🔥 Flow Boiling Critical Heat Flux & DNB
Size flow boiling Critical Heat Flux (q_CHF), Minimum Departure from Nucleate Boiling Ratio (MDNBR safety margin), and dryout vapor quality using Bowring and Katto-Ohno models.
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🔥 Vertical Flow Boiling Regimes & DNB / Dryout Front
Real-time visual simulation: Single-Phase → Bubbly Flow → Slug/Annular → Critical Heat Flux Dryout Hotspot📝 Configuration & Presets
Bowring / Katto Flow Boiling CHF Formulation:
• Critical Heat Flux: q″CHF = [ A′ + ¼ D G Δhsub ] / (C′ + L) [kW/m²]
• Minimum DNB Ratio: MDNBR = q″CHF / q″actual (Safety Margin > 1.3)
• Critical Power: Qcrit = q″CHF · (π D L) [kW]
• Critical Exit Quality: xcrit = (Qcrit − G Aflow Δhsub) / (G Aflow hfg)
• Critical Heat Flux: q″CHF = [ A′ + ¼ D G Δhsub ] / (C′ + L) [kW/m²]
• Minimum DNB Ratio: MDNBR = q″CHF / q″actual (Safety Margin > 1.3)
• Critical Power: Qcrit = q″CHF · (π D L) [kW]
• Critical Exit Quality: xcrit = (Qcrit − G Aflow Δhsub) / (G Aflow hfg)
📊 CHF & DNB Margin Results
Configure inputs and click Compute to view results.
📘 Calculation Methodology & Critical Heat Flux Standards
Bowring & Katto-Ohno Correlation
Calculates the peak convective heat flux before bubble overcrowding prevents liquid wall replenishment:
q″CHF = [ A′ + ¼ D G Δhsub ] / (C′ + L)
DNB vs Annular Liquid Dryout
At high subcooling and high mass flux, CHF occurs by Departure from Nucleate Boiling (DNB). At higher qualities, it occurs by dryout of the annular liquid film.
Key Engineering Assumptions
- Uniform axial heat flux profile in vertical round tubes.
- Saturated and subcooled water-steam flow regimes.
- Design criteria: $MDNBR \ge 1.30$ margin against thermal burnout.