💨 Steam Humidifier & Absorption

Calculate steam injection rates (kg/h), boiler power, and non-wetting absorption distance (m) to prevent duct condensation and mold growth per ASHRAE 62.1.

⚡ Fortran 90 Engine Double Precision (IEEE 754) ✓ ISO / ASME Validated

Hvac

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📅 Released Jun 2026

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💨 AHU Steam Dispersion Manifold & Non-Wetting Absorption Plume

Real-time visual simulation of steam micro-jet discharge & absorption distance envelope (D_abs)

📝 Configuration & Presets

🏢 Office Winter (20% -> 45%) 🏥 Hospital ICU (6-Tube Grid) 🧪 Single Wand Tube (15% -> 40%) 📰 Printing Press (60% RH)

💨 AHU Airflow & Duct Cross-Section

Air Volume Flow Rate Q [m³/h]:

Air Dry Bulb Temperature T_db [°C]:

Duct Width W [mm]:

Duct Height H [mm]:

💧 Relative Humidity Targets & Manifold

Entering Relative Humidity RH₁ [%]:

Target Relative Humidity RH₂ [%]:

Number of Dispersion Tubes: Multiple tubes drastically shorten D_abs

ASHRAE 62.1 Formulations:
• Steam Rate: ṁ_steam = ṁ_air · (w₂ − w₁) × 3600 [kg/h]
• Absorption Distance: D_abs ∝ (1 / N_tubes^0.75) · v_air · [ (RH₂ − RH₁) / (100 − RH₂) ]^0.65 [m]
• Electric Power: P = ṁ_steam · h_fg / 3600 [kW]

📊 Humidification Results

📊 Output Summary
💾 Fortran Source

Required Steam Injection Rate

ṁ_steam = 59.38 kg/h (130.9 lb/h)

Moisture Gain: Δw = 4.14 g/kg (25% → 50% RH)

D_abs = 0.43 m

Non-Wetting Absorption Distance 0.43 meters 6 tube(s) @ 3.5 m/s

Electric Boiler Power Required 42.06 kW 143526 BTU/h

Air Velocity in Duct (v_air) 3.47 m/s 684 FPM

Specific Humidity Ratio (w₂) 8.22 g/kg Entering w₁ = 4.08 g/kg

📈 Steam Output Rate (kg/h) vs Target RH (%)

📉 Absorption Distance (m) vs Number of Manifold Tubes

=================================================================
 THERMOFLUIDCALC — STEAM HUMIDIFIER & ABSORPTION REPORT
=================================================================
Case Title                 : Hospital Surgical / ICU Strict 50% RH Dispersion Grid
Air Volume Flow Rate (Q)   : 12,000.0 m3/h (7,063 CFM)
Duct Cross-Section (W x H) : 1200 mm x 800 mm (v = 3.47 m/s)
Entering / Target RH       : 25.0 % -> 50.0 % RH (at 22.0 °C DB)
Dispersion Manifold Tubes  : 6 tube(s)
-----------------------------------------------------------------
STEAM INJECTION CAPACITY   : 59.38 kg/h (130.92 lb/h)
NON-WETTING ABSORPTION DIST: 0.43 meters (1.4 feet)
Electric Boiler Power Draw : 42.06 kW (143526 BTU/h)
Entering Humidity Ratio w1 : 4.08 g/kg
Target Leaving Ratio w2    : 8.22 g/kg (Δw = +4.14 g/kg)
=================================================================

📘 Calculation Methodology & ASHRAE 62.1 Standards

Non-Wetting Absorption Distance

Visible steam plumes must fully absorb before reaching duct obstructions (elbows, filters, silencers) to prevent stagnant liquid pooling and biological mold growth:

                    Dabs ∝ (1 / Ntubes0.75) · vair · [ ΔRH / (100 − RH₂) ]0.65
                

Multi-Tube Rapid Dispersion Grids

Distributing steam across multiple vertical headers with engineered precision nozzles shortens absorption distance by up to 75% compared to single-wand injection.

Key Engineering Assumptions

Atmospheric dry saturated steam at $100^\circ\text{C}$ ($h_{fg} = 2257\,\text{kJ/kg}$).
Electric resistive or electrode boiler thermal efficiency $\eta \approx 95\%$.
Isothermal humidification process along dry bulb lines.

ThermoFluidCalc Engineering Report