Chun-Seban Falling-Film Evaporator Nusselt Correlation (Wavy vs. Turbulent)

Why falling-film heat transfer FIRST drops as films thicken—then surges once turbulence kicks in!

Vertical falling-film evaporators concentrate heat-sensitive dairy milk, fruit juices, pharmaceuticals, and desalination brines without hydrostatic boiling-point elevation! K. R. Chun and Ralph A. Seban (ASME Journal of Heat Transfer, 1971) discovered two competing regimes governed by film Reynolds number Re_f = 4 * Γ / μ_l: in the wavy-laminar regime, thicker films increase conduction resistance so dimensionless film Nusselt number Nu_f = (h / k_l) * (ν_l^2 / g)^(1/3) = 0.821 * Re_f^(-0.22) DECREASES with Re_f; above transition Re_tr = 5,800 * Pr_l^(-1.06), eddy mixing takes over and Nu_f = 0.0038 * Re_f^0.4 * Pr_l^0.65 RISES with Re_f!

Taking MAX(Nu_wavy, Nu_turb) automatically captures the exact Chun-Seban crossover: for 100 °C water (Pr_l = 1.75, Re_tr = 3,205), wavy-laminar Re_f = 1,200 gives Nu_f = 0.1726, whereas turbulent Re_f = 8,000 climbs to Nu_f = 0.1991!

Composite Chun-Seban Falling-Film Nusselt Number Nu_f

Evaluates MAX(0.821 * Re_f^(-0.22), 0.0038 * Re_f^0.4 * Pr_l^0.65) across film Reynolds number B2 and liquid Prandtl number B3.

=IF(OR(B2 <= 0, B3 <= 0), "Invalid Film Parameters", ROUND(MAX(0.821 * (B2 ^ (-0.22)), 0.0038 * (B2 ^ 0.4) * (B3 ^ 0.65)), 4))

Wavy-to-Turbulent Transition Reynolds Number Re_tr = 5800 * Pr_l^(-1.06)

Computes the exact Reynolds number where Chun-Seban wavy-laminar and turbulent curves intersect.

=IF(B3 <= 0, "Invalid Film Parameters", ROUND(5800 * (B3 ^ (-1.06)), 0))

Further reading

• Microsoft Support — MAX function