Cooling Towers

The usual function of a cooling tower is to cool the water of a steam power plant by air which is brought into direct contact with the water.  The water is mix with vapor which diffuses from the condensate into the air.  The formation of the vapor needs a considerable elimination of internal energy from the water; the internal energy turns into "latent heat" of the vapor.  Heat and mass exchange are united in this procedure that is a steady-state process such as the heat exchange in the ordinary heat exchanger.

The wooden cooling towers are at times used in nuclear facilities and in factories of different industries.  They usually consist of large chambers loosely packed with trays or similar wooden elements of building.  The water to be cooled is pumped to the top of the tower where it is dispersed by spray or wooden troughs.  It then falls via the tower, splashing down from deck to deck.  A portion of it evaporates into the air which passes via the tower.  The enthalpy required for the evaporation is taken from the water and transferred to the air, that is heated whereas the water cools. The flow of air is either horizontal due to wind currents (i.e., cross flow) or vertically upward in counter-flow to the falling water. The counter-flow is the basis by the chimney consequence of the warm humid air in the tower or by fans at the bottom (i.e., forced draft) or at the top (i.e., induced flow) of the tower.  The mechanical draft towers are more economical to build and smaller in size than natural-convection towers of the similar cooling capacity.