Humidification Capacity (kg/h)

Detailed Explanation

Humidification capacity is the maximum mass of water a unit can deliver to the airstream per hour. Industrial steam systems typically offer 5–1000+ kg/h; adiabatic atomisation systems can reach 50–2000+ kg/h. Units are kg/h (SI) or lb/h (Imperial); with the 1 kg ≈ 1 L approximation, l/h is also used.

Fundamental formula:

m_water (kg/h) = ρ_air (kg/m³) × V_air (m³/h) × Δx (kg_water/kg_dry_air)

Here ρ_air ≈ 1.2 kg/m³ (sea-level standard), V_air is the airflow being humidified, and Δx is the difference between target and current absolute humidity. Correct capacity calculation is the single most critical step in equipment selection; an error can produce a 30–100% sizing mismatch.

Why It Matters

Undersizing causes the facility to miss its winter RH target — leading to yarn breakage in textile, print drift in printing, or artefact cracking in museums. Oversizing brings (a) unnecessary CAPEX (price, installed power, cable cross-section); (b) poor part-load behaviour (most units modulate 20–100% and become unstable below 20%); (c) on electrode and steam-to-steam units, accelerated mineral concentration that shortens cylinder/chamber life.

The three most common sizing mistakes: (1) sizing by room volume alone (wrong — airflow is the primary input); (2) treating an RH difference as a water mass (wrong — use absolute-humidity difference); (3) ignoring outdoor-air fraction (wrong — it drives capacity). All of these inputs are requested from the facility during unit selection.

Practical Example

A printing house in Konya: 3 lines, total 30,000 m³/h supply, 40% outdoor + 60% return. Because Konya lies at ≈ 1,000 m, the calculation uses the local atmospheric pressure (≈ 90 kPa): for the same RH the humidity ratio is somewhat higher than at sea level while the air density is lower. January design outdoor air is −7°C / 75% RH (≈ 1.9 g/kg), indoor target 21°C / 50% RH (≈ 8.7 g/kg). Mixed-air state ≈ 0.4×1.9 + 0.6×8.7 ≈ 6.0 g/kg. Δx = 8.7 − 6.0 = 2.7 g/kg = 0.0027 kg/kg. Air density is taken as ≈ 1.07 kg/m³ instead of 1.2. Capacity = 1.07 × 30,000 × 0.0027 ≈ 87 kg/h (with sea-level values 1.2 × 30,000 × 0.0025 = 90 kg/h; the two corrections largely cancel). With a 15% safety margin → ≈ 100 kg/h, leading to a Neptronic SKE4-120 resistive (120 kg/h nominal). The unit runs at roughly 80–85% — inside its modulation band, enabling precise RH control.

Engineering Note

Use a psychrometric chart or calculation tool (NKT Portal, humidifier control software, Trane Trace) for Δx; hand approximations introduce 5–10% error. Air density (ρ) is 1.2 kg/m³ at sea level but falls with altitude (≈ 11% at 1,000 m, 15–20% above 1,500 m) — high-altitude provinces such as Erzurum (≈ 1,850 m), Kayseri and Konya (≈ 1,000 m) require an altitude correction.

A safety margin of 15–25% (20% in practice) is recommended. Above 50% is oversizing: the unit cycles on/off at low load and the RH band widens.

NKT Application Link

For this application NKT – Nem Kontrol Teknolojileri supplies the Neptronic SKE4 resistive steam humidifier, the Neptronic SKS4 steam-to-steam humidifier, the Neptronic SKG4 gas-fired steam humidifier and the Neptronic SKH high-pressure atomisation system. It supports unit selection with capacity calculation and technology matching based on space conditions, target temperature and RH (or dew point) and moisture load, and provides technical service and spare parts. Design, installation and commissioning remain within the scope of the facility's designer and contractor.