Condensation Nusselt

ENGINEERING – THERMODYNAMIC & HVAC CALCULATOR Condensation Nusselt A precise tool.
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What is the Condensation Nusselt & How does it work?
In film condensation on a vertical surface, a thin liquid layer forms and drains under gravity while heat is transferred through the liquid film. The rate of heat removal depends on the balance between buoyancy‑driven flow and viscous resistance, which is captured by the Nusselt condensation correlation. The classic Nusselt analysis assumes laminar flow, constant properties, and a saturated vapor in contact with a colder wall. Under these conditions the dimensionless Nusselt number, Nu, relates the convective heat transfer coefficient to the thermal conductivity of the condensate and the characteristic length of the plate. The resulting expression is widely used in HVAC design to size condensers, predict drip‑off rates, and evaluate heat‑exchanger performance. It highlights the strong influence of temperature difference, fluid properties, and gravity on the condensation heat transfer.
Nu = 0.943 left( frac{g rho_{l} (rho_{l}-rho_{v}) h_{fg} (T_{sat}-T_{w})}{mu_{l} k_{l}} right)^{1/4}
g = gravitational acceleration (m·s⁻²)
rho_{l} = liquid density (kg·m⁻³)
rho_{v} = vapor density (kg·m⁻³)
h_{fg} = latent heat of vaporization (J·kg⁻¹)
T_{sat} = saturation temperature of vapor (K)
T_{w} = wall temperature (K)
mu_{l} = liquid dynamic viscosity (PaΒ·s)
k_{l} = liquid thermal conductivity (W·m⁻¹·K⁻¹)
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Parameters
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Frequently Asked Questions
What is the Nusselt number in condensation?
The Nusselt number (Nu) is a dimensionless number used to describe the ratio of convective to conductive heat transfer in a fluid film during condensation.
When is the classic Nusselt analysis applicable?
The classic Nusselt analysis is applicable for laminar flow, constant properties, and saturated vapor in contact with a colder wall.
How does gravity affect the condensation process?
Gravity influences the condensation process by causing the thin liquid layer to drain, which affects the heat transfer dynamics.
What factors influence the Nusselt number in film condensation?
The Nusselt number is influenced by factors such as fluid properties, surface temperature difference, and flow conditions.
Can this calculator be used for horizontal surfaces?
This calculator is specifically designed for vertical surfaces. For horizontal surfaces, a different approach or correlation may be needed.
What is the significance of buoyancy-driven flow in condensation?
Buoyancy-driven flow plays a crucial role in condensation by creating a circulation that enhances heat transfer through the liquid film.
How does viscous resistance impact the condensation process?
Viscous resistance opposes the motion of the fluid and can limit the effectiveness of buoyancy-driven flow, affecting the overall heat transfer rate.

Results are for informational purposes only and do not constitute professional advice.