Natural draft cooling tower:
A large tall tower which is also wide-mouthed is used for this type of cooling. It utilises the principle of buoyancy to achieve the desired effect.The warm and moisture-laden air inside the tower will naturally rise towards the dry and cooler air outside the tower and this differential acts as a medium of heat exchange. This type of cooling tower is suitable for the huge area and heavy usage.
Mechanical Draft Cooling tower:
This method uses power-driven fans to circulate air or suck out air through the cooling tower.They are further classified into induced draft towers and Forced draft towers.
Induced Draft Towers:
This type of tower has a powerful fan unit at the top. When turned on this powerful exhaust fan pulls the hot moist air out of the system and into the atmosphere. The exit velocity of air, in this case, is quite high when compared to the entry velocity hence eliminating the risk of recirculation.
Forced Draft Towers:
This is just the opposite of induced draft system, in this set up the fan blows in the air at high velocities in to the tower rather than forcing it out. Here the entry velocity of the air is quiet high in comparison to the exit velocity. This type of cooling tower not only cools but also raises the pressure of the system. Ideal for applications where cooling and pressuring are both desired.