Evaporative condenser is an indirect heat exchanger, which means that the heat exchange is done initially through a metal surface, where the heat exchange is done through direct contact between the vapour to be condensed and water from the cooling system.
In the evaporative condensers, the vapour to be condensated is sent into a tube bundle. Outside of the tubes occurs a “rain” of cooling water at ambient temperature, water is inside a closed circuit, receiving water make up constantly (usually it is used the condensate generated inside the tube bundle and water from liquid seal of vacuum pump). The heat of condensation is transferred to “rain” and removed by evaporation of water corresponding to an air stream provided by a fan.
We can imagine therefore the evaporative condenser as a cooling tower of the compact type, which has a tube bundle mounted inside and that condenses the vapour from the process inside the tubes. This tube bundle should normally be constructed of corrosion resistant material, AISI 304 or equivalent, because the steam condensed in the process tends to be corrosive. The tubes should be preferably finned, as this construction facilitates the exchange of heat on the side of the air current. The tube bundle is generally mounted with a slight slope, in order to facilitate the removal of condensate inside the tubes and removal of incondensable gases through the top.