Background
In a world of machines and devices that are prone to extruding heat that is often capable of damaging the objects in its surroundings, heat pipes are a mechanically simple but amazing device used to redirect the damaging heat to a safe heat sink where the heat is allowed to harmlessly dissipate. From the precise machinations of NASA's spacecraft to the compact convenience of laptops and cellular phones, heat pipes are found everywhere in our contemporary world.
Modern heat pipe technology was first developed in 1962 by George Grover in the Los Alamos Scientific Laboratory as a way to supply and remove heat from energy conversion systems. Heat pipes are sealed vessels that have been evacuated and refilled with a small amount of fluid. They use a combination of evaporation and condensation in order to transfer hear across its length in an extremely efficient way. Although heat pipes have many designs, the most common version involves a sealed cylindrical shape that's insulated around the midsection with a wick along the cylinder's inner diameter. The fluid moves along the wick from the cooler side to the hotter side, where it evaporates and travels back to the cooler side and condenses, repeating the process. This is due to the fact that, as the fluid evaporates, vapor pressure is built up, forcing the vapor to travel to the cooler side, where it condenses. The condensate is then returned to the hotter side via capillary action (the ability of a fluid to move into narrow spaces, like the space between the wick/grooves in the heat pipe). The pressure difference between the liquid and vapor phases is sustained by the fluid's surface tension. Thanks to this, heat pipes require little to no maintenance and are completely passive (no external pumping power is needed, the heat that enters the pipe is all the energy the fluid in the heat pipe needs to function).
In Summary:
References:
[1] Author Unknown. (2019, January 1). Heat Pipes for Thermal Management. Retrieved April 4, 2019, from https://www.1-act.com/innovations/heat-pipes/
Modern heat pipe technology was first developed in 1962 by George Grover in the Los Alamos Scientific Laboratory as a way to supply and remove heat from energy conversion systems. Heat pipes are sealed vessels that have been evacuated and refilled with a small amount of fluid. They use a combination of evaporation and condensation in order to transfer hear across its length in an extremely efficient way. Although heat pipes have many designs, the most common version involves a sealed cylindrical shape that's insulated around the midsection with a wick along the cylinder's inner diameter. The fluid moves along the wick from the cooler side to the hotter side, where it evaporates and travels back to the cooler side and condenses, repeating the process. This is due to the fact that, as the fluid evaporates, vapor pressure is built up, forcing the vapor to travel to the cooler side, where it condenses. The condensate is then returned to the hotter side via capillary action (the ability of a fluid to move into narrow spaces, like the space between the wick/grooves in the heat pipe). The pressure difference between the liquid and vapor phases is sustained by the fluid's surface tension. Thanks to this, heat pipes require little to no maintenance and are completely passive (no external pumping power is needed, the heat that enters the pipe is all the energy the fluid in the heat pipe needs to function).
In Summary:
- Heat pipes are used to regulate temperature by transferring heat from one location to another.
- Heat pipes are airtight sealed pipes with structures along it's inner diameter and a fluid.
- The fluid is used to transport heat via evaporation and condensation.
- Vapor pressure builds up as the fluid evaporates, forcing the vapor to travel to the cooler end, where it condenses.
- Heat pipes use capillary action to draw the fluid back to the hotter side.
- This pressure difference between the vapor and the liquid phases is sustained by the surface tension of the liquid.
References:
[1] Author Unknown. (2019, January 1). Heat Pipes for Thermal Management. Retrieved April 4, 2019, from https://www.1-act.com/innovations/heat-pipes/
[2] Ku, J. (2015). Introduction To Heat Pipes [PowerPoint slides]. Retrieved April 4 2019, from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150018080.pdf
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