Copper heat pipes efficiently transfer heat through a cycle of evaporation and condensation of a working fluid within a sealed tube.
Here's a breakdown of the process:
- Construction: Copper/water heat pipes have a copper envelope and use water as the working fluid.
- Temperature Range: These heat pipes typically operate effectively in the temperature range of 20 to 150 °C.
The Evaporation-Condensation Cycle
- Heat Input (Evaporation): Heat is applied to one end of the heat pipe (the evaporator). This heat causes the working fluid (water, in this case) inside the pipe to evaporate.
- Vapor Transport: The evaporated working fluid (steam) absorbs heat and increases the pressure inside the pipe. This pressure difference drives the vapor towards the cooler end of the pipe (the condenser).
- Heat Release (Condensation): At the condenser end, the vapor releases its heat and condenses back into a liquid. The released heat is dissipated into the surroundings, for example, by a heat sink.
- Liquid Return: The condensed liquid returns to the evaporator end through a wick structure (often made of porous material or grooves) via capillary action. The wick structure allows the water to move against gravity if the condenser is higher than the evaporator.
How Water Heat Pipes are Filled
- Filling Process: According to the reference, water heat pipes are sometimes filled by partially filling the pipe with water, heating it until the water boils and displaces the air, and then sealing the pipe while it's still hot. This process helps to remove air and other non-condensable gases, which could hinder the heat pipe's performance.
Advantages of Copper/Water Heat Pipes
- High Thermal Conductivity: Copper is an excellent conductor of heat, and water has a high latent heat of vaporization. These two factors, combined with the evaporation-condensation cycle, allow heat pipes to transfer heat much more efficiently than solid copper bars of the same size.
- Passive Operation: Heat pipes operate passively without the need for external pumps or moving parts. They rely on natural processes like evaporation, condensation, and capillary action.
- Compact Size: Heat pipes can be very small and lightweight, making them suitable for applications where space and weight are limited.
- Versatile Applications: Heat pipes are used in a variety of applications, including cooling CPUs and GPUs in computers, regulating the temperature of satellites, and in solar thermal collectors.
| Component | Role |
|---|---|
| Copper Envelope | Provides structural integrity and high thermal conductivity |
| Water | Working fluid that evaporates and condenses. |
| Wick Structure | Returns the condensed water from the condenser to the evaporator |
