Student-Faculty Collaborative Research Grant Report
Engineering Physics | Physics
Project One: Mechanism of Heat Transfer in Metals
Most thermo textbooks state that free electrons inside metal are the major heat carriers for heat conduction. But no one gave a real proof. Almost every book claims that a good electric conductor will be a good thermo conductor. This statement is based on the fact that there exist free electron seas inside metals. This research set up a way to test if the free electrons dominate on heat transfer. To do so, several different pure metal bars were prepared, and a hole was drilled in one end of each bar in which a heater was placed to heat up the metal bar. Two copper clamps were made in order to run DC current through the metal bar. Heat transmission coefficients were measured when the current ran in the direction and against the direction of the heat transfer. The results showed in all the metal bars: when electric drift velocity of electron is in the direction of the heat transfer, the heat transfer coefficient will be increased. This indicates that electrons are truly the major heat carriers in all the metal tested.
Project Two: Using Nano Particles to Make a Magnetic Core for a Transformer to Increase the Efficiency
Transformers are important for modern society. Without transformers, using electric power is impossible. Most mid-sized and small-sized transformers have poor efficiency. They are in the range of 50-75% efficient, depending on the total power and the magnetic core materials used. The core efficiency lost comes mainly from the eddy current. To reduce the eddy current, increasing the permeability of core materials and reducing their electrical resistance are two major goals for many researchers. A common way to reduce the eddy current is to make laminated core and insulator film and apply it to the surface of each laminated sheet. Laminated sheets reduce the eddy current a great deal, but there is still some considerable ohm heat lost. Many scientists and engineers think a wonderful idea is to use nano particles to make the core, if the Nano-powder core materials can be relatively easily made and if these particles can be coated with some kind of insulated materials. Practically, either one of this two things is not easy to fulfill. In this project, two different sub-nano materials were used to make the core. One was Iron oxide (Fe3O4), and the other one was pure iron. Both are not really nano materials but are very close. A transformer core was successfully made from Iron oxide, and the performance of the transformer was tested. A simple test core of pure ion powder was also made and tested. For the Iron oxide we bought, the results were not as good as predicted due to the permeability being too low. For the pure ion powder, insulation coating on particles was not good enough, so the eddy current was higher than we hoped. Basically speaking, this project was not very successful. We finally leaned that coating nano or sub-nano powder itself is a big research topic. There are many groups in the world doing such research, and not many people get successful on coating nano particles for insulation purposes.
Xie, Tianbao, "Student-Faculty Collaborative Research Grant Report" (2019). Post-Grant Reports. Report. Submission 187.