Airflow Dynamics: MTL vs RDL vs DL (Ireland)
Airflow Dynamics: MTL vs RDL vs DL (Technical Reference – Ireland)
This technical document explains airflow dynamics in regulated vaping devices, comparing MTL (Mouth-to-Lung), RDL (Restricted Direct Lung), and DL (Direct Lung) inhalation profiles. It focuses on airflow resistance, pressure differential (ΔP), convective heat transfer, and aerosol particle distribution.
Technical Definition
Airflow dynamics describe the movement of air through intake ports, internal chamber geometry, coil housing, and mouthpiece during inhalation.
Flow velocity, chamber volume, and resistance determine aerosol density, temperature regulation, and particle size distribution.
Inhalation Profiles – Engineering Comparison
| Profile | Airflow Resistance | Pressure Differential (ΔP) | Air Velocity | Aerosol Volume | Particle Distribution Trend | Typical Coil Range |
|---|---|---|---|---|---|---|
| MTL | High (tight draw) | Higher suction force | Lower volumetric flow | Lower | Denser aerosol, larger aggregate clusters | ~0.8Ω – 1.4Ω |
| RDL | Moderate restriction | Balanced | Medium flow rate | Medium | Balanced dispersion profile | ~0.4Ω – 0.8Ω |
| DL | Low (open airflow) | Lower suction, high volume intake | High volumetric flow | High | Finer, more dispersed particle profile | ~0.15Ω – 0.4Ω |
Pressure Differential (ΔP) & Flow Mechanics
Inhalation creates negative pressure within the mouthpiece relative to ambient atmosphere.
In MTL systems, narrower airflow channels increase resistance, requiring higher pressure differential to sustain airflow.
In DL systems, wider channels reduce resistance, allowing higher volumetric flow with lower suction force.
Convective Cooling & Heat Transfer
Air velocity directly affects convective cooling of the heating element.
- Higher airflow increases heat dissipation.
- Restricted airflow increases chamber temperature.
- Inadequate airflow at high wattage may accelerate coil degradation.
Aerosol Particle Size Distribution
Airflow velocity influences shear forces within the chamber.
Higher airflow velocity (DL configurations) promotes rapid vapour expansion and cooling, typically generating smaller, more dispersed aerosol particles.
Lower airflow velocity (MTL configurations) results in denser, more concentrated aerosol output with comparatively larger aggregate clusters.
Particle distribution affects perceived density, throat sensation, and condensation behaviour inside the chamber.
Chamber Geometry & Turbulence
Internal chamber dimensions influence turbulence intensity.
- Smaller chambers intensify flavour concentration.
- Wider chambers increase aerosol dilution volume.
- Mesh surfaces distribute airflow differently than round-wire coils.
Ireland Climate Interaction
In colder Irish conditions, denser air slightly increases intake resistance.
Combined with higher VG viscosity, airflow perception may feel more restricted during winter months.
Rapid atmospheric pressure changes may also influence tank pressure equilibrium.
Operational Pairing Matrix
| Inhale Style | Typical Wattage | Liquid Profile | Nicotine Context (TPD IE/EU) |
|---|---|---|---|
| MTL | 8–18W | 50/50 or higher PG | Up to 20 mg/ml (regulatory limit) |
| RDL | 18–35W | 60/40 – 70/30 | Lower mg typical |
| DL | 35W+ | Higher VG | Lower mg typical |
FAQ – Airflow Physics
Ireland Notice (18+)
Technical documentation for adult users (18+) in Ireland. No medical or cessation claims are made.