High-Performance Heat Pipes for Efficient Thermal Management
A Heat Pipe is a heat-transfer device that combines the principles of thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces. Heat Pipes are closed, evacuated tubes containing a small amount of working fluid which can be deionized water, acetone, or methanol. Their inside walls are either grooved or lined by a porous wick structure of sintered powder to provide a capillary action for working fluid to return to the evaporator section.
Heat transfer in the heat pipe occurs in a continual cycle. When a portion of the heat pipe is exposed to heat, the working fluid that is at the pipe’s bottom begins to evaporate. The vapour then enters the cool condenser portion of the heat pipe due to the difference in densities of the fluid and vapour. The vapour condenses due to the difference in wall temperatures, releasing latent heat. This allows the fluid to return to the liquid pool inside the evaporator under the effect of gravity or via some form of capillary wicking structure (in case of wicked heat pipes).
This thermodynamic cycle continues as the thermal energy is transferred from one end to the other. In a heat pipe under heat load, the temperature will remain constant as the working fluid goes through the phase change inside the heat pipe chamber, making the heat pipe a very efficient heat transfer device.
Heat pipes are totally passive heat transfer systems. This means they have no moving parts to wear out, and require no electrical energy to operate. They offer the design engineer low-cost packaging and flexibility because they can be manufactured in a variety of different shapes and sizes as per the requirement and preferences of the customer / end user. Their light weight and compact size also make them the ideal choice for space-constrained applications.
At the hot interface within a heat pipe, which is typically at a very low pressure, a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. The vapor condenses back into a liquid at the cold interface, releasing the latent heat. The liquid then returns to the hot interface through capillary action where it evaporates once more, and the cycle is repeated.
Heat Pipes are used for thermal management of computers, servers, communication equipment, and more.
Advantages of Heat Pipes
- High thermal conductance – higher wattage removed. Capability to control thermal flux.
- 20 to 40% reduction in weight and volume compared to thermal solution not using heat pipe.
- Very long life (>10-20 years)
- Cost comparable to conventional extruded heat sinks.
- No maintenance as there are no moving parts.
- No restriction on its orientation.