A process for introducing a solution into an evaporative cooling apparatus (14), said process comprising a) positioning a selectively permeable membrane (16) between a first solution (18) and a second solution (20) having a higher solute concentration than the first solution (18), such that the solvent from the first solution (18) flows across the selectively permeable membrane (16) to dilute the second solution (20), b) introducing the second solution into an evaporative cooling apparatus (14) in which solvent is removed from the second solution (20) by evaporation, and c) recycling the second solution (20) from step b) to step a) to draw solvent from the first solution (18).