The air cooler: a star product for summer 2020?

Summer is fast approaching, and the prospect of prolonged lockdown on the hottest days of the year is no longer fanciful. How to deal with the heat and the scorching episodes that are becoming more and more frequent in these complicated times of a pandemic? Air conditioning is not a viable option for everyone, for two reasons: it increases the energy bill more than it should and it boosts the carbon footprint of our homes. Here's why the air cooler could well establish itself as the star product of summer 2020.

What is the air freshener?

Also called an evaporative cooler, the cooler air is a device that lowers the room temperature by 4 to 6 degrees by the evaporation of water. Evaporative cooling differs from conventional air conditioning systems, which use vapor compression or absorption refrigeration cycles. Evaporative cooling is based on a fairly simple basic principle: the water will absorb a relatively large amount of heat in order to evaporate (enthalpy of vaporization).

The temperature of dry air can be lowered significantly by the phase transition from liquid water to water vapor (evaporation). This principle therefore cools the air by using much less energy than refrigeration air conditioning. In extremely dry climates, evaporative air cooling has the added benefit of conditioning the air with more humidity for occupant comfort. It should be noted that low humidity results in dryness of the mucous membranes (especially nasal membranes), itching of the eyes, problems with skin dehydration and possibly a tendency to nervousness and irritation.

The evaporative cooling potential depends on the vacuum of the wet thermometer, that is to say the difference between the temperature of the dry thermometer and that of the wet thermometer (this is called relative humidity). In arid climates, evaporative cooling can reduce energy consumption and overall conditioning equipment as a replacement for compressor cooling. In non-arid climates, indirect evaporative cooling can still take advantage of the evaporative cooling process without increasing humidity. Passive evaporative cooling strategies can offer the same benefits as mechanical evaporative cooling systems without the complexity of equipment and ductwork.

Installation of the air cooler

In general, air fresheners, whether residential or industrial, use direct evaporation, and can be described as a closed metal or plastic box with ventilated sides. The air is moved by a fan or a centrifugal blower (usually driven by an electric motor with pulleys or a direct drive axial fan), and a water pump is used to wet the evaporative cooling plates. Cooling units can be mounted on the roof (down draft, or down drain) or on exterior walls or windows (side draft, or horizontal drain).

To lower the room temperature, the fan draws room air through openings on the sides of the unit and through the wet cushions. The heat of the air causes the water to evaporate from the cushions that are constantly rebooted to continue the cooling process without stopping (depending on the models of the air cooler available to you). The cooled moist air is then routed through an air vent in the roof or on the wall.

Since the cooling air comes from the outside, one or more large ventilation holes must be provided to allow the air to move from the inside to the outside. Air should only be able to pass through the system once, so as not to neutralize the effect of cooling. Otherwise, the saturation point is reached. Often, about fifteen air changes per hour occur in spaces served by evaporative air coolers, resulting in a relatively high air change rate.