Reconsider Prob. 3–122E. Using EES (or other) software, investigate the effects of the thermal conductivity of the spoon material and the length of its extension in the air on the temperature difference across the exposed surface of the spoon handle. Let the thermal conductivity vary from 5 Btu/h·ft·°F to 225 Btu/h·ft·°F and the length from 5 in to 12 in. Plot the temperature difference as the functions of thermal conductivity and length, and discuss the results.

Data From Problem 122

Consider a stainless steel spoon (k = 8.7 Btu/h·ft·°F) partially immersed in boiling water at 200°F in a kitchen at 75°F. The handle of the spoon has a cross section of 0.08 in × 0.5 in, and extends 7 in in the air from the free surface of the water. If the heat transfer coefficient at the exposed surfaces of the spoon handle is 3 Btu/h·ft²·°F, determine the temperature difference across the exposed surface of the spoon handle. State your assumptions.

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A, = 0.075 m² 2n DC motor Welec = 300 W - Th Air, 20°C h = 25 W/m².K Q₁ T₁ = 22°C Stainless steel shaft k = 15.1 W/m-K D = 25 mm, L= 25 cm