Evaporative cooler

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Lal Qila (Red Fort) 123

Air cooler

Qanat wind tower

Evaporative cooler is a device that cools air through the evaporation of water. Evaporative cooling differs from typical air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling works by employing water's large enthalpy of vaporization. The temperature of dry air can be significantly reduced through the phase transition of liquid water to water vapor (evaporation), which can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants.

Principle of Operation

The basic principle of an evaporative cooler is that it cools air by evaporating water. This process is also known as adiabatic cooling. Air, which is a mixture of gases, has the capacity to hold a certain amount of water vapor. The capacity to hold water vapor increases with air temperature. Therefore, when water is evaporated into the air, the energy required to evaporate the water is taken from the air, reducing its temperature. The efficiency of an evaporative cooler depends on the humidity of the ambient air. The lower the humidity, the greater the potential for cooling.

Components

An evaporative cooler typically consists of a fan, a water pump, cooling pads, and a water distribution system. The fan draws warm outside air through the moist cooling pads. As the air passes through the pads, water evaporates, absorbing heat from the air and thereby cooling it before it is circulated into the space to be cooled. The water pump circulates water from the bottom of the cooler to the top, where it flows over the cooling pads.

Types of Evaporative Coolers

There are mainly two types of evaporative coolers: direct and indirect.

• Direct Evaporative Coolers: These coolers directly cool the air by evaporating water into it. The cooled air is then blown into the space to be cooled. This method increases the humidity of the air.

• Indirect Evaporative Coolers: These coolers use a secondary air stream that is cooled through evaporation and then used to cool the main air stream without adding humidity to it.

Advantages and Disadvantages

Advantages

• Energy Efficiency: Evaporative coolers consume less electricity compared to traditional air conditioners, making them more energy-efficient and environmentally friendly.
• Adds Moisture: In dry climates, they add moisture to the air, which can improve comfort.
• Cost-Effective: Lower installation and maintenance costs compared to conventional air conditioning systems.

Disadvantages

• Limited to Dry Climates: Their cooling efficiency drops significantly in high humidity environments.
• Maintenance: Evaporative coolers require regular maintenance, including pad cleaning and replacement.
• Water Use: They consume a significant amount of water, which can be a concern in areas with water scarcity.

Applications

Evaporative coolers are used in a variety of settings, including residential homes, commercial spaces, and industrial facilities, particularly in areas with hot, dry climates. They are also used in some industrial processes that require air cooling.

Environmental Impact

Evaporative coolers have a lower environmental impact compared to traditional air conditioning systems due to their lower electricity consumption and the absence of refrigerants, which can contribute to greenhouse gas emissions. However, their water usage is a factor that must be considered, especially in regions facing water scarcity.