Bromley Film Boiling Correlation Formula: Horizontal Tube Vapor-Blanket Heat Transfer

Nusselt falling-film physics turned upside down: buoyant vapor blanketing above the Leidenfrost temperature!

Once heater wall superheat deltaT_e = T_w - T_sat exceeds the Leidenfrost minimum heat flux point, liquid can no longer wet the surface and an insulating continuous vapor film blankets the tube! LeRoy A. Bromley (1950, Chemical Engineering Progress) recognized that buoyant vapor flowing upward around a horizontal cylinder of diameter D mirrors Wilhelm Nusselt’s laminar falling-liquid condensation analysis in reverse!

Replacing liquid film properties with vapor film thermal conductivity k_v, vapor density rho_v, vapor viscosity mu_v, and Rohsenow-Bromley sensible-superheat-corrected latent enthalpy h_fg_prime = h_fg + 0.4 * c_pv * deltaT_e yields h_co = 0.62 * ((k_v^3 * rho_v * (rho_l - rho_v) * 9.81 * (h_fg + 0.4 * c_pv * deltaT_e)) / (mu_v * D * deltaT_e))^0.25! Notice that thicker vapor films at higher superheat REDUCE conductive h_co from 158.87 W/(m^2*K) at deltaT_e = 220 K to 146.14 W/(m^2*K) at deltaT_e = 320 K (before radiation h_rad is added)!

Bromley Horizontal-Tube Film Boiling Coefficient h_co (W/m²·K)

Evaluates 0.62 * ((k_v^3 * rho_v * (rho_l - rho_v) * 9.81 * (h_fg + 0.4 * c_pv * deltaT_e)) / (mu_v * D * deltaT_e))^0.25 across SI properties evaluated at vapor film temperature (T_w + T_sat)/2.

=IF(OR(MIN(B2:B9) <= 0, B4 <= B3), "Invalid Bromley Film Boiling Inputs", ROUND(0.62 * ((((B2 ^ 3) * B3 * (B4 - B3) * 9.81 * (B5 + 0.4 * B9 * B8)) / (B6 * B7 * B8)) ^ 0.25), 2))

Modified Latent-Plus-Vapor-Superheat Enthalpy h_fg’ = h_fg + 0.4 * c_pv * deltaT_e (J/kg)

Computes the Rohsenow-Bromley effective enthalpy absorbed by superheating the rising vapor boundary layer.

=IF(OR(MIN(B2:B9) <= 0, B4 <= B3), "Invalid Bromley Film Boiling Inputs", ROUND(B5 + 0.4 * B9 * B8, 0))

Further reading

• Microsoft Support — MIN function