๐ฅ 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.
โก Fortran 90 Engine
Double Precision (IEEE 754)
โ ISO / ASME Validated
Convection
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Released
Jun 2026
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< 1 ms
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Hardware & Sizing Partner: Need to size a control valve or check ASME flange bolt torque for this line?
๐ฅ Vertical Flow Boiling Regimes & DNB / Dryout Front
Real-time visual simulation: Single-Phase โ Bubbly Flow โ Slug/Annular โ Critical Heat Flux Dryout Hotspot๐ Configuration & Presets
โข๏ธ PWR Fuel Core DNB
โก BWR Channel Dryout
๐ญ Boiler Evaporator Tube
๐ Rocket Cooling Jacket
Bowring / Katto Flow Boiling CHF Formulation:
โข Critical Heat Flux: qโณCHF = [ Aโฒ + ยผ D G ฮhsub ] / (Cโฒ + L) [kW/mยฒ]
โข Minimum DNB Ratio: MDNBR = qโณCHF / qโณactual (Safety Margin > 1.3)
โข Critical Power: Qcrit = qโณCHF ยท (ฯ D L) [kW]
โข Critical Exit Quality: xcrit = (Qcrit โ G Aflow ฮhsub) / (G Aflow hfg)
โข Critical Heat Flux: qโณCHF = [ Aโฒ + ยผ D G ฮhsub ] / (Cโฒ + L) [kW/mยฒ]
โข Minimum DNB Ratio: MDNBR = qโณCHF / qโณactual (Safety Margin > 1.3)
โข Critical Power: Qcrit = qโณCHF ยท (ฯ D L) [kW]
โข Critical Exit Quality: xcrit = (Qcrit โ G Aflow ฮhsub) / (G Aflow hfg)
๐ CHF & DNB Margin Results
Configure inputs and click Compute to view results.
๐ Calculation Methodology & Critical Heat Flux Standards
Bowring & Katto-Ohno Correlation
Calculates the peak convective heat flux before bubble overcrowding prevents liquid wall replenishment:
qโณCHF = [ Aโฒ + ยผ D G ฮhsub ] / (Cโฒ + 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.