Engineering & Science
Chen Flow-Boiling Correlation: Reynolds Factor (F) & Suppression Factor (S)
Calculate John C. Chen’s (1966) two-phase convective enhancement factor F = (1 / X_tt + 0.213)^0.736 and nucleate-boiling suppression factor S = 1 / (1 + 2.53E-6 * Re_TP^1.17) in vertical evaporators.
Why high-velocity flow boiling ENHANCES forced convection (F > 1) while SUPPRESSING bubble nucleation (S < 1)!
Inside vertical thermosiphon reboilers and nuclear BWR fuel channels, two-phase heat transfer h_TP = F * h_conv,L + S * h_nb combines macroscopic forced convection and microscopic bubble nucleation—which respond OPPOSITELY as vapor quality increases! John C. Chen (I&EC Process Design and Development, 1966; Butterworth explicit fit) showed that accelerating vapor core velocity boosts liquid-film convection by Reynolds factor F = (1 / X_tt + 0.213)^0.736 (for 1 / X_tt > 0.1), while thinning the thermal boundary layer cools active wall cavities and suppresses nucleate boiling by S = 1 / (1 + 2.53 × 10^-6 * (Re_L * F^1.25)^1.17)!
Evaluate an evaporator tube at Lockhart-Martinelli parameter X_tt = 0.25 and liquid-only Reynolds number Re_L = 12,000: convective enhancement F reaches 2.882× while nucleate suppression S drops to 0.5866—and further downstream at higher vapor quality (X_tt = 0.10), F surges to 5.530×!
| Martinelli Parameter X_tt (Re_L = 12,000) | Convective Reynolds Factor F | Nucleate Suppression Factor S | Dominant Heat-Transfer Mechanism |
|---|---|---|---|
| X_tt = 0.25 (Mid-Tube Boiling) | 2.882× | 0.5866 (41.3% Nucleation Suppressed) | Balanced Convective + Nucleate |
| X_tt = 0.10 (High-Quality Annular) | 5.530× | 0.3512 (64.9% Nucleation Suppressed) | Forced Annular Evaporation |
| Invalid X_tt <= 0 or Re_L <= 0 | Undefined | "Invalid Flow-Boiling Inputs" | Positivity Guard |
Chen Two-Phase Convective Enhancement Factor F
Evaluates Butterworth’s analytical fit F = IF(1 / X_tt > 0.1, (1 / X_tt + 0.213)^0.736, 1) from Lockhart-Martinelli parameter X_tt (B2).
=IF(OR(B2 <= 0, B3 <= 0), "Invalid Flow-Boiling Inputs", ROUND(IF(1 / B2 > 0.1, (1 / B2 + 0.213) ^ 0.736, 1), 3))Chen Nucleate-Boiling Suppression Factor S (0 < S <= 1)
Computes 1 / (1 + 2.53E-6 * Re_TP^1.17) where two-phase Reynolds number Re_TP = Re_L * F^1.25.
=IF(OR(B2 <= 0, B3 <= 0), "Invalid Flow-Boiling Inputs", ROUND(1 / (1 + 0.00000253 * ((B3 * ((IF(1 / B2 > 0.1, (1 / B2 + 0.213) ^ 0.736, 1)) ^ 1.25)) ^ 1.17)), 4))Try the example
Use the original values or change them to test your understanding.