Abstract: A centrifugal liquid separator and defoamer for use in a vacuum cooling system including a cooling vessel having a vessel interior for containing a liquid to be cooled, and a vacuum system for applying a vacuum to an interior of the vessel, through a vessel vapor outlet nozzle. This separator and defoamer includes at least one impeller blade positioned in the vicinity of a juncture of the vessel interior and vessel vapor outlet nozzle, this impeller blade being rotated at a speed at which any liquid contacting the rotating impeller blade will be thrown off the blade, and any foam contacting the impeller blade will be converted to liquid and thrown off the blade, in the direction of the vessel interior, by centrifugal action.