Adiabatic cooling is an effective way of cooling and is based on cooling air by evaporating water. It is not for nothing that this method of cooling is also called evaporative cooling. The energy required for evaporation is extracted from the air, which cools it down as a result. This principle occurs frequently in nature and has also been applied by humans in the distant past.

There are two methods of evaporative cooling: direct or indirect. In both methods, air is cooled by evaporating water. The starting point here is that for 0.7 kW cooling, about 1 liter of water is needed per hour. This way of cooling works more effectively when the outside temperature increases. For example, at an outside temperature of more than 30^OC the indoor climate 10^OC or more are cooled.

Direct evaporative cooling
With direct adiabatic cooling, the air to be cooled (usually outside air) is drawn through a package saturated with water. This package is made of a material that can contain a lot of water, such as cellulose or paper. This package is kept moist.

On the package, some of the water in the supply air stream evaporates. This makes it more humid and the temperature of the air decreases as a result. The air resistance of the direct adiabatic cooling section is virtually nil, so that hardly any extra energy needs to be added to the supply fan. As a result, energy consumption is also limited. For example, only 1 kW of energy is needed to generate 10,000 m³/h to cool. This makes the air more humid.

Indirect evaporative cooling
In indirect systems, the air cooled by evaporation does not enter the room directly, but the cold is transferred to another air stream via a heat exchanger. This more complex principle is chosen if the final relative humidity in the room is not pleasant.

Indirect adiabatic cooling therefore works with two air flows, namely the humidified return air and the supply air to be cooled. The return air is humidified and passed through the heat exchanger, where it transfers its cold to the heat exchanger and is then discharged outside. In the heat exchanger, the supply air (outdoor air) can absorb cold without becoming humid itself and then cool the room to be conditioned.

Healthy indoor climate due to good relative humidity

Humidity in the house has a lot of influence on the indoor climate and on our health. In colder weather, the chance of low humidity is greater. You often notice this in dry air in the house, which can cause health problems such as dry skin or throat, but also cracks and tears in wooden furniture, floors and frames. How do you know if you are dealing with low humidity in your home and what can you do about it?

What is humidity?

First of all, it is good to know what humidity is exactly. We often talk about the relative humidity. This percentage indicates the amount of water vapor in the air in relation to the maximum amount of water vapor at a given air pressure and temperature. To give an example: if the relative humidity is 50 percent, the air contains half the maximum amount of water vapor.

When is the humidity too low?

In general, you can use these percentages to check how the humidity is in your area.

• High: 60 percent or higher
• Normal: 40 to 60 percent
• Low: lower than 40 percent

Especially in the winter months, houses are sensitive to low humidity. When it gets colder, the heating is higher in many households. In addition, active ventilation contributes to accelerating the drying process.

What are the consequences of low humidity?

Low humidity causes dry air in the house. You can often notice this:

• Dry eyes, throat or nose
• Sore or irritated throat
• irritable cough
• chapped lips
• Headache
• Concentration problems
• Dry or flaky skin
• More suffer from respiratory diseases, such as asthma and respiratory allergies
• Static electricity

In dry air, viruses can survive even longer, making you more likely to get sick. Low humidity not only affects our health, but also wooden furniture, window frames and floors. For example, parquet can crack or shrink due to the dry air. Even musical instruments, such as piano and guitar.

What to do with low humidity?

The most effective solution against dry air due to a low humidity level is a humidifier. With this you can easily keep the humidity indoors at the right level.

Automatic and safe humidification? The HomEvap humidifier is the solution. Directly connected to ducts of the heat recovery ventilation system and controlled by a control panel. Equipped with a legionella filter to ensure safe operation. No risk of moisture in the channels due to the limitation of moisture by the sensor.

A good balance in indoor humidity can help reduce the chance of spreading COVID-19. Especially on (very) cold days in winter it can get very dry in the house. Try to keep the humidity between 40-60% (you can measure this with a humidity meter and some thermostats can also measure this). Lots of plants in the house can help maintain good humidity. There are many humidifiers on the market. Research carefully which one applies to you. Most humidifiers need to be refilled manually and you will need several for a desired result. The humidifiers of HomEvap work automatically, are mounted on the ventilation system or built into, for example, the storage room.