💧 Evaporation & Humidification Calculator
Estimate evaporation rate, wet-bulb depression, outlet humidity, and psychrometric coupling using Raoult's law, Stefan diffusion, Lewis number, and convective mass transfer analogies.
🌫️ Evaporation & Humidification Schematic
📝 Configuration
Raoult surface vapor pressure: pA,s = a psat(Ts)
Stefan diffusion correction: NA = kcC ln[(1-yA,∞)/(1-yA,s)]
Lewis number: Le = α/DAB = k/(ρcpDAB)
Wet-bulb estimate from psychrometric enthalpy balance.
📊 Results & Visualization
Configure inputs and click Calculate to view results.
This tool couples vapor pressure equilibrium at a liquid surface with gas-side convective diffusion and psychrometric humidity changes. It is useful for evaporative cooling, humidifiers, wetted pads, pools, pans, and drying estimates.
📘 Calculation Methodology
Mathematical Model & Theory
The surface vapor pressure is estimated with Raoult's law and saturation pressure. The gas-side molar flux uses a Stefan diffusion logarithmic correction for diffusion of vapor A through stagnant/non-diffusing carrier gas B. Convective transfer is represented by Sherwood correlations.
Worked Engineering Example
Water at room conditions: air at 25°C and 50% RH flows over a wetted surface. The calculator estimates pA,s, pA,∞, Re, Sc, Sh, hm, then calculates NA and evaporation rate. Psychrometric coupling updates humidity ratio and estimates wet-bulb depression.
Assumptions & Notes
- Dilute vapor in air; ideal gas mixture.
- Surface liquid is at specified Ts.
- Raoult activity factor accounts for non-pure water or solution lowering of vapor pressure.
- Wet-bulb estimate uses standard moist-air enthalpy balance and is approximate.
- Outlet humidity uses specified air flow area and velocity.