Critical Heat Flux To Nucleate Pool Boiling Calculator

Critical Heat Flux Formula:

\[ Q_c = 0.18 \times \Delta H \times \rho_v \times \left( \frac{\gamma \times [g] \times (\rho_l - \rho_v)}{\rho_v^2} \right)^{0.25} \]

Change in Enthalpy of Vaporization (ΔH):

J/mol

Density of Vapour (ρ_v):

kg/m³

Surface Tension (γ):

N/m

Density of Liquid (ρ_l):

kg/m³

Critical Heat Flux (Q_c):

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1. What is Critical Heat Flux?

Critical Heat Flux (CHF) is the maximum heat flux that can be transferred from a heated surface to a boiling liquid before the boiling regime transitions from nucleate boiling to film boiling. It represents the upper limit of heat transfer in nucleate pool boiling.

2. How Does the Calculator Work?

The calculator uses the Critical Heat Flux formula:

\[ Q_c = 0.18 \times \Delta H \times \rho_v \times \left( \frac{\gamma \times [g] \times (\rho_l - \rho_v)}{\rho_v^2} \right)^{0.25} \]

Where:

\( Q_c \) — Critical Heat Flux (W/m²)
\( \Delta H \) — Change in Enthalpy of Vaporization (J/mol)
\( \rho_v \) — Density of Vapour (kg/m³)
\( \gamma \) — Surface Tension (N/m)
\( \rho_l \) — Density of Liquid (kg/m³)
\( [g] \) — Gravitational acceleration (9.80665 m/s²)

Explanation: This formula calculates the maximum heat flux before boiling crisis occurs, accounting for fluid properties and gravitational effects.

3. Importance of Critical Heat Flux Calculation

Details: Accurate CHF prediction is crucial for designing heat exchange equipment, nuclear reactors, and other thermal systems to prevent boiling crisis and ensure safe operation.

4. Using the Calculator

Tips: Enter all values in appropriate units. Ensure all input values are positive and physically meaningful for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What happens when heat flux exceeds critical heat flux?
A: When heat flux exceeds CHF, the boiling regime transitions from nucleate boiling to film boiling, causing a rapid temperature increase and potential equipment failure.

Q2: What factors affect critical heat flux?
A: CHF is influenced by surface characteristics, fluid properties, pressure, and system geometry.

Q3: Why is surface tension important in CHF calculation?
A: Surface tension affects bubble formation and departure, which directly influences the maximum heat transfer capability.

Q4: Can this formula be used for all fluids?
A: This formula provides a general estimation but may need modification for specific fluids or extreme conditions.

Q5: How does pressure affect critical heat flux?
A: Pressure affects fluid properties (density, surface tension, enthalpy), which in turn influence the critical heat flux value.