Evaporative towers: what are they?
Cooling towers, or evaporative towers, have the function of dissipating heat from a liquid through a gas. Most of the time the gas phase consists of air or water vapour and the liquid phase of water. In short, a heat exchanger between water and air, which through the subtraction of heat from the liquid leads to the evaporation of a minimum quantity of water, compared to the total in circulation.
Within industrial processes, in HVAC and in energy production, excess heat is often produced which must be disposed of in some way. Among the various alternatives available to achieve this goal, evaporative towers constitute one of the most efficient and economical solutions on the market.
Evaporative towers: what are the advantages?
The structural simplicity of the cooling towers, combined with their efficiency in terms of dissipated cost / kW ratio, make these systems widely used in both civil and industrial sectors.
Using evaporative cooling towers is more effective than using dry air cooling if a final fluid temperature below ambient is desired. In fact, as Assoclima confirms, with 1 Kg of water the subtracted heat is 2,200 kJ per °C, while with 1 Kg of air the removed heat is about 1 kJ per °C. Among other things, thanks to evaporative cooling, it is possible to reduce the outlet water temperature to approximately the wet bulb temperature, which is lower than the dry bulb temperature . The wet bulb temperature, in fact, is the lowest temperature that can be obtained by evaporation of water in the air, at constant pressure.
In terms of energy consumption, a tower can consume up to four times less than other cooling systems. If we consider the increasing attention to the issue of global warming, as well as energy consumption, it is clear that the use of an evaporative tower represents one of the most advantageous solutions.
Cooling towers: how do they work?
The principle of operation of a forced open circuit cooling tower is the most commonly used model. In evaporative towers, the process fluid (water) is cooled by a counter-current flow of cold air. The water (4) is sprayed from the nozzles positioned above the heat exchange pack (3), where it comes into contact with the flow of cold air sucked in by the grids (2). During the passage in the heat exchange pack, part of the water evaporates and the larger drops are separated from the air flow thanks to the drop eliminators above the distributor (5). The hot saturated air is released into the atmosphere from the top of the tower (6). The cooled water collects in the basin and is sucked up by the outlet equipped with a filter. The circuit is of the open type as the water to be cooled comes into contact with the atmosphere.
How to size a cooling tower?
The parameters to keep in mind when choosing to use an evaporative tower are the following:
- Thermal power to be dissipated
- Inlet water temperature
- Leaving water temperature
- Wet bulb temperature at the location where a tower is to be installed
Types of evaporative towers
- Axial evaporative towers are the best known machines, with the use of axial fans on the top of the machine. Our customers choose W-tech axial evaporative towers because of their low power consumption and small installation space.
- Cooling towers with axial pressing fans, have higher efficiency and simplified maintenance thanks to the positioning of the motor and the fan.
- Evaporative towers with centrifugal fans, used when a reduced sound emission is required, offer a classic design to achieve the goal. If quieter operation is required, inlet and outlet silencers can be fitted.
- Low height evaporative towers with centrifugal fans. For installations in buildings and for low-height spaces. Where there are pit installations, vertical air intakes can be installed.