A cooling tower as the name suggests is a device which releases excess heat from a system into the atmosphere. Cooling tower technology finds its utility in large-scale economical cooling solutions. Its also is the number one choice where work efficient long-term cooling solution is desired.
Cooling tower utilises cooling a stream of water which is at the higher temperature to a lower temperature in order to gain the required or desired cooling effect.Commonly cooling towers reach their objectives by either cooling the working fluid to near wet bulb temperature using evaporation or in case of closed circuit cooling towers the mechanism cools the working fluid to dry bulb temperature using air solely as the cooling medium.
Size of the cooling tower can vary from a small rooftop unit to huge hyperboloid units as used in nuclear power stations. However, in the real and practical sense, we seldom see such huge sized cooling towers and mostly small-sized cooling towers are common in use for discharging heat generated by air conditioning systems.
Cooling towers find wide applicability in petrochemical applications, HVAC, chemical plants and thermal power stations.
Types Of Cooling Towers-
Broadly the cooling towers are classified according to the type of air induction utilised and are classified as a natural draft and induced draft cooling towers.
Types Of Cooling Towers On The Basis Of Heat Transfer methods used-
Dry Cooling Towers:
In this type of cooling tower, the working fluid is channelled through tubes which collects the ambient heat and then this heat is exchanged with atmosphere using air as a medium. No liquid or water is hence used for cooling in this type of setup
Wet Cooling towers:
It is also known as open circuit cooling towers. The working principle of wet cooling towers is evaporative cooling and in this case the working fluid or the fluid used for heat exchange and the fluid that is actually evaporating is the same i.e. water.
Also known as closed circuit cooling towers, these devices are actually hybrid in nature and combine the best of both dry and wet cooling systems. Here the working fluid or the heat exchange fluid is encased in a tubing system and never comes in contact with the open atmosphere. The tubing or the heated tubing is then subjected to a stream of water which in turns exchanges the heat.
Types of cooling tower on basis of methods of air flow generation –
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.