Purpose:

The purpose of this lab is to explore some of the mechanisms by which heat is transported. In particular we will look at the process are called thermal conduction this week. This is a physically mediated process that is in some ways the most common in our human lives though other processes we will look at next week are more critical overall.

 

Procedure:

 
For this lab we will be observing the concsequences of the flow of heat out of containers of different materials. One would expect that certain containers will cool off faster or slower than others. You will be collecting temperature data to verify this behavior. You will be asked to vary the conditions for some of the containers to provide additional insight for future labs.
 
You will also be applying the mathematical model of thermal conductivity to the refrigerator and the materials in it. You will need to make physical measurements and identify materials in the walls of the fridge. You may complete your calculations by hand or through the use of any plotting or math/algebra system you have access to.

The variables we consider will include some drawn from different materials, with lids and without, stirred or not, size and profile. The point is to consider what each variation in the experiment might tell us about the complex behavior of the system.

 

LAB DELIVERABLES:

 

I) For the containers plot the data you collected on linear - linear graph paper. All the data from each of the three containers should be on the same plot. You should be sure that the axes are correctly labelled and appropriately scaled. Do I need to say "Don't connect the dots!"?

II) Determine the equation of a straight line (which you will draw on the plot using a ruler and scientific insight) which is a "reasonable" description of each data set by "wisely" choosing slopes and intercepts. Show and describe how the math confirms the relationship between a feature of your plot and the coefficient of thermal conductivity. Compare the slopes of these lines to the probable values of the thermal conductivities for each container and comment thoughtfully on your results. I would prefer that you do this by hand rather than linear regression.

III) Calculate the total equilibrium rate of heat flow through 1 wall of the fridge. The equilibrium heat flow is when the heat moving through each layer is the same. This is likely to involve different calculations for each wall of the fridge and relies on the understanding that equilibrium is achieved when the heat flow through each element of the wall is the same. This will also involve determining the relevant parameters and interpreting the results. Be careful -- you only know the outside temperature of the room and the interior temperature of the fridge but not the temperatures at the boundaries of between materials. This is a system of 3 equations and 3 unknowns that needs to be set up and communicated clearly.

IV) Show by trial calculation that the thickness of the steel can be changed significantly without affecting the thermal performance of the fridge. How does the temperature at the boundary between the steel and the foam and the boundary between the foam and the plastic liner change as you play with the thicknesses?

 

 
Thermal Transport I Rubric