Question

You are using a silver spoon to stir water that just started boiling so that you can achieve a more even heat distribution in your water. The spoon is partially immersed in boiling water and a thermometer in your kitchen reads 27 °C. The handle of the spoon has a cross section of 2mm × 1cm and extends 15 cm in the air from the free surface of the water. The heat transfer coefficient at the exposed surfaces of the spoon handle is 3 W/m2×K.

A) Determine the temperature difference across the exposed surface of the spoon handle.

B) Can the lumped sum analysis be applied to the water as it cools? Provide justification to support your answer.

******Note:

Your answer must provide the following:

1. Assumptions: state all assumptions necessary to solve the problem, explain their relevance and

   validate them where necessary.

2. Schematic: draw a schematic showing the flow of energy in your system

3. What are the modes of heat transfer that the spoon is exposed to?

4. Is this a time dependent or steady state problem? Why or why not?

5. Is this a 1-D, 2-D or 3-D problem? Why or why not?

6. What is the thermal conductivity of the material? Can you assume it constant and if so, for what

   ranges?

7. The heat transfer coefficient is a function of many variables. Discuss the variables and whether the

   heat transfer coefficient can be assumed to be constant

8. What boundary condition are you applying and why?

9. Concluding remarks: explain the meaning of the answers obtained

Answer 1

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