Week Four Update

Week Four Update

Construction of the heat pipe is almost complete. During this week, calculations were done to determine how much heat the pipe will transfer and the caps of the pipe were soldered. 

Heat Transfer Calculations

The page displayed below shows the calculations that describe heat transferred through the copper walls of the pipe due to conduction. This value was determined to be only 26.55 J which makes sense considering the small cross sectional area of copper and the relatively long length of pipe. The "Hot" temperature was assumed to be the maximum temperature of 533 degrees Kelvin. The "Cold" temperature was assumed to be 294 degrees Kelvin (room temperature). 

The page below displays calculations of heat transfer due to the phase transition of the working fluid. This is the essential method of heat transfer in the pipe and transfers the majority of the thermal energy that is input into the pipe. These calculations are broken down into two parts: heating liquid water to its boiling point, and vaporizing the water. Heating water vapor can be ignored since the water vapor travels to the condenser end of the pipe as soon as it vaporizes. Therefore, the vapor itself does not gain much thermal energy. The amount of energy transferred in the phase transitions of the working fluid is roughly 84 kJ. This value is much higher than the amount of heat transferred through the copper. This great different is expected. It demonstrates the working principle of heat pipes and provides a quantitative understanding of how efficient heat pipes are when compared to solid metal rods. Proportionally, the heat transferred through the copper is almost negligible when added with the heat transferred in the phase transitions of the working fluid. The total heat transferred is roughly 84 kJ.

To quantify the difference in heat transfer between the heat pipe and a solid copper rod of the same dimensions, the amount of heat that would be transferred through a solid copper rod was calculated. This is very similar to the calculation on the first page, however, the cross sectional area of the copper is much larger because it is a solid rod rather than a hollow pipe. A solid copper rod of the same dimensions as the heat pipe transfers 106.65 J of heat. When compared with the heat transferred through the heat pipe (84 kJ) it is determined that the heat pipe design is 200% more efficient at transferring heat than a solid copper rod of the same dimensions. This clearly shows the advantages of heat pipes in heat transfer applications. 

Soldering

The pipe and end caps were brought to the machine shop for soldering. The ends of the pipe and insides of the caps were cleaned with scotch brite and methanol. A machine shop technician performed the soldering with plumbing solder.