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Thermal Engineering

Heat Pipe Thermal Capacity Calculator

Calculate all five heat pipe transport limits — capillary, boiling, entrainment, viscous, and sonic — and find the maximum heat transport capacity and effective thermal conductance.

Parameters
Working Fluid
Wick Type
Pipe Length L 30.0 cm
Inner Diameter D 6.0 mm
Tilt Angle θ 0 °
Negative = adverse gravity (evaporator up) / Positive = gravity-assisted
Operating Temperature T 80 °C
Max Heat Transport Q_max [W]
Effective Conductance [W/m·K]
Governing Limit
Axial Heat Flux [W/cm²]

Theory

Capillary limit (most critical):

$$Q_{cap} = \frac{A_w K \rho_l h_{fg}}{\mu_l L_{eff}} \left(\frac{2\sigma}{r_{eff}} - \rho_l g L \sin\theta\right)$$

Laplace equation (capillary pressure):

$$\Delta P_{cap} = \frac{2\sigma}{r_{eff}}$$

Effective thermal conductance:

$$k_{eff} = \frac{Q_{max} \cdot L_{eff}}{A_{cs} \cdot \Delta T}$$
Applications: PCB and electronics cooling, spacecraft thermal control, solar collectors. Typical wick permeability K values: sintered 10⁻¹²–10⁻¹⁰ m², grooves 10⁻¹⁰–10⁻⁸ m², screen 10⁻¹²–10⁻¹⁰ m².