The handle of a ladle used for pouring molten lead is 30-cm-long. Originally the handle was made of 1.9 x 1.25 cm mild steel bar stock. To reduce the grip temperature, it is proposed to form the handle of tubing 0.15-cm-thick to the same rectangular shape. If the average heat transfer coefficient over the handle surface is 14 W/(m2 K), estimate the reduction of the temperature at the grip in air at 21°C.

GIVEN



FIND

The reduction of the temperature at the grip

ASSUMPTIONS

The lead is at the melting temperature

The handle is made of 1% carbon steel

The ladle is normally in steady state during use

The variation of the thermal conductivity is negligible

One dimensional conduction

Heat transfer from the end of the handle can be neglected

SKETCH


The ladle handle can be treated as a fin with an adiabatic end as shown below



The temperature distribution in the handle,





The only difference in the two handles is the cross-sectional area

Solid handle



The temperature of the grip is reduced 33°C by using the hollow handle.

Physics & Space Science

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