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Theory/FAQ

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Basic heat pipes function on the principal of transferring heat from one location to another through an internal heating/cooling cycle. The heat pipe structure allows for efficient and quick transfer of heat energy and thus are utilized in a number of applications such as cooling computer CPUs and HVAC systems. Heat pipes can be broken down into five main sections: the evaporator, the condenser, wick, fluid flow and vapor flow. Figure 1 shows these main components of a basic heat pipe.

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Figure 1: Basic functionality of a heat pipe

There are three main common types of heat pipes used commercially: grooved, mesh and sintered. Each of the variations have different benefits and weaknesses but all accomplish the same goal.   

Figure 2: Mesh Wick Heat Pipe
When it comes to manufacturing simplicity, a grooved heat pipe is easiest to produce as its cut grooves can be machined into the cooper. A sintered mesh is very complicated as it is composed of powdered copper and a strong binding agent that won't break down under higher temperatures. 
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Figure 3: Variations of different heat pipes

To function properly, heat pipes are usually under an internal partial vacuum which drives the vaporization cycle of vaporizing and condensing. As the working fluid inside the heat pipe is heated in the evaporator end, it vaporizes and simultaneously becomes pressurized. This causes the heat fluid to flow to an area of lower pressure and temperature, the condenser end. The vapor travels in the interior open area until the temperature is low enough for the working fluid to condense. The action of pulling heat out of the working fluid causes it to return to liquid form and stick to the walls of the heat pipe and into the wick. Then, due to capillary action and/or now the lower partial vacuum at the evaporator end, the working fluid will flow down the wick to where it will begin to heat up again and repeat the process. 

FAQ:
What is a heat pipe?
It is a device used to transfer heat from one location to another.
How does a heat pipe function?
Internally, the heat pipe uses a wick to transfer condensed liquid to the hot end where it is vaporized, absorbing heat, and moved to the colder end of the pipe.
What are some of the applications of a heat pipe?
They can be used in computers, HVAC systems and spacecraft for cooling. 
What process was used to run the thermal analysis?
In the Solidworks simulation study, a thermal analysis was conducted by putting an input heat setting to one end of the model and setting the ambient air temperature for the surrounding pipe surface area that would act as a heat conductor. Upon running the simulation, the expected heat flow in the pipe was demonstrated. 
What benefits does the vacuum provide?
Increases the efficiency by allowing partial vacuums to assist the movement of the working fluid inside the heat pipe. 
How do the fins function?
The fins pull heat away from the pipe while simultaneously increasing the surface area that heat can be dispersed on. 

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