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Heat Pipe Two-Phase Thermal Resistance & Conductivity Calculator

Heat pipes and vapor chambers provide ultra-high effective thermal conductivity by transferring heat through two-phase evaporation and capillary fluid return in a sealed evacuated envelope.

Nominal outer diameter of the copper cylindrical pipe (typically 4 to 12 mm).

Thickness of solid outer copper tube (typically 0.4 to 0.8 mm).

Thickness of the porous sintered copper powder wick layer.

Length of heat pipe section in contact with heat source.

Uninsulated or passive transport section between source and heat sink.

Length of heat pipe section attached to cooling fin stack.

Heat dissipation transported across the heat pipe.

Calculated Result
0.028 °C/W

Heat Pipe Thermal Resistance

Total Thermal Resistance (R_th)

0.028 °C/W (K/W)

End-to-End Temperature Drop (ΔT)

1.24 °C at 45W

Effective Equivalent Conductivity (k_eff)

108,227 W/m·K (~278× pure copper)

Radial Envelope Wall Resistance

0.0027 °C/W

Sintered Wick Resistance

0.0199 °C/W

Calculation Breakdown

  1. Radial Heat Pipe Envelope ConductionR_wall = ln(D_out/D_in) / (2π k_cu L) = 0.0027 °C/W
  2. Two-Phase Sintered Wick ResistanceR_wick = ln(D_in/D_v) / (2π k_wick L) = 0.0199 °C/W
  3. Total Thermal Impedance & DropR_total = R_wall + R_wick + R_vapor = 0.028 °C/W, ΔT = Q × R = 45 W × 0.028 = 1.24 °C

Heat Pipe Thermal Characteristics

Interactive visualization based on your current inputs

Value
0.014294357R_th (°C/W × 100)ΔT (°C)k_eff (kW/m·K)Wall Res (°C/W × 100)Wick Res (°C/W × 100)ParameterValue

What Is the Heat Pipe Two-Phase Thermal Resistance & Conductivity Calculator?

The Heat Pipe Two-Phase Thermal Resistance & Conductivity Calculator models internal thermal gradients and equivalent conductivity of copper-water heat pipes.

How Does the Heat Pipe Two-Phase Thermal Resistance & Conductivity Calculator Work?

It computes radial conduction resistance across the copper envelope and porous sintered wick for both evaporator and condenser zones.

Heat Pipe Two-Phase Thermal Resistance & Conductivity Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

R_{th} = \sum R_{wall} + \sum R_{wick} + R_v, \quad k_{eff} = \frac{L_{eff}}{A_{cross} R_{th}}, \quad \Delta T = Q \cdot R_{th}

Radial cylindrical conduction network coupling solid copper envelope with porous two-phase saturated wick.

How to Use the Heat Pipe Two-Phase Thermal Resistance & Conductivity Calculator

  1. Specify heat pipe diameter, wall thickness, and wick thickness.
  2. Enter evaporator, adiabatic, and condenser segment lengths in mm.
  3. Input operating thermal wattage.

Step-by-Step Example Calculation

8mm Sintered Laptop CPU Heat Pipe at 45W

Input Values:

pipeOuterDiameterMm:8
pipeWallThicknessMm:0.6
wickThicknessMm:0.4
evaporatorLengthMm:50
adiabaticLengthMm:100
condenserLengthMm:50
operatingHeatLoadWatts:45
Worked Steps: Exhibits 0.052 °C/W total resistance with a 2.34°C temperature drop and 57,400 W/m·K effective thermal conductivity (~147× pure copper).

Understanding Your Result

Total Thermal Resistance (R_th): Thermal resistance in °C/W (K/W).

End-to-End Temperature Drop (ΔT): Expected temperature rise under load.

Effective Conductivity (k_eff): Equivalent solid material thermal conductivity.

Factors That Affect the Result

  • Longer evaporator and condenser lengths provide more radial heat transfer area, lowering thermal resistance.
  • Thinner wicks decrease conduction resistance but reduce maximum capillary pumping power.

When Should You Use This Calculator?

  • Laptop thermal module design, GPU cooler sizing, power electronics heatsinks, and LED thermal management.

Assumptions & Limitations

  • Assumes operation below dry-out capillary limits and neglectable axial vapor core thermal resistance.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Based on Faghri Heat Pipe Science and Technology and Peterson Two-Phase Heat Transfer.

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