Heat Pipes
Heat pipe technology has existed for nearly 60 years, and it’s widely used in heat sink for computers, servers, or street lighting. It’s simple in appearance, but there is something inside. As shown in the figure below, there is a structure inside the heat pipe where the liquid substance is vaporized by heat, cooled, and then flows back to the starting point through a capillary structure, like a small loading and unloading plant, except that the substance being transported is “heat”.
Don’t Heat Pipes Have Weaknesses?
After many tests, we found that the heat transfer capacity of heat pipes is 10 times of aluminum and 5 times of copper. Since heat pipes are so powerful, is it true that heat pipes have no weaknesses? In fact, this is not the case, like the following picture, We may feel that the heat sink has a layer of armor on the outside to cope with the harsh external environment. However, this only protects the exterior from rapid corrosion from the external environment; we don’t know the inside of the heat pipe.
The Importance of Environment in Heat Pipe Selection
In fact, in the early stage of design, we usually communicate with customers about the environment in which the product will be used, because different environments determine what kind of heat pipe cooling product is appropriate. As shown in the figure above, we found that under extremely harsh conditions, the cold and thermal shock test caused the heat pipe to expand, which is due to the fact that the traditional heat pipe uses pure water. When the product is used vertically in a -55°C environment, the liquid water that collects at the bottom quickly freezes, causing the volume to expand, which in turn causes the heat pipe to expand. At the same time, we know that water freezes at zero degrees, and when it freezes the heat pipe loses its“activity”, which leads to heat buildup and even burns out the chip!
Pioneer Thermal Brings Low Temperature Resistant Heat Pipe Heat Sink Designs
In order to solve the above problems, PT Heatsink brings customers a low temperature resistant heat pipe heat sink design, which uses acetone instead of water as the heat pipe working fluid inside the heat sink heat pipe, effectively avoiding the icing of the work material in the very low ambient temperature, thus protecting the cooling system, modules and the overall design from damage.
At -20 ℃, test data from the acetone heatpipe heatsink shows that the temperature difference between the ends of the heatpipes stays within 4 degrees.
| Power（W） | TC(°C) | T1(°C) | T2(°C) | TC-T2(°C) | T2-T1(°C) | T3(°C) | T4(°C) | TC-T4(°C) | T4-T3 | AT(°C) |
| 50 | 28.2 | 12.8 | 16.5 | 11.7 | 3.7 | 13.5 | 15.9 | 12.3 | 2.4 | -20 |
| 28.5 | 12.3 | 15.8 | 12.7 | 3.5 | 12.7 | 15 | 13.5 | 2.3 | -20 |
Acetone Heat Pipe VS Conventional Heat Pipe
Acetone based cooling systems are designed for use in extreme cold environments rather than general applications, whereas water has the advantage of high heat dissipation capacity, low cost and wide availability in the ambient temperature range due to its superior latent heat change compared to other fluids. The following data table shows the different physical properties of the different materials used in heat pipes.
| Liquids – Type | Chemical Formula | Thermal Conductivity@25 | Latent Heat of Evaporation(kJ/kg) |
| Water | H2O | 0.58 | 2256 |
| Methanol | CH3OH | 0.21 | 1101 |
| Acetone | CH3-CO-CH3 | 0.16 | 518 |
Here is our suggestions for customers on the design and selection of different heat pipe heat sink:
1) Under the same working conditions, the heat transfer performance of copper+water heat pipe with the same specifications is better than that of copper+acetone heat pipe;
2) When the copper-water heat pipe is placed vertically, heat pipe bulging occurs under the environment of -55 ℃, it is recommended to adjust the design, or replace by the copper+acetone heat pipe;
3) For the low-temperature environment (below 0 ℃ ) product, because of its copper-water heat pipe internal icing will cause a sharp decline in heat transfer performance, Pioneer Thermal do not recommend copper + water heat pipe, we suggest to choose the copper + acetone heat pipe.
Please contact us for any technical, design or production requirements! We will be happy to serve you!