concentration ratio in evaporation cooling tower VDI 3803

In evaporative cooling towers, the supply air is enriched with process water. The salts contained in the make-up water do not leave the cooling tower with the exhaust air. They must be removed with the exhaust air. The higher the concentration ration, the lower the blow down. With an infinitely high concentration ratio only the evaporated water has to be substituted.

The higher the concentration ratio, the higher the stress on the construction materials. VDI 3803 Sheet 1 Table A5 specifies maximum values for process water at temperatures <60°C.

How to continue:

1. Enter at least one of the values oxidisability, conductivity, chloride concentration or sulphate concentration for the make-up water. Entering the hardness is optional.

The program shows for each material group which paramter determines the concentration ration. The water hardness for the make-up water is suggested in such a way that the hardness limit value according to VDI is achieved with the determining concentration ratio. The salt consumption for softening is calculated if a hardness value has been entered for the make-up water. Specific salt consumption increases with increasing concentration ratio. However, this effect is completely offset by lower water consumption. If the minimum of the concentration ratios is less or equal to 1, further treatment of the make-up water (e.g. reverse osmosis) has to be taken into consideration. There is no plausibility check of the entered values.