Using the indirect evaporative process to pre-cool the supply air stream can reduce the energy consumption of mechanical cooling equipment by up to 80%.
With indirect evaporative cooling, a secondary air stream is cooled by water. The cooled secondary air stream goes through a heat exchanger, where it cools the primary air stream. The cooled primary air stream is circulated by a fan.
This method uses the outside air to cool an internal environment, without allowing external and internal airstreams to directly mix. Cool outside air is drawn through a heat recovery unit then immediately exhausted, while internal air is drawn from the room and circulated through the heat recovery unit before being re-introduced to the space.
When the supply of air is passed through the coil, the coil gets cooler and the air then has indirect contact with the cooled water. Essentially, there are two passages during the process – dry and wet. During dry passages, the primary air is cooled, which is separated from the wet passages where the secondary air and water flow are cooled.
The outside air’s cool thermal energy is thus transferred to the internal air via the heat recovery unit without the two streams directly mixing.
By humidifying the outside air prior to it entering the heat recovery unit, its temperature is economically reduced and even more low cost cooling is applied to the internal atmosphere.
This enhances the capacity of the system and makes it effective even during periods when the outside temperature is warmer than the desired internal room condition.
As the internal air never mixes with the outside air, there is a reduced possibility of the internal atmosphere being compromised by external pollutants so this is an ideal strategy for critical environments.
It also allows the velocity of the outside air stream through the heat recovery unit to be much greater than the internally circulating air, thus “scavenging” even greater levels of cooling from the system
Indirect evaporative cooling does not add moisture to the primary air stream making it ideal for highly specialist manufacturing and production facilities.
There are also hybrid specialist solutions that you may find interesting to explore in more detail. Click here to find out more