.54-27.76-18.21)kPa respectively and the boiling points were (78-72-62) oC respectively. At each elevation of the distillation unit, different values of temperature were applied on the saline water samples (with same concentration and volume). The results indicated increasing in evaporation rate with increased elevation from ground level and with increasing of the applied temperature. This is linked with increasing in evaporation energy as a result of (boiling heat flux) increasing with the depression in absolute pressure and with increasing in temperature. The average increasing in evaporation rate was (6.78)cm3/hr for each (kPa) depressing in absolute pressure and (7.41) cm3/hr for each (oC) rising in temperature. The condensation tube was designed for each boiling and evaporation process depending on mounting the condenser at atmosphere. The design was affected by the variation in temperature and pressure applied.
Key words: Desalination, Distillation, Vacuum pressure