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Boiling Correlations Detail Simulator

Evaluate wall superheat, heat-transfer coefficient, and CHF margin from heat flux, pressure, diameter, and vapor quality.

Controls
Wall superheat ΔTₑ
K

Wall-minus-saturation temperature. Slide to move the operating point along the boiling curve.

Presets

Jump to a representative regime (natural convection → nucleate → CHF → film boiling).

Results
—
Wall superheat ΔTₑ
—
Heat flux q″
—
Boiling regime
—
CHF (Zuber)
—
Heat-transfer coeff. h
—
q″/CHF
Boiling surface (bubbles / vapor film)
Boiling curve q″(ΔTₑ)
Heat-transfer coeff. h(ΔTₑ)
Theory & Key Formulas

Nucleate boiling (Rohsenow):

$$q''_{nb}=\mu_l h_{fg}\sqrt{\frac{g(\rho_l-\rho_v)}{\sigma}}\left(\frac{c_{p,l}\,\Delta T_e}{C_{sf}\,h_{fg}\,Pr_l^{\,n}}\right)^{3}$$

Critical heat flux, CHF (Zuber):

$$q''_{max}=0.149\,h_{fg}\,\rho_v^{1/2}\left[\sigma g(\rho_l-\rho_v)\right]^{1/4}$$

Heat-transfer coefficient: $q''=h\,\Delta T_e$.

With water at 1 atm the Zuber CHF ≈ 1.1–1.3 MW/m², reached near ΔTₑ ≈ 30 K. This model uses the standard pool-boiling correlations (Incropera). Boundary conditions, surface finish, and code corrections still need separate checks.

How to read it

Use the main plot to read the controlling trend, including break points that a single result card can hide.

Use the sensitivity view to find input combinations where margin collapses quickly.

For early design, focus on which input controls margin before trusting the absolute value.

Learn Boiling Correlations Detail by dialogue

🙋
When reading Boiling Correlations Detail, where should I look first? Moving Heat flux changes both the plots and the result cards.
🎓
Start with Wall superheat, but do not treat the number as the whole answer. Use Boiling curve to confirm the assumed state, then read Heat-transfer breakdown for the distribution or trend. Use the main plot to read the controlling trend, including break points that a single result card can hide.
🙋
I can see why Heat flux changes Wall superheat. How should I judge the influence of Pressure?
🎓
Move Pressure in small steps and watch Heat-transfer coefficient. That reveals which term is controlling the result. This simplified model captures the main relationship only. Boundary conditions, losses, nonlinear effects, and code-specific corrections still need separate checks. A single operating point is not enough; sweep the realistic scatter range.
🙋
What is Heat-flux map for? It feels like the ordinary curve already tells the story.
🎓
Heat-flux map is for finding boundaries where the condition becomes risky or margin collapses quickly. Use the sensitivity view to find input combinations where margin collapses quickly. In First-pass comparison of design options before review, the important question is often what happens after a small change, not only the nominal value.
🙋
So if Wall superheat is within the target, can I accept the condition?
🎓
Treat this as a first-pass review. It helps with Narrowing controlling factors and worst-side conditions before detailed analysis and Teaching or explaining the equation, numbers, and visualization under the same inputs, but final decisions still need standards, measured data, detailed analysis, and vendor limits. For early design, focus on which input controls margin before trusting the absolute value.

Practical use

First-pass comparison of design options before review.

Narrowing controlling factors and worst-side conditions before detailed analysis.

Teaching or explaining the equation, numbers, and visualization under the same inputs.

FAQ

Start with Wall superheat and Heat-transfer coefficient. Then use Boiling curve to confirm the assumed state and Heat-transfer breakdown to read distribution or bias. Use the main plot to read the controlling trend, including break points that a single result card can hide
Move Heat flux alone, then move Pressure by a comparable amount and compare the change in Wall superheat. Heat-flux map shows combinations where margin or performance changes quickly.
Use it for First-pass comparison of design options before review. Instead of trusting a single point, widen the input range and check whether Wall superheat keeps enough margin before moving to detailed analysis.
This simplified model captures the main relationship only. Boundary conditions, losses, nonlinear effects, and code-specific corrections still need separate checks. Final decisions still require standards, measured data, detailed analysis, and vendor limits.

How to Use

  1. Enter heat flux in W/m² (typical range 100 kW/m² to 2 MW/m² for water boiling)
  2. Set system pressure in bar (e.g., 10 bar for subcooled boiling, 50 bar for pressurized water reactors)
  3. Input pipe or tube diameter in mm (e.g., 10 mm for small channels, 25 mm for industrial steam generators)
  4. Specify vapor quality as a fraction from 0 (saturated liquid) to 1 (saturated vapor)
  5. Click Calculate to receive wall superheat (°C), heat-transfer coefficient (W/m²·K), critical heat flux ratio, and nucleate-boiling index

Worked Example

Pressurized water reactor subchannel: heat flux 1.5 MW/m², system pressure 155 bar, channel diameter 8 mm, vapor quality 0.35. Simulator returns wall superheat 18.4°C (indicating nucleate boiling dominance), h-coefficient 42,600 W/m²·K, CHF ratio 1.87 (margin above critical burnout), nucleate-boiling index 0.76 (strong pool-boiling character). These values confirm safe two-phase operation without dryout risk.

Practical Notes

  1. At high pressure (>100 bar) and low quality (<0.1), expect lower wall superheat because latent heat diminishes and subcooled boiling dominates—verify h-coefficient remains >20,000 W/m²·K
  2. CHF ratio below 1.3 signals marginal departure from nucleate boiling; increase diameter or reduce flux immediately
  3. Nucleate-boiling index >0.8 indicates transition toward film boiling; monitor quality closely in once-through steam generators
  4. For cryogenic nitrogen (77 K, 1 bar): use 5 mm diameter, expect h-coefficient <8,000 W/m²·K due to low thermal conductivity and high surface tension

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