Condensation Heat Transfer Coefficient Formula

Condensation Heat Transfer Coefficient Formula:

\[ h = 0.725 \left[ \frac{k^3 \rho^2 g \lambda}{\mu \Delta T L} \right]^{1/4} \]

Thermal Conductivity (k):

W/mK

Density (ρ):

kg/m³

Gravity (g):

m/s²

Latent Heat (λ):

J/kg

Dynamic Viscosity (μ):

Pa·s

Temperature Difference (ΔT):

Characteristic Length (L):

Condensation Heat Transfer Coefficient (h):

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1. What is the Condensation Heat Transfer Coefficient?

The condensation heat transfer coefficient (h) quantifies the efficiency of heat transfer during phase change from vapor to liquid. It represents the rate of heat transfer per unit area per unit temperature difference during condensation processes.

2. How Does the Calculator Work?

The calculator uses the Nusselt condensation formula:

\[ h = 0.725 \left[ \frac{k^3 \rho^2 g \lambda}{\mu \Delta T L} \right]^{1/4} \]

Where:

\( h \) — Condensation heat transfer coefficient (W/m²K)
\( k \) — Thermal conductivity of liquid (W/mK)
\( \rho \) — Density of liquid (kg/m³)
\( g \) — Gravitational acceleration (m/s²)
\( \lambda \) — Latent heat of vaporization (J/kg)
\( \mu \) — Dynamic viscosity of liquid (Pa·s)
\( \Delta T \) — Temperature difference between vapor and surface (K)
\( L \) — Characteristic length (tube diameter or plate height) (m)

Explanation: This formula applies to film condensation on vertical surfaces and horizontal tubes, assuming laminar flow and negligible vapor shear stress.

3. Importance of Condensation Heat Transfer

Details: Accurate calculation of condensation heat transfer coefficients is crucial for designing heat exchangers, condensers, refrigeration systems, and power plant components where phase change heat transfer occurs.

4. Using the Calculator

Tips: Enter all parameters in SI units. Ensure all values are positive and physically meaningful. The characteristic length L typically represents the height of a vertical surface or diameter of a horizontal tube.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for condensation heat transfer coefficients?
A: For common fluids like steam, h ranges from 5,000-20,000 W/m²K, while for refrigerants it's typically 1,000-5,000 W/m²K depending on conditions.

Q2: When is this formula applicable?
A: This Nusselt analysis applies to laminar film condensation on vertical surfaces or horizontal tubes with pure vapors and negligible vapor velocity effects.

Q3: What are the limitations of this equation?
A: The formula assumes constant properties, laminar flow, smooth surface, pure vapor, and negligible subcooling of the condensate film.

Q4: How does surface orientation affect condensation?
A: Horizontal tubes generally have higher coefficients than vertical surfaces due to thinner condensate films. The constant 0.725 is for horizontal tubes (0.943 for vertical plates).

Q5: What factors can enhance condensation heat transfer?
A: Surface treatments, finned tubes, promoted condensation surfaces, and vapor velocity can significantly increase heat transfer coefficients beyond the Nusselt prediction.