Working of an Air Cooler
Working of an evaporative air cooler or how does air cooler works? Well, the simple answer to this question is evaporative air cooler works on the principle of evaporation of water. But to understand the complete working principle of air cooler we need to get in-depth knowledge.
So starting from its structure
Structure of Evaporative Air Cooler
An evaporative air cooler consists of a water tank, pump, cooling media and a blower or a fan. The water tank is located at the bottom of the cooler body. Cooling media is fixed on outer walls of the cooler allowing the outer air to pass through it. A blower or a fan is fixed on the opposite wall of cooling pads(media). The fan is attached to direct the inner air in the room. The pump is connected to cooling pads and water tank to raise the water above and spread it over the pads.
Now let’s see the job each of these components
Parts of an Evaporative air cooler and their working
Water Tank :
As simple as it sounds, the only job of this part is to store water. The capacity of air cooler to store water determines the type of air cooler. Air cooler having tank capacity up to 35-40 litres are called personal air cooler. And the ones having tank capacity above that are classified as Desert air coolers. There is no difference in working of desert air cooler and a personal air cooler.
The water tank has an inlet for pouring water and ice in it. Some air cooler also has a nob for filling the water through a pipe. An indicator is provided to check the level of water. Also, there is an outlet value usually at the bottom of the cooler to drain all the water out of the tank. Several elements of air cooler come in direct contact with water hence regular cleaning is required to maintain efficiency.
As seen in the figure above the water in the tank is raised above through the pump. And the excess water from the cooling media flows back to the tank.
Cooling Media ( Cooling Pads) :
Cooling media is a material that holds the water droplets. The water raised by the pump is spread over the cooling media. These pads have fine cell-like structures which can hold the water droplets. The excess water from the pads is sent back to the water tank.
There are mainly 3 types of Cooling pads:
- Honeycomb pads
- Aspen pads
- Wood wool pads
Among these, honeycomb pads are most efficient and require less maintenance. Aspen pads are also good and are moderately efficient. The wood wool pads are cheapest and require the most maintenance.
The outside air is passed through these pads and directed towards the fan or blower. When the air is passed through the water droplets the exchange of heat takes place and the air gets relatively cooler.
Working of an air cooler starts with the pump. The pump raises the water present in the water tank and spread it over the pads. This is the only job the pump does. But the pump efficiency has a huge impact on the overall performance of the cooler.
Fan or Blower :
Typically a fan is used in desert air coolers and blower in the personal air cooler. Both fan and blower are rotating objects. A fan is round in design and the blower is cylindrical shaped. Although they seem to be different from each other, they both serve the same purpose.
Their job is to pull the surrounding air into the air cooler and direct it into the desired space or room. Between this process, the air is passed through cooling pads containing water. This is where it gets cooled before entering the room.
Ice Chamber :
Some air coolers come with an ice chamber. This is a dedicated space for putting ice in an air cooler. In coolers without ice chamber, ice and water are needed to be poured in the same tank. The purpose of providing ice chamber is to get extra cool air from the air cooler.
Water from the tank is passed through the ice chamber before spreading it over the pads. Water gets cooled after passing through this chamber. And obviously, the air passing through pads also gets relatively cooler.
Working Principle of Air Cooler
Initially, the cooler is in Off state. When the cooler is switched on, the pump is triggered to raise the water in the tank. This water is then taken up and scattered all over the cooling media. The cooling pads hold the water within them. The excess water is passed back to the water tank.
Simultaneously the fan or the blower starts rotating. The air surrounding is pulled in by the fan. As the air enters from the sidewalls of the body of the cooler. This air passes through the cooling pads containing water before reaching the fan.
When the air passes through these pads the exchange of heat takes place and the temperature of the air falls down. This cold air then passes through fan or blower. At last, the air is directed out.
This continuous process lowers the surrounding temperature and cools the room.
The science behind the working of Evaporative air cooler
The temperature of the surrounding air is high as compared to the temperature of the water. According to thermodynamics heat in a body corresponds to the energy. Higher the temperature of the body more heat it holds.
And the energy always flows from high potential to low potential. More the energy gap more energy transfer takes place. Hence when air and water come in contact. The heat from the air is transferred to the water. This is because of the temperature difference. The water is evaporated because of this heat.
As the heat from the air is lowered the temperature of the air also drops down. And in this manner evaporation of water causes cooling. Also, this increases the humidity of the surrounding.
In coolers with ice chamber, the water is cooler than usual because of ice. Here the temperature gap between air and water gets more widen. This results in more heat transfer and thereby more cooling.
And this basically how an evaporative air cooler works.