Spectral Boundary Layer Regime Inversion
Evaporation is admissible as temperature-limited only if boundary layer stability remains invariant under changes in spectral energy distribution. If spectral structuring can invert stability and increase flux at equal temperature, the governing constraint is transport—not heat.
Evaporation is not limited by energy—it is limited by removal. If vapor cannot leave the interface, added heat is wasted.
Evaporation is governed by bulk temperature
Conventional models assume evaporation rate scales primarily with surface temperature and available thermal energy.
Boundary layer suppresses vapor transport
A stabilizing temperature–humidity gradient traps saturated vapor near the interface, limiting evaporation through diffusive transport.
Additional heating strengthens this stability, reinforcing the constraint rather than removing it.
Spectral gradients invert boundary layer stability
Selective absorption in water combined with minimal air heating creates an inverted temperature gradient near the interface.
This inversion destabilizes the boundary layer and initiates micro-convective vapor removal.
Boundary layer stability state
The governing variable is not temperature, but whether the boundary layer is stable or unstable.
- Stable → diffusion-limited evaporation
- Unstable → convection-enhanced evaporation
Spectral Boundary Layer Destabilization Index (SBDI)
SBDI quantifies the transition from diffusive to convective evaporation regimes under spectrally structured illumination.
It encodes the degree of instability induced at the interface.
Equal energy, different spectra
- Broadband vs spectrally filtered illumination
- Equal total energy input
- Measure evaporation rate and surface temperature
- Detect boundary layer instability via optical or humidity probes
What breaks the assumption
Pass: No increase in evaporation at equal temperature.
Fail: Increased evaporation with equal or lower surface temperature under spectral structuring.
Evaporation is transport-limited
The limiting factor is not energy input but the ability to remove vapor from the interface.
Energy does not produce flux—transport does.
If vapor cannot leave the interface, no amount of added heat will increase evaporation. The constraint is not input—it is removal.