Heat Flux To Nucleate Pool Boiling Calculator

Heat Flux Formula:

\[ Q = \mu_f \cdot \Delta H \cdot \left( \frac{[g] \cdot (\rho_l - \rho_v)}{Y} \right)^{0.5} \cdot \left( \frac{C_l \cdot \Delta T}{C_s \cdot \Delta H \cdot (Pr)^{1.7}} \right)^{3.0} \]

Dynamic Viscosity of Fluid (μf):

Pa·s

Change in Enthalpy of Vaporization (ΔH):

J/mol

Density of Liquid (ρl):

kg/m³

Density of Vapour (ρv):

kg/m³

Surface Tension (Y):

N/m

Specific Heat of Liquid (Cl):

J/kg·K

Excess Temperature (ΔT):

Constant in Nucleate Boiling (Cs):

Prandtl Number (Pr):

Heat Flux (Q):

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1. What is Heat Flux in Nucleate Pool Boiling?

Heat flux in nucleate pool boiling refers to the rate of heat transfer per unit area during the boiling process where vapor bubbles form at discrete nucleation sites on a heated surface immersed in a liquid pool. It is a critical parameter in thermal engineering applications.

2. How Does the Calculator Work?

The calculator uses the heat flux formula for nucleate pool boiling:

\[ Q = \mu_f \cdot \Delta H \cdot \left( \frac{[g] \cdot (\rho_l - \rho_v)}{Y} \right)^{0.5} \cdot \left( \frac{C_l \cdot \Delta T}{C_s \cdot \Delta H \cdot (Pr)^{1.7}} \right)^{3.0} \]

Where:

\( Q \) — Heat Flux (W/m²)
\( \mu_f \) — Dynamic Viscosity of Fluid (Pa·s)
\( \Delta H \) — Change in Enthalpy of Vaporization (J/mol)
\( [g] \) — Gravitational acceleration (9.80665 m/s²)
\( \rho_l \) — Density of Liquid (kg/m³)
\( \rho_v \) — Density of Vapour (kg/m³)
\( Y \) — Surface Tension (N/m)
\( C_l \) — Specific Heat of Liquid (J/kg·K)
\( \Delta T \) — Excess Temperature (K)
\( C_s \) — Constant in Nucleate Boiling
\( Pr \) — Prandtl Number

Explanation: This formula calculates the heat flux during nucleate boiling by considering fluid properties, thermal properties, and gravitational effects on bubble formation and growth.

3. Importance of Heat Flux Calculation

Details: Accurate heat flux calculation is essential for designing efficient heat exchangers, boiling systems, and thermal management equipment. It helps predict boiling performance and prevent critical heat flux conditions that could lead to equipment failure.

4. Using the Calculator

Tips: Enter all required parameters with appropriate units. Ensure all values are positive and within reasonable physical ranges for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is nucleate pool boiling?
A: Nucleate pool boiling is a boiling regime where vapor bubbles form at specific nucleation sites on a heated surface immersed in a stagnant liquid pool.

Q2: Why is surface tension important in boiling heat transfer?
A: Surface tension affects bubble formation, growth, and departure from the heated surface, which significantly influences heat transfer rates.

Q3: What is the significance of the Prandtl number in boiling?
A: The Prandtl number represents the ratio of momentum diffusivity to thermal diffusivity, affecting the thermal boundary layer and heat transfer characteristics.

Q4: What are typical values for the nucleate boiling constant Cs?
A: The constant Cs typically ranges from 0.005 to 0.015 for most fluid-surface combinations, with water on copper being around 0.013.

Q5: When does nucleate boiling transition to film boiling?
A: Nucleate boiling transitions to film boiling at the critical heat flux point, where vapor bubbles coalesce to form an insulating vapor film on the heated surface.