Definition
The temperature drop caused by latent heat being drawn from air as water evaporates within it; typically 2–10°C, depending on air temperature and RH. Either a side benefit or a primary goal of adiabatic humidification.
Detailed Explanation
Evaporative cooling requires approximately 585 kcal/kg (≈ 2,450 kJ/kg at 20°C) of latent heat for water to vaporise; this heat is drawn from the surrounding air, cooling it. Thermodynamic equation: ΔT = (m_water × Δh_vap) / (m_air × c_p_air); practical approximation: every 1 g/kg of added moisture ≈ 2.5°C of cooling. Maximum cooling is bounded by wet-bulb temperature (Twb) — an adiabatic system can drop Tdb to Twb at most. Summer outdoor air in Turkish inland cities has Twb ≈ 19–24°C; for an office-comfort target of 24°C, adiabatic alone may suffice.
Why It Matters
Evaporative cooling matters in two contexts: (1) ENERGY SAVING — in hot, dry air evaporative pre-cooling reduces the mechanical cooling (chiller, DX) load; the dominant choice for textile, greenhouses, data-centre free-cooling pre-cooling, and warehouse cooling. (2) UNWANTED EFFECT — facilities with tight temperature targets see unintended temperature drops; in winter it adds heating load. In strict bands like pharma cleanrooms (22°C ± 1°C) or hospital ORs (21°C ± 2°C), the adiabatic system must be balanced with a reheat coil.
Practical Example
Representative example: summer outdoor air at 33 °C / 45% RH (wet bulb ≈ 23.3 °C). Adiabatic pre-cooling can bring the air close to its wet-bulb temperature at most; in practice, at 80–90% effectiveness, it cools to ≈ 25 °C and RH rises to ≈ 85%. A cooling coil then brings the air to the required supply condition. The gain is that part of the load otherwise carried by mechanical cooling is met by the heat of evaporation; the annual effect is calculated per site from climate data and operating hours.
Engineering Note
Design limit: ΔT_max = Tdb − Twb. This "dry-bulb wet-bulb depression" is small (e.g. Black Sea summer 27°C/85% RH → Twb 25°C, ΔT_max = 2°C) where adiabatic cooling is weak and not recommended. It is large (e.g. Konya summer 35°C/25% RH → Twb 19°C, ΔT_max = 16°C) where adiabatic is very effective. The site-specific limit should always be checked on the psychrometric chart.
NKT Application Link
For this application NKT – Nem Kontrol Teknolojileri supplies the Neptronic SKVF evaporative cooler, the Neptronic SKH high-pressure atomisation system and the Neptronic SKV evaporative humidifier. Unit-selection support is based on space conditions, humidification load and the feed-water analysis; technical service and spare parts are provided. Design and installation of water treatment, as well as engineering design, installation and commissioning, remain within the scope of the facility's designer, contractor and water-treatment specialist.
