1.The definition of vacuum

When the pressure in the vessel is lower than the atmosphere, the part which lowers than the atmosphere is called vacuum in the industrial and vacuum scientific, and the real pressure of the vessel is absolute pressure. LiBr absorption chiller and LiBr absorption heat pump are kind of sealed vessel, during the operation, the internal and external atmosphere of the unit are completely isolated, and the inside of the unit is in vacuum state.

2.Why vacuum is important for LiBr absorption chiller and LiBr absorption heat pump?

2.1 Ensure the performance of LiBr absorption unit
When the vacuum degree in the unit is extremely high, the pressure in the evaporator is quite low and the boiling point of refrigerant water will be decreased. When refrigerant water sprays on the heat exchange tube, it can directly vaporize into refrigerant vapor and absorb the heat of chilled water in the tube. But once the vacuum degree is decayed, the pressure and boiling point will change and the evaporation temperature will rise, which greatly reduces the heat absorbing ability during refrigerant water evaporation and reduce the efficiency of the unit. This is why we often say: "Vacuum is the life of LiBr absorption chiller and LiBr absorption heat pump".

2.2 Prevent corrosion inside the unit
The main materials of LiBr absorption chiller and LiBr absorption heat pump are steel or copper, and LiBr solution is a kind of salts which is corrosive when it’s exposed to oxygen. If there is air inside the unit, the oxygen in the air will oxidize the metal surface, thus affecting the lifetime of the unit.