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Heat Pipes 2018-02-13T19:00:41+00:00

Features Included:

  • High conductivity (5,000 watts/meter·K to 200,000 watts/meter·K)
  • Energy-efficient
  • Light weight
  • Low cost
  • Flexibility of many different size and shape options
  • 100% Inspection of all heat pipes, before and after bending
  • Passed stringent heat transfer tests to reach a minimum temperature gradient within a minimal time period (Delta T < 4 degrees C, time period ~ 7 seconds)

What Are Heat Pipes?

A heat pipe is composed of a vacuum-tightened vessel, wick structure, and some amount of working fluid. As heat is inputted at the evaporator, the fluid vaporizes, creating a pressure gradient. This pressure gradient pushes the vapor to flow along the pipe to the cooler section where it condenses, giving up its latent heat of vaporization. The working fluid is then returned to the evaporator by capillary forces developed in the wick structure or by gravity.

Main components:

  • Container
    • High strength, high thermal conductivity
  • Working fluid
    • High latent heat, high thermal conductivity
  • Wick/capillary structure
    • State-of-the-art copper powder sintering for maximum performance
    • Maintains effective capillary action when bent or used against gravity

Heat Pipe’s Fundamental Theory Illustration

Heat is absorbed from the source through vaporization and released at a sink through condensation. The vapor travels from source to sink through the central channel, while the liquid travels from sink to source through the porous wick.

The rapid growth of the electronics and the personal computer industries have introduced challenging heat dissipation problems. Heat pipes effectively transport heat with minimal drops in temperature.

Heat Pipe’s Functional Cycle

Typical Applications

  • Laptop computers

  • High-performance processors (CPU, GPU)

  • Aerospace; spacecraft temperature equalization, component cooling

  • Constrained geometries

  • Low maintenance/high reliability applications

  • Noise-sensitive environments where heat can be dissipated to a larger, remote heat sink

  • Stagnation regions where airflow is poor

  • Limited electrical consumption

  • Constrained geometries

  • Passive solution to conserve battery power

 Wick Structure Comparison 

 Wick Structure Screen Mesh Groove Sintering Powder
 Image
Rate Process Easy Easy Hard
 Capillary Bad Good Better
Flat (Min.) t = 2.0 t = 1.5 t = 2.5
Bend (Min.) 2 * Heat Pipe Diameter [D] 2 * Heat Pipe Diameter [D] ~ 2 * Heat Pipe Diameter [D] 3 *  Heat Pipe Diameter [D]
Resistance (t = 3 mm) .250 ~ .350  .03 ~ .040 .030 ~ .045
 Heat Flux (t = 3 mm)  35 40 45
Cost Low Medium High

Heat Pipes In Stock

 Diameter x Length [mm]  Part No.  Diameter x Length [mm] Part No. Diameter x Length [mm]  Part No. Diameter x Length [mm] Part No.
 4 x 175  91-1028-175  5 x 100 91-1029-100 6 x 125 91-1030-125 8 x 125 91-1031-125
 4 x 100 91-1028-100 5 x 125 91-1029-125 6 x 150 91-1030-150 8 x 150 91-1031-150
 4 x 125  91-1028-125  5 x 150 91-1029-150 6 x 170 91-1030-170 8 x 175 91-1031-175
 4 x 200  91-1028-200 5 x 175 91-1029 -175 6 x 200 91-1030-200 8 x 200 91-1031-200
4 x 250 91-1028-250 5 x 200 91-1029-200 6 x 225  91-1030-225 8 x 300 91-1031-300
4 x 225 91-1028-225 5 x 225 91-1029-225 6 x 250  91-1030-250
 4 x 300 91-1028-300  5 x 250  91-1029-250 6 x 300  91-1030-300
5 x 300 91-1029-300

Heat Pipe Working Fluid

How to select a working fluid:

  • High surface tension – generates high capillary force and resists environment.
  • High Vapor pressure – reduces vapor velocity.
  • High latent heat – transfers more heat with less fluid.
  • High thermal conductivity – lower ΔT and reduces nucleate boiling at the wick/wall interface.
  • Low vapor viscosity – increase fluid flow capacity.
Working Fluid Relative Figure of Merit [80°C]  Useful Range [°C] Wick Vessel Material  Life [hrs]
Ammonia .45  -60~100  AL SS304  36000
Freon 113 86 -10~100  CU AL SS304 25000
Acetone 300 0~120  CU AL SS304 50000
Methanol 450 10~120  CU AL SS304 less than 50000
Ethanol 340 0~120 CU SS304 24000
Water 40000 30~250 CU 7500000

Heat Pipe Capabilities

Cofan USA’s flexible solutions:

  • Lead time of less than one week for various diameters and lengths
  • Copper; multiple plating options available to suit the application
  • Custom bending done in-house for use in any hardware layout
  • Various heat pipe diameters
  • Various heat pipe lengths of up to 600 mm

 Copper Screen Mesh
Assessment Parameter Diameter (mm)
Thickness  4 5 6 8
t = 2.0 mm  .65~.09; 15 .50~.80; 18 .35~.60; 35 .30~.55; 45
t = 2.5 mm  .55~.08; 18 .45~.65; 22  .25~.40; 40 .20~.35; 50
t =3.0 mm  .50~.70; 20 .45~.60; 22 .25~.35; 45 .20~.30; 55
Round .50~.70; 20 .40~.55; 25 .20~.35; 45 .15~.30; 60
Units: R[°C/W]; Qmax[Watt]
 Copper Groove
Assessment Parameter Diameter (mm)
Thickness  4 5 6 8
t = 2.0 mm .40~.70; 5 .40~.60; 5
t = 2.5 mm .04~.06; 25 .03~.05; 40
t =3.0 mm .03~.05; 30 .03~.04; 60
t = 4.5 mm .003~.015; 70
Round .03~.05; 35 .02~.03; 65 .002~.007; 80
Units: R[°C/W]; Qmax[Watt]
 Copper Sintering Powder
Assessment Parameter Diameter (mm)
Thickness  4 5 6 8
t = 2.0 mm .035~.60; 5
t = 2.5 mm .04~.06; 25 .03~.05; 40
t =3.0 mm .03~.05; 30 .03~.04; 60
t = 4.5 mm .003~.015; 70
Round .03~.05; 35 .02~.03; 65 .002~.007; 80
Units: R[°C/W]; Qmax[Watt]

Customized Bending & Flattening

Diameter, D [mm] 3 4 5 6  8 9 9.6  10 12 12.7 16
Minimum Bending Radius [2*D]  6  8 10 12  16 18 19 20 24 25 32
Standard Bending Radius [3*D] 9 12 15  18 24  27  29  30 36 38 48
Recommended Bending Radius [4*D] 12 16 20 24 32 36 38  40 48 51 64
Minimum Bending Angle [ø] 90°
 Recommended Bending Angle [ø] 20°

 Diameter, D [mm]  Thickness, t + 0.05 / – 0.10 [mm] Width, W ± 0.15 [mm]
3 1.2 3.94
1.5 4.10
2.0 3.65
2.5 3.32
3.0 N/A
4 1.5  5.49
2.0 5.23
2.5 4.96
3.0 4.65
4.0 N/A
5 1.4 7.14
1.5 7.01
2.0 6.77
2.3 6.60
2.5 6.50
3.0 6.26
3.5 5.95
4.0 5.63
5.0 N/A
6 1.5 8.69
2.0 8.41
2.3 8.25
2.4 8.20
2.5 8.16
2.7 8.00
3.0 7.84
3.5 7.57
4.0 7.30
4.8 6.86
5.0 6.63
5.3 6.60
6.0 N/A
8 2.0 Undone
2.5 11.26
3.0 10.97
3.5 10.71
4.0 10.45
4.5 10.20
5.0 9.96
6.0 9.36
8.0 N/A

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