🧪 Falling Film Absorber (Nusselt & Higbie)

Model vertical wetted-wall falling film tube absorbers, evaluating Nusselt laminar film thickness, surface velocity, Higbie penetration kL, and contact time.

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

Falling Film Absorber (Nusselt & Higbie)

Mass Transfer

📊 Solver Telemetry ● ACTIVE

👁️ Views 40

⚡ Solves 35

💾 Downloads 262 📦 Fortran Code 6.4 KB

📅 Released Jun 2026

⏱️ Latency < 1 ms

🧪 Vertical Wetted-Wall Tube Falling Film Hydrodynamics & Gas Absorption

Real-time visual simulation of liquid falling film gravity drain, surface velocity & interfacial solute mass transfer

📝 Configuration & Presets

🧪 HCl Graphite Absorber 💨 Ammonia (NH3) Scrubber 🌱 CO2 Amine Capture ⚗️ SO3 Sulfonation Film

📐 Tube Bundle Geometry

Tube Inside Diameter D_t [mm]:

Tube Length L_t [m]:

Number of Parallel Tubes N_t:

Total Liquid Feed Flow Rate [kg/h]:

💧 Liquid Physical Properties & Diffusivity

Liquid Density ρ_L [kg/m³]:

Liquid Dynamic Viscosity μ_L [cP]:

Solute Liquid Diffusivity D_AB [m²/s]: Typical liquids: 1.0e-9 to 4.0e-9 m²/s

Nusselt & Higbie Formulations:
• Perimeter Flow: Γ = (Ṁ_L / N_t) / (π D_t) [kg/(m·s)]
• Film Thickness: δ = [ 3 μ Γ / (ρ² g) ]^1/3 [mm]
• Surface Velocity: u_s = (ρ g δ²) / (2 μ) [m/s]
• Higbie Coefficient: k_L = 2 · √( D_AB / (π t_c) ) [m/s]

📊 Falling Film Performance Results

📊 Output Summary
💾 Fortran Source

Nusselt Film Thickness (δ)

δ = 0.434 mm

Mass Transfer: k_L = 0.10 m/h (2.86e-5 m/s)

Re_film = 1061

Surface Film Velocity (u_s) 0.920 m/s u_avg = 0.613 m/s

Liquid Exposure Time (t_c) 3.26 seconds Higbie contact time

Total Interfacial Wetted Area 3.77 m² 8 tubes

Perimeter Wetting Rate (Γ) 0.2653 kg/(m·s) Full Surface Wetting

📈 Film Thickness δ (mm) vs Total Liquid Flow (kg/h)

📉 Mass Transfer Coeff k_L (m/h) vs Tube Length (m)

=================================================================
 THERMOFLUIDCALC — FALLING FILM ABSORBER HYDRAULICS REPORT
=================================================================
Case Title                 : Ammonia (NH3) Flue Gas Wet Scrubbing Tube Bundle
Tube Bundle Dimensions     : 8 tubes x 50.0 mm ID x 3.00 m length
Total Interfacial Area     : 3.77 m2
Liquid Flow Rate           : 1200.0 kg/h (Per tube: 150.00 kg/h)
Perimeter Loading (Gamma)  : 0.2653 kg/(m.s)
Film Reynolds Number       : 1061.0 (Turbulent)
-----------------------------------------------------------------
NUSSELT FILM THICKNESS (d) : 0.4335 mm (4.34e-4 m)
Surface Film Velocity (us) : 0.9197 m/s (Average u = 0.6131 m/s)
Contact / Exposure Time    : 3.262 seconds
HIGBIE MASS TRANSFER (kL)  : 0.103 m/h (2.863e-5 m/s)
=================================================================

📘 Calculation Methodology & Falling Film Standards

Nusselt Laminar Gravity Film

Equating downward gravity body force with wall viscous shear yields the classical parabolic velocity profile across the falling film thickness $\delta$:

                    δ = [ 3 μ Γ / (ρ² g) ]1/3
                

Higbie Penetration Theory

For short contact times, solute diffusion penetrates only into the top liquid boundary layer, giving mass transfer coefficient scaling as $k_L \propto \sqrt{D_{AB} / t_c}$.

Key Engineering Assumptions

Uniform liquid distribution around tube circumference.
Wetting rate $\Gamma > 0.04\,\text{kg/(m}\cdot\text{s)}$ to prevent film dryout.
Negligible interfacial shear stress from counter-current or co-current gas.

ThermoFluidCalc Engineering Report