What is a heat pipe?
A heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces. Due to the very high heat transfer coefficients for boiling and condensation, heat pipes are highly efficient thermal conductors. In the cooling side, it needs sufficient fin area for heat dissipating to air.
What is heat pipe thermal conductivity?
Due to the working principle of two changes in the fluid, the equivalent thermal conductivity of the heat pipe is about 50~100 times that of pure aluminum.
The material and fluid of the heat pipe will affect the thermal conductivity of the heat pipe. Including copper, aluminum, stainless steel, and even ceramic structures; the choice of fluid is water, alcohol, acetone, or ammonia, the designer must consider the temperature and pressure requirements of the project application, the operating temperature and durability requirements of the radiator, and select the appropriate of pipes and fluids. At normal temperature and pressure, water and copper are the most common and best-performing heat pipe choices.
Differences in Solid Metal vs Heat Pipe Thermal Conductivity
The list to the right lists the thermal conductivity of common metals. The best conductive silver can be seen, with a conductivity of less than 500 k(W/moC).
Due to the structural design of the heat pipe, the conduction coefficient can reach 14,000 k(W/moC).
And because the heat pipe length is longer, even the conduction coefficient can be higher
| Material |
Conductivity , k (W/m°C) |
| Metal |
|
| Silver (Pure) |
410 |
| Cooper (Pure) |
385 |
| Aluminum (Pure) |
204 |
| Iron (Pure) |
73 |
| Magnesium (Pure) |
171 |
| Zinc (Pure) |
121 |
| Lead (Pure) |
35 |
| Nonmetal |
|
| Diamond |
900~2320 |
| Graphite (Natural) |
155 |
| Glass |
0.78 |
| Brick |
0.84 |
| Fluid |
|
| Mercury |
8.21 |
| Water |
0.556 |
Heat pipe Types
The prototype of the heat pipe is a round and square tube. The common outer diameters are D3, 4, 5, 6, 8, and 10mm. The heat pipe manufacturing and production also have the corresponding bending, flat, and step difference processes to suit the internal mechanism space of different product limits.
There are many options for the internal structure of the heat pipe, the following are the common types.
Heatpipe Design Guide
A heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces.
Depending on the design structure, different types of heat pipes are used. The following are common heat pipe structures
Differences in Thermal Conductivity by Heat Pipe Diameter
The structural design of the heat pipe will affect the efficiency of conduction.
The structure of the heat pipe will affect the convection and conduction effects in the heat pipe. Ideally, the rounder the shape of the heat pipe, the better the conduction efficiency.
The following is a comparison table of various types of heat pipes：
| Wick structure |
Groove |
Powder |
Composite |
Slim/3D Fiber |
| Performance |
Average |
Average |
Average |
Average |
| Anti-Gravity |
Poor |
Good |
Good |
Average |
| Stability |
Good |
Average |
Good |
Average |
| Cost |
Cheap |
Normal |
Expensive |
Expensive |
The heat pipe design is based on the internal thermal design of the machine. So the structure of the heat pipe may be round or flat. It may even need to be bent. According to the above reasons, the heat pipe efficiency and the process will be affected.
What is Heat pipe Manufacturing Process?
The heat pipe production process: is roughly divided into five stages：
Stage 1: Heat and forming.
Stage 2: Heat pipe structure sintering & pressing.
Stage 3: Cutting
Stage 4: Tail end shrinking and welding.
Stage 5: Vacuuming and adjusting the angle of the heat pipe.
Heat Pipe and Application
Heat pipes are small and have good conduction efficiency. Therefore, it is often regarded as one of the components to solve the thermal problem. Depending on the application, the heat pipe can be extended for different applications. For example, heat pipe design of 5G modules.
What is Heat sink?
The heat sink is a passive heat exchanger that cools a device by dissipating heat into the surrounding medium, which designed to extend the surface area to dissipate the heat to cooling air, aluminum and copper are the main materials for heat sink now.
Heat sink – Conduction & Convection
Heat sink is designed to extend the surface area to dissipate the heat to cooling air. Currently, with regards to conduction performance and manufacturing process, aluminum and copper are the main materials for heat sink.
According to manufacturing difference, the heat sink has various types such as extrusion, forging, skiving, crimped fin, folded fin, stacked fin, die-cast, etc.
What is Fan?
A fan is a machine used to create flow within the air to have better convection in system. The fan consists of a rotating arrangement of blades which act on the air.