Heat pipes have been used for many years to cool various components. Their main feature is utilizing phase changes for better heat transfer between two points. This heat dissipation system has passivity as the main advantage. When the temperature difference between both ends of the pipe is large enough, the heat from the hot part is transferred to the cold part.
The heat pipe is divided into three parts: a condenser, an adiabatic part and an evaporator. The evaporator is placed on a heat source and the heat is transferred to the condenser. The heat is then transferred to the cooling fins or water, in the case of water cooling.
I wanted to find out whether heat pipes can dissipate few kW of power and what are their limits. I explained the operation and its limitations, through the theoretical basis. By analyzing the literature, I wanted to further explore the feasibility of using heat pipes on ultralight aircraft. A special environment such as flying in the atmosphere, gives us additional limitations when dealing with heat pipes. I will also comment on the suitability of heat pipes to cool electric vehicle batteries.
Heat pipes are limited by external conditions, especially temperature. On ultralight aircraft, we must pay attention to the temperature limits of the components. When it comes to the way heat pipes operate, we cannot rely upon gravity. The orientation of the aircraft can vary greatly during flight. It is possible to make a heat pipe which can dissipate many kW of heat, but this requires liquid alkali metals, which are unsuitable for everyday use. Such heat pipes would also be too large for confined spaces on ultralight aircraft. Instead of using one heat pipe for high power, several heat pipes for lower power could be used. The calculation showed that in the case of 8 kW power, this cooling system would be wasteful in terms of mass and volume.
I discovered that heat pipes are not a sufficiently efficient way of cooling in the case of high power. Heat pipes can dissipate heat from the warm part to the cold part only at a few hundred W, which may be suitable for cooling smaller electronic components. They are suitable for cooling the batteries, as they can act as an intermediate component between the battery itself and the active water cooling.