Cooling of outdoor air conditioning units by a fine water mist system

Outdoor units of air conditioning and HVAC systems operate under highly variable weather conditions. At high outdoor temperatures (above 32-35°C), the efficiency of condensers drops sharply, leading to increased condensing pressure, increased power consumption and the risk of emergency shutdowns (high-pressure cut).

Integrating a fine water mist cooling system is an effective method of improving heat transfer and stabilizing the operating parameters of outdoor units.

Principle of evaporative cooling

The system uses high-pressure noozles that spray water with droplet sizes typically in the 5-20 micron range . At these sizes, the water particles evaporate completely already in the air flow without reaching the heat exchange surfaces in the liquid state.

Evaporation leads to:

• lowering the inlet air temperature by 5-15°C (depending on humidity and ambient temperature)
• increasing the temperature gradient between the condenser and the ambient air
• improved heat transfer and lower condensation pressure

Typical technical parameters of the system

Working pressure:

• 40 – 70 bar (professional systems)

Size of noozles:

• 0.1 – 0.3 mm
• material: stainless steel, brass with ceramic core or anti-drip construction

Water consumption:

• 1 – 3 l/h per noozle
• total cost significantly lower compared to traditional cooling methods

Filtration:

• multilevel (usually 5 μm + 1 μm)
• clogging protection and extended noozle life

Management:

• thermostatic (activation at preset temperature)
• timer control
• possibility of integration with BMS / PLC systems

Influence on the operating parameters of the air conditioner

When the inlet air temperature is lowered, the following effects are observed:

• reduction of condensation pressure by 10-25%
• lower condenser temperature
• reduced electrical load on the compressor
• more stable operation at extreme temperatures

In real conditions, this results in a 5-20% reduction in electricity consumption, depending on the type of air conditioner and the operating mode.

Application in grouped external fixtures

In installations with several outdoor units located in a confined space (roofs, patios, technical terraces), re-intake of heated air is often observed. A water mist system significantly reduces this effect by lowering the air temperature in the area around the units and improving overall circulation.

Operational and design advantages

• no direct wetting of electrical components
• minimal corrosion load when using softened or filtered water
• easy installation on existing installations
• modular structure – expandability

Areas of application

The technical solution is particularly suitable for:

• commercial and office buildings
• server and telecommunication rooms
• industrial and logistics centres
• supermarkets and refrigeration
• hotels and restaurants with high load on air conditioning systems

Conclusion

The cooling of outdoor air conditioning units by fine water mist is a highly efficient engineering solution based on the natural principle of evaporative cooling. By lowering the inlet air temperature, the system stabilizes the operating parameters of the HVAC equipment, reduces power consumption and extends the service life of the components, with minimal water consumption and low operating costs.