Heat Transfer->find k alum. experimentally

[lvll1988]

Hi,

we have a project where we have to find the thermal conductivity of a aluminum bar using a thermocouple.

An idea was to use the specific heat of ice water. By putting a heated rod into the ice and calculate the energy needed to melt the ice. (Or use the Q=mc(dT) equation). But after, how to relate this transferred energy from the rod and use it to find k?

Another idea was to have boiling water in a beaker, and put the bottom of the isolated bar to the beaker. By doing the q from glass = q from bar, we would be able to find the k of aluminium. However, we were told that the contact resistance between the glass and the rod would lose a lot of data...

Any idea?

Thanks,
Tom D.

 

[eljose79]

Hello Tom D.,

Thank you for sharing your project with us. It sounds like you have some good ideas for finding the thermal conductivity of aluminum using a thermocouple. I would like to offer some suggestions and advice to help you in your project.

Firstly, using the specific heat of ice water to find the thermal conductivity of aluminum is a good idea. You can use the equation Q=mc(dT) to calculate the energy needed to melt the ice and then relate it to the transferred energy from the rod. However, there are a few additional factors you need to consider in order to accurately determine the thermal conductivity.

One important factor is the thermal contact resistance between the aluminum rod and the ice. This can significantly affect the amount of energy transferred and can lead to inaccurate results. To minimize this, make sure the surface of the rod is smooth and clean, and try to minimize the time the rod spends in contact with the ice.

Another factor to consider is the temperature difference between the heated rod and the ice water. The larger the temperature difference, the more accurate your results will be. You may need to adjust the initial temperature of the rod or the temperature of the ice water to achieve a suitable temperature difference.

In regards to your second idea of using boiling water, the contact resistance between the glass and the rod can indeed affect your results. One way to minimize this is to use a thin layer of thermal paste between the rod and the glass. This will help to improve the thermal contact and reduce the resistance.

Overall, I recommend conducting multiple trials and taking an average of your results to ensure accuracy. You can also compare your results to known values of thermal conductivity for aluminum to validate your findings.

I hope this helps and good luck with your project!